From ba7fadeb1228f9c8f0217b18e5090688613f1b9e Mon Sep 17 00:00:00 2001
From: Daniel Rosenwasser <drosen@microsoft.com>
Date: Tue, 30 Jun 2015 20:40:06 -0400
Subject: [PATCH 01/20] Add support to tell whether output directs to a
 terminal emulator.

---
 src/compiler/sys.ts | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/compiler/sys.ts b/src/compiler/sys.ts
index a47d6959ba81a..f3244af0df7e8 100644
--- a/src/compiler/sys.ts
+++ b/src/compiler/sys.ts
@@ -6,6 +6,7 @@ namespace ts {
         newLine: string;
         useCaseSensitiveFileNames: boolean;
         write(s: string): void;
+        writesToTty?(): boolean;
         readFile(path: string, encoding?: string): string;
         writeFile(path: string, data: string, writeByteOrderMark?: boolean): void;
         watchFile?(path: string, callback: (path: string) => void): FileWatcher;
@@ -187,7 +188,8 @@ namespace ts {
         function getNodeSystem(): System {
             var _fs = require("fs");
             var _path = require("path");
-            var _os = require('os');
+            var _os = require("os");
+            var _tty = require("tty");
 
             var platform: string = _os.platform();
             // win32\win64 are case insensitive platforms, MacOS (darwin) by default is also case insensitive
@@ -271,6 +273,7 @@ namespace ts {
                     // 1 is a standard descriptor for stdout
                     _fs.writeSync(1, s);
                 },
+                writesToTty: () => _tty.isatty(1),
                 readFile,
                 writeFile,
                 watchFile: (fileName, callback) => {

From f660bd3652fd567c4c13fd5afafd35a070e2aed0 Mon Sep 17 00:00:00 2001
From: Daniel Rosenwasser <drosen@microsoft.com>
Date: Tue, 30 Jun 2015 22:35:17 -0400
Subject: [PATCH 02/20] Got "prettier" error printing working.

---
 src/compiler/tsc.ts | 84 +++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 78 insertions(+), 6 deletions(-)

diff --git a/src/compiler/tsc.ts b/src/compiler/tsc.ts
index 2a01774fbcaaf..5f474b861fe0a 100644
--- a/src/compiler/tsc.ts
+++ b/src/compiler/tsc.ts
@@ -80,24 +80,96 @@ namespace ts {
         return <string>diagnostic.messageText;
     }
 
-    function reportDiagnostic(diagnostic: Diagnostic) {
-        var output = "";
+    function reportDiagnostic(diagnostic: Diagnostic): void {
+        let output = "";
         
         if (diagnostic.file) {
-            var loc = getLineAndCharacterOfPosition(diagnostic.file, diagnostic.start);
+            let { line, character } = getLineAndCharacterOfPosition(diagnostic.file, diagnostic.start);
 
-            output += `${ diagnostic.file.fileName }(${ loc.line + 1 },${ loc.character + 1 }): `;
+            output += `${ diagnostic.file.fileName }(${ line + 1 },${ character + 1 }): `;
         }
 
-        var category = DiagnosticCategory[diagnostic.category].toLowerCase();
+        let category = DiagnosticCategory[diagnostic.category].toLowerCase();
         output += `${ category } TS${ diagnostic.code }: ${ flattenDiagnosticMessageText(diagnostic.messageText, sys.newLine) }${ sys.newLine }`;
 
         sys.write(output);
     }
 
+    const redColorControlChar = "\u001b[31m";
+    const resetColorControlChar = "\u001b[0m";
+
+    function reportDiagnosticAllPrettyLike(diagnostic: Diagnostic): void {
+        let output = "";
+
+        if (diagnostic.file) {
+            let { start, length, file } = diagnostic;
+            let { line: firstLine, character: firstLineChar } = getLineAndCharacterOfPosition(file, start);
+            let { line: lastLine, character: lastLineChar } = getLineAndCharacterOfPosition(file, start + length);
+            
+            output += sys.newLine;
+            for (let i = 0, indexOfLastLine = lastLine - firstLine; i <= indexOfLastLine; i++) {
+                let lineStart = getPositionOfLineAndCharacter(file, firstLine + i, 0);
+                let lineEnd = getPositionOfLineAndCharacter(file, firstLine + i + 1, 0);
+                let lineContent = file.text.slice(lineStart, lineEnd);
+                lineContent = lineContent.replace(/\s+$/g, "");  // trim from end
+                lineContent = lineContent.replace("\t", "    "); // normalize tabs to 4 spaces
+
+                output += lineContent + sys.newLine;
+                
+                if (i === 0) {
+                    let lastCharForLine = i === indexOfLastLine ? lastLineChar : undefined;
+
+                    output += lineContent.slice(0, firstLineChar).replace(/\S/g, " ");
+                    output += redColorControlChar;
+                    output += lineContent.slice(firstLineChar, lastCharForLine).replace(/./g, "~");
+                    output += resetColorControlChar;
+                }
+                else if (i === indexOfLastLine) {
+                    output += redColorControlChar;
+                    output += lineContent.slice(0, lastLineChar).replace(/./g, "~");
+                    output += resetColorControlChar;
+                    // Don't bother "filling" at the end.
+                }
+                else {
+                    output += lineContent.replace(/^(\s*)(.*)$/, replaceLineWithRedSquiggles);
+                }
+
+                output += sys.newLine;
+            }
+
+            output += `${ file.fileName }(${ firstLine + 1 },${ firstLineChar + 1 }): `;
+        }
+
+        let category = DiagnosticCategory[diagnostic.category].toLowerCase();
+        output += `${ category } TS${ diagnostic.code }: ${ flattenDiagnosticMessageText(diagnostic.messageText, sys.newLine) }`;
+        output += sys.newLine + sys.newLine;
+
+        sys.write(output);
+    }
+
+    function replaceLineWithRedSquiggles(orig: string, leadingWhitespace: string, content: string): string {
+        return leadingWhitespace + redColorControlChar + content.replace(/./g, "~") + resetColorControlChar;
+    }
+
+    /** Splits the given string on \r\n, or on only \n if that fails, or on only \r if *that* fails. */
+    function splitContentByNewlines(content: string) {
+        // Split up the input file by line
+        // Note: IE JS engine incorrectly handles consecutive delimiters here when using RegExp split, so
+        // we have to use string-based splitting instead and try to figure out the delimiting chars
+        var lines = content.split('\r\n');
+        if (lines.length === 1) {
+            lines = content.split('\n');
+
+            if (lines.length === 1) {
+                lines = content.split("\r");
+            }
+        }
+        return lines;
+    }
+
     function reportDiagnostics(diagnostics: Diagnostic[]) {
         for (var i = 0; i < diagnostics.length; i++) {
-            reportDiagnostic(diagnostics[i]);
+            reportDiagnosticAllPrettyLike(diagnostics[i]);
         }
     }
 

From 17f443ac3be562a93cb45b34dd7e9ad4d3ea1366 Mon Sep 17 00:00:00 2001
From: Daniel Rosenwasser <drosen@microsoft.com>
Date: Wed, 1 Jul 2015 03:49:58 -0400
Subject: [PATCH 03/20] Just squiggle the entire line for middle lines (sans
 trailing space).

