--moduleResolution bundler: Require ESM for module and remove node from hard-coded conditions

src/compiler/checker.ts

@@ -5019,7 +5019,12 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
              * @see https://github.com/microsoft/TypeScript/issues/42151
              */
             if (emitModuleKindIsNonNodeESM(moduleKind) || mode === ModuleKind.ESNext) {
-                return importSourceWithoutExtension + (tsExtension === Extension.Mts ? ".mjs" : tsExtension === Extension.Cts ? ".cjs" : ".js");
+                const preferTs = isDeclarationFileName(moduleReference) && shouldAllowImportingTsExtension(compilerOptions);
+                const ext =
+                    tsExtension === Extension.Mts || tsExtension === Extension.Dmts ? preferTs ? ".mts" : ".mjs" :
+                    tsExtension === Extension.Cts || tsExtension === Extension.Dmts ? preferTs ? ".cts" : ".cjs" :
+                    preferTs ? ".ts" : ".js";
+                return importSourceWithoutExtension + ext;
             }
             return importSourceWithoutExtension;
         }
@@ -43963,9 +43968,6 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                     // Import equals declaration is deprecated in es6 or above
                     grammarErrorOnNode(node, Diagnostics.Import_assignment_cannot_be_used_when_targeting_ECMAScript_modules_Consider_using_import_Asterisk_as_ns_from_mod_import_a_from_mod_import_d_from_mod_or_another_module_format_instead);
                 }
-                else if (!(node.flags & NodeFlags.Ambient) && getEmitModuleResolutionKind(compilerOptions) === ModuleResolutionKind.Bundler) {
-                    grammarErrorOnNode(node, Diagnostics.Import_assignment_is_not_allowed_when_moduleResolution_is_set_to_bundler_Consider_using_import_Asterisk_as_ns_from_mod_import_a_from_mod_import_d_from_mod_or_another_module_format_instead);
-                }
             }
         }
     }
@@ -44208,9 +44210,6 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                 // system modules does not support export assignment
                 grammarErrorOnNode(node, Diagnostics.Export_assignment_is_not_supported_when_module_flag_is_system);
             }
-            else if (getEmitModuleResolutionKind(compilerOptions) === ModuleResolutionKind.Bundler && !(node.flags & NodeFlags.Ambient)) {
-                grammarErrorOnNode(node, Diagnostics.Export_assignment_cannot_be_used_when_moduleResolution_is_set_to_bundler_Consider_using_export_default_or_another_module_format_instead);
-            }
         }
     }
 

src/compiler/diagnosticMessages.json

@@ -4265,7 +4265,7 @@
         "category": "Error",
         "code": 5094
     },
-    "Option 'preserveValueImports' can only be used when 'module' is set to 'es2015' or later.": {
+    "Option '{0}' can only be used when 'module' is set to 'es2015' or later.": {
         "category": "Error",
         "code": 5095
     },
@@ -4281,14 +4281,6 @@
         "category": "Error",
         "code": 5098
     },
-    "Import assignment is not allowed when 'moduleResolution' is set to 'bundler'. Consider using 'import * as ns from \"mod\"', 'import {a} from \"mod\"', 'import d from \"mod\"', or another module format instead.": {
-        "category": "Error",
-        "code": 5099
-    },
-    "Export assignment cannot be used when 'moduleResolution' is set to 'bundler'. Consider using 'export default' or another module format instead.": {
-        "category": "Error",
-        "code": 5100
-    },
     "Flag '{0}' is deprecated and will stop functioning in TypeScript {1}. Specify compilerOption '\"ignoreDeprecations\": \"{2}\"' to silence this error.": {
         "category": "Error",
         "code": 5101

src/compiler/moduleNameResolver.ts

@@ -70,6 +70,7 @@ import {
     ModuleResolutionHost,
     ModuleResolutionKind,
     moduleResolutionOptionDeclarations,
+    moduleResolutionSupportsPackageJsonExportsAndImports,
     noop,
     noopPush,
     normalizePath,
@@ -705,8 +706,11 @@ export function getConditions(options: CompilerOptions, esmMode?: boolean) {
     // conditions are only used by the node16/nodenext/bundler resolvers - there's no priority order in the list,
     // it's essentially a set (priority is determined by object insertion order in the object we look at).
     const conditions = esmMode || getEmitModuleResolutionKind(options) === ModuleResolutionKind.Bundler
-        ? ["node", "import"]
-        : ["node", "require"];
+        ? ["import"]
+        : ["require"];
+    if (getEmitModuleResolutionKind(options) !== ModuleResolutionKind.Bundler) {
+        conditions.unshift("node");
+    }
     if (!options.noDtsResolution) {
         conditions.push("types");
     }
@@ -1701,7 +1705,7 @@ function nodeModuleNameResolverWorker(features: NodeResolutionFeatures, moduleNa
         candidateIsFromPackageJsonField: false,
     };
 
