Adds related spans and error grouping for duplicate identifier errors

src/compiler/checker.ts

@@ -423,6 +423,7 @@ namespace ts {
         const jsObjectLiteralIndexInfo = createIndexInfo(anyType, /*isReadonly*/ false);
 
         const globals = createSymbolTable();
+        let amalgamatedDuplicates: Map<{ firstFile: SourceFile, secondFile: SourceFile, firstFileInstances: Map<{ instances: Node[], blockScoped: boolean }>, secondFileInstances: Map<{ instances: Node[], blockScoped: boolean }> }> | undefined;
         const reverseMappedCache = createMap<Type | undefined>();
         let ambientModulesCache: Symbol[] | undefined;
         /**
@@ -833,6 +834,28 @@ namespace ts {
             return emitResolver;
         }
 
+        function lookupOrIssueError(location: Node | undefined, message: DiagnosticMessage, arg0?: string | number, arg1?: string | number, arg2?: string | number, arg3?: string | number): Diagnostic {
+            const diagnostic = location
+                ? createDiagnosticForNode(location, message, arg0, arg1, arg2, arg3)
+                : createCompilerDiagnostic(message, arg0, arg1, arg2, arg3);
+            const existing = diagnostics.lookup(diagnostic);
+            if (existing) {
+                return existing;
+            }
+            else {
+                diagnostics.add(diagnostic);
+                return diagnostic;
+            }
+        }
+
+        function addRelatedInfo(diagnostic: Diagnostic, ...relatedInformation: DiagnosticRelatedInformation[]) {
+            if (!diagnostic.relatedInformation) {
+                diagnostic.relatedInformation = [];
+            }
+            diagnostic.relatedInformation.push(...relatedInformation);
+            return diagnostic;
+        }
+
         function error(location: Node | undefined, message: DiagnosticMessage, arg0?: string | number, arg1?: string | number, arg2?: string | number, arg3?: string | number): Diagnostic {
             const diagnostic = location
                 ? createDiagnosticForNode(location, message, arg0, arg1, arg2, arg3)
@@ -943,23 +966,63 @@ namespace ts {
                 error(getNameOfDeclaration(source.declarations[0]), Diagnostics.Cannot_augment_module_0_with_value_exports_because_it_resolves_to_a_non_module_entity, symbolToString(target));
             }
             else {
-                const message = target.flags & SymbolFlags.Enum || source.flags & SymbolFlags.Enum
+                const isEitherEnum = !!(target.flags & SymbolFlags.Enum || source.flags & SymbolFlags.Enum);
+                const isEitherBlockScoped = !!(target.flags & SymbolFlags.BlockScopedVariable || source.flags & SymbolFlags.BlockScopedVariable);
+                const message = isEitherEnum
                     ? Diagnostics.Enum_declarations_can_only_merge_with_namespace_or_other_enum_declarations
-                    : target.flags & SymbolFlags.BlockScopedVariable || source.flags & SymbolFlags.BlockScopedVariable
+                    : isEitherBlockScoped
                         ? Diagnostics.Cannot_redeclare_block_scoped_variable_0
                         : Diagnostics.Duplicate_identifier_0;
-                forEach(source.declarations, node => {
-                    const errorNode = (getJavascriptInitializer(node, /*isPrototypeAssignment*/ false) ? getOuterNameOfJsInitializer(node) : getNameOfDeclaration(node)) || node;
-                    error(errorNode, message, symbolToString(source));
-                });
-                forEach(target.declarations, node => {
-                    const errorNode = (getJavascriptInitializer(node, /*isPrototypeAssignment*/ false) ? getOuterNameOfJsInitializer(node) : getNameOfDeclaration(node)) || node;
-                    error(errorNode, message, symbolToString(source));
-                });
+                const sourceSymbolFile = source.declarations && getSourceFileOfNode(source.declarations[0]);
+                const targetSymbolFile = target.declarations && getSourceFileOfNode(target.declarations[0]);
+
+                // Collect top-level duplicate identifier errors into one mapping, so we can then merge their diagnostics if there are a bunch
+                if (sourceSymbolFile && targetSymbolFile && amalgamatedDuplicates && !isEitherEnum && sourceSymbolFile !== targetSymbolFile) {
+                    const firstFile = comparePaths(sourceSymbolFile.path, targetSymbolFile.path) === Comparison.LessThan ? sourceSymbolFile : targetSymbolFile;
+                    const secondFile = firstFile === sourceSymbolFile ? targetSymbolFile : sourceSymbolFile;
+                    const cacheKey = `${firstFile.path}|${secondFile.path}`;
+                    const existing = amalgamatedDuplicates.get(cacheKey) || { firstFile, secondFile, firstFileInstances: createMap(), secondFileInstances: createMap() };
+                    const symbolName = symbolToString(source);
+                    const firstInstanceList = existing.firstFileInstances.get(symbolName) || { instances: [], blockScoped: isEitherBlockScoped };
+                    const secondInstanceList = existing.secondFileInstances.get(symbolName) || { instances: [], blockScoped: isEitherBlockScoped };
+
+                    forEach(source.declarations, node => {
+                        const errorNode = (getJavascriptInitializer(node, /*isPrototypeAssignment*/ false) ? getOuterNameOfJsInitializer(node) : getNameOfDeclaration(node)) || node;
+                        const targetList = sourceSymbolFile === firstFile ? firstInstanceList : secondInstanceList;
+                        targetList.instances.push(errorNode);
+                    });
+                    forEach(target.declarations, node => {
+                        const errorNode = (getJavascriptInitializer(node, /*isPrototypeAssignment*/ false) ? getOuterNameOfJsInitializer(node) : getNameOfDeclaration(node)) || node;
+                        const targetList = targetSymbolFile === firstFile ? firstInstanceList : secondInstanceList;
+                        targetList.instances.push(errorNode);
+                    });
+
+                    existing.firstFileInstances.set(symbolName, firstInstanceList);
+                    existing.secondFileInstances.set(symbolName, secondInstanceList);
+                    amalgamatedDuplicates.set(cacheKey, existing);
+                    return target;
+                }
+                const symbolName = symbolToString(source);
+                addDuplicateDeclarationErrorsForSymbols(source, message, symbolName, target);
+                addDuplicateDeclarationErrorsForSymbols(target, message, symbolName, source);
             }
             return target;
         }
 
