Resolve JS files referenced by TypeScript declaration files if possib…

…le (#503)

* Add test & fixtures for dts files used with base-url implicit relative scenario

* Resolve TypeScript declaration file to matching js files if possible

* Include other dts extensions

* Add tsconfig file

* Fix tests

* Format changes

---------

Co-authored-by: Lars Kappert <[email protected]>

packages/eslint-config/tsconfig.json

@@ -0,0 +1,3 @@
+{
+  "compilerOptions": {}
+}

packages/knip/fixtures/dts-baseurl-implicit-relative/package.json

@@ -0,0 +1,3 @@
+{
+  "name": "@fixtures/dts-baseurl-implicit-relative"
+}

packages/knip/fixtures/dts-baseurl-implicit-relative/src/dir/subdir/index.d.ts

@@ -0,0 +1,2 @@
+const h: () => number;
+export default h;

packages/knip/fixtures/dts-baseurl-implicit-relative/src/dir/subdir/index.js

@@ -0,0 +1,4 @@
+const h = () => {
+  return 1;
+};
+export default h;

packages/knip/fixtures/dts-baseurl-implicit-relative/src/index.ts

@@ -0,0 +1,5 @@
+import h from 'dir/subdir';
+import { g } from 'utils/fn';
+
+h;
+g;

packages/knip/fixtures/dts-baseurl-implicit-relative/src/utils/fn.d.ts

@@ -0,0 +1 @@
+export const g: () => void;

packages/knip/fixtures/dts-baseurl-implicit-relative/src/utils/fn.js

@@ -0,0 +1 @@
+export const g = () => {};

packages/knip/fixtures/dts-baseurl-implicit-relative/tsconfig.json

@@ -0,0 +1,5 @@
+{
+  "compilerOptions": {
+    "baseUrl": "src"
+  }
+}

packages/knip/scripts/tsconfig.json

@@ -3,7 +3,7 @@
   "compilerOptions": {
     "esModuleInterop": true,
     "module": "NodeNext",
-    "moduleResolution": "NodeNext",
+    "moduleResolution": "NodeNext"
   },
-  "include": ["**/*.ts"],
+  "include": ["**/*.ts"]
 }

packages/knip/src/typescript/resolveModuleNames.ts

@@ -2,7 +2,7 @@ import { existsSync } from 'node:fs';
 import { isBuiltin } from 'node:module';
 import ts from 'typescript';
 import { sanitizeSpecifier } from '../util/modules.js';
-import { dirname, extname, isAbsolute, isInternal, join } from '../util/path.js';
+import { basename, dirname, extname, format, isAbsolute, isInternal, join } from '../util/path.js';
 import { isDeclarationFileExtension } from './ast-helpers.js';
 import { ensureRealFilePath, isVirtualFilePath } from './utils.js';
 
@@ -20,6 +20,31 @@ const fileExists = (name: string, containingFile: string) => {
   }
 };
 
+const DECLARATION_EXTENSIONS_MAP = {
+  [ts.Extension.Dts]: ts.Extension.Js,
+  [ts.Extension.Dmts]: ts.Extension.Mjs,
+  [ts.Extension.Dcts]: ts.Extension.Cjs,
+} as const;
+
+const jsMatchingDeclarationFileExists = (resolveDtsFileName: string, declarationFileExtension: string) => {
+  const mappedExtension =
+    DECLARATION_EXTENSIONS_MAP[declarationFileExtension as keyof typeof DECLARATION_EXTENSIONS_MAP];
+  const resolvedFileName = format({
+    ext: mappedExtension,
+    dir: dirname(resolveDtsFileName),
+    name: basename(resolveDtsFileName, declarationFileExtension),
+  });
+
+  if (existsSync(resolvedFileName)) {
+    return {
+      resolvedFileName,
+      extension: mappedExtension,
+      isExternalLibraryImport: false,
+      resolvedUsingTsExtension: false,
+    };
+  }
+};
+
 export function createCustomModuleResolver(
   customSys: typeof ts.sys,
   compilerOptions: ts.CompilerOptions,
@@ -66,8 +91,14 @@ export function createCustomModuleResolver(
       isDeclarationFileExtension(tsResolvedModule?.extension) &&
       isInternal(tsResolvedModule.resolvedFileName)
     ) {
-      const module = fileExists(sanitizedSpecifier, containingFile);
-      if (module) return module;
+      {
+        const module = jsMatchingDeclarationFileExists(tsResolvedModule.resolvedFileName, tsResolvedModule.extension);
+        if (module) return module;
+      }
+      {
+        const module = fileExists(sanitizedSpecifier, containingFile);
+        if (module) return module;
+      }
     }
 
