microsoft/TypeScript · error · Error

getPreProcessedFileInfo is not available using the server in

Error message

getPreProcessedFileInfo is not available using the server interface.

What it means

Thrown by the server-backed language service adapter (harnessLanguageService.ts:810) when a test invokes getPreProcessedFileInfo(). Like getClassifier (error 70), pre-processing of a file into triple-slash/reference/module info is a compiler-internal routine the tsserver protocol does not surface, so the server adapter refuses the call.

Source

Thrown at src/harness/harnessLanguageService.ts:810

        // Set the properties
        this.client = client;
        this.host = clientHost;
    }
    getLogger(): LoggerWithInMemoryLogs {
        return this.logger;
    }
    getHost(): SessionClientHost {
        return this.host;
    }
    getLanguageService(): ts.LanguageService {
        return this.client;
    }
    getClassifier(): ts.Classifier {
        throw new Error("getClassifier is not available using the server interface.");
    }
    getPreProcessedFileInfo(): ts.PreProcessedFileInfo {
        throw new Error("getPreProcessedFileInfo is not available using the server interface.");
    }
    assertTextConsistent(fileName: string): void {
        const serverText = this.server.getText(fileName);
        const clientText = this.host.readFile(fileName);
        ts.Debug.assert(
            serverText === clientText,
            [
                "Server and client text are inconsistent.",
                "",
                "\x1b[1mServer\x1b[0m\x1b[31m:",
                serverText,
                "",
                "\x1b[1mClient\x1b[0m\x1b[31m:",
                clientText,
                "",
                "This probably means something is wrong with the fourslash infrastructure, not with the test.",
            ].join(ts.sys.newLine),
        );

View on GitHub (pinned to b465fdbfe1)

Solutions

1. Restrict getPreProcessedFileInfo tests to the in-process language service adapter; skip the server variant.
2. For server-side coverage, drive equivalent behaviour through protocol commands (e.g. geterr / NavTree) that surface the same underlying parsing.
3. Split the test so the server variant asserts only protocol-exposed behaviour.

Example fix

// before
const info = adapter.getPreProcessedFileInfo("/a.ts");
assert.deepEqual(info.referencedFiles, []);

// after — only run on the in-process adapter
if (!isServerAdapter(adapter)) {
  const info = adapter.getPreProcessedFileInfo("/a.ts");
  assert.deepEqual(info.referencedFiles, []);
}

// Detect server-backed adapters and skip pre-processing tests for them.
function supportsPreProcessedFileInfo(adapter: unknown): boolean {
  return typeof (adapter as any).getPreProcessedFileInfo === 'function' && !isServerAdapter(adapter);
}

function isServerAdapter(adapter: unknown): boolean {
  return typeof (adapter as any)?.getHost === 'function' && !(adapter as any)._preProcessorAvailable;
}

When it happens

Trigger: A test that exercises pre-processing (e.g. triple-slash reference detection, import scanning) is run against the Session/SessionClientHost adapter instead of the in-process LanguageService.

Common situations: Sharing a pre-processing test across adapter variants; migrating a test to the server harness without removing the getPreProcessedFileInfo call; asserting on internal module-detection state.

Related errors

• getClassifier is not available using the server interface.
• No script with name '" + fileName + "'
• verifyCurrentLineContent\n
• verifyFileContent in file '${fileName}' failed:\n${showTextD
• Expected at least one js file to be emitted or at least one

AI-assisted analysis of microsoft/TypeScript@b465fdbfe1 (2026-08-12). Data as JSON: /api/errors/d49af4198a048ed9. Report an issue: GitHub.