Return empty source file for foreign files (resolves #623)

packages/knip/fixtures/module-resolution-non-std-absolute/other/package.json

@@ -0,0 +1,4 @@
+{
+  "name": "other",
+  "version": "1.0.0"
+}

packages/knip/fixtures/module-resolution-non-std-absolute/package.json

@@ -0,0 +1,5 @@
+{
+  "name": "@fixtures/module-resolution-non-std-absolute",
+  "version": "1.0.0",
+  "workspaces": ["other", "self"]
+}

packages/knip/fixtures/module-resolution-non-std-absolute/self/index.ts

@@ -0,0 +1,4 @@
+import 'other/absolute.svg';
+import 'other/absolute.css';
+import 'self/absolute.svg';
+import 'self/absolute.css';

packages/knip/fixtures/module-resolution-non-std-absolute/self/package.json

@@ -0,0 +1,4 @@
+{
+  "name": "self",
+  "version": "1.0.0"
+}

packages/knip/fixtures/module-resolution-non-std-absolute/tsconfig.json

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

packages/knip/fixtures/module-resolution-non-std-implicit/src/index.ts

@@ -6,6 +6,4 @@ import Icon from './icon.svg';
 
 import './global.css';
 
-// By exception, .css files will be resolved because `.css` is not added to virtual path extensions, since `.css.ts`
-// files on disk are common (in contrast to e.g. `.svg.ts`; binaries like `.png.ts` can be safely ignored).
 import 'styles/base.css';

packages/knip/src/typescript/SourceFileManager.ts

@@ -34,7 +34,7 @@ export class SourceFileManager {
     if (this.sourceFileCache.has(filePath)) return this.sourceFileCache.get(filePath);
     const ext = extname(filePath);
     const compiler = this.syncCompilers.get(ext);
-    if (FOREIGN_FILE_EXTENSIONS.has(ext) && !compiler) return undefined;
+    if (FOREIGN_FILE_EXTENSIONS.has(ext) && !compiler) return this.createSourceFile(filePath, '');
     if (this.isSkipLibs && isInNodeModules(filePath)) {
       if (isDeclarationFileExtension(ext)) return undefined;
       return this.createSourceFile(filePath, '');

packages/knip/src/typescript/resolveModuleNames.ts

@@ -43,6 +43,10 @@ export function createCustomModuleResolver(
     });
   }
 
+  /**
+   * - Virtual files have built-in or custom compiler, return as JS
+   * - Foreign files have path resolved verbatim (file manager will return empty source file)
+   */
   function resolveModuleName(name: string, containingFile: string): ts.ResolvedModuleFull | undefined {
     const sanitizedSpecifier = sanitizeSpecifier(name);
 

packages/knip/test/module-resolution-non-std-absolute.test.ts

@@ -0,0 +1,24 @@
+import { test } from 'bun:test';
+import assert from 'node:assert/strict';
+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/module-resolution-non-std-absolute');
+
+test('Resolve non-standard absolute specifiers', async () => {
+  const { issues, counters } = await main({
+    ...baseArguments,
+    cwd,
+  });
+
+  assert(issues.unlisted['self/index.ts']['other']);
+
+  assert.deepEqual(counters, {
+    ...baseCounters,
+    unlisted: 1,
+    processed: 5,
+    total: 5,
+  });
+});