nestjs脚手架生成库出错 - 搞搞震

最近把nestjs写的程序调整了一下，项目结构从Standard Mode该为Monorepo Mode，且把一些共用的模块提取出来，做成库。使用Nest CLI脚手架，执行了nest g lib db生成一个库，但是报错了：

Error: Invalid JSON character: "\"" at 13:6.
    at _token (/root/recovery-backend/node_modules/@angular-devkit/core/src/json/parser.js:81:19)
    at _readProperty (/root/recovery-backend/node_modules/@angular-devkit/core/src/json/parser.js:490:5)
    at _readObject (/root/recovery-backend/node_modules/@angular-devkit/core/src/json/parser.js:524:30)
    at _readValue (/root/recovery-backend/node_modules/@angular-devkit/core/src/json/parser.js:674:22)
    at _readProperty (/root/recovery-backend/node_modules/@angular-devkit/core/src/json/parser.js:491:19)
    at _readObject (/root/recovery-backend/node_modules/@angular-devkit/core/src/json/parser.js:515:26)
    at _readValue (/root/recovery-backend/node_modules/@angular-devkit/core/src/json/parser.js:674:22)
    at parseJsonAst (/root/recovery-backend/node_modules/@angular-devkit/core/src/json/parser.js:721:17)
    at Object.parseJson (/root/recovery-backend/node_modules/@angular-devkit/core/src/json/parser.js:750:24)
    at updateJsonFile (/root/recovery-backend/node_modules/@nestjs/schematics/dist/lib/library/library.factory.js:110:29)

Failed to execute command: "/root/recovery-backend/node_modules/.bin/schematics" @nestjs/schematics:library --name=db --no-dry-run --collection="@nestjs/schematics" --language="ts" --sourceRoot="apps/server/src" --spec

虽然从错误信息得知是脚手架在解析JSON的时候出错了，但是却不知道具体的原因。我们先从报错的栈中/root/recovery-backend/node_modules/@nestjs/schematics/dist/lib/library/library.factory.js文件updateJsonFile函数中打印一下，看看sourceText是什么。

function updateJsonFile(host, path, callback) {
    const source = host.read(path);
    if (source) {
        const sourceText = source.toString('utf-8');
        console.log(sourceText) // 打印信息
        const json = core_1.parseJson(sourceText);
        callback(json);
        host.overwrite(path, JSON.stringify(json, null, 2));
    }
    return host;
}