---
 src/compiler/tsc.ts | 12 +++---------
 1 file changed, 3 insertions(+), 9 deletions(-)

diff --git a/src/compiler/tsc.ts b/src/compiler/tsc.ts
index 5f474b861fe0a..b920949c00450 100644
--- a/src/compiler/tsc.ts
+++ b/src/compiler/tsc.ts
@@ -116,23 +116,21 @@ namespace ts {
 
                 output += lineContent + sys.newLine;
                 
+                output += redColorControlChar;
                 if (i === 0) {
                     let lastCharForLine = i === indexOfLastLine ? lastLineChar : undefined;
 
                     output += lineContent.slice(0, firstLineChar).replace(/\S/g, " ");
-                    output += redColorControlChar;
                     output += lineContent.slice(firstLineChar, lastCharForLine).replace(/./g, "~");
-                    output += resetColorControlChar;
                 }
                 else if (i === indexOfLastLine) {
-                    output += redColorControlChar;
                     output += lineContent.slice(0, lastLineChar).replace(/./g, "~");
-                    output += resetColorControlChar;
                     // Don't bother "filling" at the end.
                 }
                 else {
-                    output += lineContent.replace(/^(\s*)(.*)$/, replaceLineWithRedSquiggles);
+                    output += lineContent.replace(/./g, "~");
                 }
+                output += resetColorControlChar;
 
                 output += sys.newLine;
             }
@@ -147,10 +145,6 @@ namespace ts {
         sys.write(output);
     }
 
-    function replaceLineWithRedSquiggles(orig: string, leadingWhitespace: string, content: string): string {
-        return leadingWhitespace + redColorControlChar + content.replace(/./g, "~") + resetColorControlChar;
-    }
-
     /** Splits the given string on \r\n, or on only \n if that fails, or on only \r if *that* fails. */
     function splitContentByNewlines(content: string) {
         // Split up the input file by line

From fdbea8b6828d8dd5822b21634fd6c3057ff7a81d Mon Sep 17 00:00:00 2001
From: Daniel Rosenwasser <drosen@microsoft.com>
Date: Wed, 1 Jul 2015 12:23:10 -0400
Subject: [PATCH 04/20] Give the new reporter a more reasonable name.

---
 src/compiler/tsc.ts | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/compiler/tsc.ts b/src/compiler/tsc.ts
index b920949c00450..d724a54742f09 100644
--- a/src/compiler/tsc.ts
+++ b/src/compiler/tsc.ts
@@ -98,7 +98,7 @@ namespace ts {
     const redColorControlChar = "\u001b[31m";
     const resetColorControlChar = "\u001b[0m";
 
-    function reportDiagnosticAllPrettyLike(diagnostic: Diagnostic): void {
+    function reportDiagnosticWithColorAndContext(diagnostic: Diagnostic): void {
         let output = "";
 
         if (diagnostic.file) {
@@ -163,7 +163,7 @@ namespace ts {
 
     function reportDiagnostics(diagnostics: Diagnostic[]) {
         for (var i = 0; i < diagnostics.length; i++) {
-            reportDiagnosticAllPrettyLike(diagnostics[i]);
+            reportDiagnosticWithColorAndContext(diagnostics[i]);
         }
     }
 

From d8e462d6e767893ae6ac2bff997f509e3d605ba8 Mon Sep 17 00:00:00 2001
From: Daniel Rosenwasser <drosen@microsoft.com>
Date: Wed, 1 Jul 2015 12:40:01 -0400
Subject: [PATCH 05/20] Make output reliant on whether stdout redirects to a
 terminal; use forEach.

---
 src/compiler/tsc.ts | 22 ++++++++++------------
 1 file changed, 10 insertions(+), 12 deletions(-)

diff --git a/src/compiler/tsc.ts b/src/compiler/tsc.ts
index d724a54742f09..2e577b8b0f933 100644
--- a/src/compiler/tsc.ts
+++ b/src/compiler/tsc.ts
@@ -145,6 +145,10 @@ namespace ts {
         sys.write(output);
     }
 
+    const diagnosticReporter = sys.writesToTty && sys.writesToTty() ?
+            reportDiagnosticWithColorAndContext :
+            reportDiagnostic;
+
     /** Splits the given string on \r\n, or on only \n if that fails, or on only \r if *that* fails. */
     function splitContentByNewlines(content: string) {
         // Split up the input file by line
@@ -161,12 +165,6 @@ namespace ts {
         return lines;
     }
 
-    function reportDiagnostics(diagnostics: Diagnostic[]) {
-        for (var i = 0; i < diagnostics.length; i++) {
-            reportDiagnosticWithColorAndContext(diagnostics[i]);
-        }
-    }
-
     function padLeft(s: string, length: number) {
         while (s.length < length) {
             s = " " + s;
@@ -220,7 +218,7 @@ namespace ts {
         // If there are any errors due to command line parsing and/or
         // setting up localization, report them and quit.
         if (commandLine.errors.length > 0) {
-            reportDiagnostics(commandLine.errors);
+            forEach(commandLine.errors, diagnosticReporter);
             return sys.exit(ExitStatus.DiagnosticsPresent_OutputsSkipped);
         }
 
@@ -285,7 +283,7 @@ namespace ts {
                     let configObject = result.config;
                     let configParseResult = parseConfigFile(configObject, sys, getDirectoryPath(configFileName));
                     if (configParseResult.errors.length > 0) {
-                        reportDiagnostics(configParseResult.errors);
+                        forEach(configParseResult.errors, diagnosticReporter);
                         return sys.exit(ExitStatus.DiagnosticsPresent_OutputsSkipped);
                     }
                     rootFileNames = configParseResult.fileNames;
@@ -422,17 +420,17 @@ namespace ts {
         function compileProgram(): ExitStatus {
             // First get any syntactic errors. 
             var diagnostics = program.getSyntacticDiagnostics();
-            reportDiagnostics(diagnostics);
+            forEach(diagnostics, diagnosticReporter);
 
             // If we didn't have any syntactic errors, then also try getting the global and 
             // semantic errors.
             if (diagnostics.length === 0) {
                 var diagnostics = program.getGlobalDiagnostics();
-                reportDiagnostics(diagnostics);
+                forEach(diagnostics, diagnosticReporter);
 
                 if (diagnostics.length === 0) {
                     var diagnostics = program.getSemanticDiagnostics();
-                    reportDiagnostics(diagnostics);
+                    forEach(diagnostics, diagnosticReporter);
                 }
             }
 
@@ -445,7 +443,7 @@ namespace ts {
 
             // Otherwise, emit and report any errors we ran into.
             var emitOutput = program.emit();
-            reportDiagnostics(emitOutput.diagnostics);
+            forEach(emitOutput.diagnostics, diagnosticReporter);
 
             // If the emitter didn't emit anything, then pass that value along.
             if (emitOutput.emitSkipped) {

From cc6b04c7a62cf42d6e4423fd702d4989a509c3d0 Mon Sep 17 00:00:00 2001
From: Daniel Rosenwasser <drosen@microsoft.com>
Date: Wed, 1 Jul 2015 12:49:46 -0400
Subject: [PATCH 06/20] Bring back 'reportDiagnostics'.

---
 src/compiler/tsc.ts | 44 +++++++++++++++++++++++++-------------------
 1 file changed, 25 insertions(+), 19 deletions(-)

diff --git a/src/compiler/tsc.ts b/src/compiler/tsc.ts
index 2e577b8b0f933..c3b80b800c84d 100644
--- a/src/compiler/tsc.ts
+++ b/src/compiler/tsc.ts
@@ -6,6 +6,16 @@ namespace ts {
         fileWatcher: FileWatcher;
     }
 
+    const reportDiagnostic = sys.writesToTty && sys.writesToTty() ?
+            reportDiagnosticWithColorAndContext :
+            reportDiagnosticSimply;
+
+    function reportDiagnostics(diagnostics: Diagnostic[]): void {
+        for (let diagnostic of diagnostics) {
+            reportDiagnostic(diagnostic);
+        }
+    }
+
     /**
      * Checks to see if the locale is in the appropriate format,
      * and if it is, attempts to set the appropriate language.
@@ -80,7 +90,7 @@ namespace ts {
         return <string>diagnostic.messageText;
     }
 
-    function reportDiagnostic(diagnostic: Diagnostic): void {
+    function reportDiagnosticSimply(diagnostic: Diagnostic): void {
         let output = "";
         
         if (diagnostic.file) {
@@ -145,10 +155,6 @@ namespace ts {
         sys.write(output);
     }
 
