refactor(ivy): implement a virtual file-system layer in ngtsc + ngcc (#30921)

To improve cross platform support, all file access (and path manipulation)
is now done through a well known interface (`FileSystem`).

For testing a number of `MockFileSystem` implementations are provided.
These provide an in-memory file-system which emulates operating systems
like OS/X, Unix and Windows.

The current file system is always available via the static method,
`FileSystem.getFileSystem()`. This is also used by a number of static
methods on `AbsoluteFsPath` and `PathSegment`, to avoid having to pass
`FileSystem` objects around all the time. The result of this is that one
must be careful to ensure that the file-system has been initialized before
using any of these static methods. To prevent this happening accidentally
the current file system always starts out as an instance of `InvalidFileSystem`,
which will throw an error if any of its methods are called.

You can set the current file-system by calling `FileSystem.setFileSystem()`.
During testing you can call the helper function `initMockFileSystem(os)`
which takes a string name of the OS to emulate, and will also monkey-patch
aspects of the TypeScript library to ensure that TS is also using the
current file-system.

Finally there is the `NgtscCompilerHost` to be used for any TypeScript
compilation, which uses a given file-system.

All tests that interact with the file-system should be tested against each
of the mock file-systems. A series of helpers have been provided to support
such tests:

* `runInEachFileSystem()` - wrap your tests in this helper to run all the
wrapped tests in each of the mock file-systems.
* `addTestFilesToFileSystem()` - use this to add files and their contents
to the mock file system for testing.
* `loadTestFilesFromDisk()` - use this to load a mirror image of files on
disk into the in-memory mock file-system.
* `loadFakeCore()` - use this to load a fake version of `@angular/core`
into the mock file-system.

All ngcc and ngtsc source and tests now use this virtual file-system setup.

PR Close #30921

packages/compiler-cli/ngcc/src/analysis/decoration_analyzer.ts

@@ -10,14 +10,13 @@ import * as ts from 'typescript';
 
 import {BaseDefDecoratorHandler, ComponentDecoratorHandler, DirectiveDecoratorHandler, InjectableDecoratorHandler, NgModuleDecoratorHandler, PipeDecoratorHandler, ReferencesRegistry, ResourceLoader} from '../../../src/ngtsc/annotations';
 import {CycleAnalyzer, ImportGraph} from '../../../src/ngtsc/cycles';
+import {AbsoluteFsPath, FileSystem, LogicalFileSystem, absoluteFrom, dirname, resolve} from '../../../src/ngtsc/file_system';
 import {AbsoluteModuleStrategy, LocalIdentifierStrategy, LogicalProjectStrategy, ModuleResolver, NOOP_DEFAULT_IMPORT_RECORDER, ReferenceEmitter} from '../../../src/ngtsc/imports';
 import {CompoundMetadataReader, CompoundMetadataRegistry, DtsMetadataReader, LocalMetadataRegistry} from '../../../src/ngtsc/metadata';
 import {PartialEvaluator} from '../../../src/ngtsc/partial_evaluator';
-import {AbsoluteFsPath, LogicalFileSystem} from '../../../src/ngtsc/path';
 import {ClassDeclaration, ClassSymbol, Decorator} from '../../../src/ngtsc/reflection';
 import {LocalModuleScopeRegistry, MetadataDtsModuleScopeResolver} from '../../../src/ngtsc/scope';
 import {CompileResult, DecoratorHandler, DetectResult, HandlerPrecedence} from '../../../src/ngtsc/transform';
-import {FileSystem} from '../file_system/file_system';
 import {NgccReflectionHost} from '../host/ngcc_host';
 import {isDefined} from '../utils';
 
@@ -57,9 +56,9 @@ class NgccResourceLoader implements ResourceLoader {
   constructor(private fs: FileSystem) {}
   canPreload = false;
   preload(): undefined|Promise<void> { throw new Error('Not implemented.'); }
-  load(url: string): string { return this.fs.readFile(AbsoluteFsPath.resolve(url)); }
+  load(url: string): string { return this.fs.readFile(resolve(url)); }
   resolve(url: string, containingFile: string): string {
-    return AbsoluteFsPath.resolve(AbsoluteFsPath.dirname(AbsoluteFsPath.from(containingFile)), url);
+    return resolve(dirname(absoluteFrom(containingFile)), url);
   }
 }
 

packages/compiler-cli/ngcc/src/analysis/private_declarations_analyzer.ts

@@ -7,7 +7,7 @@
  */
 import * as ts from 'typescript';
 
-import {AbsoluteFsPath} from '../../../src/ngtsc/path';
+import {AbsoluteFsPath, absoluteFromSourceFile} from '../../../src/ngtsc/file_system';
 import {Declaration} from '../../../src/ngtsc/reflection';
 import {NgccReflectionHost} from '../host/ngcc_host';
 import {hasNameIdentifier, isDefined} from '../utils';
@@ -94,12 +94,11 @@ export class PrivateDeclarationsAnalyzer {
     });
 
     return Array.from(privateDeclarations.keys()).map(id => {
-      const from = AbsoluteFsPath.fromSourceFile(id.getSourceFile());
+      const from = absoluteFromSourceFile(id.getSourceFile());
       const declaration = privateDeclarations.get(id) !;
       const alias = exportAliasDeclarations.has(id) ? exportAliasDeclarations.get(id) ! : null;
       const dtsDeclaration = this.host.getDtsDeclaration(declaration.node);
-      const dtsFrom =
-          dtsDeclaration && AbsoluteFsPath.fromSourceFile(dtsDeclaration.getSourceFile());
+      const dtsFrom = dtsDeclaration && absoluteFromSourceFile(dtsDeclaration.getSourceFile());
 
       return {identifier: id.text, from, dtsFrom, alias};
     });

packages/compiler-cli/ngcc/src/dependencies/commonjs_dependency_host.ts

@@ -6,11 +6,8 @@
  * found in the LICENSE file at https://angular.io/license
  */
 import * as ts from 'typescript';
-
-import {AbsoluteFsPath, PathSegment} from '../../../src/ngtsc/path';
-import {FileSystem} from '../file_system/file_system';
+import {AbsoluteFsPath, FileSystem, PathSegment} from '../../../src/ngtsc/file_system';
 import {isRequireCall} from '../host/commonjs_host';
-
 import {DependencyHost, DependencyInfo} from './dependency_host';
 import {ModuleResolver, ResolvedDeepImport, ResolvedRelativeModule} from './module_resolver';
 

packages/compiler-cli/ngcc/src/dependencies/dependency_host.ts

@@ -6,7 +6,7 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {AbsoluteFsPath, PathSegment} from '../../../src/ngtsc/path';
+import {AbsoluteFsPath, PathSegment} from '../../../src/ngtsc/file_system';
 
 export interface DependencyHost {
   findDependencies(entryPointPath: AbsoluteFsPath): DependencyInfo;

