Follow and respect export maps when generating module specifiers

src/compiler/moduleNameResolver.ts

@@ -1708,7 +1708,8 @@ namespace ts {
         return idx === -1 ? { packageName: moduleName, rest: "" } : { packageName: moduleName.slice(0, idx), rest: moduleName.slice(idx + 1) };
     }
 
-    function allKeysStartWithDot(obj: MapLike<unknown>) {
+    /* @internal */
+    export function allKeysStartWithDot(obj: MapLike<unknown>) {
         return every(getOwnKeys(obj), k => startsWith(k, "."));
     }
 
@@ -1922,14 +1923,15 @@ namespace ts {
             }
             return toSearchResult(/*value*/ undefined);
         }
+    }
 
-        function isApplicableVersionedTypesKey(conditions: string[], key: string) {
-            if (conditions.indexOf("types") === -1) return false; // only apply versioned types conditions if the types condition is applied
-            if (!startsWith(key, "types@")) return false;
-            const range = VersionRange.tryParse(key.substring("types@".length));
-            if (!range) return false;
-            return range.test(version);
-        }
+    /* @internal */
+    export function isApplicableVersionedTypesKey(conditions: string[], key: string) {
+        if (conditions.indexOf("types") === -1) return false; // only apply versioned types conditions if the types condition is applied
+        if (!startsWith(key, "types@")) return false;
+        const range = VersionRange.tryParse(key.substring("types@".length));
+        if (!range) return false;
+        return range.test(version);
     }
 
     function loadModuleFromNearestNodeModulesDirectory(extensions: Extensions, moduleName: string, directory: string, state: ModuleResolutionState, cache: ModuleResolutionCache | undefined, redirectedReference: ResolvedProjectReference | undefined): SearchResult<Resolved> {

