--moduleFormatInterop (all names bikesheddable)

src/compiler/checker.ts

@@ -332,6 +332,7 @@ import {
     getLineAndCharacterOfPosition,
     getMembersOfDeclaration,
     getModifiers,
+    getModuleFormatInteropKind,
     getModuleInstanceState,
     getNameFromImportAttribute,
     getNameFromIndexInfo,
@@ -859,6 +860,7 @@ import {
     modifierToFlag,
     ModuleBlock,
     ModuleDeclaration,
+    ModuleFormatInteropKind,
     ModuleInstanceState,
     ModuleKind,
     ModuleResolutionKind,
@@ -3634,7 +3636,10 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
         const usageMode = file && getEmitSyntaxForModuleSpecifierExpression(usage);
         if (file && usageMode !== undefined) {
             const targetMode = host.getImpliedNodeFormatForEmit(file);
-            if (usageMode === ModuleKind.ESNext && targetMode === ModuleKind.CommonJS && ModuleKind.Node16 <= moduleKind && moduleKind <= ModuleKind.NodeNext) {
+            const moduleFormatInterop = getModuleFormatInteropKind(compilerOptions);
+            const usesNodeLikeInteropRules = moduleFormatInterop === ModuleFormatInteropKind.BundlerNode
+                || ModuleFormatInteropKind.Node16 <= moduleFormatInterop && moduleFormatInterop <= ModuleFormatInteropKind.NodeNext;
+            if (usageMode === ModuleKind.ESNext && targetMode !== ModuleKind.ESNext && usesNodeLikeInteropRules) {
                 // In Node.js, CommonJS modules always have a synthetic default when imported into ESM
                 return true;
             }
@@ -3649,6 +3654,10 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
         }
         // Declaration files (and ambient modules)
         if (!file || file.isDeclarationFile) {
+            // Unambiguously ESM files do not have a synthetic default
+            if (file && host.getImpliedNodeFormatForEmit(file) === ModuleKind.ESNext) {
+                return false;
+            }
             // Definitely cannot have a synthetic default if they have a syntactic default member specified
             const defaultExportSymbol = resolveExportByName(moduleSymbol, InternalSymbolName.Default, /*sourceNode*/ undefined, /*dontResolveAlias*/ true); // Dont resolve alias because we want the immediately exported symbol's declaration
             if (defaultExportSymbol && some(defaultExportSymbol.declarations, isSyntacticDefault)) {
@@ -4572,6 +4581,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
             ? host.getModeForUsageLocation(currentSourceFile, contextSpecifier)
             : host.getDefaultResolutionModeForFile(currentSourceFile);
         const moduleResolutionKind = getEmitModuleResolutionKind(compilerOptions);
+        const moduleFormatInterop = getModuleFormatInteropKind(compilerOptions);
         const resolvedModule = host.getResolvedModule(currentSourceFile, moduleReference, mode)?.resolvedModule;
         const resolutionDiagnostic = resolvedModule && getResolutionDiagnostic(compilerOptions, resolvedModule, currentSourceFile);
         const sourceFile = resolvedModule
@@ -4607,7 +4617,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                 if (resolvedModule.isExternalLibraryImport && !resolutionExtensionIsTSOrJson(resolvedModule.extension)) {
                     errorOnImplicitAnyModule(/*isError*/ false, errorNode, currentSourceFile, mode, resolvedModule, moduleReference);
                 }
-                if (moduleResolutionKind === ModuleResolutionKind.Node16 || moduleResolutionKind === ModuleResolutionKind.NodeNext) {
+                if (ModuleFormatInteropKind.Node16 <= moduleFormatInterop && moduleFormatInterop <= ModuleFormatInteropKind.NodeNext) {
                     const isSyncImport = (currentSourceFile.impliedNodeFormat === ModuleKind.CommonJS && !findAncestor(location, isImportCall)) || !!findAncestor(location, isImportEqualsDeclaration);
                     const overrideHost = findAncestor(location, l => isImportTypeNode(l) || isExportDeclaration(l) || isImportDeclaration(l)) as ImportTypeNode | ImportDeclaration | ExportDeclaration | undefined;
                     // An override clause will take effect for type-only imports and import types, and allows importing the types across formats, regardless of