-    const diagnosticReporter = sys.writesToTty && sys.writesToTty() ?
-            reportDiagnosticWithColorAndContext :
-            reportDiagnostic;
-
     /** Splits the given string on \r\n, or on only \n if that fails, or on only \r if *that* fails. */
     function splitContentByNewlines(content: string) {
         // Split up the input file by line
@@ -209,7 +215,7 @@ namespace ts {
 
         if (commandLine.options.locale) {
             if (!isJSONSupported()) {
-                reportDiagnostic(createCompilerDiagnostic(Diagnostics.The_current_host_does_not_support_the_0_option, "--locale"));
+                reportDiagnosticSimply(createCompilerDiagnostic(Diagnostics.The_current_host_does_not_support_the_0_option, "--locale"));
                 return sys.exit(ExitStatus.DiagnosticsPresent_OutputsSkipped);
             }
             validateLocaleAndSetLanguage(commandLine.options.locale, commandLine.errors);
@@ -218,12 +224,12 @@ namespace ts {
         // If there are any errors due to command line parsing and/or
         // setting up localization, report them and quit.
         if (commandLine.errors.length > 0) {
-            forEach(commandLine.errors, diagnosticReporter);
+            reportDiagnostics(commandLine.errors);
             return sys.exit(ExitStatus.DiagnosticsPresent_OutputsSkipped);
         }
 
         if (commandLine.options.version) {
-            reportDiagnostic(createCompilerDiagnostic(Diagnostics.Version_0, ts.version));
+            reportDiagnosticSimply(createCompilerDiagnostic(Diagnostics.Version_0, ts.version));
             return sys.exit(ExitStatus.Success);
         }
 
@@ -235,12 +241,12 @@ namespace ts {
 
         if (commandLine.options.project) {
             if (!isJSONSupported()) {
-                reportDiagnostic(createCompilerDiagnostic(Diagnostics.The_current_host_does_not_support_the_0_option, "--project"));
+                reportDiagnosticSimply(createCompilerDiagnostic(Diagnostics.The_current_host_does_not_support_the_0_option, "--project"));
                 return sys.exit(ExitStatus.DiagnosticsPresent_OutputsSkipped);
             }
             configFileName = normalizePath(combinePaths(commandLine.options.project, "tsconfig.json"));
             if (commandLine.fileNames.length !== 0) {
-                reportDiagnostic(createCompilerDiagnostic(Diagnostics.Option_project_cannot_be_mixed_with_source_files_on_a_command_line));
+                reportDiagnosticSimply(createCompilerDiagnostic(Diagnostics.Option_project_cannot_be_mixed_with_source_files_on_a_command_line));
                 return sys.exit(ExitStatus.DiagnosticsPresent_OutputsSkipped);
             }
         }
@@ -258,7 +264,7 @@ namespace ts {
         // Firefox has Object.prototype.watch
         if (commandLine.options.watch && commandLine.options.hasOwnProperty("watch")) {
             if (!sys.watchFile) {
-                reportDiagnostic(createCompilerDiagnostic(Diagnostics.The_current_host_does_not_support_the_0_option, "--watch"));
+                reportDiagnosticSimply(createCompilerDiagnostic(Diagnostics.The_current_host_does_not_support_the_0_option, "--watch"));
                 return sys.exit(ExitStatus.DiagnosticsPresent_OutputsSkipped);
             }
             if (configFileName) {
@@ -276,14 +282,14 @@ namespace ts {
 
                     let result = readConfigFile(configFileName);
                     if (result.error) {
-                        reportDiagnostic(result.error);
+                        reportDiagnosticSimply(result.error);
                         return sys.exit(ExitStatus.DiagnosticsPresent_OutputsSkipped);
                     }
 
                     let configObject = result.config;
                     let configParseResult = parseConfigFile(configObject, sys, getDirectoryPath(configFileName));
                     if (configParseResult.errors.length > 0) {
-                        forEach(configParseResult.errors, diagnosticReporter);
+                        reportDiagnostics(configParseResult.errors);
                         return sys.exit(ExitStatus.DiagnosticsPresent_OutputsSkipped);
                     }
                     rootFileNames = configParseResult.fileNames;
@@ -305,7 +311,7 @@ namespace ts {
             }
 
             setCachedProgram(compileResult.program);
-            reportDiagnostic(createCompilerDiagnostic(Diagnostics.Compilation_complete_Watching_for_file_changes));
+            reportDiagnosticSimply(createCompilerDiagnostic(Diagnostics.Compilation_complete_Watching_for_file_changes));
         }
 
         function getSourceFile(fileName: string, languageVersion: ScriptTarget, onError ?: (message: string) => void) {
@@ -367,7 +373,7 @@ namespace ts {
 
         function recompile() {
             timerHandle = undefined;
-            reportDiagnostic(createCompilerDiagnostic(Diagnostics.File_change_detected_Starting_incremental_compilation));
+            reportDiagnosticSimply(createCompilerDiagnostic(Diagnostics.File_change_detected_Starting_incremental_compilation));
             performCompilation();
         }
     }
@@ -420,17 +426,17 @@ namespace ts {
         function compileProgram(): ExitStatus {
             // First get any syntactic errors. 
             var diagnostics = program.getSyntacticDiagnostics();
-            forEach(diagnostics, diagnosticReporter);
+            reportDiagnostics(diagnostics);
 
             // If we didn't have any syntactic errors, then also try getting the global and 
             // semantic errors.
             if (diagnostics.length === 0) {
                 var diagnostics = program.getGlobalDiagnostics();
-                forEach(diagnostics, diagnosticReporter);
+                reportDiagnostics(diagnostics);
 
                 if (diagnostics.length === 0) {
                     var diagnostics = program.getSemanticDiagnostics();
-                    forEach(diagnostics, diagnosticReporter);
+                    reportDiagnostics(diagnostics);
                 }
             }
 
@@ -443,7 +449,7 @@ namespace ts {
 
             // Otherwise, emit and report any errors we ran into.
             var emitOutput = program.emit();
-            forEach(emitOutput.diagnostics, diagnosticReporter);
+            reportDiagnostics(emitOutput.diagnostics);
 
             // If the emitter didn't emit anything, then pass that value along.
             if (emitOutput.emitSkipped) {

From 99f6985115cfe26ed6f850d0d6943af3d80492f6 Mon Sep 17 00:00:00 2001
From: Daniel Rosenwasser <drosen@microsoft.com>
Date: Thu, 16 Jul 2015 19:41:23 -0700
Subject: [PATCH 07/20] Don't expand tabs; just use a space.

---
 src/compiler/tsc.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/compiler/tsc.ts b/src/compiler/tsc.ts
index c3b80b800c84d..dbd70e7557c7e 100644
--- a/src/compiler/tsc.ts
+++ b/src/compiler/tsc.ts
@@ -122,7 +122,7 @@ namespace ts {
                 let lineEnd = getPositionOfLineAndCharacter(file, firstLine + i + 1, 0);
                 let lineContent = file.text.slice(lineStart, lineEnd);
                 lineContent = lineContent.replace(/\s+$/g, "");  // trim from end
-                lineContent = lineContent.replace("\t", "    "); // normalize tabs to 4 spaces
+                lineContent = lineContent.replace("\t", " ");    // convert tabs to single spaces
 
                 output += lineContent + sys.newLine;
                 

From 85b54e8946f9c19f3237d017cff181fd199618fc Mon Sep 17 00:00:00 2001
From: Daniel Rosenwasser <drosen@microsoft.com>
Date: Thu, 16 Jul 2015 22:45:31 -0700
Subject: [PATCH 08/20] Fixed out of bounds error; made index start directly at
 the line number.

---
 src/compiler/tsc.ts | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/src/compiler/tsc.ts b/src/compiler/tsc.ts
index dbd70e7557c7e..5105d2d37194f 100644
--- a/src/compiler/tsc.ts
+++ b/src/compiler/tsc.ts
@@ -117,9 +117,9 @@ namespace ts {
             let { line: lastLine, character: lastLineChar } = getLineAndCharacterOfPosition(file, start + length);
             
             output += sys.newLine;
-            for (let i = 0, indexOfLastLine = lastLine - firstLine; i <= indexOfLastLine; i++) {
-                let lineStart = getPositionOfLineAndCharacter(file, firstLine + i, 0);
-                let lineEnd = getPositionOfLineAndCharacter(file, firstLine + i + 1, 0);
+            for (let i = firstLine; i <= lastLine; i++) {
+                let lineStart = getPositionOfLineAndCharacter(file, i, 0);
+                let lineEnd = i < lastLine ? getPositionOfLineAndCharacter(file, i + 1, 0) : file.text.length;
                 let lineContent = file.text.slice(lineStart, lineEnd);
                 lineContent = lineContent.replace(/\s+$/g, "");  // trim from end
                 lineContent = lineContent.replace("\t", " ");    // convert tabs to single spaces
@@ -127,13 +127,13 @@ namespace ts {
                 output += lineContent + sys.newLine;
                 
                 output += redColorControlChar;
-                if (i === 0) {
-                    let lastCharForLine = i === indexOfLastLine ? lastLineChar : undefined;
+                if (i === firstLine) {
+                    let lastCharForLine = i === lastLine ? lastLineChar : undefined;
 
                     output += lineContent.slice(0, firstLineChar).replace(/\S/g, " ");
                     output += lineContent.slice(firstLineChar, lastCharForLine).replace(/./g, "~");
                 }
-                else if (i === indexOfLastLine) {
+                else if (i === lastLine) {
                     output += lineContent.slice(0, lastLineChar).replace(/./g, "~");
                     // Don't bother "filling" at the end.
                 }

From dda058b85e73da1166f80364d26aaa5e62df57fb Mon Sep 17 00:00:00 2001
From: Daniel Rosenwasser <drosen@microsoft.com>
Date: Fri, 24 Jul 2015 12:18:18 -0700
Subject: [PATCH 09/20] Use 'process.stdout.write' to ensure colors get
 displayed correctly on Windows.

