refactor(ngcc): simplify cluster PackageJsonUpdater

Author: petebacondarwin

packages/compiler-cli/ngcc/src/execution/cluster/package_json_updater.ts

@@ -18,26 +18,26 @@ import {sendMessageToMaster} from './utils';
 
 
 /**
- * A `PackageJsonUpdater` that can safely handle update operations on multiple processes.
+ * A `PackageJsonUpdater` for cluster workers that will send update changes to the master process so
+ * that it can safely handle update operations on multiple processes.
  */
-export class ClusterPackageJsonUpdater implements PackageJsonUpdater {
-  constructor(private delegate: PackageJsonUpdater) {}
+export class ClusterWorkerPackageJsonUpdater implements PackageJsonUpdater {
+  constructor() {
+    if (cluster.isMaster) {
+      throw new Error('Tried to create cluster worker PackageJsonUpdater on the master process.');
+    }
+  }
 
   createUpdate(): PackageJsonUpdate {
     return new PackageJsonUpdate((...args) => this.writeChanges(...args));
   }
 
+  /**
+   * Apply the changes in-memory (if necessary) and send a message to the master process.
+   */
   writeChanges(
       changes: PackageJsonChange[], packageJsonPath: AbsoluteFsPath,
       preExistingParsedJson?: JsonObject): void {
-    if (cluster.isMaster) {
-      // This is the master process:
-      // Actually apply the changes to the file on disk.
-      return this.delegate.writeChanges(changes, packageJsonPath, preExistingParsedJson);
-    }
-
-    // This is a worker process:
-    // Apply the changes in-memory (if necessary) and send a message to the master process.
     if (preExistingParsedJson) {
       for (const [propPath, value] of changes) {
         if (propPath.length === 0) {

packages/compiler-cli/ngcc/src/execution/cluster/worker.ts

@@ -21,7 +21,7 @@ import {getCreateCompileFn} from '../create_compile_function';
 import {stringifyTask} from '../tasks/utils';
 
 import {MessageToWorker} from './api';
-import {ClusterPackageJsonUpdater} from './package_json_updater';
+import {ClusterWorkerPackageJsonUpdater} from './package_json_updater';
 import {sendMessageToMaster} from './utils';
 
 // Cluster worker entry point
@@ -55,8 +55,7 @@ if (require.main === module) {
         pathMappings = getPathMappingsFromTsConfig(tsConfig, projectPath);
       }
 
-      const pkgJsonUpdater =
-          new ClusterPackageJsonUpdater(new DirectPackageJsonUpdater(fileSystem));
+      const pkgJsonUpdater = new ClusterWorkerPackageJsonUpdater();
 
       // The function for creating the `compile()` function.
       const createCompileFn = getCreateCompileFn(

packages/compiler-cli/ngcc/src/main.ts

@@ -26,7 +26,6 @@ import {TargetedEntryPointFinder} from './entry_point_finder/targeted_entry_poin
 import {getAnalyzeEntryPointsFn} from './execution/analyze_entry_points';
 import {Executor} from './execution/api';
 import {ClusterExecutor} from './execution/cluster/executor';
-import {ClusterPackageJsonUpdater} from './execution/cluster/package_json_updater';
 import {getCreateCompileFn} from './execution/create_compile_function';
 import {SingleProcessExecutorAsync, SingleProcessExecutorSync} from './execution/single_process_executor';
 import {CreateTaskCompletedCallback, TaskProcessingOutcome} from './execution/tasks/api';
@@ -105,11 +104,7 @@ export function mainNgcc({
     return;
   }
 
-  // NOTE: To avoid file corruption, ensure that each `ngcc` invocation only creates _one_ instance
-  //       of `PackageJsonUpdater` that actually writes to disk (across all processes).
-  //       This is hard to enforce automatically, when running on multiple processes, so needs to be
-  //       enforced manually.
-  const pkgJsonUpdater = getPackageJsonUpdater(inParallel, fileSystem);
+  const pkgJsonUpdater = new DirectPackageJsonUpdater(fileSystem);
 
   const analyzeEntryPoints = getAnalyzeEntryPointsFn(
       logger, finder, fileSystem, supportedPropertiesToConsider, compileAllFormats,
@@ -151,11 +146,6 @@ function ensureSupportedProperties(properties: string[]): EntryPointJsonProperty
   return supportedProperties;
 }
 
-function getPackageJsonUpdater(inParallel: boolean, fs: FileSystem): PackageJsonUpdater {
-  const directPkgJsonUpdater = new DirectPackageJsonUpdater(fs);
-  return inParallel ? new ClusterPackageJsonUpdater(directPkgJsonUpdater) : directPkgJsonUpdater;
-}
-
 function getCreateTaskCompletedCallback(
     pkgJsonUpdater: PackageJsonUpdater, errorOnFailedEntryPoint: boolean, logger: Logger,
     fileSystem: FileSystem): CreateTaskCompletedCallback {