Prototype implementation of Source Maps v4

src/compiler/commandLineParser.ts

@@ -516,6 +516,16 @@ namespace ts {
             defaultValueDescription: false,
             description: Diagnostics.Create_source_map_files_for_emitted_JavaScript_files,
         },
+        {
+            name: "sourceMapVersion",
+            type: "number",
+            affectsEmit: true,
+            showInSimplifiedHelpView: false,
+            category: Diagnostics.Emit,
+            defaultValueDescription: 3,
+            description: Diagnostics.Specifies_the_version_3_or_4_of_source_maps_that_should_be_generated_by_compiler_Requires_the_sourceMap_option_to_be_enabled,
+            defaultInitValue: 3,
+        },
         {
             name: "outFile",
             type: "string",
@@ -3611,6 +3621,10 @@ namespace ts {
 
 
     function getDefaultValueForOption(option: CommandLineOption) {
+        if ("defaultInitValue" in option && option.defaultInitValue !== undefined) {
+            return option.defaultInitValue;
+        }
+
         switch (option.type) {
             case "number":
                 return 1;

src/compiler/diagnosticMessages.json

@@ -4161,7 +4161,7 @@
         "category": "Message",
         "code": 6041
     },
-    
+
     "Generates corresponding '.map' file.": {
         "category": "Message",
         "code": 6043
@@ -7236,5 +7236,13 @@
     "A 'return' statement cannot be used inside a class static block.": {
         "category": "Error",
         "code": 18041
+    },
+    "Specifies the version (3 or 4) of source maps that should be generated by compiler. Requires the sourceMap option to be enabled.": {
+        "category": "Message",
+        "code": 18042
+    },
+    "If the 'sourceMapVersion' option is specified, it must be set to 3 or 4.": {
+        "category": "Error",
+        "code": 18043
     }
 }

src/compiler/program.ts

@@ -3307,6 +3307,16 @@ namespace ts {
                 }
             }
 
+            if (options.sourceMapVersion) {
+                if (!options.sourceMap && !options.inlineSourceMap) {
+                    createDiagnosticForOptionName(Diagnostics.Option_0_cannot_be_specified_without_specifying_option_1_or_option_2, "sourceMapVersion", "sourceMap", "inlineSourceMap");
+                }
+
+                if (options.sourceMapVersion !== 3 && options.sourceMapVersion !== 4) {
+                    createDiagnosticForOptionName(Diagnostics.If_the_sourceMapVersion_option_is_specified_it_must_be_set_to_3_or_4, "sourceMapVersion");
+                }
+            }
+
             if (options.composite) {
                 if (options.declaration === false) {
                     createDiagnosticForOptionName(Diagnostics.Composite_projects_may_not_disable_declaration_emit, "declaration");

src/compiler/sourcemap.ts

@@ -19,6 +19,12 @@ namespace ts {
         let nameToNameIndexMap: ESMap<string, number> | undefined;
         const mappingCharCodes: number[] = [];
         let mappings = "";
+        const scopeNames: string[] = [];
+        let scopeNamesToNameIndexMap: ESMap<string, number> | undefined;
+        const scopeMappingCharCodes: number[] = [];
+        let scopes = "";
+
+        const version = host.getCompilerOptions().sourceMapVersion;
 
         // Last recorded and encoded mappings
         let lastGeneratedLine = 0;
@@ -39,13 +45,21 @@ namespace ts {
         let hasPendingSource = false;
         let hasPendingName = false;
 
+        let lastScopeSourceIndex = 0;
+        let lastScopeStartingLine = 0;
+        let lastScopeNameIndex = 0;
+        let hasScopeMappings = false;
+
         return {
             getSources: () => rawSources,
             addSource,
             setSourceContent,
             addName,
             addMapping,
             appendSourceMap,
+            addScopeName,
+            addScopeMapping,
+            shouldCollectScopeNames: () => !!version && version >= 4,
             toJSON,
             toString: () => JSON.stringify(toJSON())
         };
@@ -96,6 +110,22 @@ namespace ts {
             return nameIndex;
         }
 