---
 src/compiler/sys.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/compiler/sys.ts b/src/compiler/sys.ts
index f3244af0df7e8..8564eafa47262 100644
--- a/src/compiler/sys.ts
+++ b/src/compiler/sys.ts
@@ -271,7 +271,7 @@ namespace ts {
                 useCaseSensitiveFileNames: useCaseSensitiveFileNames,
                 write(s: string): void {
                     // 1 is a standard descriptor for stdout
-                    _fs.writeSync(1, s);
+                    process.stdout.write(s);
                 },
                 writesToTty: () => _tty.isatty(1),
                 readFile,

From 3c04dff0593acc423c9167c96f80bd6a38feee60 Mon Sep 17 00:00:00 2001
From: Daniel Rosenwasser <drosen@microsoft.com>
Date: Tue, 18 Aug 2015 00:47:09 -0700
Subject: [PATCH 10/20] Limit errors to 5 lines, fixed some other issues.

---
 src/compiler/tsc.ts | 30 +++++++++++++++++++++++++-----
 1 file changed, 25 insertions(+), 5 deletions(-)

diff --git a/src/compiler/tsc.ts b/src/compiler/tsc.ts
index 5105d2d37194f..069f87dae1f11 100644
--- a/src/compiler/tsc.ts
+++ b/src/compiler/tsc.ts
@@ -105,7 +105,7 @@ namespace ts {
         sys.write(output);
     }
 
-    const redColorControlChar = "\u001b[31m";
+    const redColorControlChar = "\u001b[91m";
     const resetColorControlChar = "\u001b[0m";
 
     function reportDiagnosticWithColorAndContext(diagnostic: Diagnostic): void {
@@ -115,19 +115,38 @@ namespace ts {
             let { start, length, file } = diagnostic;
             let { line: firstLine, character: firstLineChar } = getLineAndCharacterOfPosition(file, start);
             let { line: lastLine, character: lastLineChar } = getLineAndCharacterOfPosition(file, start + length);
-            
+            const lastLineInFile = getLineAndCharacterOfPosition(file, file.text.length).line;
+
+            let hasMoreThanFiveLines = (lastLine - firstLine) >= 4;
+            let gutterWidth = (lastLine + 1 + "").length;
+            if (hasMoreThanFiveLines) {
+                gutterWidth = Math.max("...".length, gutterWidth);
+            }
+
             output += sys.newLine;
             for (let i = firstLine; i <= lastLine; i++) {
+                // If the error spans over 5 lines, we'll only show the first 2 and last 2 lines,
+                // so we'll skip ahead to the second-to-last line.
+                if (hasMoreThanFiveLines && firstLine + 1 < i && i < lastLine - 1) {
+                    output += padLeft("...", gutterWidth) + " ||" + sys.newLine;
+                    i = lastLine - 1;
+                }
+
                 let lineStart = getPositionOfLineAndCharacter(file, i, 0);
-                let lineEnd = i < lastLine ? getPositionOfLineAndCharacter(file, i + 1, 0) : file.text.length;
+                let lineEnd = i < lastLineInFile ? getPositionOfLineAndCharacter(file, i + 1, 0) : file.text.length;
                 let lineContent = file.text.slice(lineStart, lineEnd);
                 lineContent = lineContent.replace(/\s+$/g, "");  // trim from end
                 lineContent = lineContent.replace("\t", " ");    // convert tabs to single spaces
 
-                output += lineContent + sys.newLine;
+                // Output the actual contents of the line.
+                output += padLeft(i + 1 + "", gutterWidth) + " ||" + lineContent + sys.newLine;
                 
+                // Output the error span for the line using tildes.
+                output += padLeft("", gutterWidth) + " ||";
                 output += redColorControlChar;
                 if (i === firstLine) {
+                    // If we're on the last line, then limit it to the last character of the last line.
+                    // Otherwise, we'll just squiggle the rest of the line, giving 'slice' no end position.
                     let lastCharForLine = i === lastLine ? lastLineChar : undefined;
 
                     output += lineContent.slice(0, firstLineChar).replace(/\S/g, " ");
@@ -135,9 +154,9 @@ namespace ts {
                 }
                 else if (i === lastLine) {
                     output += lineContent.slice(0, lastLineChar).replace(/./g, "~");
-                    // Don't bother "filling" at the end.
                 }
                 else {
+                    // Squiggle the entire line.
                     output += lineContent.replace(/./g, "~");
                 }
                 output += resetColorControlChar;
@@ -145,6 +164,7 @@ namespace ts {
                 output += sys.newLine;
             }
 
+            output += sys.newLine;
             output += `${ file.fileName }(${ firstLine + 1 },${ firstLineChar + 1 }): `;
         }
 

From 44f3c0ca8a4198ec17952888c038657f8e50dd61 Mon Sep 17 00:00:00 2001
From: Daniel Rosenwasser <drosen@microsoft.com>
Date: Wed, 19 Aug 2015 12:30:50 -0700
Subject: [PATCH 11/20] Stylize gutter.

---
 src/compiler/tsc.ts | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/src/compiler/tsc.ts b/src/compiler/tsc.ts
index 0d8e33413128c..10eddc41b7eee 100644
--- a/src/compiler/tsc.ts
+++ b/src/compiler/tsc.ts
@@ -106,8 +106,9 @@ namespace ts {
         sys.write(output);
     }
 
-    const redColorControlChar = "\u001b[91m";
-    const resetColorControlChar = "\u001b[0m";
+    const redForegroundEscapeSequence = "\u001b[91m";
+    const gutterStyleSequence = "\u001b[100;30m";
+    const resetEscapeSequence = "\u001b[0m";
 
     function reportDiagnosticWithColorAndContext(diagnostic: Diagnostic): void {
         let output = "";
@@ -129,7 +130,7 @@ namespace ts {
                 // If the error spans over 5 lines, we'll only show the first 2 and last 2 lines,
                 // so we'll skip ahead to the second-to-last line.
                 if (hasMoreThanFiveLines && firstLine + 1 < i && i < lastLine - 1) {
-                    output += padLeft("...", gutterWidth) + " ||" + sys.newLine;
+                    output += gutterStyleSequence + padLeft("...", gutterWidth) + resetEscapeSequence + " " + sys.newLine;
                     i = lastLine - 1;
                 }
 
@@ -140,11 +141,11 @@ namespace ts {
                 lineContent = lineContent.replace("\t", " ");    // convert tabs to single spaces
 
                 // Output the actual contents of the line.
-                output += padLeft(i + 1 + "", gutterWidth) + " ||" + lineContent + sys.newLine;
+                output += gutterStyleSequence + padLeft(i + 1 + "", gutterWidth) + resetEscapeSequence + " " + lineContent + sys.newLine;
                 
                 // Output the error span for the line using tildes.
-                output += padLeft("", gutterWidth) + " ||";
-                output += redColorControlChar;
+                output += gutterStyleSequence + padLeft("", gutterWidth) + resetEscapeSequence + " ";
+                output += redForegroundEscapeSequence;
                 if (i === firstLine) {
                     // If we're on the last line, then limit it to the last character of the last line.
                     // Otherwise, we'll just squiggle the rest of the line, giving 'slice' no end position.
@@ -160,7 +161,7 @@ namespace ts {
                     // Squiggle the entire line.
                     output += lineContent.replace(/./g, "~");
                 }
-                output += resetColorControlChar;
+                output += resetEscapeSequence;
 
                 output += sys.newLine;
             }

From ac5bed86b236da6d2746944819043cce54c9d9cc Mon Sep 17 00:00:00 2001
From: Daniel Rosenwasser <drosen@microsoft.com>
Date: Fri, 18 Sep 2015 19:12:08 -0700
Subject: [PATCH 12/20] Added '--diagnosticStyle' compiler argument with
 options 'simple' and 'pretty'.