{
  "collection": "@nestjs/schematics",
  "sourceRoot": "apps/server/src",
  "monorepo": true,
  "root": "apps/server",
  "compilerOptions": {
    "webpack": false,
    "tsConfigPath": "apps/server/tsconfig.app.json"
  },
  "projects": {
    "server": {
      "type": "application",
      "root": "apps/server",
      "entryFile": "main",
      "sourceRoot": "apps/server/src",
      "compilerOptions": {
        "webpack": false,
        "tsConfigPath": "apps/server/tsconfig.app.json"
      }
    },
    "admin": {
      "type": "application",
      "root": "apps/admin",
      "entryFile": "main",
      "sourceRoot": "apps/admin/src",
      "compilerOptions": {
        "webpack": false,
        "tsConfigPath": "apps/admin/tsconfig.app.json"
      }
    }
  }
}
{
  "name": "recovery-backend",
  "version": "0.0.1",
  "description": "",
  "author": "",
  "license": "MIT",
  "scripts": {
    "prebuild": "rimraf dist",
    "build": "nest build",
    "format": "prettier --write \"apps/**/*.ts\" \"libs/**/*.ts\"",
    "start": "nest start",
    "start:dev": "nest start --watch",
    "start:debug": "nest start --debug --watch",
    "start:prod": "node dist/main",
    "lint": "eslint '{src,apps,libs,test}/**/*.ts' --fix",
    "test": "jest",
    "test:watch": "jest --watch",
    "test:cov": "jest --coverage",
    "test:debug": "node --inspect-brk -r tsconfig-paths/register -r ts-node/register node_modules/.bin/jest --runInBand",
    "test:e2e": "jest --config ./apps/recovery-backend/test/jest-e2e.json"
  },
  "dependencies": {
    "@alicloud/pop-core": "^1.7.9",
    "@nestjs/common": "^7.0.5",
    "@nestjs/config": "^0.4.0",
    "@nestjs/core": "^7.0.5",
    "@nestjs/jwt": "^7.0.0",
    "@nestjs/passport": "^7.0.0",
    "@nestjs/platform-express": "^7.0.5",
    "class-transformer": "^0.2.3",
    "class-validator": "^0.11.1",
    "co-wechat-oauth": "^2.0.1",
    "crypto-js": "^4.0.0",
    "mikro-orm": "^3.5.2",
    "moment": "^2.24.0",
    "mysql2": "^2.1.0",
    "nestjs-mikro-orm": "^1.0.3",
    "passport": "^0.4.1",
    "passport-jwt": "^4.0.0",
    "qcloudsms_js": "^0.1.1",
    "querystring": "^0.2.0",
    "reflect-metadata": "^0.1.13",
    "rimraf": "^3.0.0",
    "rxjs": "^6.5.4",
    "wechat-jssdk": "^5.0.4"
  },
  "devDependencies": {
    "@nestjs/cli": "^6.13.2",
    "@nestjs/schematics": "^6.8.1",
    "@nestjs/testing": "^6.11.11",
    "@types/express": "^4.17.3",
    "@types/jest": "25.1.1",
    "@types/node": "^13.9.4",
    "@types/passport-jwt": "^3.0.3",
    "@types/supertest": "^2.0.8",
    "@typescript-eslint/eslint-plugin": "^2.25.0",
    "@typescript-eslint/parser": "^2.25.0",
    "eslint": "^6.7.2",
    "eslint-config-prettier": "^6.10.1",
    "eslint-plugin-import": "^2.19.1",
    "jest": "^24.9.0",
    "prettier": "^1.18.2",
    "supertest": "^4.0.2",
    "ts-jest": "25.1.0",
    "ts-loader": "^6.2.2",
    "ts-node": "^8.8.1",
    "tsconfig-paths": "^3.9.0",
    "typescript": "^3.7.4"
  },
  "jest": {
    "moduleFileExtensions": [
      "js",
      "json",
      "ts"
    ],
    "rootDir": ".",
    "testRegex": ".spec.ts$",
    "transform": {
      "^.+\\.(t|j)s$": "ts-jest"
    },
    "coverageDirectory": "./coverage",
    "testEnvironment": "node",
    "roots": [
      "<rootDir>/apps/"
    ]
  },
  "mikro-orm": {
    "useTsNode": true,
    "configPaths": [
      "./apps/server/src/mikro-orm.config.ts",
      "./dist/apps/server/mikro-orm.config.js"
    ]
  }
}

{
  "compilerOptions": {
    "module": "commonjs",
    "declaration": true,
    "removeComments": true,
    "emitDecoratorMetadata": true,
    "experimentalDecorators": true,
    "target": "es2017",
    "sourceMap": true,
    "outDir": "./dist",
    "baseUrl": "./",
    "incremental": true,
    "esModuleInterop": true,
    // "paths": {}
  },
  "exclude": [
    "node_modules",
    "dist"
  ]
}

我们可以看到，打印出来的信息最下面的部分：

{
  "compilerOptions": {
    "module": "commonjs",
    "declaration": true,
    "removeComments": true,
    "emitDecoratorMetadata": true,
    "experimentalDecorators": true,
    "target": "es2017",
    "sourceMap": true,
    "outDir": "./dist",
    "baseUrl": "./",
    "incremental": true,
    "esModuleInterop": true,
    // "paths": {}
  },
  "exclude": [
    "node_modules",
    "dist"
  ]
}

其中的这一行被注释了

"paths": {}

// "paths": {}

被注释掉了，我们知道，标准严格的JSON格式是不能有注释的。把该行改正问题即可解决。