src/compiler/commandLineParser.ts

@@ -83,6 +83,7 @@ import {
     mapIterator,
     MapLike,
     ModuleDetectionKind,
+    ModuleFormatInteropKind,
     ModuleKind,
     ModuleResolutionKind,
     NewLineKind,
@@ -1196,6 +1197,20 @@ const commandOptionsWithoutBuild: CommandLineOption[] = [
         category: Diagnostics.Modules,
         description: Diagnostics.Conditions_to_set_in_addition_to_the_resolver_specific_defaults_when_resolving_imports,
     },
+    {
+        name: "moduleFormatInterop",
+        type: new Map(Object.entries({
+            bundler: ModuleFormatInteropKind.Bundler,
+            bundlernode: ModuleFormatInteropKind.BundlerNode,
+            node16: ModuleFormatInteropKind.Node16,
+            nodenext: ModuleFormatInteropKind.NodeNext,
+        })),
+        affectsSemanticDiagnostics: true,
+        affectsBuildInfo: true,
+        category: Diagnostics.Modules,
+        description: Diagnostics.Specify_the_target_runtime_s_rules_for_ESM_CommonJS_interoperation,
+        defaultValueDescription: Diagnostics.node16_when_module_is_node16_nodenext_when_module_is_nodenext_bundler_otherwise,
+    },
 
     // Source Maps
     {

src/compiler/diagnosticMessages.json

@@ -6392,6 +6392,10 @@
         "category": "Message",
         "code": 6805
     },
+    "Specify the target runtime's rules for ESM-CommonJS interoperation.": {
+        "category": "Message",
+        "code": 6806
+    },
 
     "one of:": {
         "category": "Message",
@@ -6521,6 +6525,10 @@
         "category": "Error",
         "code": 6931
     },
+    "'node16' when 'module' is 'node16'; 'nodenext' when 'module' is 'nodenext'; 'bundler' otherwise.": {
+        "category": "Message",
+        "code": 6932
+    },
 
     "Variable '{0}' implicitly has an '{1}' type.": {
         "category": "Error",

src/compiler/types.ts

@@ -7290,6 +7290,7 @@ export interface CompilerOptions {
     mapRoot?: string;
     maxNodeModuleJsDepth?: number;
     module?: ModuleKind;
+    moduleFormatInterop?: ModuleFormatInteropKind;
     moduleResolution?: ModuleResolutionKind;
     moduleSuffixes?: string[];
     moduleDetection?: ModuleDetectionKind;
@@ -7423,6 +7424,14 @@ export enum ModuleKind {
     Preserve = 200,
 }
 
+export enum ModuleFormatInteropKind {
+    Bundler = 1,
+    BundlerNode = 2,
+
+    Node16 = 100,
+    NodeNext = 199,
+}
+
 export const enum JsxEmit {
     None = 0,
     Preserve = 1,