---
 src/compiler/commandLineParser.ts             | 11 ++++++++
 .../diagnosticInformationMap.generated.ts     |  2 ++
 src/compiler/diagnosticMessages.json          |  9 ++++++
 src/compiler/tsc.ts                           | 28 +++++++++++--------
 src/compiler/types.ts                         |  6 ++++
 5 files changed, 45 insertions(+), 11 deletions(-)

diff --git a/src/compiler/commandLineParser.ts b/src/compiler/commandLineParser.ts
index 9a984b9a2f12a..5d7c1bc169070 100644
--- a/src/compiler/commandLineParser.ts
+++ b/src/compiler/commandLineParser.ts
@@ -20,6 +20,17 @@ namespace ts {
             name: "diagnostics",
             type: "boolean",
         },
+        {
+            name: "diagnosticStyle",
+            paramType: Diagnostics.KIND,
+            description: Diagnostics.Specify_diagnostic_printing_style_Colon_simple_default_or_pretty,
+            type: {
+                "simple": DiagnosticStyle.Simple,
+                "pretty": DiagnosticStyle.Pretty,
+            },
+            error: Diagnostics.Argument_for_diagnosticStyle_must_be_simple_or_pretty,
+            experimental: true,
+        },
         {
             name: "emitBOM",
             type: "boolean"
diff --git a/src/compiler/diagnosticInformationMap.generated.ts b/src/compiler/diagnosticInformationMap.generated.ts
index 5ccc0a0db9b40..4fdb2221762aa 100644
--- a/src/compiler/diagnosticInformationMap.generated.ts
+++ b/src/compiler/diagnosticInformationMap.generated.ts
@@ -567,6 +567,8 @@ namespace ts {
         Specifies_the_end_of_line_sequence_to_be_used_when_emitting_files_Colon_CRLF_dos_or_LF_unix: { code: 6060, category: DiagnosticCategory.Message, key: "Specifies the end of line sequence to be used when emitting files: 'CRLF' (dos) or 'LF' (unix)." },
         NEWLINE: { code: 6061, category: DiagnosticCategory.Message, key: "NEWLINE" },
         Argument_for_newLine_option_must_be_CRLF_or_LF: { code: 6062, category: DiagnosticCategory.Error, key: "Argument for '--newLine' option must be 'CRLF' or 'LF'." },
+        Specify_diagnostic_printing_style_Colon_simple_default_or_pretty: { code: 6063, category: DiagnosticCategory.Message, key: "Specify diagnostic printing style: 'simple' (default) or 'pretty'." },
+        Argument_for_diagnosticStyle_must_be_simple_or_pretty: { code: 6064, category: DiagnosticCategory.Error, key: "Argument for '--diagnosticStyle' must be 'simple' or 'pretty'." },
         Specify_JSX_code_generation_Colon_preserve_or_react: { code: 6080, category: DiagnosticCategory.Message, key: "Specify JSX code generation: 'preserve' or 'react'" },
         Argument_for_jsx_must_be_preserve_or_react: { code: 6081, category: DiagnosticCategory.Message, key: "Argument for '--jsx' must be 'preserve' or 'react'." },
         Option_experimentalDecorators_must_also_be_specified_when_option_emitDecoratorMetadata_is_specified: { code: 6064, category: DiagnosticCategory.Error, key: "Option 'experimentalDecorators' must also be specified when option 'emitDecoratorMetadata' is specified." },
diff --git a/src/compiler/diagnosticMessages.json b/src/compiler/diagnosticMessages.json
index e138e2ddac489..4a7280f5fda18 100644
--- a/src/compiler/diagnosticMessages.json
+++ b/src/compiler/diagnosticMessages.json
@@ -2258,6 +2258,15 @@
         "category": "Error",
         "code": 6062
     },
+    "Specify diagnostic printing style: 'simple' (default) or 'pretty'.": {
+        "category": "Message",
+        "code": 6063
+    },
+    "Argument for '--diagnosticStyle' must be 'simple' or 'pretty'.": {
+        "category": "Error",
+        "code": 6064
+    },
+
     "Specify JSX code generation: 'preserve' or 'react'": {
         "category": "Message",
         "code": 6080
diff --git a/src/compiler/tsc.ts b/src/compiler/tsc.ts
index 10eddc41b7eee..ae1a7cda22036 100644
--- a/src/compiler/tsc.ts
+++ b/src/compiler/tsc.ts
@@ -6,9 +6,11 @@ namespace ts {
         fileWatcher?: FileWatcher;
     }
 
-    const reportDiagnostic = sys.writesToTty && sys.writesToTty() ?
-            reportDiagnosticWithColorAndContext :
-            reportDiagnosticSimply;
+    export interface CompilerOptions {
+        diagnosticStyle?: DiagnosticStyle;
+    }
+
+    let reportDiagnostic = reportDiagnosticSimply;
 
     function reportDiagnostics(diagnostics: Diagnostic[]): void {
         for (let diagnostic of diagnostics) {
@@ -221,7 +223,7 @@ namespace ts {
 
         if (commandLine.options.locale) {
             if (!isJSONSupported()) {
-                reportDiagnosticSimply(createCompilerDiagnostic(Diagnostics.The_current_host_does_not_support_the_0_option, "--locale"));
+                reportDiagnostic(createCompilerDiagnostic(Diagnostics.The_current_host_does_not_support_the_0_option, "--locale"));
                 return sys.exit(ExitStatus.DiagnosticsPresent_OutputsSkipped);
             }
             validateLocaleAndSetLanguage(commandLine.options.locale, commandLine.errors);
@@ -235,7 +237,7 @@ namespace ts {
         }
 
         if (commandLine.options.version) {
-            reportDiagnosticSimply(createCompilerDiagnostic(Diagnostics.Version_0, ts.version));
+            reportDiagnostic(createCompilerDiagnostic(Diagnostics.Version_0, ts.version));
             return sys.exit(ExitStatus.Success);
         }
 
@@ -247,12 +249,12 @@ namespace ts {
 
         if (commandLine.options.project) {
             if (!isJSONSupported()) {
-                reportDiagnosticSimply(createCompilerDiagnostic(Diagnostics.The_current_host_does_not_support_the_0_option, "--project"));
+                reportDiagnostic(createCompilerDiagnostic(Diagnostics.The_current_host_does_not_support_the_0_option, "--project"));
                 return sys.exit(ExitStatus.DiagnosticsPresent_OutputsSkipped);
             }
             configFileName = normalizePath(combinePaths(commandLine.options.project, "tsconfig.json"));
             if (commandLine.fileNames.length !== 0) {
-                reportDiagnosticSimply(createCompilerDiagnostic(Diagnostics.Option_project_cannot_be_mixed_with_source_files_on_a_command_line));
+                reportDiagnostic(createCompilerDiagnostic(Diagnostics.Option_project_cannot_be_mixed_with_source_files_on_a_command_line));
                 return sys.exit(ExitStatus.DiagnosticsPresent_OutputsSkipped);
             }
         }
@@ -270,7 +272,7 @@ namespace ts {
         // Firefox has Object.prototype.watch
         if (commandLine.options.watch && commandLine.options.hasOwnProperty("watch")) {
             if (!sys.watchFile) {
-                reportDiagnosticSimply(createCompilerDiagnostic(Diagnostics.The_current_host_does_not_support_the_0_option, "--watch"));
+                reportDiagnostic(createCompilerDiagnostic(Diagnostics.The_current_host_does_not_support_the_0_option, "--watch"));
                 return sys.exit(ExitStatus.DiagnosticsPresent_OutputsSkipped);
             }
             if (configFileName) {
@@ -288,7 +290,7 @@ namespace ts {
 
                     let result = readConfigFile(configFileName);
                     if (result.error) {
-                        reportDiagnosticSimply(result.error);
+                        reportDiagnostic(result.error);
                         return sys.exit(ExitStatus.DiagnosticsPresent_OutputsSkipped);
                     }
 
