feat(@angular-devkit/core): add a recording host

Doing changes to that host will create records for CREATE, OVERWRITE, RENAME
and DELETE. Those records can then be applied to other hosts.

This directly goes in sync with Tree, and will replace the backend for Trees.

packages/angular_devkit/core/src/exception/exception.ts

@@ -13,6 +13,11 @@ export class BaseException extends Error {
 }
 
 
+export class UnknownException extends Error {
+  constructor(message: string) { super(message); }
+}
+
+
 // Exceptions
 export class FileDoesNotExistException extends BaseException {
   constructor(path: string) { super(`Path "${path}" does not exist.`); }

packages/angular_devkit/core/src/virtual-fs/host/memory.ts

@@ -38,11 +38,13 @@ export interface SimpleMemoryHostStats {
 }
 
 export class SimpleMemoryHost implements Host<{}> {
-  private _cache = new Map<Path, Stats<SimpleMemoryHostStats>>();
+  protected readonly _cache = new Map<Path, Stats<SimpleMemoryHostStats>>();
   private _watchers = new Map<Path, [HostWatchOptions, Subject<HostWatchEvent>][]>();
 
   protected _newDirStats() {
     return {
+      inspect() { return '<Directory>'; },
+
       isFile() { return false; },
       isDirectory() { return true; },
       size: 0,
@@ -57,6 +59,8 @@ export class SimpleMemoryHost implements Host<{}> {
   }
   protected _newFileStats(content: FileBuffer, oldStats?: Stats<SimpleMemoryHostStats>) {
     return {
+      inspect() { return `<File size(${content.byteLength})>`; },
+
       isFile() { return true; },
       isDirectory() { return false; },
       size: content.byteLength,
@@ -158,7 +162,7 @@ export class SimpleMemoryHost implements Host<{}> {
     this._cache.set(path, stats);
     this._updateWatchers(path, old ? HostWatchEventType.Changed : HostWatchEventType.Created);
   }
-  _read(path: Path): FileBuffer {
+  protected _read(path: Path): FileBuffer {
     path = this._toAbsolute(path);
     const maybeStats = this._cache.get(path);
     if (!maybeStats) {
@@ -171,7 +175,7 @@ export class SimpleMemoryHost implements Host<{}> {
       return maybeStats.content;
     }
   }
-  _delete(path: Path): void {
+  protected _delete(path: Path): void {
     path = this._toAbsolute(path);
     if (this._isDirectory(path)) {
       for (const [cachePath, _] of this._cache.entries()) {
@@ -184,7 +188,7 @@ export class SimpleMemoryHost implements Host<{}> {
     }
     this._updateWatchers(path, HostWatchEventType.Deleted);
   }
-  _rename(from: Path, to: Path): void {
+  protected _rename(from: Path, to: Path): void {
     from = this._toAbsolute(from);
     to = this._toAbsolute(to);
     if (!this._cache.has(from)) {
@@ -214,7 +218,7 @@ export class SimpleMemoryHost implements Host<{}> {
     this._updateWatchers(from, HostWatchEventType.Renamed);
   }
 
-  _list(path: Path): PathFragment[] {
+  protected _list(path: Path): PathFragment[] {
     path = this._toAbsolute(path);
     if (this._isFile(path)) {
       throw new PathIsFileException(path);
@@ -239,21 +243,21 @@ export class SimpleMemoryHost implements Host<{}> {
     return [...result];
   }
 
-  _exists(path: Path): boolean {
+  protected _exists(path: Path): boolean {
     return !!this._cache.get(this._toAbsolute(path));
   }
-  _isDirectory(path: Path): boolean {
+  protected _isDirectory(path: Path): boolean {
     const maybeStats = this._cache.get(this._toAbsolute(path));
 
     return maybeStats ? maybeStats.isDirectory() : false;
   }
-  _isFile(path: Path): boolean {
+  protected _isFile(path: Path): boolean {
     const maybeStats = this._cache.get(this._toAbsolute(path));
 
     return maybeStats ? maybeStats.isFile() : false;
   }
 
-  _stat(path: Path): Stats<SimpleMemoryHostStats> {
+  protected _stat(path: Path): Stats<SimpleMemoryHostStats> {
     const maybeStats = this._cache.get(this._toAbsolute(path));
 
     if (!maybeStats) {
@@ -263,6 +267,21 @@ export class SimpleMemoryHost implements Host<{}> {
     }
   }
 
+  protected _watch(path: Path, options?: HostWatchOptions): Observable<HostWatchEvent> {
+    path = this._toAbsolute(path);
+
+    const subject = new Subject<HostWatchEvent>();
+    let maybeWatcherArray = this._watchers.get(path);
+    if (!maybeWatcherArray) {
+      maybeWatcherArray = [];
+      this._watchers.set(path, maybeWatcherArray);
+    }
+
+    maybeWatcherArray.push([options || {}, subject]);
+
+    return subject.asObservable();
+  }
+
   write(path: Path, content: FileBuffer): Observable<void> {
     return new Observable<void>(obs => {
       this._write(path, content);
@@ -332,17 +351,6 @@ export class SimpleMemoryHost implements Host<{}> {
   }
 
   watch(path: Path, options?: HostWatchOptions): Observable<HostWatchEvent> | null {
-    path = this._toAbsolute(path);
-
-    const subject = new Subject<HostWatchEvent>();
-    let maybeWatcherArray = this._watchers.get(path);
-    if (!maybeWatcherArray) {
-      maybeWatcherArray = [];
-      this._watchers.set(path, maybeWatcherArray);
-    }
-
-    maybeWatcherArray.push([options || {}, subject]);
-
-    return subject.asObservable();
+    return this._watch(path, options);
   }
 }