Delegate .tsbuildinfo reads to the real ts.sys.readFile

Only the default `tsconfig.tsbuildinfo` name was guarded, so a project
with a custom `tsBuildInfoFile` (e.g. "declarations/.tsbuildinfo") that
hasn't been built yet crashed type-aware linting of every file with
`Parsing error: ENOENT`. The watch program reads the buildinfo without a
fileExists probe, so readFile must report missing as absent per the
ts.sys contract.

Buildinfo is never a .gts/.gjs file, so instead of guarding with our own
fs call, delegate to the unpatched host readFile: content when present,
undefined when missing.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: NullVoxPopuli

src/parser/ts-patch.js

@@ -37,17 +37,15 @@ try {
         let fileName = fname;
         let content = '';
         if (fileName.endsWith('.tsbuildinfo')) {
-          // Incremental build state is optional: return it when present, but
-          // report a missing file as absent instead of throwing. The watch
-          // program reads `tsBuildInfoFile` without a fileExists probe
-          // (readBuilderProgram -> host.readFile), so a fresh/cleaned project
-          // with a custom buildinfo path (e.g. "declarations/.tsbuildinfo")
-          // would otherwise abort linting with a Parsing error: ENOENT.
-          try {
-            return fs.readFileSync(fileName).toString();
-          } catch {
-            return content;
-          }
+          // Incremental build state is optional and never a .gts/.gjs file, so
+          // delegate to the real host: it returns the content when present and
+          // reports a missing file as absent (undefined) instead of throwing.
+          // The watch program reads `tsBuildInfoFile` without a fileExists
+          // probe (readBuilderProgram -> host.readFile), so a fresh/cleaned
+          // project with a custom buildinfo path (e.g.
+          // "declarations/.tsbuildinfo") would otherwise abort linting of
+          // every file with a Parsing error: ENOENT.
+          return sys.readFile(fileName);
         }
 
         try {

tests/ts-patch.test.js

@@ -20,26 +20,26 @@ const ts = require(require.resolve('typescript', { paths: [parserPath] }));
 // linting of every file in the project with
 // `Parsing error: ENOENT ... <project>/declarations/.tsbuildinfo`.
 describe('patched ts.sys.readFile — .tsbuildinfo handling', () => {
-	patchTs();
+  patchTs();
 
-	it('treats a missing custom-named .tsbuildinfo as absent instead of throwing', () => {
-		// e.g. { "tsBuildInfoFile": "declarations/.tsbuildinfo" } — only the
-		// default `tsconfig.tsbuildinfo` name was guarded before.
-		const missing = path.join(os.tmpdir(), 'ee-parser-no-such-dir', 'declarations', '.tsbuildinfo');
+  it('treats a missing custom-named .tsbuildinfo as absent instead of throwing', () => {
+    // e.g. { "tsBuildInfoFile": "declarations/.tsbuildinfo" } — only the
+    // default `tsconfig.tsbuildinfo` name was guarded before.
+    const missing = path.join(os.tmpdir(), 'ee-parser-no-such-dir', 'declarations', '.tsbuildinfo');
 
-		expect(() => ts.sys.readFile(missing)).not.toThrow();
-		expect(ts.sys.readFile(missing)).toBe('');
-	});
+    expect(() => ts.sys.readFile(missing)).not.toThrow();
+    expect(ts.sys.readFile(missing)).toBeUndefined();
+  });
 
-	it('returns the real content when the .tsbuildinfo exists', () => {
-		const dir = fs.mkdtempSync(path.join(os.tmpdir(), 'ee-parser-buildinfo-'));
-		const buildInfo = path.join(dir, 'custom.tsbuildinfo');
-		fs.writeFileSync(buildInfo, '{"version":"5.9.3"}');
+  it('returns the real content when the .tsbuildinfo exists', () => {
+    const dir = fs.mkdtempSync(path.join(os.tmpdir(), 'ee-parser-buildinfo-'));
+    const buildInfo = path.join(dir, 'custom.tsbuildinfo');
+    fs.writeFileSync(buildInfo, '{"version":"5.9.3"}');
 
-		try {
-			expect(ts.sys.readFile(buildInfo)).toBe('{"version":"5.9.3"}');
-		} finally {
-			fs.rmSync(dir, { recursive: true, force: true });
-		}
-	});
+    try {
+      expect(ts.sys.readFile(buildInfo)).toBe('{"version":"5.9.3"}');
+    } finally {
+      fs.rmSync(dir, { recursive: true, force: true });
+    }
+  });
 });