src/compiler/utilities.ts

@@ -420,6 +420,7 @@ import {
     ModuleBlock,
     ModuleDeclaration,
     ModuleDetectionKind,
+    ModuleFormatInteropKind,
     ModuleKind,
     ModuleResolutionKind,
     moduleResolutionOptionDeclarations,
@@ -8852,6 +8853,22 @@ export const computedOptions = createComputedCompilerOptions({
                         computedOptions.module.computeValue(compilerOptions) === ModuleKind.NodeNext ? ModuleDetectionKind.Force : ModuleDetectionKind.Auto);
         },
     },
+    moduleFormatInterop: {
+        dependencies: ["module", "target"],
+        computeValue: (compilerOptions): ModuleFormatInteropKind => {
+            if (compilerOptions.moduleFormatInterop !== undefined) {
+                return compilerOptions.moduleFormatInterop;
+            }
+            switch (computedOptions.module.computeValue(compilerOptions)) {
+                case ModuleKind.Node16:
+                    return ModuleFormatInteropKind.Node16;
+                case ModuleKind.NodeNext:
+                    return ModuleFormatInteropKind.NodeNext;
+                default:
+                    return ModuleFormatInteropKind.Bundler;
+            }
+        },
+    },
     isolatedModules: {
         dependencies: ["verbatimModuleSyntax"],
         computeValue: compilerOptions => {
@@ -9028,6 +9045,8 @@ export const getEmitModuleResolutionKind = computedOptions.moduleResolution.comp
 /** @internal */
 export const getEmitModuleDetectionKind = computedOptions.moduleDetection.computeValue;
 /** @internal */
+export const getModuleFormatInteropKind = computedOptions.moduleFormatInterop.computeValue;
+/** @internal */
 export const getIsolatedModules = computedOptions.isolatedModules.computeValue;
 /** @internal */
 export const getESModuleInterop = computedOptions.esModuleInterop.computeValue;

src/testRunner/compilerRunner.ts

@@ -142,6 +142,7 @@ class CompilerTest {
         "jsx",
         "module",
         "moduleDetection",
+        "moduleFormatInterop",
         "moduleResolution",
         "noEmit",
         "noImplicitAny",

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

@@ -6942,6 +6942,7 @@ declare namespace ts {
         mapRoot?: string;
         maxNodeModuleJsDepth?: number;
         module?: ModuleKind;
+        moduleFormatInterop?: ModuleFormatInteropKind;
         moduleResolution?: ModuleResolutionKind;
         moduleSuffixes?: string[];
         moduleDetection?: ModuleDetectionKind;
@@ -7044,6 +7045,12 @@ declare namespace ts {
         NodeNext = 199,
         Preserve = 200,
     }
+    enum ModuleFormatInteropKind {
+        Bundler = 1,
+        BundlerNode = 2,
+        Node16 = 100,
+        NodeNext = 199,
+    }
     enum JsxEmit {
         None = 0,
         Preserve = 1,

tests/baselines/reference/config/initTSConfig/Default initialized TSConfig/tsconfig.json

@@ -39,6 +39,7 @@
     // "resolvePackageJsonExports": true,                /* Use the package.json 'exports' field when resolving package imports. */
     // "resolvePackageJsonImports": true,                /* Use the package.json 'imports' field when resolving imports. */
     // "customConditions": [],                           /* Conditions to set in addition to the resolver-specific defaults when resolving imports. */
+    // "moduleFormatInterop": "bundler",                 /* Specify the target runtime's rules for ESM-CommonJS interoperation. */
     // "resolveJsonModule": true,                        /* Enable importing .json files. */
     // "allowArbitraryExtensions": true,                 /* Enable importing files with any extension, provided a declaration file is present. */
     // "noResolve": true,                                /* Disallow 'import's, 'require's or '<reference>'s from expanding the number of files TypeScript should add to a project. */

tests/baselines/reference/config/initTSConfig/Initialized TSConfig with --help/tsconfig.json

@@ -39,6 +39,7 @@
     // "resolvePackageJsonExports": true,                /* Use the package.json 'exports' field when resolving package imports. */
     // "resolvePackageJsonImports": true,                /* Use the package.json 'imports' field when resolving imports. */
     // "customConditions": [],                           /* Conditions to set in addition to the resolver-specific defaults when resolving imports. */
+    // "moduleFormatInterop": "bundler",                 /* Specify the target runtime's rules for ESM-CommonJS interoperation. */
     // "resolveJsonModule": true,                        /* Enable importing .json files. */
     // "allowArbitraryExtensions": true,                 /* Enable importing files with any extension, provided a declaration file is present. */
     // "noResolve": true,                                /* Disallow 'import's, 'require's or '<reference>'s from expanding the number of files TypeScript should add to a project. */

tests/baselines/reference/config/initTSConfig/Initialized TSConfig with --watch/tsconfig.json