packages/compiler-cli/ngcc/src/dependencies/dependency_resolver.ts

@@ -7,8 +7,7 @@
  */
 
 import {DepGraph} from 'dependency-graph';
-import {AbsoluteFsPath} from '../../../src/ngtsc/path';
-import {FileSystem} from '../file_system/file_system';
+import {AbsoluteFsPath, FileSystem, resolve} from '../../../src/ngtsc/file_system';
 import {Logger} from '../logging/logger';
 import {EntryPoint, EntryPointFormat, EntryPointJsonProperty, getEntryPointFormat} from '../packages/entry_point';
 import {DependencyHost} from './dependency_host';
@@ -176,7 +175,7 @@ export class DependencyResolver {
 
       if (format === 'esm2015' || format === 'esm5' || format === 'umd' || format === 'commonjs') {
         const formatPath = entryPoint.packageJson[property] !;
-        return {format, path: AbsoluteFsPath.resolve(entryPoint.path, formatPath)};
+        return {format, path: resolve(entryPoint.path, formatPath)};
       }
     }
     throw new Error(

packages/compiler-cli/ngcc/src/dependencies/esm_dependency_host.ts

@@ -6,13 +6,10 @@
  * found in the LICENSE file at https://angular.io/license
  */
 import * as ts from 'typescript';
-
-import {AbsoluteFsPath, PathSegment} from '../../../src/ngtsc/path';
-import {FileSystem} from '../file_system/file_system';
+import {AbsoluteFsPath, FileSystem, PathSegment} from '../../../src/ngtsc/file_system';
 import {DependencyHost, DependencyInfo} from './dependency_host';
 import {ModuleResolver, ResolvedDeepImport, ResolvedRelativeModule} from './module_resolver';
 
-
 /**
  * Helper functions for computing dependencies.
  */

packages/compiler-cli/ngcc/src/dependencies/module_resolver.ts

@@ -6,10 +6,11 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {AbsoluteFsPath} from '../../../src/ngtsc/path';
-import {FileSystem} from '../file_system/file_system';
+import {AbsoluteFsPath, FileSystem, absoluteFrom, dirname, isRoot, join, resolve} from '../../../src/ngtsc/file_system';
 import {PathMappings, isRelativePath} from '../utils';
 
+
+
 /**
  * This is a very cut-down implementation of the TypeScript module resolution strategy.
  *
@@ -55,7 +56,7 @@ export class ModuleResolver {
    * Convert the `pathMappings` into a collection of `PathMapper` functions.
    */
   private processPathMappings(pathMappings: PathMappings): ProcessedPathMapping[] {
-    const baseUrl = AbsoluteFsPath.from(pathMappings.baseUrl);
+    const baseUrl = absoluteFrom(pathMappings.baseUrl);
     return Object.keys(pathMappings.paths).map(pathPattern => {
       const matcher = splitOnStar(pathPattern);
       const templates = pathMappings.paths[pathPattern].map(splitOnStar);
@@ -71,9 +72,8 @@ export class ModuleResolver {
    * If neither of these files exist then the method returns `null`.
    */
   private resolveAsRelativePath(moduleName: string, fromPath: AbsoluteFsPath): ResolvedModule|null {
-    const resolvedPath = this.resolvePath(
-        AbsoluteFsPath.resolve(AbsoluteFsPath.dirname(fromPath), moduleName),
-        this.relativeExtensions);
+    const resolvedPath =
+        this.resolvePath(resolve(dirname(fromPath), moduleName), this.relativeExtensions);
     return resolvedPath && new ResolvedRelativeModule(resolvedPath);
   }
 
@@ -118,13 +118,13 @@ export class ModuleResolver {
    */
   private resolveAsEntryPoint(moduleName: string, fromPath: AbsoluteFsPath): ResolvedModule|null {
     let folder = fromPath;
-    while (!AbsoluteFsPath.isRoot(folder)) {
-      folder = AbsoluteFsPath.dirname(folder);
+    while (!isRoot(folder)) {
+      folder = dirname(folder);
       if (folder.endsWith('node_modules')) {
         // Skip up if the folder already ends in node_modules
-        folder = AbsoluteFsPath.dirname(folder);
+        folder = dirname(folder);
       }
-      const modulePath = AbsoluteFsPath.resolve(folder, 'node_modules', moduleName);
+      const modulePath = resolve(folder, 'node_modules', moduleName);
       if (this.isEntryPoint(modulePath)) {
         return new ResolvedExternalModule(modulePath);
       } else if (this.resolveAsRelativePath(modulePath, fromPath)) {
@@ -141,7 +141,7 @@ export class ModuleResolver {
    */
   private resolvePath(path: AbsoluteFsPath, postFixes: string[]): AbsoluteFsPath|null {
     for (const postFix of postFixes) {
-      const testPath = AbsoluteFsPath.fromUnchecked(path + postFix);
+      const testPath = absoluteFrom(path + postFix);
       if (this.fs.exists(testPath)) {
         return testPath;
       }
@@ -155,7 +155,7 @@ export class ModuleResolver {
    * This is achieved by checking for the existence of `${modulePath}/package.json`.
    */
   private isEntryPoint(modulePath: AbsoluteFsPath): boolean {
-    return this.fs.exists(AbsoluteFsPath.join(modulePath, 'package.json'));
+    return this.fs.exists(join(modulePath, 'package.json'));
   }
 
   /**
@@ -215,8 +215,7 @@ export class ModuleResolver {
    */
   private computeMappedTemplates(mapping: ProcessedPathMapping, match: string) {
     return mapping.templates.map(
-        template =>
-            AbsoluteFsPath.resolve(mapping.baseUrl, template.prefix + match + template.postfix));
+        template => resolve(mapping.baseUrl, template.prefix + match + template.postfix));
   }
 
   /**
@@ -225,9 +224,9 @@ export class ModuleResolver {
    */
   private findPackagePath(path: AbsoluteFsPath): AbsoluteFsPath|null {
     let folder = path;
-    while (!AbsoluteFsPath.isRoot(folder)) {
-      folder = AbsoluteFsPath.dirname(folder);
-      if (this.fs.exists(AbsoluteFsPath.join(folder, 'package.json'))) {
+    while (!isRoot(folder)) {
+      folder = dirname(folder);
+      if (this.fs.exists(join(folder, 'package.json'))) {
         return folder;
       }
     }

packages/compiler-cli/ngcc/src/dependencies/umd_dependency_host.ts

@@ -6,16 +6,11 @@
  * found in the LICENSE file at https://angular.io/license
  */
 import * as ts from 'typescript';
-
-import {AbsoluteFsPath, PathSegment} from '../../../src/ngtsc/path';
-import {FileSystem} from '../file_system/file_system';
+import {AbsoluteFsPath, FileSystem, PathSegment} from '../../../src/ngtsc/file_system';
 import {getImportsOfUmdModule, parseStatementForUmdModule} from '../host/umd_host';
-
 import {DependencyHost, DependencyInfo} from './dependency_host';
 import {ModuleResolver, ResolvedDeepImport, ResolvedRelativeModule} from './module_resolver';
 