+        function addScopeName(name: string): number {
+            if (version !== 4) {
+                return 0;
+            }
+            enter();
+            if (!scopeNamesToNameIndexMap) scopeNamesToNameIndexMap = new Map();
+            let nameIndex = scopeNamesToNameIndexMap.get(name);
+            if (nameIndex === undefined) {
+                nameIndex = scopeNames.length;
+                scopeNames.push(name);
+                scopeNamesToNameIndexMap.set(name, nameIndex);
+            }
+            exit();
+            return nameIndex;
+        }
+
         function isNewGeneratedPosition(generatedLine: number, generatedCharacter: number) {
             return !hasPending
                 || pendingGeneratedLine !== generatedLine
@@ -142,6 +172,42 @@ namespace ts {
             exit();
         }
 
+        function addScopeMapping(sourceIndex: number, start: LineAndCharacter, end: LineAndCharacter, scopeNameIndex: number) {
+            if (version !== 4) {
+                return;
+            }
+            enter();
+
+            if (hasScopeMappings) {
+                appendScopeMappingCharCode(CharacterCodes.comma);
+            }
+
+            // 1. Relative source index
+            appendBase64VLQForScopeMapping(sourceIndex - lastScopeSourceIndex);
+            lastScopeSourceIndex = sourceIndex;
+
+            // 2. Relative starting line
+            appendBase64VLQForScopeMapping(start.line - lastScopeStartingLine);
+            lastScopeStartingLine = start.line;
+
+            // 3. Starting column, absolute
+            appendBase64VLQForScopeMapping(start.character);
+
+            // 4. Ending line, relative to STARTING LINE
+            appendBase64VLQForScopeMapping(end.line - start.line);
+
+            // 5. Ending column, absolute
+            appendBase64VLQForScopeMapping(end.character);
+
+            // 6. Relative index into scopeNames array
+            appendBase64VLQForScopeMapping(scopeNameIndex - lastScopeNameIndex);
+            lastScopeNameIndex = scopeNameIndex;
+
+            hasScopeMappings = true;
+
+            exit();
+        }
+
         function appendSourceMap(generatedLine: number, generatedCharacter: number, map: RawSourceMap, sourceMapPath: string, start?: LineAndCharacter, end?: LineAndCharacter) {
             Debug.assert(generatedLine >= pendingGeneratedLine, "generatedLine cannot backtrack");
             Debug.assert(generatedCharacter >= 0, "generatedCharacter cannot be negative");
@@ -211,6 +277,15 @@ namespace ts {
                 || lastNameIndex !== pendingNameIndex;
         }
 
+        function appendScopeMappingCharCode(charCode: number) {
+            scopeMappingCharCodes.push(charCode);
+            // String.fromCharCode accepts its arguments on the stack, so we have to chunk the input,
+            // otherwise we can get stack overflows for large source maps
+            if (scopeMappingCharCodes.length >= 1024) {
+                flushScopeMappingBuffer();
+            }
+        }
+
         function appendMappingCharCode(charCode: number) {
             mappingCharCodes.push(charCode);
             // String.fromCharCode accepts its arguments on the stack, so we have to chunk the input,
@@ -274,6 +349,13 @@ namespace ts {
             exit();
         }
 
+        function flushScopeMappingBuffer(): void {
+            if (scopeMappingCharCodes.length > 0) {
+                scopes += String.fromCharCode.apply(undefined, scopeMappingCharCodes);
+                scopeMappingCharCodes.length = 0;
+            }
+        }
+
         function flushMappingBuffer(): void {
             if (mappingCharCodes.length > 0) {
                 mappings += String.fromCharCode.apply(undefined, mappingCharCodes);
@@ -284,6 +366,22 @@ namespace ts {
         function toJSON(): RawSourceMap {
             commitPendingMapping();
             flushMappingBuffer();
+            flushScopeMappingBuffer();
+
+            if (version === 4) {
+                return {
+                    version,
+                    file,
+                    sourceRoot,
+                    sources,
+                    names,
+                    mappings,
+                    sourcesContent,
+                    scopeNames,
+                    scopes,
+                };
+            }
+
             return {
                 version: 3,
                 file,
@@ -295,6 +393,31 @@ namespace ts {
             };
         }
 