src/compiler/moduleSpecifiers.ts

@@ -555,6 +555,77 @@ namespace ts.moduleSpecifiers {
         }
     }
 
+    const enum MatchingMode {
+        Exact,
+        Directory,
+        Pattern
+    }
+
+    function tryGetModuleNameFromExports(options: CompilerOptions, targetFilePath: string, packageDirectory: string, packageName: string, exports: unknown, conditions: string[], mode = MatchingMode.Exact): { moduleFileToTry: string } | undefined {
+        if (typeof exports === "string") {
+            const pathOrPattern = getNormalizedAbsolutePath(combinePaths(packageDirectory, exports), /*currentDirectory*/ undefined);
+            const extensionSwappedTarget = hasTSFileExtension(targetFilePath) ? removeFileExtension(targetFilePath) + tryGetJSExtensionForFile(targetFilePath, options) : undefined;
+            switch (mode) {
+                case MatchingMode.Exact:
+                    if (comparePaths(targetFilePath, pathOrPattern) === Comparison.EqualTo || (extensionSwappedTarget && comparePaths(extensionSwappedTarget, pathOrPattern) === Comparison.EqualTo)) {
+                        return { moduleFileToTry: packageName };
+                    }
+                    break;
+                case MatchingMode.Directory:
+                    if (containsPath(pathOrPattern, targetFilePath)) {
+                        const fragment = getRelativePathFromDirectory(pathOrPattern, targetFilePath, /*ignoreCase*/ false);
+                        return { moduleFileToTry: getNormalizedAbsolutePath(combinePaths(combinePaths(packageName, exports), fragment), /*currentDirectory*/ undefined) };
+                    }
+                    break;
+                case MatchingMode.Pattern:
+                    const starPos = pathOrPattern.indexOf("*");
+                    const leadingSlice = pathOrPattern.slice(0, starPos);
+                    const trailingSlice = pathOrPattern.slice(starPos + 1);
+                    if (startsWith(targetFilePath, leadingSlice) && endsWith(targetFilePath, trailingSlice)) {
+                        const starReplacement = targetFilePath.slice(leadingSlice.length, targetFilePath.length - trailingSlice.length);
+                        return { moduleFileToTry: packageName.replace("*", starReplacement) };
+                    }
+                    if (extensionSwappedTarget && startsWith(extensionSwappedTarget, leadingSlice) && endsWith(extensionSwappedTarget, trailingSlice)) {
+                        const starReplacement = extensionSwappedTarget.slice(leadingSlice.length, extensionSwappedTarget.length - trailingSlice.length);
+                        return { moduleFileToTry: packageName.replace("*", starReplacement) };
+                    }
+                    break;
+            }
+        }
+        else if (Array.isArray(exports)) {
+            return forEach(exports, e => tryGetModuleNameFromExports(options, targetFilePath, packageDirectory, packageName, e, conditions));
+        }
+        else if (typeof exports === "object" && exports !== null) { // eslint-disable-line no-null/no-null
+            if (allKeysStartWithDot(exports as MapLike<unknown>)) {
+                // sub-mappings
+                // 3 cases:
+                // * directory mappings (legacyish, key ends with / (technically allows index/extension resolution under cjs mode))
+                // * pattern mappings (contains a *)
+                // * exact mappings (no *, does not end with /)
+                return forEach(getOwnKeys(exports as MapLike<unknown>), k => {
+                    const subPackageName = getNormalizedAbsolutePath(combinePaths(packageName, k), /*currentDirectory*/ undefined);
+                    const mode = endsWith(k, "/") ? MatchingMode.Directory
+                        : stringContains(k, "*") ? MatchingMode.Pattern
+                        : MatchingMode.Exact;
+                    return tryGetModuleNameFromExports(options, targetFilePath, packageDirectory, subPackageName, (exports as MapLike<unknown>)[k], conditions, mode);
+                });
+            }
+            else {
+                // conditional mapping
+                for (const key of getOwnKeys(exports as MapLike<unknown>)) {
+                    if (key === "default" || conditions.indexOf(key) >= 0 || isApplicableVersionedTypesKey(conditions, key)) {
+                        const subTarget = (exports as MapLike<unknown>)[key];
+                        const result = tryGetModuleNameFromExports(options, targetFilePath, packageDirectory, packageName, subTarget, conditions);
+                        if (result) {
+                            return result;
+                        }
+                    }
+                }
+            }
+        }
+        return undefined;
+    }
+
     function tryGetModuleNameFromRootDirs(rootDirs: readonly string[], moduleFileName: string, sourceDirectory: string, getCanonicalFileName: (file: string) => string, ending: Ending, compilerOptions: CompilerOptions): string | undefined {
         const normalizedTargetPath = getPathRelativeToRootDirs(moduleFileName, rootDirs, getCanonicalFileName);
         if (normalizedTargetPath === undefined) {
@@ -586,7 +657,15 @@ namespace ts.moduleSpecifiers {
             let moduleFileNameForExtensionless: string | undefined;
             while (true) {
                 // If the module could be imported by a directory name, use that directory's name
-                const { moduleFileToTry, packageRootPath } = tryDirectoryWithPackageJson(packageRootIndex);
+                const { moduleFileToTry, packageRootPath, blockedByExports, verbatimFromExports } = tryDirectoryWithPackageJson(packageRootIndex);
+                if (getEmitModuleResolutionKind(options) !== ModuleResolutionKind.Classic) {
+                    if (blockedByExports) {
+                        return undefined; // File is under this package.json, but is not publicly exported - there's no way to name it via `node_modules` resolution
+                    }
+                    if (verbatimFromExports) {
+                        return moduleFileToTry;
+                    }
+                }
                 if (packageRootPath) {
                     moduleSpecifier = packageRootPath;
                     isPackageRootPath = true;
@@ -621,12 +700,21 @@ namespace ts.moduleSpecifiers {
         // For classic resolution, only allow importing from node_modules/@types, not other node_modules
         return getEmitModuleResolutionKind(options) === ModuleResolutionKind.Classic && packageName === nodeModulesDirectoryName ? undefined : packageName;
 
-        function tryDirectoryWithPackageJson(packageRootIndex: number) {
+        function tryDirectoryWithPackageJson(packageRootIndex: number): { moduleFileToTry: string, packageRootPath?: string, blockedByExports?: true, verbatimFromExports?: true } {
             const packageRootPath = path.substring(0, packageRootIndex);
             const packageJsonPath = combinePaths(packageRootPath, "package.json");
             let moduleFileToTry = path;
             if (host.fileExists(packageJsonPath)) {
                 const packageJsonContent = JSON.parse(host.readFile!(packageJsonPath)!);
+                // TODO: Inject `require` or `import` condition based on the intended import mode
+                const fromExports = packageJsonContent.exports && typeof packageJsonContent.name === "string" ? tryGetModuleNameFromExports(options, path, packageRootPath, packageJsonContent.name, packageJsonContent.exports, ["node", "types"]) : undefined;
+                if (fromExports) {
+                    const withJsExtension = !hasTSFileExtension(fromExports.moduleFileToTry) ? fromExports : { moduleFileToTry: removeFileExtension(fromExports.moduleFileToTry) + tryGetJSExtensionForFile(fromExports.moduleFileToTry, options) };
+                    return { ...withJsExtension, verbatimFromExports: true };
+                }
+                if (packageJsonContent.exports) {
+                    return { moduleFileToTry: path, blockedByExports: true };
+                }
                 const versionPaths = packageJsonContent.typesVersions
                     ? getPackageJsonTypesVersionsPaths(packageJsonContent.typesVersions)
                     : undefined;
@@ -641,7 +729,6 @@ namespace ts.moduleSpecifiers {
                         moduleFileToTry = combinePaths(packageRootPath, fromPaths);
                     }
                 }
-
                 // If the file is the main module, it can be imported by the package name
                 const mainFileRelative = packageJsonContent.typings || packageJsonContent.types || packageJsonContent.main;
                 if (isString(mainFileRelative)) {

