fix: lib setting from custom config is ignored (#1576)

When a user provides a custom `tsconfig.json` file, they have the
ability to override the `lib` setting, which provides a number of
libraries that should be loaded at compile time.

This config setting is not passed directly into the TypeScript compiler.
Instead, it is resolved and translated into a list of `.d.ts` file that
are passed as `rootNames` to the compiler, along with the actual source
files.

In that resolution, we failed to look at the `lib` setting the user
provided, and instead always used the default config.

Fix by looking at the user-provided config, falling back to the default
config only if the user config doesn't have a `lib` setting (mirroring
the behavior of tsc).

Fixes aws/jsii#4706.

---

By submitting this pull request, I confirm that my contribution is made
under the terms of the [Apache 2.0 license].

[Apache 2.0 license]: https://www.apache.org/licenses/LICENSE-2.0

src/compiler.ts

@@ -253,7 +253,7 @@ export class Compiler implements Emitter {
     const tsconf = this.tsconfig!;
 
     const prog = ts.createIncrementalProgram({
-      rootNames: this.rootFiles.concat(_pathOfLibraries(this.compilerHost)),
+      rootNames: this.rootFiles.concat(_pathOfLibraries(tsconf.compilerOptions, this.compilerHost)),
       options: tsconf.compilerOptions,
       // Make the references absolute for the compiler
       projectReferences: tsconf.references?.map((ref) => ({
@@ -585,17 +585,19 @@ export interface NonBlockingWatchOptions {
   readonly compilationComplete: (emitResult: ts.EmitResult) => void;
 }
 
-function _pathOfLibraries(host: ts.CompilerHost | ts.WatchCompilerHost<any>): string[] {
-  if (!BASE_COMPILER_OPTIONS.lib || BASE_COMPILER_OPTIONS.lib.length === 0) {
+function _pathOfLibraries(options: ts.CompilerOptions, host: ts.CompilerHost | ts.WatchCompilerHost<any>): string[] {
+  // Prefer user libraries, falling back to a library based on the target if not supplied by the user.
+  // This matches tsc behavior.
+  const libs = options.lib ?? [ts.getDefaultLibFileName(options)] ?? [];
+  if (libs.length === 0) {
     return [];
   }
-  const lib = host.getDefaultLibLocation?.();
-  if (!lib) {
-    throw new Error(
-      `Compiler host doesn't have a default library directory available for ${BASE_COMPILER_OPTIONS.lib.join(', ')}`,
-    );
+
+  const libDir = host.getDefaultLibLocation?.();
+  if (!libDir) {
+    throw new Error(`Compiler host doesn't have a default library directory available for ${libs.join(', ')}`);
   }
-  return BASE_COMPILER_OPTIONS.lib.map((name) => path.join(lib, name));
+  return libs.map((name) => path.join(libDir, name));
 }
 
 function parseConfigHostFromCompilerHost(host: ts.CompilerHost): ts.ParseConfigHost {

test/compiler.test.ts

@@ -2,12 +2,21 @@ import { mkdirSync, existsSync, mkdtempSync, rmSync, writeFileSync, readFileSync
 import { tmpdir } from 'node:os';
 import { dirname, join } from 'node:path';
 import { loadAssemblyFromPath, SPEC_FILE_NAME, SPEC_FILE_NAME_COMPRESSED } from '@jsii/spec';
+import * as ts from 'typescript';
 import { compile, Lock } from './fixtures';
 import { Compiler } from '../src/compiler';
 import { ProjectInfo } from '../src/project-info';
 import { TypeScriptConfigValidationRuleSet } from '../src/tsconfig';
 import { TypeScriptConfigValidator } from '../src/tsconfig/tsconfig-validator';
 
