TypeScriptLanguageServiceTester

Provides components for testing the typescript language-server and language-services.

Installing the package

This package can be added to your dependencies by invoking:

npm i -D @manuth/typescript-languageservice-tester

LanguageServiceTester

The LanguageServiceTester allows you to analyze code for ensuring all expected diagnostics are being delivered.

A LanguageServiceTester can be initialized by passing a directory to run the tsserver in:

import { LanguageServiceTester } from "@manuth/typescript-languageservice-tester";

let tester = new LanguageServiceTester("/tmp/test-workspace");

Installing dependencies

If typescript is not installed in your workspace, you can install it using the LanguageServiceTester.Install method:

await tester.Install();

Live-Updating Plugins

You can perform a live-update of plugin-configurations by invoking the LanguageServiceTester.ConfigurePlugin by passing the plugin-name and the configuration to apply at runtime:

await tester.ConfigurePlugin("typescript-eslint-language-service", { watchDirs: "." });

Analyzing Diagnostics

The LanguageServiceTester.AnalyzeCode-method allows you to analyze a code and getting all diagnostics for the specified code.

You can optionally pass a script-kind (such as TS, JSX etc.) and a file-name to be used. Otherwise the code is assumed to be TS and a generic file-name is used.

import { writeFile } from "fs-extra";

await writeFile(
    tester.MakePath("tsconfig.json"),
    {
        compilerOptions: {
            plugins: [
                {
                    name: "typescript-eslint-language-service"
                }
            ]
        }
    });

let diagnosticResponse = await AnalyzeCode("let x;;;");

Getting Code-Fixes

You can then either get all code-fixes for the analyzed code or code-fixes for a specific diagnostic:

await diagnosticResponse.GetCodeFixes();
await diagnosticResponse.Diagnostics[0].GetCodeFixes();

Running and controlling a TSServer

You can run an instance of typescript/lib/tsserver by creating a new instance of the TSServer-class. The TSServer class allows you to communicate with the tsserver by sending requests and awaiting answers or events:

let tsServer = new TSServer("/tmp/test-workspace");

Sending Requests

The TSServer.Send-method allows you to send requests to the tsserver easily:

import { server } from "typescript/lib/tsserverlibrary";

await tsServer.Send(
    {
        type: "request",
        command: server.protocol.CommandTypes.ReloadProjects
    },
    false);

The second argument allows you to specify whether a response is expected.

Some requests such as the SemanticDiagnosticsSyncRequest return a response. In that case you can pass true as the second argument which will cause the Send-method to resolve with the Response to the request.

import { join } from "upath";
import { server } from "typescript/lib/tsserverlibrary";

let response = await tsServer.Send<server.protocol.SemanticDiagnosticsSyncRequest>(
    {
        type: "request",
        command: server.protocol.CommandTypes.SemanticDiagnosticsSync,
        arguments: {
            file: "/tmp/test-workspace/example.js",
            includeLinePosition: false
        }
    });

console.log(response.body); // Logs the diagnostics which have been found

Waiting for Events

The WaitEvent method allows you to wait for an event to be emitted:

await tsServer.WaitEvent("typingsInstallerPid");

Disposing the TSServer

By disposing the TSServer, the underlying tsserver-process is closed by sending an ExitRequest and closing the stdin-stream.

await tsServer.Dispose();

Working with Workspaces

In some cases you might want to analyze code from a different workspace-folder to see how typescript is acting if files from a foreign project are being opened.

You can test the behaviour by creating temporary workspaces. Workspaces provide the same features like the LanguageServiceTester.

let workspace = await tester.CreateTemporaryWorkspace();
await workspace.Install();
await workspace.AnalyzeCode("let x;;;", "JSX");