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/util/BUILD.bazel

@@ -9,7 +9,7 @@ ts_library(
     ]),
     deps = [
         "//packages:types",
-        "//packages/compiler-cli/src/ngtsc/path",
+        "//packages/compiler-cli/src/ngtsc/file_system",
         "@npm//@types/node",
         "@npm//typescript",
     ],

packages/compiler-cli/src/ngtsc/util/src/path.ts

@@ -5,26 +5,23 @@
  * 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
  */
-
-/// <reference types="node" />
-
-import * as path from 'path';
+import {dirname, relative, resolve} from '../../file_system';
 
 const TS_DTS_JS_EXTENSION = /(?:\.d)?\.ts$|\.js$/;
 
 export function relativePathBetween(from: string, to: string): string|null {
-  let relative = path.posix.relative(path.dirname(from), to).replace(TS_DTS_JS_EXTENSION, '');
+  let relativePath = relative(dirname(resolve(from)), resolve(to)).replace(TS_DTS_JS_EXTENSION, '');
 
-  if (relative === '') {
+  if (relativePath === '') {
     return null;
   }
 
   // path.relative() does not include the leading './'.
-  if (!relative.startsWith('.')) {
-    relative = `./${relative}`;
+  if (!relativePath.startsWith('.')) {
+    relativePath = `./${relativePath}`;
   }
 
-  return relative;
+  return relativePath;
 }
 
 export function normalizeSeparators(path: string): string {

packages/compiler-cli/src/ngtsc/util/src/typescript.ts

@@ -10,7 +10,7 @@ const TS = /\.tsx?$/i;
 const D_TS = /\.d\.ts$/i;
 
 import * as ts from 'typescript';
-import {AbsoluteFsPath} from '../../path';
+import {AbsoluteFsPath, absoluteFrom} from '../../file_system';
 
 export function isDtsPath(filePath: string): boolean {
   return D_TS.test(filePath);
@@ -47,6 +47,12 @@ export function getSourceFile(node: ts.Node): ts.SourceFile {
   return directSf !== undefined ? directSf : ts.getOriginalNode(node).getSourceFile();
 }
 
+export function getSourceFileOrNull(program: ts.Program, fileName: AbsoluteFsPath): ts.SourceFile|
+    null {
+  return program.getSourceFile(fileName) || null;
+}
+
+
 export function identifierOfNode(decl: ts.Node & {name?: ts.Node}): ts.Identifier|null {
   if (decl.name !== undefined && ts.isIdentifier(decl.name)) {
     return decl.name;
@@ -83,7 +89,7 @@ export function getRootDirs(host: ts.CompilerHost, options: ts.CompilerOptions):
   // See:
   // https://github.com/Microsoft/TypeScript/blob/3f7357d37f66c842d70d835bc925ec2a873ecfec/src/compiler/sys.ts#L650
   // Also compiler options might be set via an API which doesn't normalize paths
-  return rootDirs.map(rootDir => AbsoluteFsPath.from(rootDir));
+  return rootDirs.map(rootDir => absoluteFrom(rootDir));
 }
 
 export function nodeDebugInfo(node: ts.Node): string {

packages/compiler-cli/src/ngtsc/util/test/BUILD.bazel

@@ -10,6 +10,8 @@ ts_library(
     ]),
     deps = [
         "//packages:types",
+        "//packages/compiler-cli/src/ngtsc/file_system",
+        "//packages/compiler-cli/src/ngtsc/file_system/testing",
         "//packages/compiler-cli/src/ngtsc/testing",
         "//packages/compiler-cli/src/ngtsc/util",
         "@npm//typescript",

packages/compiler-cli/src/ngtsc/util/test/visitor_spec.ts

@@ -5,10 +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 ts from 'typescript';
-
-import {makeProgram} from '../../testing/in_memory_typescript';
+import {absoluteFrom, getSourceFileOrError} from '../../file_system';
+import {runInEachFileSystem} from '../../file_system/testing';
+import {makeProgram} from '../../testing';
 import {VisitListEntryResult, Visitor, visit} from '../src/visitor';
 
 class TestAstVisitor extends Visitor {
@@ -43,37 +43,41 @@ function testTransformerFactory(context: ts.TransformationContext): ts.Transform
   return (file: ts.SourceFile) => visit(file, new TestAstVisitor(), context);
 }
 
-describe('AST Visitor', () => {
-  it('should add a statement before class in plain file', () => {
-    const {program, host} =
-        makeProgram([{name: 'main.ts', contents: `class A { static id = 3; }`}]);
-    const sf = program.getSourceFile('main.ts') !;
-    program.emit(sf, undefined, undefined, undefined, {before: [testTransformerFactory]});
-    const main = host.readFile('/main.js');
-    expect(main).toMatch(/^var A_id = 3;/);
-  });
+runInEachFileSystem(() => {
+  describe('AST Visitor', () => {
+    let _: typeof absoluteFrom;
+    beforeEach(() => _ = absoluteFrom);
 
-  it('should add a statement before class inside function definition', () => {
-    const {program, host} = makeProgram([{
-      name: 'main.ts',
-      contents: `
+    it('should add a statement before class in plain file', () => {
+      const {program, host} =
+          makeProgram([{name: _('/main.ts'), contents: `class A { static id = 3; }`}]);
+      const sf = getSourceFileOrError(program, _('/main.ts'));
+      program.emit(sf, undefined, undefined, undefined, {before: [testTransformerFactory]});
+      const main = host.readFile('/main.js');
+      expect(main).toMatch(/^var A_id = 3;/);
+    });
+
+    it('should add a statement before class inside function definition', () => {
+      const {program, host} = makeProgram([{
+        name: _('/main.ts'),
+        contents: `
       export function foo() {
         var x = 3;
         class A { static id = 2; }
         return A;
       }
     `
-    }]);
-    const sf = program.getSourceFile('main.ts') !;
-    program.emit(sf, undefined, undefined, undefined, {before: [testTransformerFactory]});
-    const main = host.readFile('/main.js');
-    expect(main).toMatch(/var x = 3;\s+var A_id = 2;\s+var A =/);
-  });
+      }]);
+      const sf = getSourceFileOrError(program, _('/main.ts'));
+      program.emit(sf, undefined, undefined, undefined, {before: [testTransformerFactory]});
+      const main = host.readFile(_('/main.js'));
+      expect(main).toMatch(/var x = 3;\s+var A_id = 2;\s+var A =/);
+    });
 
-  it('handles nested statements', () => {
-    const {program, host} = makeProgram([{
-      name: 'main.ts',
-      contents: `
+    it('handles nested statements', () => {
+      const {program, host} = makeProgram([{
+        name: _('/main.ts'),
+        contents: `
       export class A {
         static id = 3;
 
@@ -84,11 +88,12 @@ describe('AST Visitor', () => {
           return B;
         }
     }`
-    }]);
-    const sf = program.getSourceFile('main.ts') !;
-    program.emit(sf, undefined, undefined, undefined, {before: [testTransformerFactory]});
-    const main = host.readFile('/main.js');
-    expect(main).toMatch(/var A_id = 3;\s+var A = /);
-    expect(main).toMatch(/var B_id = 4;\s+var B = /);
+      }]);
+      const sf = getSourceFileOrError(program, _('/main.ts'));
+      program.emit(sf, undefined, undefined, undefined, {before: [testTransformerFactory]});
+      const main = host.readFile(_('/main.js'));
+      expect(main).toMatch(/var A_id = 3;\s+var A = /);
+      expect(main).toMatch(/var B_id = 4;\s+var B = /);
+    });
   });
 });