@@ -39,6 +39,7 @@
     // "resolvePackageJsonExports": true,                /* Use the package.json 'exports' field when resolving package imports. */
     // "resolvePackageJsonImports": true,                /* Use the package.json 'imports' field when resolving imports. */
     // "customConditions": [],                           /* Conditions to set in addition to the resolver-specific defaults when resolving imports. */
+    // "moduleFormatInterop": "bundler",                 /* Specify the target runtime's rules for ESM-CommonJS interoperation. */
     // "resolveJsonModule": true,                        /* Enable importing .json files. */
     // "allowArbitraryExtensions": true,                 /* Enable importing files with any extension, provided a declaration file is present. */
     // "noResolve": true,                                /* Disallow 'import's, 'require's or '<reference>'s from expanding the number of files TypeScript should add to a project. */

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

@@ -39,6 +39,7 @@
     // "resolvePackageJsonExports": true,                /* Use the package.json 'exports' field when resolving package imports. */
     // "resolvePackageJsonImports": true,                /* Use the package.json 'imports' field when resolving imports. */
     // "customConditions": [],                           /* Conditions to set in addition to the resolver-specific defaults when resolving imports. */
+    // "moduleFormatInterop": "bundler",                 /* Specify the target runtime's rules for ESM-CommonJS interoperation. */
     // "resolveJsonModule": true,                        /* Enable importing .json files. */
     // "allowArbitraryExtensions": true,                 /* Enable importing files with any extension, provided a declaration file is present. */
     // "noResolve": true,                                /* Disallow 'import's, 'require's or '<reference>'s from expanding the number of files TypeScript should add to a project. */

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

@@ -39,6 +39,7 @@
     // "resolvePackageJsonExports": true,                /* Use the package.json 'exports' field when resolving package imports. */
     // "resolvePackageJsonImports": true,                /* Use the package.json 'imports' field when resolving imports. */
     // "customConditions": [],                           /* Conditions to set in addition to the resolver-specific defaults when resolving imports. */
+    // "moduleFormatInterop": "bundler",                 /* Specify the target runtime's rules for ESM-CommonJS interoperation. */
     // "resolveJsonModule": true,                        /* Enable importing .json files. */
     // "allowArbitraryExtensions": true,                 /* Enable importing files with any extension, provided a declaration file is present. */
     // "noResolve": true,                                /* Disallow 'import's, 'require's or '<reference>'s from expanding the number of files TypeScript should add to a project. */

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

@@ -39,6 +39,7 @@
     // "resolvePackageJsonExports": true,                /* Use the package.json 'exports' field when resolving package imports. */
     // "resolvePackageJsonImports": true,                /* Use the package.json 'imports' field when resolving imports. */
     // "customConditions": [],                           /* Conditions to set in addition to the resolver-specific defaults when resolving imports. */
+    // "moduleFormatInterop": "bundler",                 /* Specify the target runtime's rules for ESM-CommonJS interoperation. */
     // "resolveJsonModule": true,                        /* Enable importing .json files. */
     // "allowArbitraryExtensions": true,                 /* Enable importing files with any extension, provided a declaration file is present. */
     // "noResolve": true,                                /* Disallow 'import's, 'require's or '<reference>'s from expanding the number of files TypeScript should add to a project. */

tests/baselines/reference/config/initTSConfig/Initialized TSConfig with files options/tsconfig.json

@@ -39,6 +39,7 @@
     // "resolvePackageJsonExports": true,                /* Use the package.json 'exports' field when resolving package imports. */
     // "resolvePackageJsonImports": true,                /* Use the package.json 'imports' field when resolving imports. */
     // "customConditions": [],                           /* Conditions to set in addition to the resolver-specific defaults when resolving imports. */
+    // "moduleFormatInterop": "bundler",                 /* Specify the target runtime's rules for ESM-CommonJS interoperation. */
     // "resolveJsonModule": true,                        /* Enable importing .json files. */
     // "allowArbitraryExtensions": true,                 /* Enable importing files with any extension, provided a declaration file is present. */
     // "noResolve": true,                                /* Disallow 'import's, 'require's or '<reference>'s from expanding the number of files TypeScript should add to a project. */

tests/baselines/reference/config/initTSConfig/Initialized TSConfig with incorrect compiler option value/tsconfig.json