-    if (traceEnabled && getEmitModuleResolutionKind(compilerOptions) >= ModuleResolutionKind.Node16 && getEmitModuleResolutionKind(compilerOptions) <= ModuleResolutionKind.NodeNext) {
+    if (traceEnabled && moduleResolutionSupportsPackageJsonExportsAndImports(getEmitModuleResolutionKind(compilerOptions))) {
         trace(host, Diagnostics.Resolving_in_0_mode_with_conditions_1, features & NodeResolutionFeatures.EsmMode ? "ESM" : "CJS", conditions.map(c => `'${c}'`).join(", "));
     }
 

src/compiler/program.ts

@@ -69,6 +69,7 @@ import {
     DirectoryStructureHost,
     emitFiles,
     EmitHost,
+    emitModuleKindIsNonNodeESM,
     EmitOnly,
     EmitResult,
     emptyArray,
@@ -4241,11 +4242,11 @@ export function createProgram(rootNamesOrOptions: readonly string[] | CreateProg
         }
 
         if (options.preserveValueImports && getEmitModuleKind(options) < ModuleKind.ES2015) {
-            createDiagnosticForOptionName(Diagnostics.Option_preserveValueImports_can_only_be_used_when_module_is_set_to_es2015_or_later, "preserveValueImports");
+            createDiagnosticForOptionName(Diagnostics.Option_0_can_only_be_used_when_module_is_set_to_es2015_or_later, "preserveValueImports");
         }
 
+        const moduleKind = getEmitModuleKind(options);
         if (options.verbatimModuleSyntax) {
-            const moduleKind = getEmitModuleKind(options);
             if (moduleKind === ModuleKind.AMD || moduleKind === ModuleKind.UMD || moduleKind === ModuleKind.System) {
                 createDiagnosticForOptionName(Diagnostics.Option_verbatimModuleSyntax_cannot_be_used_when_module_is_set_to_UMD_AMD_or_System, "verbatimModuleSyntax");
             }
@@ -4266,13 +4267,17 @@ export function createProgram(rootNamesOrOptions: readonly string[] | CreateProg
 
         const moduleResolution = getEmitModuleResolutionKind(options);
         if (options.resolvePackageJsonExports && !moduleResolutionSupportsPackageJsonExportsAndImports(moduleResolution)) {
-            createOptionValueDiagnostic("resolvePackageJsonExports", Diagnostics.Option_0_can_only_be_used_when_moduleResolution_is_set_to_node16_nodenext_or_bundler, "resolvePackageJsonExports");
+            createDiagnosticForOptionName(Diagnostics.Option_0_can_only_be_used_when_moduleResolution_is_set_to_node16_nodenext_or_bundler, "resolvePackageJsonExports");
         }
         if (options.resolvePackageJsonImports && !moduleResolutionSupportsPackageJsonExportsAndImports(moduleResolution)) {
-            createOptionValueDiagnostic("resolvePackageJsonImports", Diagnostics.Option_0_can_only_be_used_when_moduleResolution_is_set_to_node16_nodenext_or_bundler, "resolvePackageJsonImports");
+            createDiagnosticForOptionName(Diagnostics.Option_0_can_only_be_used_when_moduleResolution_is_set_to_node16_nodenext_or_bundler, "resolvePackageJsonImports");
         }
         if (options.customConditions && !moduleResolutionSupportsPackageJsonExportsAndImports(moduleResolution)) {
-            createOptionValueDiagnostic("customConditions", Diagnostics.Option_0_can_only_be_used_when_moduleResolution_is_set_to_node16_nodenext_or_bundler, "customConditions");
+            createDiagnosticForOptionName(Diagnostics.Option_0_can_only_be_used_when_moduleResolution_is_set_to_node16_nodenext_or_bundler, "customConditions");
+        }
+
+        if (moduleResolution === ModuleResolutionKind.Bundler && !emitModuleKindIsNonNodeESM(moduleKind)) {
+            createOptionValueDiagnostic("moduleResolution", Diagnostics.Option_0_can_only_be_used_when_module_is_set_to_es2015_or_later, "bundler");
         }
 
         // If the emit is enabled make sure that every output file is unique and not overwriting any of the input files

tests/baselines/reference/allowImportingTsExtensions(moduleresolution=bundler).errors.txt

@@ -1,6 +1,8 @@
+error TS5095: Option 'bundler' can only be used when 'module' is set to 'es2015' or later.
 /c.ts(1,16): error TS2307: Cannot find module './thisfiledoesnotexist.ts' or its corresponding type declarations.
 