+        function appendBase64VLQForScopeMapping(inValue: number): void {
+            // Add a new least significant bit that has the sign of the value.
+            // if negative number the least significant bit that gets added to the number has value 1
+            // else least significant bit value that gets added is 0
+            // eg. -1 changes to binary : 01 [1] => 3
+            //     +1 changes to binary : 01 [0] => 2
+            if (inValue < 0) {
+                inValue = ((-inValue) << 1) + 1;
+            }
+            else {
+                inValue = inValue << 1;
+            }
+
+            // Encode 5 bits at a time starting from least significant bits
+            do {
+                let currentDigit = inValue & 31; // 11111
+                inValue = inValue >> 5;
+                if (inValue > 0) {
+                    // There are still more digits to decode, set the msb (6th bit)
+                    currentDigit = currentDigit | 32;
+                }
+                appendScopeMappingCharCode(base64FormatEncode(currentDigit));
+            } while (inValue > 0);
+        }
+
         function appendBase64VLQ(inValue: number): void {
             // Add a new least significant bit that has the sign of the value.
             // if negative number the least significant bit that gets added to the number has value 1

src/compiler/types.ts

@@ -6145,6 +6145,7 @@ namespace ts {
         skipLibCheck?: boolean;
         skipDefaultLibCheck?: boolean;
         sourceMap?: boolean;
+        sourceMapVersion?: 3 | 4;
         sourceRoot?: string;
         strict?: boolean;
         strictFunctionTypes?: boolean;  // Always combine with strict property
@@ -6351,30 +6352,35 @@ namespace ts {
         affectsProgramStructure?: true;                         // true if program should be reconstructed from root files if option changes and does not affect module resolution as affectsModuleResolution indirectly means program needs to reconstructed
         transpileOptionValue?: boolean | undefined;             // If set this means that the option should be set to this value when transpiling
         extraValidation?: (value: CompilerOptionsValue) => [DiagnosticMessage, ...string[]] | undefined; // Additional validation to be performed for the value to be valid
+        defaultInitValue?: string | number | boolean;           // A custom default value to be used when generating tsconfig.json
     }
 
     /* @internal */
     export interface CommandLineOptionOfStringType extends CommandLineOptionBase {
         type: "string";
         defaultValueDescription?: string | undefined | DiagnosticMessage;
+        defaultInitValue?: string | undefined;
     }
 
     /* @internal */
     export interface CommandLineOptionOfNumberType extends CommandLineOptionBase {
         type: "number";
         defaultValueDescription: number | undefined | DiagnosticMessage;
+        defaultInitValue?: number | undefined;
     }
 
     /* @internal */
     export interface CommandLineOptionOfBooleanType extends CommandLineOptionBase {
         type: "boolean";
         defaultValueDescription: boolean | undefined | DiagnosticMessage;
+        defaultInitValue?: boolean | undefined;
     }
 
     /* @internal */
     export interface CommandLineOptionOfCustomType extends CommandLineOptionBase {
         type: ESMap<string, number | string>;  // an object literal mapping named values to actual values
         defaultValueDescription: number | string | undefined | DiagnosticMessage;
+        defaultInitValue?: number | string | undefined;
     }
 
     /* @internal */
@@ -8232,7 +8238,7 @@ namespace ts {
     }
 
     /* @internal */
-    export interface RawSourceMap {
+    export interface RawSourceMapV3 {
         version: 3;
         file: string;
         sourceRoot?: string | null;
@@ -8242,6 +8248,22 @@ namespace ts {
         names?: string[] | null;
     }
 
+    /* @internal */
+    export interface RawSourceMapV4 {
+        version: 4;
+        file: string;
+        sourceRoot?: string | null;
+        sources: string[];
+        sourcesContent?: (string | null)[] | null;
+        mappings: string;
+        names?: string[] | null;
+        scopeNames: string[];
+        scopes: string;
+    }
+
+    /* @internal */
+    export type RawSourceMap = RawSourceMapV3 | RawSourceMapV4;
+
     /**
      * Generates a source map.
      */
@@ -8272,6 +8294,20 @@ namespace ts {
          * Appends a source map.
          */
         appendSourceMap(generatedLine: number, generatedCharacter: number, sourceMap: RawSourceMap, sourceMapPath: string, start?: LineAndCharacter, end?: LineAndCharacter): void;
+        /**
+         * Appends a 'scope name,' a concept in V4 of Source Maps which represents the original-source name of a function scope.
+         */
+        addScopeName(name: string): number;
+        /**
+         * Appends a 'scope mapping,' a concept in V4 of Source Maps which associates a runtime name of a function to the original source name.
+         */
+        addScopeMapping(sourceIndex: number, start: LineAndCharacter, end: LineAndCharacter, scopeNameIndex: number): void;
+        /**
+         * Whether the compiler should collect scope names during compilation. This should be true for version 4+ of
+         * source maps, and false for version 3. This is exposed because collecting scope names might negatively
+         * impact the performance of compilation.
+         */
+        shouldCollectScopeNames(): boolean;
         /**
          * Gets the source map as a `RawSourceMap` object.
          */