src/testRunner/unittests/tsbuild/moduleSpecifiers.ts

@@ -88,4 +88,101 @@ namespace ts {
             commandLineArgs: ["-b", "/src", "--verbose"]
         });
     });
+
+    // https://github.com/microsoft/TypeScript/issues/44434 but with `module: node12`, some `exports` maps blocking direct access, and no `baseUrl`
+    describe("unittests:: tsbuild:: moduleSpecifiers:: synthesized module specifiers across referenced projects resolve correctly", () => {
+        verifyTsc({
+            scenario: "moduleSpecifiers",
+            subScenario: `synthesized module specifiers across projects resolve correctly`,
+            fs: () => loadProjectFromFiles({
+                "/src/src-types/index.ts": Utils.dedent`
+                    export * from './dogconfig.js';`,
+                "/src/src-types/dogconfig.ts": Utils.dedent`
+                    export interface DogConfig {
+                        name: string;
+                    }`,
+                "/src/src-dogs/index.ts": Utils.dedent`
+                    export * from 'src-types';
+                    export * from './lassie/lassiedog.js';
+                    `,
+                "/src/src-dogs/dogconfig.ts": Utils.dedent`
+                    import { DogConfig } from 'src-types';
+
+                    export const DOG_CONFIG: DogConfig = {
+                        name: 'Default dog',
+                    };
+                    `,
+                "/src/src-dogs/dog.ts": Utils.dedent`
+                    import { DogConfig } from 'src-types';
+                    import { DOG_CONFIG } from './dogconfig.js';
+                    
+                    export abstract class Dog {
+                    
+                        public static getCapabilities(): DogConfig {
+                            return DOG_CONFIG;
+                        }
+                    }
+                    `,
+                "/src/src-dogs/lassie/lassiedog.ts": Utils.dedent`
+                    import { Dog } from '../dog.js';
+                    import { LASSIE_CONFIG } from './lassieconfig.js';
+                    
+                    export class LassieDog extends Dog {
+                        protected static getDogConfig = () => LASSIE_CONFIG;
+                    }
+                    `,
+                "/src/src-dogs/lassie/lassieconfig.ts": Utils.dedent`
+                    import { DogConfig } from 'src-types';
+
+                    export const LASSIE_CONFIG: DogConfig = { name: 'Lassie' };
+                    `,
+                "/src/tsconfig-base.json": Utils.dedent`
+                    {
+                        "compilerOptions": {
+                            "declaration": true,
+                            "module": "node12"
+                        }
+                    }`,
+                "/src/src-types/package.json": Utils.dedent`
+                    {
+                        "type": "module",
+                        "exports": "./index.js"
+                    }`,
+                "/src/src-dogs/package.json": Utils.dedent`
+                    {
+                        "type": "module",
+                        "exports": "./index.js"
+                    }`,
+                "/src/src-types/tsconfig.json": Utils.dedent`
+                    {
+                        "extends": "../tsconfig-base.json",
+                        "compilerOptions": {
+                            "composite": true
+                        },
+                        "include": [
+                            "**/*"
+                        ]
+                    }`,
+                "/src/src-dogs/tsconfig.json": Utils.dedent`
+                    {
+                        "extends": "../tsconfig-base.json",
+                        "compilerOptions": {
+                            "composite": true
+                        },
+                        "references": [
+                            { "path": "../src-types" }
+                        ],
+                        "include": [
+                            "**/*"
+                        ]
+                    }`,
+            }, ""),
+            modifyFs: fs => {
+                fs.writeFileSync("/lib/lib.es2020.full.d.ts", tscWatch.libFile.content);
+                fs.symlinkSync("/src", "/src/src-types/node_modules");
+                fs.symlinkSync("/src", "/src/src-dogs/node_modules");
+            },
+            commandLineArgs: ["-b", "src/src-types", "src/src-dogs", "--verbose"]
+        });
+    });
 }

tests/baselines/reference/nodeModulesExportsBlocksSpecifierResolution(module=node12).errors.txt

