Add moduleDetection compiler flag to allow for changing how modules are parsed

src/compiler/commandLineParser.ts

@@ -1251,7 +1251,7 @@ namespace ts {
             affectsModuleResolution: true,
             description: Diagnostics.Control_what_method_is_used_to_detect_module_format_JS_files,
             category: Diagnostics.Language_and_Environment,
-            defaultValueDescription: Diagnostics.auto_Colon_Assume_jsx_containing_under_react_jsx_or_esm_mode_under_module_Colon_node12_files_are_modules_along_with_files_with_imports_exports_or_import_meta,
+            defaultValueDescription: Diagnostics.auto_Colon_Treat_files_with_imports_exports_imporpt_meta_jsx_with_jsx_Colon_react_jsx_or_esm_format_with_module_Colon_node12_as_modules,
         }
     ];
 

src/compiler/diagnosticMessages.json

@@ -1453,7 +1453,7 @@
         "category": "Message",
         "code": 1475
     },
-    "\"auto\": Assume jsx-containing (under react-jsx) or esm mode (under module: node12+) files are modules, along with files with imports, exports, or import.meta.": {
+    "\"auto\": Treat files with imports, exports, imporpt.meta, jsx (with jsx: react-jsx), or esm format (with module: node12+) as modules.": {
         "category": "Message",
         "code": 1476
     },

src/compiler/parser.ts

@@ -703,14 +703,19 @@ namespace ts {
         let result: SourceFile;
 
         perfLogger.logStartParseSourceFile(fileName);
-        const languageVersion = typeof languageVersionOrOptions === "object" ? languageVersionOrOptions.languageVersion : languageVersionOrOptions;
+        const {
+            languageVersion,
+            setExternalModuleIndicator: overrideSetExternalModuleIndicator,
+            impliedNodeFormat: format
+        } = typeof languageVersionOrOptions === "object" ? languageVersionOrOptions : ({ languageVersion: languageVersionOrOptions } as CreateSourceFileOptions);
         if (languageVersion === ScriptTarget.JSON) {
             result = Parser.parseSourceFile(fileName, sourceText, languageVersion, /*syntaxCursor*/ undefined, setParentNodes, ScriptKind.JSON, noop);
         }
         else {
-            const overrideSetExternalModuleIndicator = typeof languageVersionOrOptions === "object" ? languageVersionOrOptions.setExternalModuleIndicator : undefined;
-            const format = typeof languageVersionOrOptions === "object" ? languageVersionOrOptions.impliedNodeFormat : undefined;
-            const setIndicator = format !== undefined ? (file: SourceFile) => (file.impliedNodeFormat = format, void (overrideSetExternalModuleIndicator || setExternalModuleIndicator)(file)) : overrideSetExternalModuleIndicator;
+            const setIndicator = format === undefined ? overrideSetExternalModuleIndicator : (file: SourceFile) => {
+                file.impliedNodeFormat = format;
+                return (overrideSetExternalModuleIndicator || setExternalModuleIndicator)(file);
+            };
             result = Parser.parseSourceFile(fileName, sourceText, languageVersion, /*syntaxCursor*/ undefined, setParentNodes, scriptKind, setIndicator);
         }
         perfLogger.logStopParseSourceFile();

src/compiler/utilities.ts

@@ -6211,12 +6211,13 @@ namespace ts {
      * Unfortunately, there's no `NodeFlag` space to do the same for JSX.
      */
     function walkTreeForJSXTags(node: Node): Node | undefined {
+        if (!(node.transformFlags & TransformFlags.ContainsJsx)) return undefined;
         return isJsxOpeningLikeElement(node) || isJsxFragment(node) ? node : forEachChild(node, walkTreeForJSXTags);
     }
 
     function isFileModuleFromUsingJSXTag(file: SourceFile): Node | undefined {
         // Excludes declaration files - they still require an explicit `export {}` or the like
-        // for back compat purposes. (not that declaration files should contian JSX tags!)
+        // for back compat purposes. (not that declaration files should contain JSX tags!)
         return !file.isDeclarationFile ? walkTreeForJSXTags(file) : undefined;
     }
 