-
-
 /**
  * Helper functions for computing dependencies.
  */

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

@@ -1,38 +0,0 @@
-/**
- * @license
- * Copyright Google Inc. All Rights Reserved.
- *
- * 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 {AbsoluteFsPath, PathSegment} from '../../../src/ngtsc/path';
-
-/**
- * A basic interface to abstract the underlying file-system.
- *
- * This makes it easier to provide mock file-systems in unit tests,
- * but also to create clever file-systems that have features such as caching.
- */
-export interface FileSystem {
-  exists(path: AbsoluteFsPath): boolean;
-  readFile(path: AbsoluteFsPath): string;
-  writeFile(path: AbsoluteFsPath, data: string): void;
-  readdir(path: AbsoluteFsPath): PathSegment[];
-  lstat(path: AbsoluteFsPath): FileStats;
-  stat(path: AbsoluteFsPath): FileStats;
-  pwd(): AbsoluteFsPath;
-  copyFile(from: AbsoluteFsPath, to: AbsoluteFsPath): void;
-  moveFile(from: AbsoluteFsPath, to: AbsoluteFsPath): void;
-  ensureDir(path: AbsoluteFsPath): void;
-}
-
-/**
- * Information about an object in the FileSystem.
- * This is analogous to the `fs.Stats` class in Node.js.
- */
-export interface FileStats {
-  isFile(): boolean;
-  isDirectory(): boolean;
-  isSymbolicLink(): boolean;
-}

packages/compiler-cli/ngcc/src/file_system/node_js_file_system.ts

@@ -1,30 +0,0 @@
-/**
- * @license
- * Copyright Google Inc. All Rights Reserved.
- *
- * 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 * as fs from 'fs';
-import {cp, mkdir, mv} from 'shelljs';
-import {AbsoluteFsPath, PathSegment} from '../../../src/ngtsc/path';
-import {FileSystem} from './file_system';
-
-/**
- * A wrapper around the Node.js file-system (i.e the `fs` package).
- */
-export class NodeJSFileSystem implements FileSystem {
-  exists(path: AbsoluteFsPath): boolean { return fs.existsSync(path); }
-  readFile(path: AbsoluteFsPath): string { return fs.readFileSync(path, 'utf8'); }
-  writeFile(path: AbsoluteFsPath, data: string): void {
-    return fs.writeFileSync(path, data, 'utf8');
-  }
-  readdir(path: AbsoluteFsPath): PathSegment[] { return fs.readdirSync(path) as PathSegment[]; }
-  lstat(path: AbsoluteFsPath): fs.Stats { return fs.lstatSync(path); }
-  stat(path: AbsoluteFsPath): fs.Stats { return fs.statSync(path); }
-  pwd() { return AbsoluteFsPath.from(process.cwd()); }
-  copyFile(from: AbsoluteFsPath, to: AbsoluteFsPath): void { cp(from, to); }
-  moveFile(from: AbsoluteFsPath, to: AbsoluteFsPath): void { mv(from, to); }
-  ensureDir(path: AbsoluteFsPath): void { mkdir('-p', path); }
-}

packages/compiler-cli/ngcc/src/host/commonjs_host.ts

@@ -7,7 +7,7 @@
  */
 
 import * as ts from 'typescript';
-
+import {absoluteFrom} from '../../../src/ngtsc/file_system';
 import {Declaration, Import} from '../../../src/ngtsc/reflection';
 import {Logger} from '../logging/logger';
 import {BundleProgram} from '../packages/bundle_program';
@@ -122,13 +122,13 @@ export class CommonJsReflectionHost extends Esm5ReflectionHost {
     if (this.compilerHost.resolveModuleNames) {
       const moduleInfo =
           this.compilerHost.resolveModuleNames([moduleName], containingFile.fileName)[0];
-      return moduleInfo && this.program.getSourceFile(moduleInfo.resolvedFileName);
+      return moduleInfo && this.program.getSourceFile(absoluteFrom(moduleInfo.resolvedFileName));
     } else {
       const moduleInfo = ts.resolveModuleName(
           moduleName, containingFile.fileName, this.program.getCompilerOptions(),
           this.compilerHost);
       return moduleInfo.resolvedModule &&
-          this.program.getSourceFile(moduleInfo.resolvedModule.resolvedFileName);
+          this.program.getSourceFile(absoluteFrom(moduleInfo.resolvedModule.resolvedFileName));
     }
   }
 }

packages/compiler-cli/ngcc/src/host/esm2015_host.ts

@@ -8,6 +8,7 @@
 
 import * as ts from 'typescript';
 
+import {AbsoluteFsPath} from '../../../src/ngtsc/file_system';
 import {ClassDeclaration, ClassMember, ClassMemberKind, ClassSymbol, CtorParameter, Declaration, Decorator, Import, TypeScriptReflectionHost, reflectObjectLiteral} from '../../../src/ngtsc/reflection';
 import {Logger} from '../logging/logger';
 import {BundleProgram} from '../packages/bundle_program';
@@ -1281,7 +1282,7 @@ export class Esm2015ReflectionHost extends TypeScriptReflectionHost implements N
    * @param dtsProgram The program containing all the typings files.
    * @returns a map of class names to class declarations.
    */
-  protected computeDtsDeclarationMap(dtsRootFileName: string, dtsProgram: ts.Program):
+  protected computeDtsDeclarationMap(dtsRootFileName: AbsoluteFsPath, dtsProgram: ts.Program):
       Map<string, ts.Declaration> {
     const dtsDeclarationMap = new Map<string, ts.Declaration>();
     const checker = dtsProgram.getTypeChecker();

packages/compiler-cli/ngcc/src/host/umd_host.ts

@@ -8,6 +8,7 @@
 
 import * as ts from 'typescript';
 
+import {absoluteFrom} from '../../../src/ngtsc/file_system';
 import {Declaration, Import} from '../../../src/ngtsc/reflection';
 import {Logger} from '../logging/logger';
 import {BundleProgram} from '../packages/bundle_program';
@@ -154,13 +155,13 @@ export class UmdReflectionHost extends Esm5ReflectionHost {
     if (this.compilerHost.resolveModuleNames) {
       const moduleInfo =
           this.compilerHost.resolveModuleNames([moduleName], containingFile.fileName)[0];
-      return moduleInfo && this.program.getSourceFile(moduleInfo.resolvedFileName);
+      return moduleInfo && this.program.getSourceFile(absoluteFrom(moduleInfo.resolvedFileName));
     } else {
       const moduleInfo = ts.resolveModuleName(
           moduleName, containingFile.fileName, this.program.getCompilerOptions(),
           this.compilerHost);
       return moduleInfo.resolvedModule &&
-          this.program.getSourceFile(moduleInfo.resolvedModule.resolvedFileName);
+          this.program.getSourceFile(absoluteFrom(moduleInfo.resolvedModule.resolvedFileName));
     }
   }
 }

