test-repo/tests/integration/run-cli.js

import childProcess from "node:child_process";
import path from "node:path";
import url from "node:url";

/**
@typedef {{
  isTTY?: boolean,
  stdoutIsTTY?: boolean,
  ci?: boolean,
  mockWriteFileErrors?: Record<string, string>,
  nodeOptions?: string[],
  input?: string,
}} CliTestOptions
*/

// Though the doc says `childProcess.fork` accepts `URL`, but seems not true
// TODO: Use `URL` directly when we drop support for Node.js v14
const CLI_WORKER_FILE = url.fileURLToPath(
  new URL("./cli-worker.js", import.meta.url),
);
const INTEGRATION_TEST_DIRECTORY = url.fileURLToPath(
  new URL("./", import.meta.url),
);
const IS_CI = Boolean(process.env.CI);
const removeFinalNewLine = (string) =>
  string.endsWith("\n") ? string.slice(0, -1) : string;
const SUPPORTS_DISABLE_WARNING_FLAG =
  Number(process.versions.node.split(".")[0]) >= 20;
const promiseWithResolvers = Promise.withResolvers
  ? Promise.withResolvers.bind(Promise)
  : () => {
      let resolve;
      let reject;
      const promise = new Promise(
        (_resolve, _reject) => ([resolve, reject] = [_resolve, _reject]),
      );
      return { promise, resolve, reject };
    };

/**
 * @param {string} dir
 * @param {string[]} args
 * @param {CliTestOptions} options
 */
function runCliWorker(dir, args, options) {
  const result = {
    status: undefined,
    stdout: "",
    stderr: "",
    write: [],
  };
  const { promise, resolve, reject } = promiseWithResolvers();
  const createEpipeErrorHandler = (event) => (error) => {
    if (!error) {
      return;
    }

    // It can fail with `write EPIPE` error when running node with unsupported flags like `--experimental-strip-types`
    // Let's ignore and wait for the `close` event
    if (
      error.code === "EPIPE" &&
      error.syscall === "write" &&
      nodeOptions.length > 0
    ) {
      if (IS_CI) {
        // eslint-disable-next-line no-console
        console.error(
          Object.assign(error, { event, dir, args, options, worker }),
        );
      }
      return;
    }

    reject(error);
  };

  const nodeOptions = options?.nodeOptions ?? [];
  const worker = childProcess.fork(CLI_WORKER_FILE, args, {
    cwd: dir,
    execArgv: [
      "--trace-deprecation",
      ...(SUPPORTS_DISABLE_WARNING_FLAG
        ? ["--disable-warning=ExperimentalWarning"]
        : []),
      ...nodeOptions,
    ],
    stdio: [options.input ? "pipe" : "ignore", "pipe", "pipe", "ipc"],
    env: {
      ...process.env,
      ...options.env,
      NO_COLOR: "1",
    },
    serialization: "advanced",
  });

  worker.on("message", (message) => {
    if (message.type === "cli:write-file") {
      result.write.push(message.data);
    } else if (message.type === "worker:fault") {
      reject(message.error);
    }
  });

  for (const stream of ["stdout", "stderr"]) {
    worker[stream].on("data", (data) => {
      result[stream] += data.toString();
    });
  }

  const removeStdioFinalNewLine = () => {
    for (const stream of ["stdout", "stderr"]) {
      result[stream] = removeFinalNewLine(result[stream]);
    }
  };

  worker.once("close", (code) => {
    result.status = code;
    removeStdioFinalNewLine();
    resolve(result);
  });

  worker.once("error", (error) => {
    reject(error);
  });

  worker.once("spawn", () => {
    if (options.input) {
      worker.stdin.once("error", createEpipeErrorHandler("worker.stdin.end()"));
      worker.stdin.end(options.input);
    }

    worker.send(options, createEpipeErrorHandler("worker.send()"));
  });

  return promise;
}

function runPrettierCli(dir, args, options) {
  dir = path.resolve(INTEGRATION_TEST_DIRECTORY, dir);
  args = Array.isArray(args) ? args : [args];

  return runCliWorker(dir, args, options);
}

/**
 * @param {string} dir
 * @param {string[]} [args]
 * @param {CliTestOptions} [options]
 */
function runCli(dir, args = [], options = {}) {
  const promise = runPrettierCli(dir, args, options);
  const getters = {
    get status() {
      return promise.then(({ status }) => status);
    },
    get stdout() {
      return promise.then(({ stdout }) => stdout);
    },
    get stderr() {
      return promise.then(({ stderr }) => stderr);
    },
    get write() {
      return promise.then(({ write }) => write);
    },
    test: testResult,
    then(onFulfilled, onRejected) {
      return promise.then(onFulfilled, onRejected);
    },
  };

  return getters;

  function testResult(testOptions) {
    test(options.title || "", async () => {
      const result = await promise;

      let snapshot;
      for (const name of ["status", "stdout", "stderr", "write"]) {
        let value = result[name];
        // \r is trimmed from jest snapshots by default;
        // manually replacing this character with /*CR*/ to test its true presence
        // If ignoreLineEndings is specified, \r is simply deleted instead
        if (name === "stdout" || name === "stderr") {
          value = result[name].replace(
            /\r/gu,
            options.ignoreLineEndings ? "" : "/*CR*/",
          );
        }

        if (name in testOptions) {
          if (name === "status" && testOptions[name] === "non-zero") {
            expect(value).not.toBe(0);
          } else if (typeof testOptions[name] === "function") {
            testOptions[name](value);
          } else {
            expect(value).toEqual(testOptions[name]);
          }
        } else {
          snapshot = snapshot ?? {};
          snapshot[name] = value;
        }
      }

      if (snapshot) {
        expect(snapshot).toMatchSnapshot();
      }
    });

    return getters;
  }
}

export default runCli;