Initial support for module: node12

Author: weswigham

src/compiler/binder.ts

@@ -2370,7 +2370,7 @@ namespace ts {
 
         function checkStrictModeLabeledStatement(node: LabeledStatement) {
             // Grammar checking for labeledStatement
-            if (inStrictMode && options.target! >= ScriptTarget.ES2015) {
+            if (inStrictMode && getEmitScriptTarget(options) >= ScriptTarget.ES2015) {
                 if (isDeclarationStatement(node.statement) || isVariableStatement(node.statement)) {
                     errorOnFirstToken(node.label, Diagnostics.A_label_is_not_allowed_here);
                 }

src/compiler/checker.ts

@@ -381,7 +381,9 @@ namespace ts {
                 es6: ModuleKind.ES2015,
                 es2015: ModuleKind.ES2015,
                 es2020: ModuleKind.ES2020,
-                esnext: ModuleKind.ESNext
+                esnext: ModuleKind.ESNext,
+                node12: ModuleKind.Node12,
+                nodenext: ModuleKind.NodeNext,
             })),
             affectsModuleResolution: true,
             affectsEmit: true,

src/compiler/commandLineParser.ts

@@ -944,7 +944,7 @@
         "category": "Error",
         "code": 1322
     },
-    "Dynamic imports are only supported when the '--module' flag is set to 'es2020', 'esnext', 'commonjs', 'amd', 'system', or 'umd'.": {
+    "Dynamic imports are only supported when the '--module' flag is set to 'es2020', 'esnext', 'commonjs', 'amd', 'system', 'umd', 'node12', or 'nodenext'.": {
         "category": "Error",
         "code": 1323
     },
@@ -1020,7 +1020,7 @@
         "category": "Error",
         "code": 1342
     },
-    "The 'import.meta' meta-property is only allowed when the '--module' option is 'es2020', 'esnext', or 'system'.": {
+    "The 'import.meta' meta-property is only allowed when the '--module' option is 'es2020', 'esnext', 'system', 'node12', or 'nodenext'.": {
         "category": "Error",
         "code": 1343
     },
@@ -1152,7 +1152,7 @@
         "category": "Message",
         "code": 1377
     },
-    "Top-level 'await' expressions are only allowed when the 'module' option is set to 'esnext' or 'system', and the 'target' option is set to 'es2017' or higher.": {
+    "Top-level 'await' expressions are only allowed when the 'module' option is set to 'esnext', 'system', or 'nodenext', and the 'target' option is set to 'es2017' or higher.": {
         "category": "Error",
         "code": 1378
     },
@@ -1368,14 +1368,22 @@
         "category": "Error",
         "code": 1431
     },
-    "Top-level 'for await' loops are only allowed when the 'module' option is set to 'esnext' or 'system', and the 'target' option is set to 'es2017' or higher.": {
+    "Top-level 'for await' loops are only allowed when the 'module' option is set to 'esnext', 'system', or 'nodenext', and the 'target' option is set to 'es2017' or higher.": {
         "category": "Error",
         "code": 1432
     },
     "Decorators may not be applied to 'this' parameters.": {
         "category": "Error",
         "code": 1433
     },
+    "The 'import.meta' meta-property is not allowed in files which will build into CommonJS output.": {
+        "category": "Error",
+        "code": 1434
+    },
+    "Module '{0}' cannot be imported using this construct. The specifier only resolves to an es module, which cannot be imported synchronously. Use dynamic import instead.": {
+        "category": "Error",
+        "code": 1435
+    },
 
