From 6f179bf48e3d2a93e09a30f28c9ed1ddeec06fba Mon Sep 17 00:00:00 2001
From: Vladimir Matveev <vladima@microsoft.com>
Date: Fri, 18 Nov 2016 22:13:08 -0800
Subject: [PATCH 1/2] recompute character to column when comparing indentations

---
 src/services/formatting/formatting.ts   | 10 +++++++++-
 tests/cases/fourslash/formatWithTabs.ts | 16 ++++++++++++++++
 2 files changed, 25 insertions(+), 1 deletion(-)
 create mode 100644 tests/cases/fourslash/formatWithTabs.ts

diff --git a/src/services/formatting/formatting.ts b/src/services/formatting/formatting.ts
index 7f594ad82b1fd..712ab7bec20e1 100644
--- a/src/services/formatting/formatting.ts
+++ b/src/services/formatting/formatting.ts
@@ -886,12 +886,20 @@ namespace ts.formatting {
             else {
                 const tokenStart = sourceFile.getLineAndCharacterOfPosition(pos);
                 const startLinePosition = getStartPositionOfLine(tokenStart.line, sourceFile);
-                if (indentation !== tokenStart.character || indentationIsDifferent(indentationString, startLinePosition)) {
+                if (indentation !== characterToColumn(startLinePosition, tokenStart.character) || indentationIsDifferent(indentationString, startLinePosition)) {
                     recordReplace(startLinePosition, tokenStart.character, indentationString);
                 }
             }
         }
 
+        function characterToColumn(startLinePosition: number, characterInLine: number): number {
+            let column = 0;
+            for (let i = 0; i < characterInLine; i++) {
+                column += sourceFile.text.charCodeAt(startLinePosition + i) === CharacterCodes.tab ? options.tabSize : 1;
+            }
+            return column;
+        }
+
         function indentationIsDifferent(indentationString: string, startLinePosition: number): boolean {
             return indentationString !== sourceFile.text.substr(startLinePosition, indentationString.length);
         }
diff --git a/tests/cases/fourslash/formatWithTabs.ts b/tests/cases/fourslash/formatWithTabs.ts
new file mode 100644
index 0000000000000..c33808bd26acf
--- /dev/null
+++ b/tests/cases/fourslash/formatWithTabs.ts
@@ -0,0 +1,16 @@
+/// <reference path="fourslash.ts"/>
+
+////const foo = [
+////		1
+////];
+
+const options = format.copyFormatOptions();
+options.IndentSize = 2;
+options.TabSize = 2;
+options.ConvertTabsToSpaces = false;
+format.setFormatOptions(options);
+format.document();
+verify.currentFileContentIs(
+`const foo = [
+	1
+];`);
\ No newline at end of file

From 5c5ee58d00ba3ce16914571bd69732367eca67d0 Mon Sep 17 00:00:00 2001
From: Vladimir Matveev <vladima@microsoft.com>
Date: Fri, 18 Nov 2016 23:21:35 -0800
Subject: [PATCH 2/2] update column computation math

---
 src/services/formatting/formatting.ts    |  7 ++++++-
 tests/cases/fourslash/formatWithTabs2.ts | 16 ++++++++++++++++
 2 files changed, 22 insertions(+), 1 deletion(-)
 create mode 100644 tests/cases/fourslash/formatWithTabs2.ts

diff --git a/src/services/formatting/formatting.ts b/src/services/formatting/formatting.ts
index 712ab7bec20e1..bcd8cebb017e7 100644
--- a/src/services/formatting/formatting.ts
+++ b/src/services/formatting/formatting.ts
@@ -895,7 +895,12 @@ namespace ts.formatting {
         function characterToColumn(startLinePosition: number, characterInLine: number): number {
             let column = 0;
             for (let i = 0; i < characterInLine; i++) {
-                column += sourceFile.text.charCodeAt(startLinePosition + i) === CharacterCodes.tab ? options.tabSize : 1;
+                if (sourceFile.text.charCodeAt(startLinePosition + i) === CharacterCodes.tab) {
+                    column += options.tabSize - column % options.tabSize;
+                }
+                else {
+                    column++;
+                }
             }
             return column;
         }
diff --git a/tests/cases/fourslash/formatWithTabs2.ts b/tests/cases/fourslash/formatWithTabs2.ts
new file mode 100644
index 0000000000000..cda82b9cf80cb
--- /dev/null
+++ b/tests/cases/fourslash/formatWithTabs2.ts
@@ -0,0 +1,16 @@
+/// <reference path="fourslash.ts"/>
+
+////const foo = [
+//// 	1
+////];
+
+const options = format.copyFormatOptions();
+options.IndentSize = 2;
+options.TabSize = 2;
+options.ConvertTabsToSpaces = false;
+format.setFormatOptions(options);
+format.document();
+verify.currentFileContentIs(
+`const foo = [
+	1
+];`);
\ No newline at end of file