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

@@ -5,15 +5,12 @@
  * 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 {AbsoluteFsPath} from '../../src/ngtsc/path';
-
+import {AbsoluteFsPath, FileSystem, absoluteFrom, getFileSystem, resolve} from '../../src/ngtsc/file_system';
 import {CommonJsDependencyHost} from './dependencies/commonjs_dependency_host';
 import {DependencyResolver} from './dependencies/dependency_resolver';
 import {EsmDependencyHost} from './dependencies/esm_dependency_host';
 import {ModuleResolver} from './dependencies/module_resolver';
 import {UmdDependencyHost} from './dependencies/umd_dependency_host';
-import {FileSystem} from './file_system/file_system';
-import {NodeJSFileSystem} from './file_system/node_js_file_system';
 import {ConsoleLogger, LogLevel} from './logging/console_logger';
 import {Logger} from './logging/logger';
 import {hasBeenProcessed, markAsProcessed} from './packages/build_marker';
@@ -79,7 +76,7 @@ export function mainNgcc(
     {basePath, targetEntryPointPath, propertiesToConsider = SUPPORTED_FORMAT_PROPERTIES,
      compileAllFormats = true, createNewEntryPointFormats = false,
      logger = new ConsoleLogger(LogLevel.info), pathMappings}: NgccOptions): void {
-  const fs = new NodeJSFileSystem();
+  const fs = getFileSystem();
   const transformer = new Transformer(fs, logger);
   const moduleResolver = new ModuleResolver(fs, pathMappings);
   const esmDependencyHost = new EsmDependencyHost(fs, moduleResolver);
@@ -95,7 +92,7 @@ export function mainNgcc(
   const fileWriter = getFileWriter(fs, createNewEntryPointFormats);
 
   const absoluteTargetEntryPointPath =
-      targetEntryPointPath ? AbsoluteFsPath.resolve(basePath, targetEntryPointPath) : undefined;
+      targetEntryPointPath ? resolve(basePath, targetEntryPointPath) : undefined;
 
   if (absoluteTargetEntryPointPath &&
       hasProcessedTargetEntryPoint(
@@ -104,8 +101,8 @@ export function mainNgcc(
     return;
   }
 
-  const {entryPoints, invalidEntryPoints} = finder.findEntryPoints(
-      AbsoluteFsPath.from(basePath), absoluteTargetEntryPointPath, pathMappings);
+  const {entryPoints, invalidEntryPoints} =
+      finder.findEntryPoints(absoluteFrom(basePath), absoluteTargetEntryPointPath, pathMappings);
 
   invalidEntryPoints.forEach(invalidEntryPoint => {
     logger.debug(
@@ -119,14 +116,13 @@ export function mainNgcc(
     return;
   }
 
-  entryPoints.forEach(entryPoint => {
+  for (const entryPoint of entryPoints) {
     // Are we compiling the Angular core?
     const isCore = entryPoint.name === '@angular/core';
 
     const compiledFormats = new Set<string>();
     const entryPointPackageJson = entryPoint.packageJson;
-    const entryPointPackageJsonPath =
-        AbsoluteFsPath.fromUnchecked(`${entryPoint.path}/package.json`);
+    const entryPointPackageJsonPath = fs.resolve(entryPoint.path, 'package.json');
 
     const hasProcessedDts = hasBeenProcessed(entryPointPackageJson, 'typings');
 
@@ -180,7 +176,7 @@ export function mainNgcc(
       throw new Error(
           `Failed to compile any formats for entry-point at (${entryPoint.path}). Tried ${propertiesToConsider}.`);
     }
-  });
+  }
 }
 
 function getFileWriter(fs: FileSystem, createNewEntryPointFormats: boolean): FileWriter {
@@ -190,7 +186,7 @@ function getFileWriter(fs: FileSystem, createNewEntryPointFormats: boolean): Fil
 function hasProcessedTargetEntryPoint(
     fs: FileSystem, targetPath: AbsoluteFsPath, propertiesToConsider: string[],
     compileAllFormats: boolean) {
-  const packageJsonPath = AbsoluteFsPath.resolve(targetPath, 'package.json');
+  const packageJsonPath = resolve(targetPath, 'package.json');
   const packageJson = JSON.parse(fs.readFile(packageJsonPath));
 
   for (const property of propertiesToConsider) {
@@ -221,7 +217,7 @@ function hasProcessedTargetEntryPoint(
  */
 function markNonAngularPackageAsProcessed(
     fs: FileSystem, path: AbsoluteFsPath, propertiesToConsider: string[]) {
-  const packageJsonPath = AbsoluteFsPath.resolve(path, 'package.json');
+  const packageJsonPath = resolve(path, 'package.json');
   const packageJson = JSON.parse(fs.readFile(packageJsonPath));
   propertiesToConsider.forEach(formatProperty => {
     if (packageJson[formatProperty])

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

@@ -5,9 +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 {AbsoluteFsPath} from '../../../src/ngtsc/path';
-import {FileSystem} from '../file_system/file_system';
+import {AbsoluteFsPath, FileSystem} from '../../../src/ngtsc/file_system';
 import {EntryPointJsonProperty, EntryPointPackageJson} from './entry_point';
 
 export const NGCC_VERSION = '0.0.0-PLACEHOLDER';

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

@@ -6,9 +6,7 @@
  * found in the LICENSE file at https://angular.io/license
  */
 import * as ts from 'typescript';
-
-import {AbsoluteFsPath} from '../../../src/ngtsc/path';
-import {FileSystem} from '../file_system/file_system';
+import {AbsoluteFsPath, FileSystem, dirname, resolve} from '../../../src/ngtsc/file_system';
 import {patchTsGetExpandoInitializer, restoreGetExpandoInitializer} from './patch_ts_expando_initializer';
 
 /**
@@ -35,12 +33,14 @@ export interface BundleProgram {
 export function makeBundleProgram(
     fs: FileSystem, isCore: boolean, path: AbsoluteFsPath, r3FileName: string,
     options: ts.CompilerOptions, host: ts.CompilerHost): BundleProgram {
-  const r3SymbolsPath =
-      isCore ? findR3SymbolsPath(fs, AbsoluteFsPath.dirname(path), r3FileName) : null;
+  const r3SymbolsPath = isCore ? findR3SymbolsPath(fs, dirname(path), r3FileName) : null;
   const rootPaths = r3SymbolsPath ? [path, r3SymbolsPath] : [path];
 
   const originalGetExpandoInitializer = patchTsGetExpandoInitializer();
   const program = ts.createProgram(rootPaths, options, host);
+  // Ask for the typeChecker to trigger the binding phase of the compilation.
+  // This will then exercise the patched function.
+  program.getTypeChecker();
   restoreGetExpandoInitializer(originalGetExpandoInitializer);
 
   const file = program.getSourceFile(path) !;
@@ -54,7 +54,7 @@ export function makeBundleProgram(
  */
 export function findR3SymbolsPath(
     fs: FileSystem, directory: AbsoluteFsPath, filename: string): AbsoluteFsPath|null {
-  const r3SymbolsFilePath = AbsoluteFsPath.resolve(directory, filename);
+  const r3SymbolsFilePath = resolve(directory, filename);
   if (fs.exists(r3SymbolsFilePath)) {
     return r3SymbolsFilePath;
   }
@@ -67,13 +67,12 @@ export function findR3SymbolsPath(
           .filter(p => p !== 'node_modules')
           // Only interested in directories (and only those that are not symlinks)
           .filter(p => {
-            const stat = fs.lstat(AbsoluteFsPath.resolve(directory, p));
+            const stat = fs.lstat(resolve(directory, p));
             return stat.isDirectory() && !stat.isSymbolicLink();
           });
 
   for (const subDirectory of subDirectories) {
-    const r3SymbolsFilePath =
-        findR3SymbolsPath(fs, AbsoluteFsPath.resolve(directory, subDirectory), filename);
+    const r3SymbolsFilePath = findR3SymbolsPath(fs, resolve(directory, subDirectory), filename);
     if (r3SymbolsFilePath) {
       return r3SymbolsFilePath;
     }