     "The types of '{0}' are incompatible between these types.": {
         "category": "Error",

src/compiler/diagnosticMessages.json

@@ -133,7 +133,7 @@ namespace ts {
         // ES2018 Helpers
 
         function createAssignHelper(attributesSegments: Expression[]) {
-            if (context.getCompilerOptions().target! >= ScriptTarget.ES2015) {
+            if (getEmitScriptTarget(context.getCompilerOptions()) >= ScriptTarget.ES2015) {
                 return factory.createCallExpression(factory.createPropertyAccessExpression(factory.createIdentifier("Object"), "assign"),
                                   /*typeArguments*/ undefined,
                                   attributesSegments);

src/compiler/factory/emitHelpers.ts

@@ -5055,6 +5055,7 @@ namespace ts {
             node.transformFlags =
                 propagateChildrenFlags(node.statements) |
                 propagateChildFlags(node.endOfFileToken);
+            node.impliedNodeFormat = source.impliedNodeFormat;
             return node;
         }
 

src/compiler/factory/nodeFactory.ts

@@ -405,7 +405,7 @@ namespace ts {
         if (compilerOptions.importHelpers && isEffectiveExternalModule(sourceFile, compilerOptions)) {
             let namedBindings: NamedImportBindings | undefined;
             const moduleKind = getEmitModuleKind(compilerOptions);
-            if (moduleKind >= ModuleKind.ES2015 && moduleKind <= ModuleKind.ESNext) {
+            if ((moduleKind >= ModuleKind.ES2015 && moduleKind <= ModuleKind.ESNext) || sourceFile.impliedNodeFormat === ModuleKind.ESNext) {
                 // use named imports
                 const helpers = getEmitHelpers(sourceFile);
                 if (helpers) {
@@ -462,9 +462,9 @@ namespace ts {
             }
 
             const moduleKind = getEmitModuleKind(compilerOptions);
-            let create = (hasExportStarsToExportValues || (compilerOptions.esModuleInterop && hasImportStarOrImportDefault))
+            let create = (hasExportStarsToExportValues || (getESModuleInterop(compilerOptions) && hasImportStarOrImportDefault))
                 && moduleKind !== ModuleKind.System
-                && moduleKind < ModuleKind.ES2015;
+                && (moduleKind < ModuleKind.ES2015 || node.impliedNodeFormat === ModuleKind.CommonJS);
             if (!create) {
                 const helpers = getEmitHelpers(node);
                 if (helpers) {

src/compiler/factory/utilities.ts

@@ -113,6 +113,7 @@ namespace ts {
         typesVersions?: MapLike<MapLike<string[]>>;
         main?: string;
         tsconfig?: string;
+        type?: string;
     }
 
     interface PackageJson extends PackageJsonPathFields {
@@ -816,7 +817,20 @@ namespace ts {
         else {
             let moduleResolution = compilerOptions.moduleResolution;
             if (moduleResolution === undefined) {
-                moduleResolution = getEmitModuleKind(compilerOptions) === ModuleKind.CommonJS ? ModuleResolutionKind.NodeJs : ModuleResolutionKind.Classic;
+                switch (getEmitModuleKind(compilerOptions)) {
+                    case ModuleKind.CommonJS:
+                        moduleResolution = ModuleResolutionKind.NodeJs;
+                        break;
+                    case ModuleKind.Node12:
+                        moduleResolution = ModuleResolutionKind.Node12;
+                        break;
+                    case ModuleKind.NodeNext:
+                        moduleResolution = ModuleResolutionKind.NodeNext;
+                        break;
+                    default:
+                        moduleResolution = ModuleResolutionKind.Classic;
+                        break;
+                }
                 if (traceEnabled) {
                     trace(host, Diagnostics.Module_resolution_kind_is_not_specified_using_0, ModuleResolutionKind[moduleResolution]);
                 }
@@ -829,6 +843,8 @@ namespace ts {
 
             perfLogger.logStartResolveModule(moduleName /* , containingFile, ModuleResolutionKind[moduleResolution]*/);
             switch (moduleResolution) {
+                case ModuleResolutionKind.Node12:
+                case ModuleResolutionKind.NodeNext: // TODO: Implement node12/nodenext resolution rules
                 case ModuleResolutionKind.NodeJs:
                     result = nodeModuleNameResolver(moduleName, containingFile, compilerOptions, host, cache, redirectedReference);
                     break;
@@ -1310,7 +1326,8 @@ namespace ts {
         versionPaths: VersionPaths | undefined;
     }
 
