fix(@angular-devkit/schematics): handle updating renamed files

With this change we fix an issue which caused a file not found error when trying to modify the file after it was renamed.

Closes #14255 and closes #21083

(cherry picked from commit a30525b)

Author: alan-agius4

packages/angular_devkit/schematics/src/sink/host.ts

@@ -36,13 +36,22 @@ export class HostSink extends SimpleSinkBase {
   protected _validateFileExists(p: Path): Observable<boolean> {
     if (this._filesToCreate.has(p) || this._filesToUpdate.has(p)) {
       return observableOf(true);
-    } else if (this._filesToDelete.has(p)) {
-      return observableOf(false);
-    } else if ([...this._filesToRename.values()].some(([from]) => from == p)) {
+    }
+
+    if (this._filesToDelete.has(p)) {
       return observableOf(false);
-    } else {
-      return this._host.exists(p);
     }
+
+    for (const [from, to] of this._filesToRename.values()) {
+      switch (p) {
+        case from:
+          return observableOf(false);
+        case to:
+          return observableOf(true);
+      }
+    }
+
+    return this._host.exists(p);
   }
 
   protected _overwriteFile(path: Path, content: Buffer): Observable<void> {
@@ -82,12 +91,12 @@ export class HostSink extends SimpleSinkBase {
       ),
       observableFrom([...this._filesToCreate.entries()]).pipe(
         concatMap(([path, buffer]) => {
-          return this._host.write(path, (buffer.generate() as {}) as virtualFs.FileBuffer);
+          return this._host.write(path, buffer.generate() as {} as virtualFs.FileBuffer);
         }),
       ),
       observableFrom([...this._filesToUpdate.entries()]).pipe(
         concatMap(([path, buffer]) => {
-          return this._host.write(path, (buffer.generate() as {}) as virtualFs.FileBuffer);
+          return this._host.write(path, buffer.generate() as {} as virtualFs.FileBuffer);
         }),
       ),
     ).pipe(reduce(() => {}));

packages/angular_devkit/schematics/src/sink/host_spec.ts

@@ -135,5 +135,22 @@ describe('FileSystemSink', () => {
         })
         .then(done, done.fail);
     });
+
+    it('can rename then modify the same file', async () => {
+      const host = new virtualFs.test.TestHost({
+        '/file0': 'world',
+      });
+      const tree = new HostTree(host);
+
+      tree.rename('/file0', '/file1');
+      expect(tree.exists('/file0')).toBeFalsy();
+      expect(tree.exists('/file1')).toBeTruthy();
+
+      tree.overwrite('/file1', 'hello');
+
+      const sink = new HostSink(host);
+      await sink.commit(tree).toPromise();
+      expect(virtualFs.fileBufferToString(host.sync.read(normalize('/file1')))).toBe('hello');
+    });
   });
 });