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

@@ -6,8 +6,7 @@
  * found in the LICENSE file at https://angular.io/license
  */
 import * as ts from 'typescript';
-import {AbsoluteFsPath} from '../../../src/ngtsc/path';
-import {FileSystem} from '../file_system/file_system';
+import {AbsoluteFsPath, FileSystem, join, resolve} from '../../../src/ngtsc/file_system';
 import {parseStatementForUmdModule} from '../host/umd_host';
 import {Logger} from '../logging/logger';
 
@@ -70,7 +69,7 @@ export const SUPPORTED_FORMAT_PROPERTIES: EntryPointJsonProperty[] =
 export function getEntryPointInfo(
     fs: FileSystem, logger: Logger, packagePath: AbsoluteFsPath,
     entryPointPath: AbsoluteFsPath): EntryPoint|null {
-  const packageJsonPath = AbsoluteFsPath.resolve(entryPointPath, 'package.json');
+  const packageJsonPath = resolve(entryPointPath, 'package.json');
   if (!fs.exists(packageJsonPath)) {
     return null;
   }
@@ -88,15 +87,14 @@ export function getEntryPointInfo(
   }
 
   // Also there must exist a `metadata.json` file next to the typings entry-point.
-  const metadataPath =
-      AbsoluteFsPath.resolve(entryPointPath, typings.replace(/\.d\.ts$/, '') + '.metadata.json');
+  const metadataPath = resolve(entryPointPath, typings.replace(/\.d\.ts$/, '') + '.metadata.json');
 
   const entryPointInfo: EntryPoint = {
     name: entryPointPackageJson.name,
     packageJson: entryPointPackageJson,
     package: packagePath,
     path: entryPointPath,
-    typings: AbsoluteFsPath.resolve(entryPointPath, typings),
+    typings: resolve(entryPointPath, typings),
     compiledByAngular: fs.exists(metadataPath),
   };
 
@@ -127,7 +125,7 @@ export function getEntryPointFormat(
       if (mainFile === undefined) {
         return undefined;
       }
-      const pathToMain = AbsoluteFsPath.join(entryPoint.path, mainFile);
+      const pathToMain = join(entryPoint.path, mainFile);
       return isUmdModule(fs, pathToMain) ? 'umd' : 'commonjs';
     case 'module':
       return 'esm5';

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

@@ -6,13 +6,13 @@
  * found in the LICENSE file at https://angular.io/license
  */
 import * as ts from 'typescript';
-
-import {AbsoluteFsPath} from '../../../src/ngtsc/path';
-import {FileSystem} from '../file_system/file_system';
+import {AbsoluteFsPath, FileSystem, absoluteFrom, resolve} from '../../../src/ngtsc/file_system';
+import {NgtscCompilerHost} from '../../../src/ngtsc/file_system/src/compiler_host';
 import {PathMappings} from '../utils';
 import {BundleProgram, makeBundleProgram} from './bundle_program';
 import {EntryPointFormat, EntryPointJsonProperty} from './entry_point';
-import {NgccCompilerHost, NgccSourcesCompilerHost} from './ngcc_compiler_host';
+import {NgccSourcesCompilerHost} from './ngcc_compiler_host';
+
 
 /**
  * A bundle of files and paths (and TS programs) that correspond to a particular
@@ -49,17 +49,16 @@ export function makeEntryPointBundle(
     rootDir: entryPointPath, ...pathMappings
   };
   const srcHost = new NgccSourcesCompilerHost(fs, options, entryPointPath);
-  const dtsHost = new NgccCompilerHost(fs, options);
-  const rootDirs = [AbsoluteFsPath.from(entryPointPath)];
+  const dtsHost = new NgtscCompilerHost(fs, options);
+  const rootDirs = [absoluteFrom(entryPointPath)];
 
   // Create the bundle programs, as necessary.
   const src = makeBundleProgram(
-      fs, isCore, AbsoluteFsPath.resolve(entryPointPath, formatPath), 'r3_symbols.js', options,
-      srcHost);
-  const dts = transformDts ? makeBundleProgram(
-                                 fs, isCore, AbsoluteFsPath.resolve(entryPointPath, typingsPath),
-                                 'r3_symbols.d.ts', options, dtsHost) :
-                             null;
+      fs, isCore, resolve(entryPointPath, formatPath), 'r3_symbols.js', options, srcHost);
+  const dts = transformDts ?
+      makeBundleProgram(
+          fs, isCore, resolve(entryPointPath, typingsPath), 'r3_symbols.d.ts', options, dtsHost) :
+      null;
   const isFlatCore = isCore && src.r3SymbolsFile === null;
 
   return {format, formatProperty, rootDirs, isCore, isFlatCore, src, dts};

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

@@ -5,11 +5,11 @@
  * 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 {AbsoluteFsPath} from '../../../src/ngtsc/path';
+import {AbsoluteFsPath, FileSystem, join, resolve} from '../../../src/ngtsc/file_system';
 import {DependencyResolver, SortedEntryPointsInfo} from '../dependencies/dependency_resolver';
-import {FileSystem} from '../file_system/file_system';
 import {Logger} from '../logging/logger';
 import {PathMappings} from '../utils';
+
 import {EntryPoint, getEntryPointInfo} from './entry_point';
 
 export class EntryPointFinder {
@@ -55,9 +55,9 @@ export class EntryPointFinder {
       AbsoluteFsPath[] {
     const basePaths = [sourceDirectory];
     if (pathMappings) {
-      const baseUrl = AbsoluteFsPath.resolve(pathMappings.baseUrl);
+      const baseUrl = resolve(pathMappings.baseUrl);
       values(pathMappings.paths).forEach(paths => paths.forEach(path => {
-        basePaths.push(AbsoluteFsPath.join(baseUrl, extractPathPrefix(path)));
+        basePaths.push(join(baseUrl, extractPathPrefix(path)));
       }));
     }
     basePaths.sort();  // Get the paths in order with the shorter ones first.
@@ -84,17 +84,17 @@ export class EntryPointFinder {
         .filter(p => p !== 'node_modules')
         // Only interested in directories (and only those that are not symlinks)
         .filter(p => {
-          const stat = this.fs.lstat(AbsoluteFsPath.resolve(sourceDirectory, p));
+          const stat = this.fs.lstat(resolve(sourceDirectory, p));
           return stat.isDirectory() && !stat.isSymbolicLink();
         })
         .forEach(p => {
           // Either the directory is a potential package or a namespace containing packages (e.g
           // `@angular`).
-          const packagePath = AbsoluteFsPath.join(sourceDirectory, p);
+          const packagePath = join(sourceDirectory, p);
           entryPoints.push(...this.walkDirectoryForEntryPoints(packagePath));
 