@@ -0,0 +1,36 @@
+tests/cases/conformance/node/index.ts(2,23): error TS2307: Cannot find module 'inner/other' or its corresponding type declarations.
+tests/cases/conformance/node/index.ts(3,14): error TS2742: The inferred type of 'a' cannot be named without a reference to './node_modules/inner/other.js'. This is likely not portable. A type annotation is necessary.
+tests/cases/conformance/node/index.ts(3,19): error TS1378: Top-level 'await' expressions are only allowed when the 'module' option is set to 'es2022', 'esnext', 'system', or 'nodenext', and the 'target' option is set to 'es2017' or higher.
+
+
+==== tests/cases/conformance/node/index.ts (3 errors) ====
+    // esm format file
+    import { Thing } from "inner/other";
+                          ~~~~~~~~~~~~~
+!!! error TS2307: Cannot find module 'inner/other' or its corresponding type declarations.
+    export const a = (await import("inner")).x();
+                 ~
+!!! error TS2742: The inferred type of 'a' cannot be named without a reference to './node_modules/inner/other.js'. This is likely not portable. A type annotation is necessary.
+                      ~~~~~
+!!! error TS1378: Top-level 'await' expressions are only allowed when the 'module' option is set to 'es2022', 'esnext', 'system', or 'nodenext', and the 'target' option is set to 'es2017' or higher.
+==== tests/cases/conformance/node/node_modules/inner/index.d.ts (0 errors) ====
+    // esm format file
+    export { x } from "./other.js";
+==== tests/cases/conformance/node/node_modules/inner/other.d.ts (0 errors) ====
+    // esm format file
+    export interface Thing {}
+    export const x: () => Thing;
+==== tests/cases/conformance/node/package.json (0 errors) ====
+    {
+        "name": "package",
+        "private": true,
+        "type": "module",
+        "exports": "./index.js"
+    }
+==== tests/cases/conformance/node/node_modules/inner/package.json (0 errors) ====
+    {
+        "name": "inner",
+        "private": true,
+        "type": "module",
+        "exports": "./index.js"
+    }

tests/baselines/reference/nodeModulesExportsBlocksSpecifierResolution(module=node12).js

@@ -0,0 +1,30 @@
+//// [tests/cases/conformance/node/nodeModulesExportsBlocksSpecifierResolution.ts] ////
+
+//// [index.ts]
+// esm format file
+import { Thing } from "inner/other";
+export const a = (await import("inner")).x();
+//// [index.d.ts]
+// esm format file
+export { x } from "./other.js";
+//// [other.d.ts]
+// esm format file
+export interface Thing {}
+export const x: () => Thing;
+//// [package.json]
+{
+    "name": "package",
+    "private": true,
+    "type": "module",
+    "exports": "./index.js"
+}
+//// [package.json]
+{
+    "name": "inner",
+    "private": true,
+    "type": "module",
+    "exports": "./index.js"
+}
+
+//// [index.js]
+export const a = (await import("inner")).x();

tests/baselines/reference/nodeModulesExportsBlocksSpecifierResolution(module=node12).symbols

@@ -0,0 +1,25 @@
+=== tests/cases/conformance/node/index.ts ===
+// esm format file
+import { Thing } from "inner/other";
+>Thing : Symbol(Thing, Decl(index.ts, 1, 8))
+
+export const a = (await import("inner")).x();
+>a : Symbol(a, Decl(index.ts, 2, 12))
+>(await import("inner")).x : Symbol(x, Decl(index.d.ts, 1, 8))
+>"inner" : Symbol("tests/cases/conformance/node/node_modules/inner/index", Decl(index.d.ts, 0, 0))
+>x : Symbol(x, Decl(index.d.ts, 1, 8))
+
+=== tests/cases/conformance/node/node_modules/inner/index.d.ts ===
+// esm format file
+export { x } from "./other.js";
+>x : Symbol(x, Decl(index.d.ts, 1, 8))
+
+=== tests/cases/conformance/node/node_modules/inner/other.d.ts ===
+// esm format file
+export interface Thing {}
+>Thing : Symbol(Thing, Decl(other.d.ts, 0, 0))
+
+export const x: () => Thing;
+>x : Symbol(x, Decl(other.d.ts, 2, 12))
+>Thing : Symbol(Thing, Decl(other.d.ts, 0, 0))
+