+        function addDuplicateDeclarationErrorsForSymbols(target: Symbol, message: DiagnosticMessage, symbolName: string, source: Symbol) {
+            forEach(target.declarations, node => {
+                const errorNode = (getJavascriptInitializer(node, /*isPrototypeAssignment*/ false) ? getOuterNameOfJsInitializer(node) : getNameOfDeclaration(node)) || node;
+                addDuplicateDeclarationError(errorNode, message, symbolName, source.declarations && source.declarations[0]);
+            });
+        }
+
+        function addDuplicateDeclarationError(errorNode: Node, message: DiagnosticMessage, symbolName: string, relatedNode: Node | undefined) {
+            const err = lookupOrIssueError(errorNode, message, symbolName);
+            if (relatedNode && length(err.relatedInformation) < 5) {
+                addRelatedInfo(err, !length(err.relatedInformation) ? createDiagnosticForNode(relatedNode, Diagnostics._0_was_also_declared_here, symbolName) : createDiagnosticForNode(relatedNode, Diagnostics.and_here));
+            }
+        }
+
         function combineSymbolTables(first: SymbolTable | undefined, second: SymbolTable | undefined): SymbolTable | undefined {
             if (!hasEntries(first)) return second;
             if (!hasEntries(second)) return first;
@@ -27571,6 +27634,8 @@ namespace ts {
                 bindSourceFile(file, compilerOptions);
             }
 