           // Also check for any nested node_modules in this package
-          const nestedNodeModulesPath = AbsoluteFsPath.join(packagePath, 'node_modules');
+          const nestedNodeModulesPath = join(packagePath, 'node_modules');
           if (this.fs.exists(nestedNodeModulesPath)) {
             entryPoints.push(...this.walkDirectoryForEntryPoints(nestedNodeModulesPath));
           }
@@ -145,11 +145,11 @@ export class EntryPointFinder {
         .filter(p => p !== 'node_modules')
         // Only interested in directories (and only those that are not symlinks)
         .filter(p => {
-          const stat = this.fs.lstat(AbsoluteFsPath.resolve(dir, p));
+          const stat = this.fs.lstat(resolve(dir, p));
           return stat.isDirectory() && !stat.isSymbolicLink();
         })
         .forEach(subDir => {
-          const resolvedSubDir = AbsoluteFsPath.resolve(dir, subDir);
+          const resolvedSubDir = resolve(dir, subDir);
           fn(resolvedSubDir);
           this.walkDirectory(resolvedSubDir, fn);
         });

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

@@ -5,74 +5,19 @@
  * 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 * as os from 'os';
 import * as ts from 'typescript';
 
-import {AbsoluteFsPath} from '../../../src/ngtsc/path';
-import {FileSystem} from '../file_system/file_system';
+import {FileSystem} from '../../../src/ngtsc/file_system';
+import {NgtscCompilerHost} from '../../../src/ngtsc/file_system/src/compiler_host';
 import {isRelativePath} from '../utils';
 
-export class NgccCompilerHost implements ts.CompilerHost {
-  private _caseSensitive = this.fs.exists(AbsoluteFsPath.fromUnchecked(__filename.toUpperCase()));
-
-  constructor(protected fs: FileSystem, protected options: ts.CompilerOptions) {}
-
-  getSourceFile(fileName: string, languageVersion: ts.ScriptTarget): ts.SourceFile|undefined {
-    const text = this.readFile(fileName);
-    return text !== undefined ? ts.createSourceFile(fileName, text, languageVersion) : undefined;
-  }
-
-  getDefaultLibFileName(options: ts.CompilerOptions): string {
-    return this.getDefaultLibLocation() + '/' + ts.getDefaultLibFileName(options);
-  }
-
-  getDefaultLibLocation(): string {
-    const nodeLibPath = AbsoluteFsPath.from(require.resolve('typescript'));
-    return AbsoluteFsPath.join(nodeLibPath, '..');
-  }
-
-  writeFile(fileName: string, data: string): void {
-    this.fs.writeFile(AbsoluteFsPath.fromUnchecked(fileName), data);
-  }
-
-  getCurrentDirectory(): string { return this.fs.pwd(); }
-
-  getCanonicalFileName(fileName: string): string {
-    return this.useCaseSensitiveFileNames ? fileName : fileName.toLowerCase();
-  }
-
-  useCaseSensitiveFileNames(): boolean { return this._caseSensitive; }
-
-  getNewLine(): string {
-    switch (this.options.newLine) {
-      case ts.NewLineKind.CarriageReturnLineFeed:
-        return '\r\n';
-      case ts.NewLineKind.LineFeed:
-        return '\n';
-      default:
-        return os.EOL;
-    }
-  }
-
-  fileExists(fileName: string): boolean {
-    return this.fs.exists(AbsoluteFsPath.fromUnchecked(fileName));
-  }
-
-  readFile(fileName: string): string|undefined {
-    if (!this.fileExists(fileName)) {
-      return undefined;
-    }
-    return this.fs.readFile(AbsoluteFsPath.fromUnchecked(fileName));
-  }
-}
-
 /**
  * Represents a compiler host that resolves a module import as a JavaScript source file if
  * available, instead of the .d.ts typings file that would have been resolved by TypeScript. This
  * is necessary for packages that have their typings in the same directory as the sources, which
  * would otherwise let TypeScript prefer the .d.ts file instead of the JavaScript source file.
  */
-export class NgccSourcesCompilerHost extends NgccCompilerHost {
+export class NgccSourcesCompilerHost extends NgtscCompilerHost {
   private cache = ts.createModuleResolutionCache(
       this.getCurrentDirectory(), file => this.getCanonicalFileName(file));
 

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

@@ -6,13 +6,12 @@
  * found in the LICENSE file at https://angular.io/license
  */
 import * as ts from 'typescript';
-
+import {FileSystem} from '../../../src/ngtsc/file_system';
 import {CompiledFile, DecorationAnalyzer} from '../analysis/decoration_analyzer';
 import {ModuleWithProvidersAnalyses, ModuleWithProvidersAnalyzer} from '../analysis/module_with_providers_analyzer';
 import {NgccReferencesRegistry} from '../analysis/ngcc_references_registry';
 import {ExportInfo, PrivateDeclarationsAnalyzer} from '../analysis/private_declarations_analyzer';
 import {SwitchMarkerAnalyses, SwitchMarkerAnalyzer} from '../analysis/switch_marker_analyzer';
-import {FileSystem} from '../file_system/file_system';
 import {CommonJsReflectionHost} from '../host/commonjs_host';
 import {Esm2015ReflectionHost} from '../host/esm2015_host';
 import {Esm5ReflectionHost} from '../host/esm5_host';
@@ -27,11 +26,8 @@ import {Renderer} from '../rendering/renderer';
 import {RenderingFormatter} from '../rendering/rendering_formatter';
 import {UmdRenderingFormatter} from '../rendering/umd_rendering_formatter';
 import {FileToWrite} from '../rendering/utils';
-
 import {EntryPointBundle} from './entry_point_bundle';
 
-
-
 /**
  * A Package is stored in a directory on disk and that directory can contain one or more package
  * formats - e.g. fesm2015, UMD, etc. Additionally, each package provides typings (`.d.ts` files).