+// This is necessary to be able to jest.spyOn to functions in the 'ts' module. Replace the read-only
+// object descriptors with a plain object.
+jest.mock('typescript', () => ({ ...jest.requireActual('typescript') }));
+
+beforeEach(() => {
+  jest.restoreAllMocks();
+});
+
 describe(Compiler, () => {
   describe('generated tsconfig', () => {
     test('default is tsconfig.json', () => {
@@ -226,9 +235,17 @@ describe(Compiler, () => {
   });
 
   describe('user-provided tsconfig', () => {
+    let sourceDir: string;
+    const tsconfigPath = 'tsconfig.dev.json';
+    beforeEach(() => {
+      sourceDir = mkdtempSync(join(tmpdir(), 'jsii-compiler-user-tsconfig-'));
+    });
+
+    afterEach(() => {
+      rmSync(sourceDir, { force: true, recursive: true });
+    });
+
     test('will use user-provided config', () => {
-      const sourceDir = mkdtempSync(join(tmpdir(), 'jsii-compiler-user-tsconfig-'));
-      const tsconfigPath = 'tsconfig.dev.json';
       writeFileSync(join(sourceDir, tsconfigPath), JSON.stringify(tsconfigForNode18Strict(), null, 2));
 
       writeFileSync(join(sourceDir, 'index.ts'), 'export class MarkerA {}');
@@ -244,9 +261,7 @@ describe(Compiler, () => {
     });
 
     test('use user-provided config uses include and exclude', () => {
-      const sourceDir = mkdtempSync(join(tmpdir(), 'jsii-compiler-user-tsconfig-'));
       mkdirSync(join(sourceDir, 'sub'));
-      const tsconfigPath = 'tsconfig.dev.json';
       writeFileSync(
         join(sourceDir, tsconfigPath),
         JSON.stringify(
@@ -281,9 +296,48 @@ describe(Compiler, () => {
       expect(result.emitSkipped).toBe(false);
     });
 
+    test('respect "lib" setting from user-provided config', () => {
+      const tsconfig = tsconfigForNode18Strict();
+      tsconfig.compilerOptions.lib = ['Decorators.Legacy']; // Something very nonstandard
+      writeFileSync(join(sourceDir, tsconfigPath), JSON.stringify(tsconfig, null, 2));
+
+      const createIncrementalProgram = jest.spyOn(ts, 'createIncrementalProgram');
+
+      const compiler = new Compiler({
+        projectInfo: _makeProjectInfo(sourceDir, 'index.d.ts'),
+        typeScriptConfig: tsconfigPath,
+      });
+      compiler.emit();
+
+      expect(createIncrementalProgram).toHaveBeenCalledWith(
+        expect.objectContaining({
+          rootNames: expect.arrayContaining([expect.stringContaining('lib.decorators.legacy.d.ts')]),
+        }),
+      );
+    });
+
+    test('missing "lib" setting is based on compilation target', () => {
+      const tsconfig = tsconfigForNode18Strict();
+      tsconfig.compilerOptions.target = 'es6';
+      delete tsconfig.compilerOptions.lib;
+      writeFileSync(join(sourceDir, tsconfigPath), JSON.stringify(tsconfig, null, 2));
+
+      const createIncrementalProgram = jest.spyOn(ts, 'createIncrementalProgram');
+
+      const compiler = new Compiler({
+        projectInfo: _makeProjectInfo(sourceDir, 'index.d.ts'),
+        typeScriptConfig: tsconfigPath,
+      });
+      compiler.emit();
+
+      expect(createIncrementalProgram).toHaveBeenCalledWith(
+        expect.objectContaining({
+          rootNames: expect.arrayContaining([expect.stringContaining('lib.es6.d.ts')]),
+        }),
+      );
+    });
+
     test('"watch" mode', async () => {
-      const sourceDir = mkdtempSync(join(tmpdir(), 'jsii-compiler-watch-mode-'));
-      const tsconfigPath = 'tsconfig.dev.json';
       writeFileSync(join(sourceDir, tsconfigPath), JSON.stringify(tsconfigForNode18Strict(), null, 2));
 
       try {
@@ -464,7 +518,7 @@ function expectedTypeScriptConfig() {
 function tsconfigForNode18Strict() {
   return {
     compilerOptions: {
-      lib: ['es2022'],
+      lib: ['es2022'] as string[] | undefined,
       module: 'node16',
       target: 'es2022',