+            amalgamatedDuplicates = createMap();
+
             // Initialize global symbol table
             let augmentations: ReadonlyArray<StringLiteral | Identifier>[] | undefined;
             for (const file of host.getSourceFiles()) {
@@ -27648,6 +27713,39 @@ namespace ts {
                     }
                 }
             }
+
+            amalgamatedDuplicates.forEach(({ firstFile, secondFile, firstFileInstances, secondFileInstances }) => {
+                const conflictingKeys = arrayFrom(firstFileInstances.keys());
+                // If not many things conflict, issue individual errors
+                if (conflictingKeys.length < 8) {
+                    addErrorsForDuplicates(firstFileInstances, secondFileInstances);
+                    addErrorsForDuplicates(secondFileInstances, firstFileInstances);
+                    return;
+                }
+                // Otheriwse issue top-level error since the files appear very identical in terms of what they appear
+                const list = conflictingKeys.join(", ");
+                diagnostics.add(addRelatedInfo(
+                    createDiagnosticForNode(firstFile, Diagnostics.Definitions_of_the_following_identifiers_conflict_with_those_in_another_file_Colon_0, list),
+                    createDiagnosticForNode(secondFile, Diagnostics.Conflicts_are_in_this_file)
+                ));
+                diagnostics.add(addRelatedInfo(
+                    createDiagnosticForNode(secondFile, Diagnostics.Definitions_of_the_following_identifiers_conflict_with_those_in_another_file_Colon_0, list),
+                    createDiagnosticForNode(firstFile, Diagnostics.Conflicts_are_in_this_file)
+                ));
+            });
+            amalgamatedDuplicates = undefined;
+
+            function addErrorsForDuplicates(secondFileInstances: Map<{ instances: Node[]; blockScoped: boolean; }>, firstFileInstances: Map<{ instances: Node[]; blockScoped: boolean; }>) {
+                secondFileInstances.forEach((locations, symbolName) => {
+                    const firstFileEquivalent = firstFileInstances.get(symbolName)!;
+                    const message = locations.blockScoped
+                        ? Diagnostics.Cannot_redeclare_block_scoped_variable_0
+                        : Diagnostics.Duplicate_identifier_0;
+                    locations.instances.forEach(node => {
+                        addDuplicateDeclarationError(node, message, symbolName, firstFileEquivalent.instances[0]);
+                    });
+                });
+            }
         }
 
         function checkExternalEmitHelpers(location: Node, helpers: ExternalEmitHelpers) {

src/compiler/diagnosticMessages.json

@@ -3603,6 +3603,22 @@
         "code": 6199,
         "reportsUnnecessary": true
     },
+    "Definitions of the following identifiers conflict with those in another file: {0}": {
+        "category": "Error",
+        "code": 6200
+    },
+    "Conflicts are in this file.": {
+        "category": "Message",
+        "code": 6201
+    },
+    "'{0}' was also declared here.": {
+        "category": "Message",
+        "code": 6203
+    },
+    "and here.": {
+        "category": "Message",
+        "code": 6204
+    },
 
     "Projects to reference": {
         "category": "Message",

src/compiler/program.ts

@@ -329,16 +329,17 @@ namespace ts {
         return context;
     }
 
-    function formatLocation(file: SourceFile, start: number, host: FormatDiagnosticsHost) {
+    /* @internal */
+    export function formatLocation(file: SourceFile, start: number, host: FormatDiagnosticsHost, color = formatColorAndReset) {
         const { line: firstLine, character: firstLineChar } = getLineAndCharacterOfPosition(file, start); // TODO: GH#18217
         const relativeFileName = host ? convertToRelativePath(file.fileName, host.getCurrentDirectory(), fileName => host.getCanonicalFileName(fileName)) : file.fileName;
 
         let output = "";
-        output += formatColorAndReset(relativeFileName, ForegroundColorEscapeSequences.Cyan);
+        output += color(relativeFileName, ForegroundColorEscapeSequences.Cyan);
         output += ":";
-        output += formatColorAndReset(`${firstLine + 1}`, ForegroundColorEscapeSequences.Yellow);
+        output += color(`${firstLine + 1}`, ForegroundColorEscapeSequences.Yellow);
         output += ":";
-        output += formatColorAndReset(`${firstLineChar + 1}`, ForegroundColorEscapeSequences.Yellow);
+        output += color(`${firstLineChar + 1}`, ForegroundColorEscapeSequences.Yellow);
         return output;
     }
 

src/compiler/types.ts

@@ -5351,6 +5351,9 @@ namespace ts {
         // Adds a diagnostic to this diagnostic collection.
         add(diagnostic: Diagnostic): void;
 
