refactor: simplify Logger in schematics context

Before it was a full Logger, now we properly export a new LoggerApi
that only contain logging APIs. We also added a facade to avoid
recasting shenanigans.

Author: hansl

packages/angular_devkit/core/src/logger/logger.ts

@@ -22,11 +22,20 @@ export interface LogEntry extends LoggerMetadata {
   message: string;
   timestamp: number;
 }
+export interface LoggerApi {
+  createChild(name: string): Logger;
+  log(level: LogLevel, message: string, metadata?: JsonObject): void;
+  debug(message: string, metadata?: JsonObject): void;
+  info(message: string, metadata?: JsonObject): void;
+  warn(message: string, metadata?: JsonObject): void;
+  error(message: string, metadata?: JsonObject): void;
+  fatal(message: string, metadata?: JsonObject): void;
+}
 
 export type LogLevel = 'debug' | 'info' | 'warn' | 'error' | 'fatal';
 
 
-export class Logger extends Observable<LogEntry> {
+export class Logger extends Observable<LogEntry> implements LoggerApi {
   protected readonly _subject: Subject<LogEntry> = new Subject<LogEntry>();
   protected _metadata: LoggerMetadata;
 
@@ -74,6 +83,24 @@ export class Logger extends Observable<LogEntry> {
     }
   }
 
+  asApi(): LoggerApi {
+    return {
+      createChild: (name: string) => this.createChild(name),
+      log: (level: LogLevel, message: string, metadata?: JsonObject) => {
+        return this.log(level, message, metadata);
+      },
+      debug: (message: string, metadata?: JsonObject) => this.debug(message, metadata),
+      info: (message: string, metadata?: JsonObject) => this.info(message, metadata),
+      warn: (message: string, metadata?: JsonObject) => this.warn(message, metadata),
+      error: (message: string, metadata?: JsonObject) => this.error(message, metadata),
+      fatal: (message: string, metadata?: JsonObject) => this.fatal(message, metadata),
+    };
+  }
+
+  createChild(name: string) {
+    return new Logger(name, this);
+  }
+
   complete() {
     this._subject.complete();
   }

packages/angular_devkit/core/src/logger/logger_spec.ts

@@ -52,4 +52,22 @@ describe('Logger', () => {
     childLogger.info('world');
     logger.complete();
   });
+
+  it('misses messages if not subscribed', (done: DoneFn) => {
+    const logger = new Logger('test');
+    logger.debug('woah');
+
+    logger
+      .toArray()
+      .toPromise()
+      .then((observed: JsonValue[]) => {
+        expect(observed).toEqual([
+          jasmine.objectContaining({ message: 'hello', level: 'debug', name: 'test' }) as any,
+        ]);
+      })
+      .then(() => done(), err => done.fail(err));
+
+    logger.debug('hello');
+    logger.complete();
+  });
 });

packages/angular_devkit/core/src/logger/null-logger.ts

@@ -7,12 +7,24 @@
  */
 import { Observable } from 'rxjs/Observable';
 import 'rxjs/add/observable/empty';
-import { Logger } from './logger';
+import { Logger, LoggerApi } from './logger';
 
 
 export class NullLogger extends Logger {
   constructor(parent: Logger | null = null) {
     super('', parent);
     this._observable = Observable.empty();
   }
+
+  asApi(): LoggerApi {
+    return {
+      createChild: () => new NullLogger(this),
+      log() {},
+      debug() {},
+      info() {},
+      warn() {},
+      error() {},
+      fatal() {},
+    } as LoggerApi;
+  }
 }

packages/angular_devkit/schematics/bin/schematics.ts

@@ -244,7 +244,7 @@ delete args._;
  * Then we proceed to run the dryRun commit. We run this before we then commit to the filesystem
  * (if --dry-run was not passed or an error was detected by dryRun).
  */
-schematic.call(args, host, { debug, logger })
+schematic.call(args, host, { debug, logger: logger.asApi() })
   .map((tree: Tree) => Tree.optimize(tree))
   .concatMap((tree: Tree) => {
     return dryRunSink.commit(tree).ignoreElements().concat(Observable.of(tree));

packages/angular_devkit/schematics/src/engine/interface.ts

@@ -5,7 +5,7 @@
  * Use of this source code is governed by an MIT-style license that can be
  * found in the LICENSE file at https://angular.io/license
  */
-import { Logger } from '@angular-devkit/core';
+import { LoggerApi } from '@angular-devkit/core';
 import { Observable } from 'rxjs/Observable';
 import { Url } from 'url';
 import { FileEntry, MergeStrategy, Tree } from '../tree/interface';
@@ -128,7 +128,7 @@ export interface TypedSchematicContext<CollectionMetadataT extends object,
                                        SchematicMetadataT extends object> {
   readonly debug: boolean;
   readonly engine: Engine<CollectionMetadataT, SchematicMetadataT>;
-  readonly logger: Logger;
+  readonly logger: LoggerApi;
   readonly schematic: Schematic<CollectionMetadataT, SchematicMetadataT>;
   readonly strategy: MergeStrategy;
 }