@@ -6235,10 +6236,10 @@ namespace ts {
         switch (getEmitModuleDetectionKind(options)) {
             case ModuleDetectionKind.Force:
                 // All non-declaration files are modules, declaration files still do the usual isFileProbablyExternalModule
-                return (file: SourceFile) => void (file.externalModuleIndicator = !file.isDeclarationFile || isFileProbablyExternalModule(file));
+                return (file: SourceFile) => { file.externalModuleIndicator = !file.isDeclarationFile || isFileProbablyExternalModule(file); };
             case ModuleDetectionKind.Legacy:
                 // Files are modules if they have imports, exports, or import.meta
-                return (file: SourceFile) => void (file.externalModuleIndicator = isFileProbablyExternalModule(file));
+                return (file: SourceFile) => { file.externalModuleIndicator = isFileProbablyExternalModule(file); };
             case ModuleDetectionKind.Auto:
                 // If module is nodenext or node12, all esm format files are modules
                 // If jsx is react-jsx or react-jsxdev then jsx tags force module-ness

src/services/transpile.ts

@@ -73,7 +73,15 @@ namespace ts {
 
         // if jsx is specified then treat file as .tsx
         const inputFileName = transpileOptions.fileName || (transpileOptions.compilerOptions && transpileOptions.compilerOptions.jsx ? "module.tsx" : "module.ts");
-        const sourceFile = createSourceFile(inputFileName, input, { languageVersion: getEmitScriptTarget(options), impliedNodeFormat: getImpliedNodeFormatForFile(toPath(inputFileName, "", compilerHost.getCanonicalFileName), /*cache*/ undefined, compilerHost, options), setExternalModuleIndicator: getSetExternalModuleIndicator(options) });
+        const sourceFile = createSourceFile(
+            inputFileName,
+            input,
+            {
+                languageVersion: getEmitScriptTarget(options),
+                impliedNodeFormat: getImpliedNodeFormatForFile(toPath(inputFileName, "", compilerHost.getCanonicalFileName), /*cache*/ undefined, compilerHost, options),
+                setExternalModuleIndicator: getSetExternalModuleIndicator(options)
+            }
+        );
         if (transpileOptions.moduleName) {
             sourceFile.moduleName = transpileOptions.moduleName;
         }

src/services/types.ts

@@ -261,12 +261,15 @@ namespace ts {
         /*
          * LS host can optionally implement these methods to support completions for module specifiers.
          * Without these methods, only completions for ambient modules will be provided.
-         *
-         * `readFile` and `fileExists` are now _required_ to properly acquire and setup source files under module: node12+ modes.
          */
         readDirectory?(path: string, extensions?: readonly string[], exclude?: readonly string[], include?: readonly string[], depth?: number): string[];
-        readFile(path: string, encoding?: string): string | undefined;
         realpath?(path: string): string;
+
+        /*
+         * Unlike `realpath and `readDirectory`, `readFile` and `fileExists` are now _required_
+         * to properly acquire and setup source files under module: node12+ modes.
+         */
+        readFile(path: string, encoding?: string): string | undefined;
         fileExists(path: string): boolean;
 
         /*

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

@@ -5731,8 +5731,8 @@ declare namespace ts {
         error?(s: string): void;
         useCaseSensitiveFileNames?(): boolean;
         readDirectory?(path: string, extensions?: readonly string[], exclude?: readonly string[], include?: readonly string[], depth?: number): string[];
-        readFile(path: string, encoding?: string): string | undefined;
         realpath?(path: string): string;
+        readFile(path: string, encoding?: string): string | undefined;
         fileExists(path: string): boolean;
         getTypeRootsVersion?(): number;
         resolveModuleNames?(moduleNames: string[], containingFile: string, reusedNames: string[] | undefined, redirectedReference: ResolvedProjectReference | undefined, options: CompilerOptions, containingSourceFile?: SourceFile): (ResolvedModule | undefined)[];

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

@@ -5731,8 +5731,8 @@ declare namespace ts {
         error?(s: string): void;
         useCaseSensitiveFileNames?(): boolean;
         readDirectory?(path: string, extensions?: readonly string[], exclude?: readonly string[], include?: readonly string[], depth?: number): string[];
-        readFile(path: string, encoding?: string): string | undefined;
         realpath?(path: string): string;
+        readFile(path: string, encoding?: string): string | undefined;
         fileExists(path: string): boolean;
         getTypeRootsVersion?(): number;
         resolveModuleNames?(moduleNames: string[], containingFile: string, reusedNames: string[] | undefined, redirectedReference: ResolvedProjectReference | undefined, options: CompilerOptions, containingSourceFile?: SourceFile): (ResolvedModule | undefined)[];