+        // Returns the first existing diagnostic that is equivalent to the given one (sans related information)
+        lookup(diagnostic: Diagnostic): Diagnostic | undefined;
+
         // Gets all the diagnostics that aren't associated with a file.
         getGlobalDiagnostics(): Diagnostic[];
 

src/compiler/utilities.ts

@@ -2887,6 +2887,7 @@ namespace ts {
 
         return {
             add,
+            lookup,
             getGlobalDiagnostics,
             getDiagnostics,
             reattachFileDiagnostics
@@ -2896,6 +2897,24 @@ namespace ts {
             forEach(fileDiagnostics.get(newFile.fileName), diagnostic => diagnostic.file = newFile);
         }
 
+        function lookup(diagnostic: Diagnostic): Diagnostic | undefined {
+            let diagnostics: SortedArray<Diagnostic> | undefined;
+            if (diagnostic.file) {
+                diagnostics = fileDiagnostics.get(diagnostic.file.fileName);
+            }
+            else {
+                diagnostics = nonFileDiagnostics;
+            }
+            if (!diagnostics) {
+                return undefined;
+            }
+            const result = binarySearch(diagnostics, diagnostic, identity, compareDiagnosticsSkipRelatedInformation);
+            if (result >= 0) {
+                return diagnostics[result];
+            }
+            return undefined;
+        }
+
         function add(diagnostic: Diagnostic): void {
             let diagnostics: SortedArray<Diagnostic> | undefined;
             if (diagnostic.file) {
@@ -6852,6 +6871,13 @@ namespace ts {
 
     /* @internal */
     export function compareDiagnostics(d1: Diagnostic, d2: Diagnostic): Comparison {
+        return compareDiagnosticsSkipRelatedInformation(d1, d2) ||
+            compareRelatedInformation(d1, d2) ||
+            Comparison.EqualTo;
+    }
+
+    /* @internal */
+    export function compareDiagnosticsSkipRelatedInformation(d1: Diagnostic, d2: Diagnostic): Comparison {
         return compareStringsCaseSensitive(getDiagnosticFilePath(d1), getDiagnosticFilePath(d2)) ||
             compareValues(d1.start, d2.start) ||
             compareValues(d1.length, d2.length) ||
@@ -6860,6 +6886,19 @@ namespace ts {
             Comparison.EqualTo;
     }
 
+    function compareRelatedInformation(d1: Diagnostic, d2: Diagnostic): Comparison {
+        if (!d1.relatedInformation && !d2.relatedInformation) {
+            return Comparison.EqualTo;
+        }
+        if (d1.relatedInformation && d2.relatedInformation) {
+            return compareValues(d1.relatedInformation.length, d2.relatedInformation.length) || forEach(d1.relatedInformation, (d1i, index) => {
+                const d2i = d2.relatedInformation![index];
+                return compareDiagnostics(d1i, d2i); // EqualTo is 0, so falsy, and will cause the next item to be compared
+            }) || Comparison.EqualTo;
+        }
+        return d1.relatedInformation ? Comparison.LessThan : Comparison.GreaterThan;
+    }
+
     function compareMessageText(t1: string | DiagnosticMessageChain, t2: string | DiagnosticMessageChain): Comparison {
         let text1: string | DiagnosticMessageChain | undefined = t1;
         let text2: string | DiagnosticMessageChain | undefined = t2;

src/harness/harness.ts

@@ -1348,6 +1348,12 @@ namespace Harness {
                 return "\r\n";
             }
 