@@ -310,6 +312,10 @@ namespace ts {
                 compilerHost.getSourceFile = getSourceFile;
             }
 
+            if (compilerOptions.diagnosticStyle === DiagnosticStyle.Pretty) {
+                reportDiagnostic = reportDiagnosticWithColorAndContext;
+            }
+
             let compileResult = compile(rootFileNames, compilerOptions, compilerHost);
 
             if (!compilerOptions.watch) {
@@ -317,7 +323,7 @@ namespace ts {
             }
 
             setCachedProgram(compileResult.program);
-            reportDiagnosticSimply(createCompilerDiagnostic(Diagnostics.Compilation_complete_Watching_for_file_changes));
+            reportDiagnostic(createCompilerDiagnostic(Diagnostics.Compilation_complete_Watching_for_file_changes));
         }
 
         function getSourceFile(fileName: string, languageVersion: ScriptTarget, onError?: (message: string) => void) {
@@ -379,7 +385,7 @@ namespace ts {
 
         function recompile() {
             timerHandle = undefined;
-            reportDiagnosticSimply(createCompilerDiagnostic(Diagnostics.File_change_detected_Starting_incremental_compilation));
+            reportDiagnostic(createCompilerDiagnostic(Diagnostics.File_change_detected_Starting_incremental_compilation));
             performCompilation();
         }
     }
diff --git a/src/compiler/types.ts b/src/compiler/types.ts
index 1338d19e1a747..01a791237ad93 100644
--- a/src/compiler/types.ts
+++ b/src/compiler/types.ts
@@ -2094,6 +2094,12 @@ namespace ts {
         JSX
     }
 
+    /* @internal */
+    export const enum DiagnosticStyle {
+        Simple,
+        Pretty,
+    }
+
     export interface ParsedCommandLine {
         options: CompilerOptions;
         fileNames: string[];

From 2b4febee1c9eddaa8497a8dcfce0aedc49469db5 Mon Sep 17 00:00:00 2001
From: Daniel Rosenwasser <drosen@microsoft.com>
Date: Mon, 5 Oct 2015 23:10:04 -0700
Subject: [PATCH 13/20] Moved JSX diagnostics to a more sensical spot.

---
 src/compiler/diagnosticMessages.json | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/src/compiler/diagnosticMessages.json b/src/compiler/diagnosticMessages.json
index 03d890bffa1db..8880544798582 100644
--- a/src/compiler/diagnosticMessages.json
+++ b/src/compiler/diagnosticMessages.json
@@ -2258,14 +2258,6 @@
         "code": 6063
     },
 
-    "Specify JSX code generation: 'preserve' or 'react'": {
-        "category": "Message",
-        "code": 6080
-    },
-    "Argument for '--jsx' must be 'preserve' or 'react'.": {
-        "category": "Message",
-        "code": 6081
-    },
     "Enables experimental support for ES7 decorators.": {
         "category": "Message",
         "code": 6065
@@ -2307,6 +2299,15 @@
         "code": 6074
     },
 
+    "Specify JSX code generation: 'preserve' or 'react'": {
+        "category": "Message",
+        "code": 6080
+    },
+    "Argument for '--jsx' must be 'preserve' or 'react'.": {
+        "category": "Message",
+        "code": 6081
+    },
+
     "Variable '{0}' implicitly has an '{1}' type.": {
         "category": "Error",
         "code": 7005

From c3e00a24f3fccd5dfd126703fa3dbeb95e3261c9 Mon Sep 17 00:00:00 2001
From: Daniel Rosenwasser <drosen@microsoft.com>
Date: Mon, 5 Oct 2015 23:37:50 -0700
Subject: [PATCH 14/20] Only use colors if we are certain we are using a
 pseudoterminal.

---
 src/compiler/sys.ts |  2 +-
 src/compiler/tsc.ts | 19 +++++++++++--------
 2 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/src/compiler/sys.ts b/src/compiler/sys.ts
index c50291e60b8c0..fdf6d075cbfd7 100644
--- a/src/compiler/sys.ts
+++ b/src/compiler/sys.ts
@@ -272,7 +272,7 @@ namespace ts {
                 args: process.argv.slice(2),
                 newLine: _os.EOL,
                 useCaseSensitiveFileNames: useCaseSensitiveFileNames,
-                write(s: string): void {  
+                write(s: string): void {
                     process.stdout.write(s);
                 },
                 writesToTty: () => _tty.isatty(1),
diff --git a/src/compiler/tsc.ts b/src/compiler/tsc.ts
index 5222ca2fccf13..d849425a885b6 100644
--- a/src/compiler/tsc.ts
+++ b/src/compiler/tsc.ts
@@ -108,9 +108,11 @@ namespace ts {
         sys.write(output);
     }
 
-    const redForegroundEscapeSequence = "\u001b[91m";
-    const gutterStyleSequence = "\u001b[100;30m";
-    const resetEscapeSequence = "\u001b[0m";
+    const shouldUseColors = sys.writesToTty && sys.writesToTty();
+    const redForegroundEscapeSequence = shouldUseColors ? "\u001b[91m" : "";
+    const gutterStyleSequence = shouldUseColors ? "\u001b[100;30m" : "";
+    const gutterSeparator = shouldUseColors ? " " : " | "
+    const resetEscapeSequence = shouldUseColors ? "\u001b[0m" : "";
 
     function reportDiagnosticWithColorAndContext(diagnostic: Diagnostic): void {
         let output = "";
@@ -132,7 +134,7 @@ namespace ts {
                 // If the error spans over 5 lines, we'll only show the first 2 and last 2 lines,
                 // so we'll skip ahead to the second-to-last line.
                 if (hasMoreThanFiveLines && firstLine + 1 < i && i < lastLine - 1) {
-                    output += gutterStyleSequence + padLeft("...", gutterWidth) + resetEscapeSequence + " " + sys.newLine;
+                    output += gutterStyleSequence + padLeft("...", gutterWidth) + resetEscapeSequence + gutterSeparator + sys.newLine;
                     i = lastLine - 1;
                 }
 
@@ -142,11 +144,12 @@ namespace ts {
                 lineContent = lineContent.replace(/\s+$/g, "");  // trim from end
                 lineContent = lineContent.replace("\t", " ");    // convert tabs to single spaces
 
-                // Output the actual contents of the line.
-                output += gutterStyleSequence + padLeft(i + 1 + "", gutterWidth) + resetEscapeSequence + " " + lineContent + sys.newLine;
+                // Output the gutter and the actual contents of the line.
+                output += gutterStyleSequence + padLeft(i + 1 + "", gutterWidth) + resetEscapeSequence + gutterSeparator;
+                output += lineContent + sys.newLine;
                 
-                // Output the error span for the line using tildes.
-                output += gutterStyleSequence + padLeft("", gutterWidth) + resetEscapeSequence + " ";
+                // Output the gutter and the error span for the line using tildes.
+                output += gutterStyleSequence + padLeft("", gutterWidth) + resetEscapeSequence + gutterSeparator;
                 output += redForegroundEscapeSequence;
                 if (i === firstLine) {
                     // If we're on the last line, then limit it to the last character of the last line.

From 5c5fca64f03eff1eb9d1519d2181b5ddda429057 Mon Sep 17 00:00:00 2001
From: Daniel Rosenwasser <drosen@microsoft.com>
Date: Mon, 5 Oct 2015 23:41:44 -0700
Subject: [PATCH 15/20] Just make the compiler option internal.