packages/compiler-cli/ngcc/src/rendering/dts_renderer.ts

@@ -7,20 +7,19 @@
  */
 import MagicString from 'magic-string';
 import * as ts from 'typescript';
-
+import {FileSystem} from '../../../src/ngtsc/file_system';
+import {CompileResult} from '../../../src/ngtsc/transform';
 import {translateType, ImportManager} from '../../../src/ngtsc/translator';
 import {DecorationAnalyses} from '../analysis/decoration_analyzer';
 import {ModuleWithProvidersInfo, ModuleWithProvidersAnalyses} from '../analysis/module_with_providers_analyzer';
 import {PrivateDeclarationsAnalyses, ExportInfo} from '../analysis/private_declarations_analyzer';
 import {IMPORT_PREFIX} from '../constants';
-import {FileSystem} from '../file_system/file_system';
 import {NgccReflectionHost} from '../host/ngcc_host';
 import {EntryPointBundle} from '../packages/entry_point_bundle';
 import {Logger} from '../logging/logger';
 import {FileToWrite, getImportRewriter} from './utils';
 import {RenderingFormatter} from './rendering_formatter';
 import {extractSourceMap, renderSourceAndMap} from './source_maps';
-import {CompileResult} from '@angular/compiler-cli/src/ngtsc/transform';
 
 /**
  * A structure that captures information about what needs to be rendered

packages/compiler-cli/ngcc/src/rendering/esm_rendering_formatter.ts

@@ -7,7 +7,7 @@
  */
 import MagicString from 'magic-string';
 import * as ts from 'typescript';
-import {PathSegment, AbsoluteFsPath} from '../../../src/ngtsc/path';
+import {relative, dirname, AbsoluteFsPath, absoluteFromSourceFile} from '../../../src/ngtsc/file_system';
 import {Import, ImportManager} from '../../../src/ngtsc/translator';
 import {isDtsPath} from '../../../src/ngtsc/util/src/typescript';
 import {CompiledClass} from '../analysis/decoration_analyzer';
@@ -46,8 +46,7 @@ export class EsmRenderingFormatter implements RenderingFormatter {
 
       if (from) {
         const basePath = stripExtension(from);
-        const relativePath =
-            './' + PathSegment.relative(AbsoluteFsPath.dirname(entryPointBasePath), basePath);
+        const relativePath = './' + relative(dirname(entryPointBasePath), basePath);
         exportFrom = entryPointBasePath !== basePath ? ` from '${relativePath}'` : '';
       }
 
@@ -136,12 +135,11 @@ export class EsmRenderingFormatter implements RenderingFormatter {
       importManager: ImportManager): void {
     moduleWithProviders.forEach(info => {
       const ngModuleName = info.ngModule.node.name.text;
-      const declarationFile = AbsoluteFsPath.fromSourceFile(info.declaration.getSourceFile());
-      const ngModuleFile = AbsoluteFsPath.fromSourceFile(info.ngModule.node.getSourceFile());
+      const declarationFile = absoluteFromSourceFile(info.declaration.getSourceFile());
+      const ngModuleFile = absoluteFromSourceFile(info.ngModule.node.getSourceFile());
       const importPath = info.ngModule.viaModule ||
           (declarationFile !== ngModuleFile ?
-               stripExtension(
-                   `./${PathSegment.relative(AbsoluteFsPath.dirname(declarationFile), ngModuleFile)}`) :
+               stripExtension(`./${relative(dirname(declarationFile), ngModuleFile)}`) :
                null);
       const ngModule = generateImportString(importManager, importPath, ngModuleName);
 

packages/compiler-cli/ngcc/src/rendering/renderer.ts

@@ -8,14 +8,13 @@
 import {ConstantPool, Expression, Statement, WrappedNodeExpr, WritePropExpr} from '@angular/compiler';
 import MagicString from 'magic-string';
 import * as ts from 'typescript';
-
-import {NOOP_DEFAULT_IMPORT_RECORDER} from '@angular/compiler-cli/src/ngtsc/imports';
+import {NOOP_DEFAULT_IMPORT_RECORDER} from '../../../src/ngtsc/imports';
 import {translateStatement, ImportManager} from '../../../src/ngtsc/translator';
 import {CompiledClass, CompiledFile, DecorationAnalyses} from '../analysis/decoration_analyzer';
 import {PrivateDeclarationsAnalyses} from '../analysis/private_declarations_analyzer';
 import {SwitchMarkerAnalyses, SwitchMarkerAnalysis} from '../analysis/switch_marker_analyzer';
 import {IMPORT_PREFIX} from '../constants';
-import {FileSystem} from '../file_system/file_system';
+import {FileSystem} from '../../../src/ngtsc/file_system';
 import {NgccReflectionHost} from '../host/ngcc_host';
 import {EntryPointBundle} from '../packages/entry_point_bundle';
 import {Logger} from '../logging/logger';

packages/compiler-cli/ngcc/src/rendering/source_maps.ts

@@ -9,8 +9,7 @@ import {SourceMapConverter, commentRegex, fromJSON, fromObject, fromSource, gene
 import MagicString from 'magic-string';
 import {RawSourceMap, SourceMapConsumer, SourceMapGenerator} from 'source-map';
 import * as ts from 'typescript';
-import {AbsoluteFsPath, PathSegment} from '../../../src/ngtsc/path';
-import {FileSystem} from '../file_system/file_system';
+import {resolve, FileSystem, absoluteFromSourceFile, dirname, basename, absoluteFrom} from '../../../src/ngtsc/file_system';
 import {Logger} from '../logging/logger';
 import {FileToWrite} from './utils';
 
@@ -39,19 +38,18 @@ export function extractSourceMap(
     let externalSourceMap: SourceMapConverter|null = null;
     try {
       const fileName = external[1] || external[2];
-      const filePath = AbsoluteFsPath.resolve(
-          AbsoluteFsPath.dirname(AbsoluteFsPath.fromSourceFile(file)), fileName);
+      const filePath = resolve(dirname(absoluteFromSourceFile(file)), fileName);
       const mappingFile = fs.readFile(filePath);
       externalSourceMap = fromJSON(mappingFile);
     } catch (e) {
       if (e.code === 'ENOENT') {
         logger.warn(
             `The external map file specified in the source code comment "${e.path}" was not found on the file system.`);
-        const mapPath = AbsoluteFsPath.fromUnchecked(file.fileName + '.map');
-        if (PathSegment.basename(e.path) !== PathSegment.basename(mapPath) && fs.exists(mapPath) &&
+        const mapPath = absoluteFrom(file.fileName + '.map');
+        if (basename(e.path) !== basename(mapPath) && fs.exists(mapPath) &&
             fs.stat(mapPath).isFile()) {
           logger.warn(
-              `Guessing the map file name from the source file name: "${PathSegment.basename(mapPath)}"`);
+              `Guessing the map file name from the source file name: "${basename(mapPath)}"`);
           try {
             externalSourceMap = fromObject(JSON.parse(fs.readFile(mapPath)));
           } catch (e) {
@@ -76,9 +74,9 @@ export function extractSourceMap(
  */
 export function renderSourceAndMap(
     sourceFile: ts.SourceFile, input: SourceMapInfo, output: MagicString): FileToWrite[] {
-  const outputPath = AbsoluteFsPath.fromSourceFile(sourceFile);
-  const outputMapPath = AbsoluteFsPath.fromUnchecked(`${outputPath}.map`);
-  const relativeSourcePath = PathSegment.basename(outputPath);
+  const outputPath = absoluteFromSourceFile(sourceFile);
+  const outputMapPath = absoluteFrom(`${outputPath}.map`);
+  const relativeSourcePath = basename(outputPath);
   const relativeMapPath = `${relativeSourcePath}.map`;
 
   const outputMap = output.generateMap({

packages/compiler-cli/ngcc/src/rendering/utils.ts

@@ -6,8 +6,8 @@
  * found in the LICENSE file at https://angular.io/license
  */
 import * as ts from 'typescript';
+import {AbsoluteFsPath} from '../../../src/ngtsc/file_system';
 import {ImportRewriter, NoopImportRewriter, R3SymbolsImportRewriter} from '../../../src/ngtsc/imports';
-import {AbsoluteFsPath} from '../../../src/ngtsc/path';
 import {NgccFlatImportRewriter} from './ngcc_import_rewriter';
 