     if (virtualFileExtensions.length === 0) return tsResolvedModule;

packages/knip/src/util/path.ts

@@ -12,6 +12,8 @@ export const extname = path.posix.extname;
 
 export const basename = path.posix.basename;
 
+export const format = path.posix.format;
+
 export const join = path.posix.join;
 
 export const toPosix = (value: string) => value.split(path.sep).join(path.posix.sep);

packages/knip/src/util/tsconfig-loader.ts

@@ -3,12 +3,14 @@ import { isFile } from './fs.js';
 import { FAKE_PATH } from './loader.js';
 import { dirname } from './path.js';
 
+const dtsMatch = /\.d\.(c|m)?ts$/;
+
 export const loadTSConfig = async (tsConfigFilePath: string) => {
   if (tsConfigFilePath !== FAKE_PATH && isFile(tsConfigFilePath)) {
     const config = ts.readConfigFile(tsConfigFilePath, ts.sys.readFile);
     const parsedConfig = ts.parseJsonConfigFileContent(config.config, ts.sys, dirname(tsConfigFilePath));
     const compilerOptions = parsedConfig.options ?? {};
-    const definitionPaths = parsedConfig.fileNames.filter(filePath => filePath.endsWith('.d.ts'));
+    const definitionPaths = parsedConfig.fileNames.filter(filePath => dtsMatch.test(filePath));
     return { compilerOptions, definitionPaths };
   }
   return { compilerOptions: {}, definitionPaths: [] };

packages/knip/test/dts-baseurl-implicit-relative.test.ts

@@ -0,0 +1,21 @@
+import assert from 'node:assert/strict';
+import test from 'node:test';
+import { main } from '../src/index.js';
+import { resolve } from '../src/util/path.js';
+import baseArguments from './helpers/baseArguments.js';
+import baseCounters from './helpers/baseCounters.js';
+
+const cwd = resolve('fixtures/dts-baseurl-implicit-relative');
+
+test('Include js files referred by the declaration files', async () => {
+  const { counters } = await main({
+    ...baseArguments,
+    cwd,
+  });
+
+  assert.deepEqual(counters, {
+    ...baseCounters,
+    processed: 5,
+    total: 5,
+  });
+});

packages/knip/test/subpath-imports.test.ts

@@ -18,7 +18,6 @@ test('Allows subpath-imports', async () => {
   assert.deepEqual(counters, {
     ...baseCounters,
     dependencies: 1,
-    files: 1,
     processed: 3,
     total: 3,
   });
@@ -36,7 +35,6 @@ test('Allows subpath-imports (production)', async () => {
   assert.deepEqual(counters, {
     ...baseCounters,
     dependencies: 1,
-    files: 1,
     processed: 3,
     total: 3,
   });
@@ -55,7 +53,6 @@ test('Allows subpath-imports (strict)', async () => {
   assert.deepEqual(counters, {
     ...baseCounters,
     dependencies: 1,
-    files: 1,
     processed: 3,
     total: 3,
   });

packages/knip/test/tsconfig.json

@@ -5,7 +5,7 @@
     "allowJs": true,
     "rootDir": ".",
     "baseUrl": ".",
-    "jsx": "preserve",
+    "jsx": "preserve"
   },
-  "include": [".", "../src"],
+  "include": [".", "../src"]
 }

packages/knip/test/workspaces-self-reference.test.ts

@@ -15,7 +15,7 @@ test('Find unused files, dependencies and exports in workspaces with cross self-
 
   assert.deepEqual(counters, {
     ...baseCounters,
-    processed: 4,
-    total: 4,
+    processed: 8,
+    total: 8,
   });
 });