 
+!!! error TS5095: Option 'bundler' can only be used when 'module' is set to 'es2015' or later.
 ==== /ts.ts (0 errors) ====
     export {};
 

tests/baselines/reference/bundlerConditionsExcludesNode.errors.txt

@@ -0,0 +1,44 @@
+error TS6504: File '/node_modules/conditions/index.node.js' is a JavaScript file. Did you mean to enable the 'allowJs' option?
+  The file is in the program because:
+    Root file specified for compilation
+error TS6504: File '/node_modules/conditions/index.web.js' is a JavaScript file. Did you mean to enable the 'allowJs' option?
+  The file is in the program because:
+    Root file specified for compilation
+
+
+!!! error TS6504: File '/node_modules/conditions/index.node.js' is a JavaScript file. Did you mean to enable the 'allowJs' option?
+!!! error TS6504:   The file is in the program because:
+!!! error TS6504:     Root file specified for compilation
+!!! error TS6504: File '/node_modules/conditions/index.web.js' is a JavaScript file. Did you mean to enable the 'allowJs' option?
+!!! error TS6504:   The file is in the program because:
+!!! error TS6504:     Root file specified for compilation
+==== /node_modules/conditions/package.json (0 errors) ====
+    {
+        "name": "conditions",
+        "version": "1.0.0",
+        "type": "module",
+        "main": "index.cjs",
+        "types": "index.d.cts",
+        "exports": {
+          ".": {
+            "node": "./index.node.js",
+            "default": "./index.web.js"
+          }
+        }
+      }
+
+==== /node_modules/conditions/index.node.js (0 errors) ====
+    export const node = 0;
+
+==== /node_modules/conditions/index.node.d.ts (0 errors) ====
+    export const node: number;
+
+==== /node_modules/conditions/index.web.js (0 errors) ====
+    export const web = 0;
+
+==== /node_modules/conditions/index.web.d.ts (0 errors) ====
+    export const web: number;
+
+==== /main.ts (0 errors) ====
+    import { web } from "conditions";
+

tests/baselines/reference/bundlerConditionsExcludesNode.js

@@ -0,0 +1,35 @@
+//// [tests/cases/conformance/moduleResolution/bundler/bundlerConditionsExcludesNode.ts] ////
+
+//// [package.json]
+{
+    "name": "conditions",
+    "version": "1.0.0",
+    "type": "module",
+    "main": "index.cjs",
+    "types": "index.d.cts",
+    "exports": {
+      ".": {
+        "node": "./index.node.js",
+        "default": "./index.web.js"
+      }
+    }
+  }
+
+//// [index.node.js]
+export const node = 0;
+
+//// [index.node.d.ts]
+export const node: number;
+
+//// [index.web.js]
+export const web = 0;
+
+//// [index.web.d.ts]
+export const web: number;
+
+//// [main.ts]
+import { web } from "conditions";
+
+
+//// [main.js]
+export {};

tests/baselines/reference/bundlerConditionsExcludesNode.symbols

@@ -0,0 +1,12 @@
+=== /node_modules/conditions/index.node.d.ts ===
+export const node: number;
+>node : Symbol(node, Decl(index.node.d.ts, 0, 12))
+
+=== /node_modules/conditions/index.web.d.ts ===
+export const web: number;
+>web : Symbol(web, Decl(index.web.d.ts, 0, 12))
+
+=== /main.ts ===
+import { web } from "conditions";
+>web : Symbol(web, Decl(main.ts, 0, 8))
+

tests/baselines/reference/bundlerConditionsExcludesNode.trace.json

@@ -0,0 +1,20 @@
+[
+    "======== Resolving module 'conditions' from '/main.ts'. ========",
+    "Explicitly specified module resolution kind: 'Bundler'.",
+    "Resolving in CJS mode with conditions 'import', 'types'.",
+    "File '/package.json' does not exist.",
+    "Loading module 'conditions' from 'node_modules' folder, target file types: TypeScript, JavaScript, Declaration, JSON.",
+    "Found 'package.json' at '/node_modules/conditions/package.json'.",
+    "Entering conditional exports.",
+    "Saw non-matching condition 'node'.",
+    "Matched 'exports' condition 'default'.",
+    "Using 'exports' subpath '.' with target './index.web.js'.",
+    "File name '/node_modules/conditions/index.web.js' has a '.js' extension - stripping it.",
+    "File '/node_modules/conditions/index.web.ts' does not exist.",
+    "File '/node_modules/conditions/index.web.tsx' does not exist.",
+    "File '/node_modules/conditions/index.web.d.ts' exists - use it as a name resolution result.",
+    "Resolved under condition 'default'.",
+    "Exiting conditional exports.",
+    "Resolving real path for '/node_modules/conditions/index.web.d.ts', result '/node_modules/conditions/index.web.d.ts'.",
+    "======== Module name 'conditions' was successfully resolved to '/node_modules/conditions/index.web.d.ts' with Package ID 'conditions/[email protected]'. ========"
+]

tests/baselines/reference/bundlerConditionsExcludesNode.types

@@ -0,0 +1,12 @@
+=== /node_modules/conditions/index.node.d.ts ===
+export const node: number;
+>node : number
+
+=== /node_modules/conditions/index.web.d.ts ===
+export const web: number;
+>web : number
+
+=== /main.ts ===
+import { web } from "conditions";
+>web : number
+

tests/baselines/reference/bundlerImportESM.js

@@ -14,13 +14,8 @@ import { esm } from "./esm.mjs";
 