-    function getPackageJsonInfo(packageDirectory: string, onlyRecordFailures: boolean, state: ModuleResolutionState): PackageJsonInfo | undefined {
+    /*@internal*/
+    export function getPackageJsonInfo(packageDirectory: string, onlyRecordFailures: boolean, state: ModuleResolutionState): PackageJsonInfo | undefined {
         const { host, traceEnabled } = state;
         const packageJsonPath = combinePaths(packageDirectory, "package.json");
         if (onlyRecordFailures) {

src/compiler/moduleNameResolver.ts

@@ -683,6 +683,14 @@ namespace ts.moduleSpecifiers {
                 return ext;
             case Extension.TsBuildInfo:
                 return Debug.fail(`Extension ${Extension.TsBuildInfo} is unsupported:: FileName:: ${fileName}`);
+            case Extension.Dmts:
+            case Extension.Mts:
+            case Extension.Mjs:
+                return Extension.Mjs;
+            case Extension.Dcts:
+            case Extension.Cts:
+            case Extension.Cjs:
+                return Extension.Cjs;
             default:
                 return Debug.assertNever(ext);
         }

src/compiler/moduleSpecifiers.ts

@@ -738,6 +738,55 @@ namespace ts {
             configFileParseResult.errors;
     }
 
+    /**
+     * A function for determining if a given file is esm or cjs format, assuming modern node module resolution rules, as configured by the
+     * `options` parameter.
+     *
+     * @param fileName The normalized absolute path to check the format of (it need not exist on disk)
+     * @param packageJsonInfoCache (Optional) A cache for package file lookups - it's best to have a cache when this function is called often
+     * @param host The ModuleResolutionHost which can perform the filesystem lookups for package json data
+     * @param options The compiler options to perform the analysis under - relevant options are `moduleResolution` and `traceResolution`
+     * @returns `undefined` if the path has no relevant implied format, `ModuleKind.ESNext` for esm format, and `ModuleKind.CommonJS` for cjs format
+     */
+    export function getImpliedNodeFormatForFile(fileName: Path, packageJsonInfoCache: PackageJsonInfoCache | undefined, host: ModuleResolutionHost, options: CompilerOptions): ModuleKind.ESNext | ModuleKind.CommonJS | undefined {
+        switch (getEmitModuleResolutionKind(options)) {
+            case ModuleResolutionKind.Node12:
+            case ModuleResolutionKind.NodeNext:
+                return fileExtensionIsOneOf(fileName, [Extension.Dmts, Extension.Mts, Extension.Mjs]) ? ModuleKind.ESNext :
+                    fileExtensionIsOneOf(fileName, [Extension.Dcts, Extension.Cts, Extension.Cjs]) ? ModuleKind.CommonJS :
+                    fileExtensionIsOneOf(fileName, [Extension.Dts, Extension.Ts, Extension.Tsx, Extension.Js, Extension.Jsx]) ? lookupFromPackageJson() :
+                    undefined; // other extensions, like `json` or `tsbuildinfo`, are set as `undefined` here but they should never be fed through the transformer pipeline
+            default:
+                return undefined;
+        }
+        function lookupFromPackageJson(): ModuleKind.ESNext | ModuleKind.CommonJS {
+            const state: {
+                host: ModuleResolutionHost;
+                compilerOptions: CompilerOptions;
+                traceEnabled: boolean;
+                failedLookupLocations: Push<string>;
+                resultFromCache?: ResolvedModuleWithFailedLookupLocations;
+                packageJsonInfoCache: PackageJsonInfoCache | undefined;
+            } = {
+                host,
+                compilerOptions: options,
+                traceEnabled: isTraceEnabled(options, host),
+                failedLookupLocations: [],
+                packageJsonInfoCache
+            };
+            const parts = getPathComponents(fileName);
+            parts.pop();
+            while (parts.length > 0) {
+                const pkg = getPackageJsonInfo(getPathFromPathComponents(parts), /*onlyRecordFailures*/ false, state);
+                if (pkg) {
+                    return pkg.packageJsonContent?.type === "module" ? ModuleKind.ESNext : ModuleKind.CommonJS;
+                }
+                parts.pop();
+            }
+            return ModuleKind.CommonJS;
+        }
+    }
+
     /**
      * Determine if source file needs to be re-created even if its text hasn't changed
      */
@@ -1453,8 +1502,8 @@ namespace ts {
 