 /**

packages/compiler-cli/ngcc/src/writing/file_writer.ts

@@ -10,7 +10,6 @@ import {EntryPoint} from '../packages/entry_point';
 import {EntryPointBundle} from '../packages/entry_point_bundle';
 import {FileToWrite} from '../rendering/utils';
 
-
 /**
  * Responsible for writing out the transformed files to disk.
  */

packages/compiler-cli/ngcc/src/writing/in_place_file_writer.ts

@@ -6,8 +6,7 @@
  * 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 {AbsoluteFsPath} from '../../../src/ngtsc/path';
-import {FileSystem} from '../file_system/file_system';
+import {FileSystem, absoluteFrom, dirname} from '../../../src/ngtsc/file_system';
 import {EntryPoint} from '../packages/entry_point';
 import {EntryPointBundle} from '../packages/entry_point_bundle';
 import {FileToWrite} from '../rendering/utils';
@@ -25,8 +24,8 @@ export class InPlaceFileWriter implements FileWriter {
   }
 
   protected writeFileAndBackup(file: FileToWrite): void {
-    this.fs.ensureDir(AbsoluteFsPath.dirname(file.path));
-    const backPath = AbsoluteFsPath.fromUnchecked(`${file.path}.__ivy_ngcc_bak`);
+    this.fs.ensureDir(dirname(file.path));
+    const backPath = absoluteFrom(`${file.path}.__ivy_ngcc_bak`);
     if (this.fs.exists(backPath)) {
       throw new Error(
           `Tried to overwrite ${backPath} with an ngcc back up file, which is disallowed.`);

packages/compiler-cli/ngcc/src/writing/new_entry_point_file_writer.ts

@@ -6,7 +6,7 @@
  * 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 {AbsoluteFsPath, PathSegment} from '../../../src/ngtsc/path';
+import {AbsoluteFsPath, absoluteFromSourceFile, dirname, join, relative} from '../../../src/ngtsc/file_system';
 import {isDtsPath} from '../../../src/ngtsc/util/src/typescript';
 import {EntryPoint, EntryPointJsonProperty} from '../packages/entry_point';
 import {EntryPointBundle} from '../packages/entry_point_bundle';
@@ -27,7 +27,7 @@ const NGCC_DIRECTORY = '__ivy_ngcc__';
 export class NewEntryPointFileWriter extends InPlaceFileWriter {
   writeBundle(entryPoint: EntryPoint, bundle: EntryPointBundle, transformedFiles: FileToWrite[]) {
     // The new folder is at the root of the overall package
-    const ngccFolder = AbsoluteFsPath.join(entryPoint.package, NGCC_DIRECTORY);
+    const ngccFolder = join(entryPoint.package, NGCC_DIRECTORY);
     this.copyBundle(bundle, entryPoint.package, ngccFolder);
     transformedFiles.forEach(file => this.writeFile(file, entryPoint.package, ngccFolder));
     this.updatePackageJson(entryPoint, bundle.formatProperty, ngccFolder);
@@ -36,13 +36,12 @@ export class NewEntryPointFileWriter extends InPlaceFileWriter {
   protected copyBundle(
       bundle: EntryPointBundle, packagePath: AbsoluteFsPath, ngccFolder: AbsoluteFsPath) {
     bundle.src.program.getSourceFiles().forEach(sourceFile => {
-      const relativePath =
-          PathSegment.relative(packagePath, AbsoluteFsPath.fromSourceFile(sourceFile));
+      const relativePath = relative(packagePath, absoluteFromSourceFile(sourceFile));
       const isOutsidePackage = relativePath.startsWith('..');
       if (!sourceFile.isDeclarationFile && !isOutsidePackage) {
-        const newFilePath = AbsoluteFsPath.join(ngccFolder, relativePath);
-        this.fs.ensureDir(AbsoluteFsPath.dirname(newFilePath));
-        this.fs.copyFile(AbsoluteFsPath.fromSourceFile(sourceFile), newFilePath);
+        const newFilePath = join(ngccFolder, relativePath);
+        this.fs.ensureDir(dirname(newFilePath));
+        this.fs.copyFile(absoluteFromSourceFile(sourceFile), newFilePath);
       }
     });
   }
@@ -53,24 +52,20 @@ export class NewEntryPointFileWriter extends InPlaceFileWriter {
       // This is either `.d.ts` or `.d.ts.map` file
       super.writeFileAndBackup(file);
     } else {
-      const relativePath = PathSegment.relative(packagePath, file.path);
-      const newFilePath = AbsoluteFsPath.join(ngccFolder, relativePath);
-      this.fs.ensureDir(AbsoluteFsPath.dirname(newFilePath));
+      const relativePath = relative(packagePath, file.path);
+      const newFilePath = join(ngccFolder, relativePath);
+      this.fs.ensureDir(dirname(newFilePath));
       this.fs.writeFile(newFilePath, file.contents);
     }
   }
 
   protected updatePackageJson(
       entryPoint: EntryPoint, formatProperty: EntryPointJsonProperty, ngccFolder: AbsoluteFsPath) {
-    const formatPath =
-        AbsoluteFsPath.join(entryPoint.path, entryPoint.packageJson[formatProperty] !);
-    const newFormatPath =
-        AbsoluteFsPath.join(ngccFolder, PathSegment.relative(entryPoint.package, formatPath));
+    const formatPath = join(entryPoint.path, entryPoint.packageJson[formatProperty] !);
+    const newFormatPath = join(ngccFolder, relative(entryPoint.package, formatPath));
     const newFormatProperty = formatProperty + '_ivy_ngcc';
-    (entryPoint.packageJson as any)[newFormatProperty] =
-        PathSegment.relative(entryPoint.path, newFormatPath);
+    (entryPoint.packageJson as any)[newFormatProperty] = relative(entryPoint.path, newFormatPath);
     this.fs.writeFile(
-        AbsoluteFsPath.join(entryPoint.path, 'package.json'),
-        JSON.stringify(entryPoint.packageJson));
+        join(entryPoint.path, 'package.json'), JSON.stringify(entryPoint.packageJson));
   }
 }