fix(@angular/build): rewrite paths from sandboxed execroots when running under Bazel

rewriteForBazel only maps paths that fall inside BAZEL_BINDIR relative to
JS_BINARY__EXECROOT. Locally sandboxed actions (darwin-sandbox,
linux-sandbox) stage inputs as symlinks into a differently rooted copy of
the execroot, so realpath resolves entry points to the unsandboxed
execroot while the TypeScript program is keyed by sandbox paths. The
compiler plugin then fails with "File 'main.ts' is missing from the
TypeScript compilation".

Derive the effective execroot from the working directory and re-anchor
paths that resolve outside of it.

Author: FrankPortman

packages/angular/build/src/tools/esbuild/angular/rewrite-bazel-paths.ts

@@ -6,25 +6,55 @@
  * found in the LICENSE file at https://angular.dev/license
  */
 
-import { join, relative } from 'node:path';
+import { join, relative, sep } from 'node:path';
 
 const bazelBinDirectory = process.env['BAZEL_BINDIR'];
 const bazelExecRoot = process.env['JS_BINARY__EXECROOT'];
+const execRootMarker = `${sep}execroot${sep}`;
+
+/**
+ * Sandboxed actions run in a copy of the execroot whose absolute path differs from
+ * `JS_BINARY__EXECROOT`, so the effective execroot is derived from the working directory.
+ */
+function effectiveExecRoot(): string | undefined {
+  const cwd = process.cwd();
+  const markerIndex = cwd.indexOf(execRootMarker);
+  if (markerIndex === -1) {
+    return bazelExecRoot;
+  }
+
+  const workspaceEnd = cwd.indexOf(sep, markerIndex + execRootMarker.length);
+
+  return workspaceEnd === -1 ? cwd : cwd.slice(0, workspaceEnd);
+}
 
 export function rewriteForBazel(path: string): string {
   if (!bazelBinDirectory || !bazelExecRoot) {
     return path;
   }
 
-  const fromExecRoot = relative(bazelExecRoot, path);
+  const execRoot = effectiveExecRoot() ?? bazelExecRoot;
+
+  const fromExecRoot = relative(execRoot, path);
   if (!fromExecRoot.startsWith('..')) {
     return path;
   }
 
   const fromBinDirectory = relative(bazelBinDirectory, path);
-  if (fromBinDirectory.startsWith('..')) {
-    return path;
+  if (!fromBinDirectory.startsWith('..')) {
+    return join(execRoot, fromBinDirectory);
+  }
+
+  // A path that realpath resolved out of a symlink-staged sandbox into the
+  // unsandboxed execroot: re-anchor its execroot-relative tail.
+  const markerIndex = path.indexOf(execRootMarker);
+  if (markerIndex !== -1) {
+    const tail = path.slice(markerIndex + execRootMarker.length);
+    const workspaceEnd = tail.indexOf(sep);
+    if (workspaceEnd !== -1) {
+      return join(execRoot, tail.slice(workspaceEnd + 1));
+    }
   }
 
-  return join(bazelExecRoot, fromBinDirectory);
+  return path;
 }