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/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';
 
 /**