             for (const oldSourceFile of oldSourceFiles) {
                 let newSourceFile = host.getSourceFileByPath
-                    ? host.getSourceFileByPath(oldSourceFile.fileName, oldSourceFile.resolvedPath, options.target!, /*onError*/ undefined, shouldCreateNewSourceFile)
-                    : host.getSourceFile(oldSourceFile.fileName, options.target!, /*onError*/ undefined, shouldCreateNewSourceFile); // TODO: GH#18217
+                    ? host.getSourceFileByPath(oldSourceFile.fileName, oldSourceFile.resolvedPath, getEmitScriptTarget(options), /*onError*/ undefined, shouldCreateNewSourceFile)
+                    : host.getSourceFile(oldSourceFile.fileName, getEmitScriptTarget(options), /*onError*/ undefined, shouldCreateNewSourceFile); // TODO: GH#18217
 
                 if (!newSourceFile) {
                     return StructureIsReused.Not;
@@ -2609,7 +2658,7 @@ namespace ts {
             // We haven't looked for this file, do so now and cache result
             const file = host.getSourceFile(
                 fileName,
-                options.target!,
+                getEmitScriptTarget(options),
                 hostErrorMessage => addFilePreprocessingFileExplainingDiagnostic(/*file*/ undefined, reason, Diagnostics.Cannot_read_file_0_Colon_1, [fileName, hostErrorMessage]),
                 shouldCreateNewSourceFile
             );
@@ -2642,6 +2691,10 @@ namespace ts {
                 file.path = path;
                 file.resolvedPath = toPath(fileName);
                 file.originalFileName = originalFileName;
+                // It's a _little odd_ that we can't set `impliedNodeFormat` until the program step - but it's the first and only time we have a resolution cache
+                // and a freshly made source file node on hand at the same time, and we need both to set the field. Persisting the resolution cache all the way
+                // to the check and emit steps would be bad - so we much prefer detecting and storing the format information on the source file node upfront.
+                file.impliedNodeFormat = getImpliedNodeFormatForFile(file.resolvedPath, moduleResolutionCache?.getPackageJsonInfoCache(), host, options);
                 addFileIncludeReason(file, reason);
 
                 if (host.useCaseSensitiveFileNames()) {
@@ -3176,7 +3229,7 @@ namespace ts {
                 createDiagnosticForOptionName(Diagnostics.Option_0_cannot_be_specified_with_option_1, "noImplicitUseStrict", "alwaysStrict");
             }
 
-            const languageVersion = options.target || ScriptTarget.ES3;
+            const languageVersion = getEmitScriptTarget(options);
 
             const firstNonAmbientExternalModuleSourceFile = find(files, f => isExternalModule(f) && !f.isDeclarationFile);
             if (options.isolatedModules) {
@@ -3461,7 +3514,7 @@ namespace ts {
                         message = Diagnostics.File_is_library_specified_here;
                         break;
                     }
-                    const target = forEachEntry(targetOptionDeclaration.type, (value, key) => value === options.target ? key : undefined);
+                    const target = forEachEntry(targetOptionDeclaration.type, (value, key) => value === getEmitScriptTarget(options) ? key : undefined);
                     configFileNode = target ? getOptionsSyntaxByValue("target", target) : undefined;
                     message = Diagnostics.File_is_default_library_for_target_specified_here;
                     break;