---
 src/compiler/tsc.ts   | 10 +++-------
 src/compiler/types.ts |  1 +
 2 files changed, 4 insertions(+), 7 deletions(-)

diff --git a/src/compiler/tsc.ts b/src/compiler/tsc.ts
index d849425a885b6..b58f59e8a43ed 100644
--- a/src/compiler/tsc.ts
+++ b/src/compiler/tsc.ts
@@ -6,10 +6,6 @@ namespace ts {
         fileWatcher?: FileWatcher;
     }
 
-    export interface CompilerOptions {
-        diagnosticStyle?: DiagnosticStyle;
-    }
-
     let reportDiagnostic = reportDiagnosticSimply;
 
     function reportDiagnostics(diagnostics: Diagnostic[]): void {
@@ -95,7 +91,7 @@ namespace ts {
 
     function reportDiagnosticSimply(diagnostic: Diagnostic): void {
         let output = "";
-        
+
         if (diagnostic.file) {
             let { line, character } = getLineAndCharacterOfPosition(diagnostic.file, diagnostic.start);
 
@@ -111,7 +107,7 @@ namespace ts {
     const shouldUseColors = sys.writesToTty && sys.writesToTty();
     const redForegroundEscapeSequence = shouldUseColors ? "\u001b[91m" : "";
     const gutterStyleSequence = shouldUseColors ? "\u001b[100;30m" : "";
-    const gutterSeparator = shouldUseColors ? " " : " | "
+    const gutterSeparator = shouldUseColors ? " " : " | ";
     const resetEscapeSequence = shouldUseColors ? "\u001b[0m" : "";
 
     function reportDiagnosticWithColorAndContext(diagnostic: Diagnostic): void {
@@ -147,7 +143,7 @@ namespace ts {
                 // Output the gutter and the actual contents of the line.
                 output += gutterStyleSequence + padLeft(i + 1 + "", gutterWidth) + resetEscapeSequence + gutterSeparator;
                 output += lineContent + sys.newLine;
-                
+
                 // Output the gutter and the error span for the line using tildes.
                 output += gutterStyleSequence + padLeft("", gutterWidth) + resetEscapeSequence + gutterSeparator;
                 output += redForegroundEscapeSequence;
diff --git a/src/compiler/types.ts b/src/compiler/types.ts
index 48a31c417b7d2..d271f0d47aba3 100644
--- a/src/compiler/types.ts
+++ b/src/compiler/types.ts
@@ -2043,6 +2043,7 @@ namespace ts {
         charset?: string;
         declaration?: boolean;
         diagnostics?: boolean;
+        /* @internal */diagnosticStyle?: DiagnosticStyle;
         emitBOM?: boolean;
         help?: boolean;
         init?: boolean;

From 48c2bb1c5005c100e599612fb756b025d70d8fb5 Mon Sep 17 00:00:00 2001
From: Daniel Rosenwasser <drosen@microsoft.com>
Date: Fri, 30 Oct 2015 18:10:31 -0700
Subject: [PATCH 16/20] Fixed 'tsconfig.json' ordering.

---
 src/compiler/tsconfig.json | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/compiler/tsconfig.json b/src/compiler/tsconfig.json
index fd541a8ca80c1..ca297c087cf0c 100644
--- a/src/compiler/tsconfig.json
+++ b/src/compiler/tsconfig.json
@@ -11,6 +11,7 @@
         "core.ts",
         "sys.ts",
         "types.ts",
+        "diagnosticInformationMap.generated.ts",
         "scanner.ts",
         "parser.ts",
         "utilities.ts",
@@ -19,7 +20,6 @@
         "emitter.ts",
         "program.ts",
         "commandLineParser.ts",
-        "tsc.ts",
-        "diagnosticInformationMap.generated.ts"
+        "tsc.ts"
     ]
 }

From 4219c5ffecbefea92b507cf57652a0f1ec40c306 Mon Sep 17 00:00:00 2001
From: Daniel Rosenwasser <drosen@microsoft.com>
Date: Mon, 2 Nov 2015 13:12:19 -0800
Subject: [PATCH 17/20] Added colors to diagnostic types, addressed some CR
 feedback.

---
 src/compiler/tsc.ts | 29 +++++++++++++++++++++--------
 1 file changed, 21 insertions(+), 8 deletions(-)

diff --git a/src/compiler/tsc.ts b/src/compiler/tsc.ts
index ab2a83c90d49c..cedfacba9e305 100644
--- a/src/compiler/tsc.ts
+++ b/src/compiler/tsc.ts
@@ -104,11 +104,23 @@ namespace ts {
         sys.write(output);
     }
 
-    const shouldUseColors = sys.writesToTty && sys.writesToTty();
+    const shouldUseColors = !!sys.writesToTty && sys.writesToTty();
     const redForegroundEscapeSequence = shouldUseColors ? "\u001b[91m" : "";
+    const yellowForegroundEscapeSequence = shouldUseColors ? "\u001b[93m" : "";
+    const blueForegroundEscapeSequence = shouldUseColors ? "\u001b[93m" : "";
     const gutterStyleSequence = shouldUseColors ? "\u001b[100;30m" : "";
     const gutterSeparator = shouldUseColors ? " " : " | ";
     const resetEscapeSequence = shouldUseColors ? "\u001b[0m" : "";
+    const elipsis = "...";
+    const categoryFormatMap: Map<string> = {
+        [DiagnosticCategory.Warning]: yellowForegroundEscapeSequence,
+        [DiagnosticCategory.Error]: redForegroundEscapeSequence,
+        [DiagnosticCategory.Message]: blueForegroundEscapeSequence,
+    }
+
+    function formatAndReset(text: string, formatStyle: string) {
+        return formatStyle + text + resetEscapeSequence;
+    }
 
     function reportDiagnosticWithColorAndContext(diagnostic: Diagnostic): void {
         let output = "";
@@ -122,7 +134,7 @@ namespace ts {
             let hasMoreThanFiveLines = (lastLine - firstLine) >= 4;
             let gutterWidth = (lastLine + 1 + "").length;
             if (hasMoreThanFiveLines) {
-                gutterWidth = Math.max("...".length, gutterWidth);
+                gutterWidth = Math.max(elipsis.length, gutterWidth);
             }
 
             output += sys.newLine;
@@ -130,7 +142,7 @@ namespace ts {
                 // If the error spans over 5 lines, we'll only show the first 2 and last 2 lines,
                 // so we'll skip ahead to the second-to-last line.
                 if (hasMoreThanFiveLines && firstLine + 1 < i && i < lastLine - 1) {
-                    output += gutterStyleSequence + padLeft("...", gutterWidth) + resetEscapeSequence + gutterSeparator + sys.newLine;
+                    output += formatAndReset(padLeft(elipsis, gutterWidth), gutterStyleSequence) + gutterSeparator + sys.newLine;
                     i = lastLine - 1;
                 }
 
@@ -141,16 +153,16 @@ namespace ts {
                 lineContent = lineContent.replace("\t", " ");    // convert tabs to single spaces
 
                 // Output the gutter and the actual contents of the line.
-                output += gutterStyleSequence + padLeft(i + 1 + "", gutterWidth) + resetEscapeSequence + gutterSeparator;
+                output += formatAndReset(padLeft(i + 1 + "", gutterWidth), gutterStyleSequence) + gutterSeparator;
                 output += lineContent + sys.newLine;
 
                 // Output the gutter and the error span for the line using tildes.
-                output += gutterStyleSequence + padLeft("", gutterWidth) + resetEscapeSequence + gutterSeparator;
+                output += formatAndReset(padLeft("", gutterWidth), gutterStyleSequence) + gutterSeparator;
                 output += redForegroundEscapeSequence;
                 if (i === firstLine) {
                     // If we're on the last line, then limit it to the last character of the last line.
                     // Otherwise, we'll just squiggle the rest of the line, giving 'slice' no end position.
-                    let lastCharForLine = i === lastLine ? lastLineChar : undefined;
+                    const lastCharForLine = i === lastLine ? lastLineChar : undefined;
 
                     output += lineContent.slice(0, firstLineChar).replace(/\S/g, " ");
                     output += lineContent.slice(firstLineChar, lastCharForLine).replace(/./g, "~");
@@ -171,8 +183,9 @@ namespace ts {
             output += `${ file.fileName }(${ firstLine + 1 },${ firstLineChar + 1 }): `;
         }
 
-        let category = DiagnosticCategory[diagnostic.category].toLowerCase();
-        output += `${ category } TS${ diagnostic.code }: ${ flattenDiagnosticMessageText(diagnostic.messageText, sys.newLine) }`;
+        const categoryColor = categoryFormatMap[diagnostic.category];
+        const category = DiagnosticCategory[diagnostic.category].toLowerCase();
+        output += `${ formatAndReset(category, categoryColor) } TS${ diagnostic.code }: ${ flattenDiagnosticMessageText(diagnostic.messageText, sys.newLine) }`;
         output += sys.newLine + sys.newLine;
 
         sys.write(output);

From 654cbd977940b367962500f3d89dd28b21383704 Mon Sep 17 00:00:00 2001
From: Daniel Rosenwasser <drosen@microsoft.com>
Date: Mon, 2 Nov 2015 13:20:48 -0800
Subject: [PATCH 18/20] Just name the option 'pretty' for now.