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

@@ -2978,6 +2978,7 @@ declare namespace ts {
         skipLibCheck?: boolean;
         skipDefaultLibCheck?: boolean;
         sourceMap?: boolean;
+        sourceMapVersion?: 3 | 4;
         sourceRoot?: string;
         strict?: boolean;
         strictFunctionTypes?: boolean;

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

@@ -2978,6 +2978,7 @@ declare namespace ts {
         skipLibCheck?: boolean;
         skipDefaultLibCheck?: boolean;
         sourceMap?: boolean;
+        sourceMapVersion?: 3 | 4;
         sourceRoot?: string;
         strict?: boolean;
         strictFunctionTypes?: boolean;

tests/baselines/reference/tsConfig/Default initialized TSConfig/tsconfig.json

@@ -46,6 +46,7 @@
     // "declarationMap": true,                           /* Create sourcemaps for d.ts files. */
     // "emitDeclarationOnly": true,                      /* Only output d.ts files and not JavaScript files. */
     // "sourceMap": true,                                /* Create source map files for emitted JavaScript files. */
+    // "sourceMapVersion": 3,                            /* Specifies the version (3 or 4) of source maps that should be generated by compiler. Requires the sourceMap option to be enabled. */
     // "outFile": "./",                                  /* Specify a file that bundles all outputs into one JavaScript file. If `declaration` is true, also designates a file that bundles all .d.ts output. */
     // "outDir": "./",                                   /* Specify an output folder for all emitted files. */
     // "removeComments": true,                           /* Disable emitting comments. */

tests/baselines/reference/tsConfig/Initialized TSConfig with advanced options/tsconfig.json

@@ -46,6 +46,7 @@
     // "declarationMap": true,                           /* Create sourcemaps for d.ts files. */
     // "emitDeclarationOnly": true,                      /* Only output d.ts files and not JavaScript files. */
     // "sourceMap": true,                                /* Create source map files for emitted JavaScript files. */
+    // "sourceMapVersion": 3,                            /* Specifies the version (3 or 4) of source maps that should be generated by compiler. Requires the sourceMap option to be enabled. */
     // "outFile": "./",                                  /* Specify a file that bundles all outputs into one JavaScript file. If `declaration` is true, also designates a file that bundles all .d.ts output. */
     // "outDir": "./",                                   /* Specify an output folder for all emitted files. */
     // "removeComments": true,                           /* Disable emitting comments. */

tests/baselines/reference/tsConfig/Initialized TSConfig with boolean value compiler options/tsconfig.json

@@ -46,6 +46,7 @@
     // "declarationMap": true,                           /* Create sourcemaps for d.ts files. */
     // "emitDeclarationOnly": true,                      /* Only output d.ts files and not JavaScript files. */
     // "sourceMap": true,                                /* Create source map files for emitted JavaScript files. */
+    // "sourceMapVersion": 3,                            /* Specifies the version (3 or 4) of source maps that should be generated by compiler. Requires the sourceMap option to be enabled. */
     // "outFile": "./",                                  /* Specify a file that bundles all outputs into one JavaScript file. If `declaration` is true, also designates a file that bundles all .d.ts output. */
     // "outDir": "./",                                   /* Specify an output folder for all emitted files. */
     // "removeComments": true,                           /* Disable emitting comments. */

tests/baselines/reference/tsConfig/Initialized TSConfig with enum value compiler options/tsconfig.json

@@ -46,6 +46,7 @@
     // "declarationMap": true,                           /* Create sourcemaps for d.ts files. */
     // "emitDeclarationOnly": true,                      /* Only output d.ts files and not JavaScript files. */
     // "sourceMap": true,                                /* Create source map files for emitted JavaScript files. */
+    // "sourceMapVersion": 3,                            /* Specifies the version (3 or 4) of source maps that should be generated by compiler. Requires the sourceMap option to be enabled. */
     // "outFile": "./",                                  /* Specify a file that bundles all outputs into one JavaScript file. If `declaration` is true, also designates a file that bundles all .d.ts output. */
     // "outDir": "./",                                   /* Specify an output folder for all emitted files. */
     // "removeComments": true,                           /* Disable emitting comments. */