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/src/ngtsc/shims/BUILD.bazel

@@ -9,8 +9,8 @@ ts_library(
     ]),
     deps = [
         "//packages/compiler",
+        "//packages/compiler-cli/src/ngtsc/file_system",
         "//packages/compiler-cli/src/ngtsc/imports",
-        "//packages/compiler-cli/src/ngtsc/path",
         "//packages/compiler-cli/src/ngtsc/util",
         "@npm//@types/node",
         "@npm//typescript",

packages/compiler-cli/src/ngtsc/shims/src/factory_generator.ts

@@ -5,12 +5,10 @@
  * 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 path from 'path';
 import * as ts from 'typescript';
 
+import {AbsoluteFsPath, absoluteFrom, basename} from '../../file_system';
 import {ImportRewriter} from '../../imports';
-import {AbsoluteFsPath} from '../../path/src/types';
 import {isNonDeclarationTsPath} from '../../util/src/typescript';
 
 import {ShimGenerator} from './host';
@@ -38,8 +36,7 @@ export class FactoryGenerator implements ShimGenerator {
       return null;
     }
 
-    const relativePathToSource =
-        './' + path.posix.basename(original.fileName).replace(TS_DTS_SUFFIX, '');
+    const relativePathToSource = './' + basename(original.fileName).replace(TS_DTS_SUFFIX, '');
     // Collect a list of classes that need to have factory types emitted for them. This list is
     // overly broad as at this point the ts.TypeChecker hasn't been created, and can't be used to
     // semantically understand which decorated types are actually decorated with Angular decorators.
@@ -103,9 +100,8 @@ export class FactoryGenerator implements ShimGenerator {
     const map = new Map<AbsoluteFsPath, string>();
     files.filter(sourceFile => isNonDeclarationTsPath(sourceFile))
         .forEach(
-            sourceFile => map.set(
-                AbsoluteFsPath.fromUnchecked(sourceFile.replace(/\.ts$/, '.ngfactory.ts')),
-                sourceFile));
+            sourceFile =>
+                map.set(absoluteFrom(sourceFile.replace(/\.ts$/, '.ngfactory.ts')), sourceFile));
     return new FactoryGenerator(map);
   }
 }

packages/compiler-cli/src/ngtsc/shims/src/host.ts

@@ -5,9 +5,8 @@
  * 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 ts from 'typescript';
-import {AbsoluteFsPath} from '../../path/src/types';
+import {AbsoluteFsPath, absoluteFrom, resolve} from '../../file_system';
 
 export interface ShimGenerator {
   /**
@@ -73,7 +72,7 @@ export class GeneratedShimsHostWrapper implements ts.CompilerHost {
     for (let i = 0; i < this.shimGenerators.length; i++) {
       const generator = this.shimGenerators[i];
       // TypeScript internal paths are guaranteed to be POSIX-like absolute file paths.
-      const absoluteFsPath = AbsoluteFsPath.fromUnchecked(fileName);
+      const absoluteFsPath = resolve(fileName);
       if (generator.recognize(absoluteFsPath)) {
         const readFile = (originalFile: string) => {
           return this.delegate.getSourceFile(
@@ -118,7 +117,7 @@ export class GeneratedShimsHostWrapper implements ts.CompilerHost {
     // Note that we can pass the file name as branded absolute fs path because TypeScript
     // internally only passes POSIX-like paths.
     return this.delegate.fileExists(fileName) ||
-        this.shimGenerators.some(gen => gen.recognize(AbsoluteFsPath.fromUnchecked(fileName)));
+        this.shimGenerators.some(gen => gen.recognize(absoluteFrom(fileName)));
   }
 
   readFile(fileName: string): string|undefined { return this.delegate.readFile(fileName); }

packages/compiler-cli/src/ngtsc/shims/src/summary_generator.ts

@@ -8,7 +8,7 @@
 
 import * as ts from 'typescript';
 
-import {AbsoluteFsPath} from '../../path/src/types';
+import {AbsoluteFsPath, absoluteFrom} from '../../file_system';
 import {isNonDeclarationTsPath} from '../../util/src/typescript';
 
 import {ShimGenerator} from './host';
@@ -81,9 +81,8 @@ export class SummaryGenerator implements ShimGenerator {
     const map = new Map<AbsoluteFsPath, string>();
     files.filter(sourceFile => isNonDeclarationTsPath(sourceFile))
         .forEach(
-            sourceFile => map.set(
-                AbsoluteFsPath.fromUnchecked(sourceFile.replace(/\.ts$/, '.ngsummary.ts')),
-                sourceFile));
+            sourceFile =>
+                map.set(absoluteFrom(sourceFile.replace(/\.ts$/, '.ngsummary.ts')), sourceFile));
     return new SummaryGenerator(map);
   }
 }

packages/compiler-cli/src/ngtsc/shims/src/typecheck_shim.ts

@@ -8,7 +8,7 @@
 
 import * as ts from 'typescript';
 
-import {AbsoluteFsPath} from '../../path';
+import {AbsoluteFsPath} from '../../file_system';
 
 import {ShimGenerator} from './host';