---
 src/compiler/commandLineParser.ts    | 17 ++++++-----------
 src/compiler/diagnosticMessages.json |  6 +-----
 src/compiler/tsc.ts                  |  2 +-
 src/compiler/types.ts                |  2 +-
 4 files changed, 9 insertions(+), 18 deletions(-)

diff --git a/src/compiler/commandLineParser.ts b/src/compiler/commandLineParser.ts
index ee1a36ec45e02..141ab85929e62 100644
--- a/src/compiler/commandLineParser.ts
+++ b/src/compiler/commandLineParser.ts
@@ -21,17 +21,6 @@ namespace ts {
             name: "diagnostics",
             type: "boolean",
         },
-        {
-            name: "diagnosticStyle",
-            paramType: Diagnostics.KIND,
-            description: Diagnostics.Specify_diagnostic_printing_style_Colon_simple_default_or_pretty,
-            type: {
-                "simple": DiagnosticStyle.Simple,
-                "pretty": DiagnosticStyle.Pretty,
-            },
-            error: Diagnostics.Argument_for_diagnosticStyle_must_be_simple_or_pretty,
-            experimental: true,
-        },
         {
             name: "emitBOM",
             type: "boolean"
@@ -162,6 +151,12 @@ namespace ts {
             type: "boolean",
             description: Diagnostics.Do_not_erase_const_enum_declarations_in_generated_code
         },
+        {
+            name: "pretty",
+            paramType: Diagnostics.KIND,
+            description: Diagnostics.Stylize_errors_and_messages_using_colors_if_available_experimental,
+            type: "boolean"
+        },
         {
             name: "project",
             shortName: "p",
diff --git a/src/compiler/diagnosticMessages.json b/src/compiler/diagnosticMessages.json
index 0abe92299bf39..ed17c2a77b015 100644
--- a/src/compiler/diagnosticMessages.json
+++ b/src/compiler/diagnosticMessages.json
@@ -2286,14 +2286,10 @@
         "category": "Message",
         "code": 6072
     },
-    "Specify diagnostic printing style: 'simple' (default) or 'pretty'.": {
+    "Stylize errors and messages using colors if available. (experimental)": {
         "category": "Message",
         "code": 6073
     },
-    "Argument for '--diagnosticStyle' must be 'simple' or 'pretty'.": {
-        "category": "Error",
-        "code": 6074
-    },
 
     "Specify JSX code generation: 'preserve' or 'react'": {
         "category": "Message",
diff --git a/src/compiler/tsc.ts b/src/compiler/tsc.ts
index cedfacba9e305..66a6cbb65bd1a 100644
--- a/src/compiler/tsc.ts
+++ b/src/compiler/tsc.ts
@@ -374,7 +374,7 @@ namespace ts {
                 compilerHost.fileExists = cachedFileExists;
             }
 
-            if (compilerOptions.diagnosticStyle === DiagnosticStyle.Pretty) {
+            if (compilerOptions.pretty) {
                 reportDiagnostic = reportDiagnosticWithColorAndContext;
             }
 
diff --git a/src/compiler/types.ts b/src/compiler/types.ts
index ca8a001492451..363c3a4a29f05 100644
--- a/src/compiler/types.ts
+++ b/src/compiler/types.ts
@@ -2053,7 +2053,6 @@ namespace ts {
         charset?: string;
         declaration?: boolean;
         diagnostics?: boolean;
-        /* @internal */diagnosticStyle?: DiagnosticStyle;
         emitBOM?: boolean;
         help?: boolean;
         init?: boolean;
@@ -2076,6 +2075,7 @@ namespace ts {
         outFile?: string;
         outDir?: string;
         preserveConstEnums?: boolean;
+        /* @internal */ pretty?: DiagnosticStyle;
         project?: string;
         removeComments?: boolean;
         rootDir?: string;

From 40f10abe01b3765193c62f7eacb7e17e2f911cd7 Mon Sep 17 00:00:00 2001
From: Daniel Rosenwasser <drosen@microsoft.com>
Date: Mon, 2 Nov 2015 14:48:28 -0800
Subject: [PATCH 19/20] Forget about tty detection. It won't work in build
 tools.

---
 src/compiler/sys.ts |  2 --
 src/compiler/tsc.ts | 13 ++++++-------
 2 files changed, 6 insertions(+), 9 deletions(-)

diff --git a/src/compiler/sys.ts b/src/compiler/sys.ts
index ee9d1a9653c72..6263f7237f609 100644
--- a/src/compiler/sys.ts
+++ b/src/compiler/sys.ts
@@ -6,7 +6,6 @@ namespace ts {
         newLine: string;
         useCaseSensitiveFileNames: boolean;
         write(s: string): void;
-        writesToTty?(): boolean;
         readFile(path: string, encoding?: string): string;
         writeFile(path: string, data: string, writeByteOrderMark?: boolean): void;
         watchFile?(path: string, callback: (path: string, removed?: boolean) => void): FileWatcher;
@@ -379,7 +378,6 @@ namespace ts {
                 write(s: string): void {
                     process.stdout.write(s);
                 },
-                writesToTty: () => _tty.isatty(1),
                 readFile,
                 writeFile,
                 watchFile: (fileName, callback) => {
diff --git a/src/compiler/tsc.ts b/src/compiler/tsc.ts
index 66a6cbb65bd1a..f996797db6ec0 100644
--- a/src/compiler/tsc.ts
+++ b/src/compiler/tsc.ts
@@ -104,13 +104,12 @@ namespace ts {
         sys.write(output);
     }
 
-    const shouldUseColors = !!sys.writesToTty && sys.writesToTty();
-    const redForegroundEscapeSequence = shouldUseColors ? "\u001b[91m" : "";
-    const yellowForegroundEscapeSequence = shouldUseColors ? "\u001b[93m" : "";
-    const blueForegroundEscapeSequence = shouldUseColors ? "\u001b[93m" : "";
-    const gutterStyleSequence = shouldUseColors ? "\u001b[100;30m" : "";
-    const gutterSeparator = shouldUseColors ? " " : " | ";
-    const resetEscapeSequence = shouldUseColors ? "\u001b[0m" : "";
+    const redForegroundEscapeSequence = "\u001b[91m";
+    const yellowForegroundEscapeSequence = "\u001b[93m";
+    const blueForegroundEscapeSequence = "\u001b[93m";
+    const gutterStyleSequence = "\u001b[100;30m";
+    const gutterSeparator = " ";
+    const resetEscapeSequence = "\u001b[0m";
     const elipsis = "...";
     const categoryFormatMap: Map<string> = {
         [DiagnosticCategory.Warning]: yellowForegroundEscapeSequence,

From ce24bcb2eecec7c0d5cdc5d760a28b2428d79345 Mon Sep 17 00:00:00 2001
From: Daniel Rosenwasser <drosen@microsoft.com>
Date: Mon, 2 Nov 2015 15:45:57 -0800
Subject: [PATCH 20/20] ;

---
 src/compiler/tsc.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/compiler/tsc.ts b/src/compiler/tsc.ts
index de43ce103328d..083df70be0f76 100644
--- a/src/compiler/tsc.ts
+++ b/src/compiler/tsc.ts
@@ -119,7 +119,7 @@ namespace ts {
         [DiagnosticCategory.Warning]: yellowForegroundEscapeSequence,
         [DiagnosticCategory.Error]: redForegroundEscapeSequence,
         [DiagnosticCategory.Message]: blueForegroundEscapeSequence,
-    }
+    };
 
     function formatAndReset(text: string, formatStyle: string) {
         return formatStyle + text + resetEscapeSequence;