fix(language-service): include compilerOptions.rootDir in rootDirs (#40243)

When resolving references, the Ivy compiler has a few strategies it could use.

For relative path, one of strategies is [`RelativePathStrategy`](
https://github.com/angular/angular/blob/master/packages/compiler-cli/src/
ngtsc/imports/README.md#relativepathstrategy). This strategy
relies on `compilerOptions.rootDir` and `compilerOptions.rootDirs` to perform
the resolution, but language service only passes `rootDirs` to the compiler,
and not `rootDir`.

In reality, `rootDir` is very different from `rootDirs` even though they
sound the same.
According to the official [TS documentation][1],
> `rootDir` specifies the root directory of input files. Only use to control
> the output directory structure with --outDir.

> `rootDirs` is a list of root folders whose combined content represent the
> structure of the project at runtime. See [Module Resolution documentation](
> https://www.typescriptlang.org/docs/handbook/
> module-resolution.html#virtual-directories-with-rootdirs)
> for more details.

For now, we keep the behavior between compiler and language service consistent,
but we will revisit the notion of `rootDir` and how it is used later.

Fix angular/vscode-ng-language-service#1039

[1]: https://www.typescriptlang.org/docs/handbook/compiler-options.html

PR Close #40243

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

@@ -92,7 +92,9 @@ export function isExported(node: DeclarationNode): boolean {
       topLevel.modifiers.some(modifier => modifier.kind === ts.SyntaxKind.ExportKeyword);
 }
 
-export function getRootDirs(host: ts.CompilerHost, options: ts.CompilerOptions): AbsoluteFsPath[] {
+export function getRootDirs(
+    host: Pick<ts.CompilerHost, 'getCurrentDirectory'|'getCanonicalFileName'>,
+    options: ts.CompilerOptions): AbsoluteFsPath[] {
   const rootDirs: string[] = [];
   if (options.rootDirs !== undefined) {
     rootDirs.push(...options.rootDirs);

packages/language-service/ivy/BUILD.bazel

@@ -18,6 +18,7 @@ ts_library(
         "//packages/compiler-cli/src/ngtsc/shims",
         "//packages/compiler-cli/src/ngtsc/typecheck",
         "//packages/compiler-cli/src/ngtsc/typecheck/api",
+        "//packages/compiler-cli/src/ngtsc/util",
         "@npm//@types/node",
         "@npm//typescript",
     ],

packages/language-service/ivy/adapters.ts

@@ -10,8 +10,9 @@
 
 import {ConfigurationHost} from '@angular/compiler-cli';
 import {NgCompilerAdapter} from '@angular/compiler-cli/src/ngtsc/core/api';
-import {absoluteFrom, AbsoluteFsPath, FileStats, PathSegment, PathString} from '@angular/compiler-cli/src/ngtsc/file_system';
+import {AbsoluteFsPath, FileStats, PathSegment, PathString} from '@angular/compiler-cli/src/ngtsc/file_system';
 import {isShim} from '@angular/compiler-cli/src/ngtsc/shims';
+import {getRootDirs} from '@angular/compiler-cli/src/ngtsc/util/src/typescript';
 import * as p from 'path';
 import * as ts from 'typescript/lib/tsserverlibrary';
 
@@ -27,7 +28,7 @@ export class LanguageServiceAdapter implements NgCompilerAdapter {
   private readonly templateVersion = new Map<string, string>();
 
   constructor(private readonly project: ts.server.Project) {
-    this.rootDirs = project.getCompilationSettings().rootDirs?.map(absoluteFrom) || [];
+    this.rootDirs = getRootDirs(this, project.getCompilationSettings());
   }
 
   isShim(sf: ts.SourceFile): boolean {