fix(js): avoid double-prefixing node executor output paths (#35050)

## Summary
- avoid prepending `outputPath` twice when `@nx/js:node` derives the
runnable file for `@nx/js:tsc` and `@nx/js:swc`
- keep the existing source-relative behavior for normal `src/...`
entries while preserving nested paths already inside the output
directory
- respect a configured `rootDir` on the build target so the node
executor does not add an extra path segment that tsc/swc stripped from
the output
- reuse the canonical `normalizePath` and
`getRelativeDirectoryToProjectRoot` utilities instead of re-declaring
them
- add focused coverage for the `dist/main.js`, source-entry,
nested-output, and `rootDir` cases

Fixes #35044
Fixes #33577

## Validation
- `corepack pnpm exec prettier --check
packages/js/src/executors/node/node.impl.ts
packages/js/src/executors/node/lib/output-file.ts
packages/js/src/executors/node/lib/output-file.spec.ts`
- `corepack pnpm exec eslint packages/js/src/executors/node/node.impl.ts
packages/js/src/executors/node/lib/output-file.ts
packages/js/src/executors/node/lib/output-file.spec.ts`
- `pnpm nx test js --testPathPatterns=output-file` — all 4 cases pass

---------

Co-authored-by: FrozenPandaz <[email protected]>

Author: raashish1601

packages/js/src/executors/node/lib/output-file.spec.ts

@@ -0,0 +1,47 @@
+import { getOutputFileName } from './output-file';
+
+describe('getOutputFileName', () => {
+  it('does not double-prefix outputPath when main is already inside the build output', () => {
+    expect(
+      getOutputFileName({
+        buildTargetExecutor: '@nx/js:tsc',
+        main: 'packages/failing-project/dist/main.js',
+        outputPath: 'packages/failing-project/dist',
+        rootDir: 'packages/failing-project',
+      })
+    ).toBe('main.js');
+  });
+
+  it('keeps project-root-relative subdirectories for source entries', () => {
+    expect(
+      getOutputFileName({
+        buildTargetExecutor: '@nx/js:tsc',
+        main: 'packages/failing-project/src/main.ts',
+        outputPath: 'dist/packages/failing-project',
+        rootDir: 'packages/failing-project',
+      })
+    ).toBe('src/main.js');
+  });
+
+  it('preserves nested subdirectories that already live under outputPath', () => {
+    expect(
+      getOutputFileName({
+        buildTargetExecutor: '@nx/js:swc',
+        main: 'packages/failing-project/dist/server/main.js',
+        outputPath: 'packages/failing-project/dist',
+        rootDir: 'packages/failing-project',
+      })
+    ).toBe('server/main.js');
+  });
+
+  it('resolves main relative to rootDir when tsc strips the rootDir prefix from the output', () => {
+    expect(
+      getOutputFileName({
+        buildTargetExecutor: '@nx/js:tsc',
+        main: 'apps/project_a/src/main.ts',
+        outputPath: 'dist/apps/project_a',
+        rootDir: 'apps/project_a/src',
+      })
+    ).toBe('main.js');
+  });
+});

packages/js/src/executors/node/lib/output-file.ts

@@ -0,0 +1,38 @@
+import { dirname, parse } from 'path';
+import { joinPathFragments, normalizePath } from 'nx/src/utils/path';
+import { getRelativeDirectoryToProjectRoot } from '../../../utils/get-main-file-dir';
+
+interface OutputFileNameOptions {
+  buildTargetExecutor: string;
+  main: string;
+  outputPath: string;
+  rootDir: string;
+}
+
+export function getOutputFileName({
+  buildTargetExecutor,
+  main,
+  outputPath,
+  rootDir,
+}: OutputFileNameOptions): string {
+  const fileName = `${parse(main).name}.js`;
+
+  if (
+    buildTargetExecutor !== '@nx/js:tsc' &&
+    buildTargetExecutor !== '@nx/js:swc'
+  ) {
+    return fileName;
+  }
+
+  const mainDirectory = normalizePath(dirname(main));
+  const normalizedOutputPath = normalizePath(outputPath);
+  const isMainInsideOutputPath =
+    mainDirectory === normalizedOutputPath ||
+    mainDirectory.startsWith(`${normalizedOutputPath}/`);
+  const base = isMainInsideOutputPath ? normalizedOutputPath : rootDir;
+
+  return joinPathFragments(
+    getRelativeDirectoryToProjectRoot(main, base),
+    fileName
+  );
+}

packages/js/src/executors/node/node.impl.ts

@@ -22,9 +22,9 @@ import { killTree } from './lib/kill-tree';
 import { LineAwareWriter } from './lib/line-aware-writer';
 import { createCoalescingDebounce } from './lib/coalescing-debounce';
 import { fileExists } from 'nx/src/utils/fileutils';
-import { getRelativeDirectoryToProjectRoot } from '../../utils/get-main-file-dir';
 import { interpolate } from 'nx/src/tasks-runner/utils';
 import { detectModuleFormat } from './lib/detect-module-format';
+import { getOutputFileName } from './lib/output-file';
 
 interface ActiveTask {
   id: string;
@@ -478,18 +478,12 @@ function getFileToRun(
   let outputFileName = buildOptions.outputFileName;
 
   if (!outputFileName) {
-    const fileName = `${path.parse(buildOptions.main).name}.js`;
-    if (
-      buildTargetExecutor === '@nx/js:tsc' ||
-      buildTargetExecutor === '@nx/js:swc'
-    ) {
-      outputFileName = path.join(
-        getRelativeDirectoryToProjectRoot(buildOptions.main, project.data.root),
-        fileName
-      );
-    } else {
-      outputFileName = fileName;
-    }
+    outputFileName = getOutputFileName({
+      buildTargetExecutor,
+      main: buildOptions.main,
+      outputPath: buildOptions.outputPath,
+      rootDir: buildOptions.rootDir ?? project.data.root,
+    });
   }
 
   return join(context.root, buildOptions.outputPath, outputFileName);