@@ -39,6 +39,7 @@
     // "resolvePackageJsonExports": true,                /* Use the package.json 'exports' field when resolving package imports. */
     // "resolvePackageJsonImports": true,                /* Use the package.json 'imports' field when resolving imports. */
     // "customConditions": [],                           /* Conditions to set in addition to the resolver-specific defaults when resolving imports. */
+    // "moduleFormatInterop": "bundler",                 /* Specify the target runtime's rules for ESM-CommonJS interoperation. */
     // "resolveJsonModule": true,                        /* Enable importing .json files. */
     // "allowArbitraryExtensions": true,                 /* Enable importing files with any extension, provided a declaration file is present. */
     // "noResolve": true,                                /* Disallow 'import's, 'require's or '<reference>'s from expanding the number of files TypeScript should add to a project. */

tests/baselines/reference/config/initTSConfig/Initialized TSConfig with incorrect compiler option/tsconfig.json

@@ -39,6 +39,7 @@
     // "resolvePackageJsonExports": true,                /* Use the package.json 'exports' field when resolving package imports. */
     // "resolvePackageJsonImports": true,                /* Use the package.json 'imports' field when resolving imports. */
     // "customConditions": [],                           /* Conditions to set in addition to the resolver-specific defaults when resolving imports. */
+    // "moduleFormatInterop": "bundler",                 /* Specify the target runtime's rules for ESM-CommonJS interoperation. */
     // "resolveJsonModule": true,                        /* Enable importing .json files. */
     // "allowArbitraryExtensions": true,                 /* Enable importing files with any extension, provided a declaration file is present. */
     // "noResolve": true,                                /* Disallow 'import's, 'require's or '<reference>'s from expanding the number of files TypeScript should add to a project. */

tests/baselines/reference/config/initTSConfig/Initialized TSConfig with list compiler options with enum value/tsconfig.json

@@ -39,6 +39,7 @@
     // "resolvePackageJsonExports": true,                /* Use the package.json 'exports' field when resolving package imports. */
     // "resolvePackageJsonImports": true,                /* Use the package.json 'imports' field when resolving imports. */
     // "customConditions": [],                           /* Conditions to set in addition to the resolver-specific defaults when resolving imports. */
+    // "moduleFormatInterop": "bundler",                 /* Specify the target runtime's rules for ESM-CommonJS interoperation. */
     // "resolveJsonModule": true,                        /* Enable importing .json files. */
     // "allowArbitraryExtensions": true,                 /* Enable importing files with any extension, provided a declaration file is present. */
     // "noResolve": true,                                /* Disallow 'import's, 'require's or '<reference>'s from expanding the number of files TypeScript should add to a project. */

tests/baselines/reference/config/initTSConfig/Initialized TSConfig with list compiler options/tsconfig.json

@@ -39,6 +39,7 @@
     // "resolvePackageJsonExports": true,                /* Use the package.json 'exports' field when resolving package imports. */
     // "resolvePackageJsonImports": true,                /* Use the package.json 'imports' field when resolving imports. */
     // "customConditions": [],                           /* Conditions to set in addition to the resolver-specific defaults when resolving imports. */
+    // "moduleFormatInterop": "bundler",                 /* Specify the target runtime's rules for ESM-CommonJS interoperation. */
     // "resolveJsonModule": true,                        /* Enable importing .json files. */
     // "allowArbitraryExtensions": true,                 /* Enable importing files with any extension, provided a declaration file is present. */
     // "noResolve": true,                                /* Disallow 'import's, 'require's or '<reference>'s from expanding the number of files TypeScript should add to a project. */

tests/baselines/reference/config/showConfig/Shows tsconfig for single option/moduleFormatInterop/tsconfig.json

@@ -0,0 +1,5 @@
+{
+    "compilerOptions": {
+        "moduleFormatInterop": "bundler"
+    }
+}