如何在 graphQL 控制器中使用 fs.watch

Question

我正在尝试在 graphQL 控制器中使用 fs.watch() 来观察测试输出 json 文件中的变化，并将测试是否通过他们提出的解决方案返回给用户。

现在，我的突变总是得到null 的答案。 所有测试都运行正常，output.json文件也正确写入，但是控制器函数在返回正确值之前返回null。

我的控制器如下：

import { Context } from "../typescript/types";
import TestModel from "../models/TestModel";

const fs = require("fs-extra");

interface InputSolution {
  userId: string;
  exerciseId: string;
  testIDs: string[];
  solution: string;
}

export default class SandboxController {
  async postSolution(
    parent: any,
    args: { input: InputSolution },
    context: Context
  ) {

    // 1. delete all files in src and spec, and the output json file
    try {
      await fs.emptyDir("./userCode/src");
      await fs.emptyDir("./userCode/spec");
      console.log("success!");
    } catch (err) {
      console.error(err);
    }

    // 2. create new files for: the function that is tested, and the tests
    const tests = await TestModel.find()
      .where("_id")
      .in(args.input.testIDs)
      .exec();

    try {
      await fs.writeFile("./userCode/src/solution.js", args.input.solution);
      tests.forEach(async (test, index) => {
        await fs.writeFile(
          `./userCode/spec/test${index}.spec.js`,
          test.content
        );
      });
      console.log("success!");
    } catch (err) {
      console.error(err);
    }

    // 3. create the flag file to show changes were made
    try {
      await fs.writeFile(
        "./userCode/flag.txt",
        args.input.exerciseId + " - " + args.input.userId
      );
      console.log("success!");
    } catch (err) {
      console.error(err);
    }


    // 4. Watch the output file
    fs.watch(
      "./userCode/flag.txt",
      async (eventType: string, filename: string) => {
        console.log(`event type is: ${eventType}`);

        const json = await fs.readFile(
          "./userCode/testLogs/output.json",
          "utf8"
        );

        const output: any = json ? JSON.parse(json) : null;

        if (
          output &&
          (output.numTotalTestSuites > 0 || output.numTotalTests > 0)
        ) {
          //
          console.log("numTotalTestSuites", output.numTotalTestSuites);

          if (output.numFailedTestSuites === 0 && output.numFailedTests === 0) {
            console.log("all good");
            return [{ testId: "12", passed: true }];
          } else {
            console.log("tests failed", output.numFailedTestSuites);
            return [{ testId: "12", passed: false }];
          }
          //
        } else {
          return [{ testId: "12", passed: false }];
        }
      }
    );
  }
}

任何帮助将不胜感激。

Answer 1

在这里回答我自己的问题：这是我使用的一个包装函数，使用 Promises，以确保 fs.watch 将运行正确的时间（即，直到满足条件），并且能够等待它。

function watchOnceUntil(
  url: string,
  condition: () => boolean,
  timeout: number
) {
  const startTime = Date.now();
  const promise = new Promise((resolve, reject) => {
    const watcher = fs.watch(url, (eventType: string, filename: string) => {
      const result = condition(); // boolean
      if (result) {
        watcher.close();
        resolve({ eventType, filename });
      } else if (Date.now() - startTime > timeout) {
        watcher.close();
        reject();
      }
    });
  });
  return promise;
}

我的控制器现在看起来像第 4 步：

    // 4. Watch the output file
    await watchOnceUntil(
      "./userCode/testLogs/output.json",
      () => {
        const json = fs.readFileSync("./userCode/testLogs/output.json", "utf8");

        const output: FullJestOutput | null = json ? JSON.parse(json) : null;
        if (output === null) return false;
        return output.numTotalTestSuites > 0 || output.numTotalTests > 0;
      },
      10000
    );

    const json = fs.readFileSync("./userCode/testLogs/output.json", "utf8");

    const output: FullJestOutput | null = json ? JSON.parse(json) : null;

    const result: TestResult | null = !output
      ? null
      : {
          success: output.success,
          testResults: output.testResults,
        };

    return result;