+            const formatDiagnsoticHost = {
+                getCurrentDirectory: () => options && options.currentDirectory ? options.currentDirectory : "",
+                getNewLine: () => IO.newLine(),
+                getCanonicalFileName: ts.createGetCanonicalFileName(options && options.caseSensitive !== undefined ? options.caseSensitive : true),
+            };
+
             function outputErrorText(error: ts.Diagnostic) {
                 const message = ts.flattenDiagnosticMessageText(error.messageText, IO.newLine());
 
@@ -1356,6 +1362,11 @@ namespace Harness {
                     .map(s => s.length > 0 && s.charAt(s.length - 1) === "\r" ? s.substr(0, s.length - 1) : s)
                     .filter(s => s.length > 0)
                     .map(s => "!!! " + ts.diagnosticCategoryName(error) + " TS" + error.code + ": " + s);
+                if (error.relatedInformation) {
+                    for (const info of error.relatedInformation) {
+                        errLines.push(`!!! related TS${info.code}${info.file ? " " + ts.formatLocation(info.file, info.start!, formatDiagnsoticHost, ts.identity) : ""}: ${ts.flattenDiagnosticMessageText(info.messageText, IO.newLine())}`);
+                    }
+                }
                 errLines.forEach(e => outputLines += (newLine() + e));
                 errorsReported++;
 

tests/baselines/reference/api/tsserverlibrary.d.ts

@@ -4527,6 +4527,7 @@ declare namespace ts {
     }
     interface DiagnosticCollection {
         add(diagnostic: Diagnostic): void;
+        lookup(diagnostic: Diagnostic): Diagnostic | undefined;
         getGlobalDiagnostics(): Diagnostic[];
         getDiagnostics(fileName: string): DiagnosticWithLocation[];
         getDiagnostics(): Diagnostic[];
@@ -5738,6 +5739,10 @@ declare namespace ts {
         Include_modules_imported_with_json_extension: DiagnosticMessage;
         All_destructured_elements_are_unused: DiagnosticMessage;
         All_variables_are_unused: DiagnosticMessage;
+        Definitions_of_the_following_identifiers_conflict_with_those_in_another_file_Colon_0: DiagnosticMessage;
+        Conflicts_are_in_this_file: DiagnosticMessage;
+        _0_was_also_declared_here: DiagnosticMessage;
+        and_here: DiagnosticMessage;
         Projects_to_reference: DiagnosticMessage;
         Enable_project_compilation: DiagnosticMessage;
         Project_references_may_not_form_a_circular_graph_Cycle_detected_Colon_0: DiagnosticMessage;
@@ -7116,6 +7121,7 @@ declare namespace ts {
     function chainDiagnosticMessages(details: DiagnosticMessageChain | undefined, message: DiagnosticMessage, ...args: (string | undefined)[]): DiagnosticMessageChain;
     function concatenateDiagnosticMessageChains(headChain: DiagnosticMessageChain, tailChain: DiagnosticMessageChain): DiagnosticMessageChain;
     function compareDiagnostics(d1: Diagnostic, d2: Diagnostic): Comparison;
+    function compareDiagnosticsSkipRelatedInformation(d1: Diagnostic, d2: Diagnostic): Comparison;
     function getEmitScriptTarget(compilerOptions: CompilerOptions): ScriptTarget;
     function getEmitModuleKind(compilerOptions: {
         module?: CompilerOptions["module"];
@@ -8946,6 +8952,7 @@ declare namespace ts {
     }
     /** @internal */
     function formatColorAndReset(text: string, formatStyle: string): string;
+    function formatLocation(file: SourceFile, start: number, host: FormatDiagnosticsHost, color?: typeof formatColorAndReset): string;
     function formatDiagnosticsWithColorAndContext(diagnostics: ReadonlyArray<Diagnostic>, host: FormatDiagnosticsHost): string;
     function flattenDiagnosticMessageText(messageText: string | DiagnosticMessageChain | undefined, newLine: string): string;
     /**