 
 //// [esm.mjs]
-"use strict";
-Object.defineProperty(exports, "__esModule", { value: true });
-exports.esm = void 0;
-exports.esm = 0;
+export var esm = 0;
 //// [not-actually-cjs.cjs]
-"use strict";
-Object.defineProperty(exports, "__esModule", { value: true });
+export {};
 //// [still-not-cjs.js]
-"use strict";
-Object.defineProperty(exports, "__esModule", { value: true });
+export {};

tests/baselines/reference/bundlerImportTsExtensions(allowimportingtsextensions=false,noemit=false).errors.txt

@@ -5,12 +5,12 @@ error TS6054: File '/project/e.txt' has an unsupported extension. The only suppo
     Root file specified for compilation
 /project/main.ts(3,16): error TS5097: An import path can only end with a '.ts' extension when 'allowImportingTsExtensions' is enabled.
 /project/main.ts(7,16): error TS5097: An import path can only end with a '.ts' extension when 'allowImportingTsExtensions' is enabled.
-/project/main.ts(8,16): error TS2846: A declaration file cannot be imported without 'import type'. Did you mean to import an implementation file './b' instead?
+/project/main.ts(8,16): error TS2846: A declaration file cannot be imported without 'import type'. Did you mean to import an implementation file './b.js' instead?
 /project/main.ts(11,16): error TS5097: An import path can only end with a '.ts' extension when 'allowImportingTsExtensions' is enabled.
 /project/main.ts(12,16): error TS5097: An import path can only end with a '.tsx' extension when 'allowImportingTsExtensions' is enabled.
 /project/main.ts(12,16): error TS6142: Module './c.tsx' was resolved to '/project/c.tsx', but '--jsx' is not set.
 /project/main.ts(16,16): error TS5097: An import path can only end with a '.ts' extension when 'allowImportingTsExtensions' is enabled.
-/project/types.d.ts(2,16): error TS2846: A declaration file cannot be imported without 'import type'. Did you mean to import an implementation file './a' instead?
+/project/types.d.ts(2,16): error TS2846: A declaration file cannot be imported without 'import type'. Did you mean to import an implementation file './a.js' instead?
 
 
 !!! error TS5056: Cannot write file 'out/b.js' because it would be overwritten by multiple input files.
@@ -68,7 +68,7 @@ error TS6054: File '/project/e.txt' has an unsupported extension. The only suppo
 !!! error TS5097: An import path can only end with a '.ts' extension when 'allowImportingTsExtensions' is enabled.
     import {} from "./b.d.ts";
                    ~~~~~~~~~~
-!!! error TS2846: A declaration file cannot be imported without 'import type'. Did you mean to import an implementation file './b' instead?
+!!! error TS2846: A declaration file cannot be imported without 'import type'. Did you mean to import an implementation file './b.js' instead?
     import type {} from "./b.d.ts";
 
     import {} from "./c.ts";
@@ -96,5 +96,5 @@ error TS6054: File '/project/e.txt' has an unsupported extension. The only suppo
     import {} from "./a.ts";
     import {} from "./a.d.ts";
                    ~~~~~~~~~~
-!!! error TS2846: A declaration file cannot be imported without 'import type'. Did you mean to import an implementation file './a' instead?
+!!! error TS2846: A declaration file cannot be imported without 'import type'. Did you mean to import an implementation file './a.js' instead?
     import type {} from "./a.d.ts";

tests/baselines/reference/bundlerImportTsExtensions(allowimportingtsextensions=false,noemit=false).js

@@ -66,17 +66,12 @@ import {} from "./a.d.ts";
 import type {} from "./a.d.ts";
 
 //// [a.js]
-"use strict";
-Object.defineProperty(exports, "__esModule", { value: true });
+export {};
 //// [index.js]
-"use strict";
-Object.defineProperty(exports, "__esModule", { value: true });
+export {};
 //// [e.js]
-"use strict";
-Object.defineProperty(exports, "__esModule", { value: true });
+export {};
 //// [e.txt.js]
-"use strict";
-Object.defineProperty(exports, "__esModule", { value: true });
+export {};
 //// [main.js]
-"use strict";
-Object.defineProperty(exports, "__esModule", { value: true });
+export {};