Question

我正在将TypeORM与Babel 7和Typescript一起使用，似乎元数据不存在于已编译的代码中。可以做些什么吗？还是使用Babel的限制？

错误

ColumnTypeUndefinedError：Photo＃isPublished的列类型不是定义，无法猜测。确保您已打开 “ emitDecoratorMetadata”：tsconfig.json中的true选项。同时确保您已经在以下位置的主条目文件中导入了“ reflect-metadata” 您的应用程序（在导入任何实体之前）。如果您使用的是必须使用JavaScript而不是TypeScript显式提供一列类型。在新的ColumnTypeUndefinedError处

Photo.js

import { Column, Entity, PrimaryGeneratedColumn } from 'typeorm'

@Entity()
export class Photo {

    @PrimaryGeneratedColumn()
    id: number


    @Column()
    isPublished: boolean
}

orm代码

import 'reflect-metadata'
import {createConnection} from 'typeorm'
import {Photo} from './entities/Photo'

createConnection({
    type: 'postgres',
    host: 'localhost',
    port: 5432,
    username: 'postgres',
    password: 'root',
    database: 'test',
    entities: [
        Photo
    ],
    synchronize: true,
    logging: false
}).then(connection => {
    // here you can start to work with your entities
}).catch(error => console.log(error))

package.json

{
    "name": "typescript-babel-node",
    "version": "0.1.0",
    "description": "",
    "main": "index.js",
    "scripts": {
        "dev": "run-p -r dev:run type-check:watch",
        "dev:run": "nodemon --exec babel-node --extensions '.ts,.js' src/index.js",
        "build": "babel src -d build --extensions '.ts,.js' src/index.js",
        "start": "node build/index.js",
        "type-check:watch": "tsc --watch",
        "test": "jest --watch"
    },
    "author": "",
    "license": "ISC",
    "dependencies": {
        "@types/node": "^10.12.0",
        "express": "^4.16.4",
        "pg": "^7.6.0",
        "ramda": "^0.25.0",
        "reflect-metadata": "^0.1.12",
        "typeorm": "^0.2.8"
    },
    "devDependencies": {
        "@babel/cli": "^7.1.2",
        "@babel/core": "^7.1.2",
        "@babel/node": "^7.0.0",
        "@babel/plugin-proposal-class-properties": "^7.1.0",
        "@babel/plugin-proposal-decorators": "^7.1.2",
        "@babel/plugin-proposal-object-rest-spread": "^7.0.0",
        "@babel/plugin-syntax-import-meta": "^7.0.0",
        "@babel/preset-env": "^7.1.0",
        "@babel/preset-typescript": "^7.1.0",
        "@types/express": "^4.16.0",
        "@types/jest": "^23.3.7",
        "@types/ramda": "^0.25.39",
        "babel-core": "^7.0.0-bridge.0",
        "babel-jest": "^23.6.0",
        "babel-plugin-module-resolver": "^3.1.1",
        "dot-env": "0.0.1",
        "eslint": "^5.7.0",
        "eslint-config-standard": "^12.0.0",
        "eslint-plugin-import": "^2.14.0",
        "eslint-plugin-node": "^7.0.1",
        "eslint-plugin-promise": "^4.0.1",
        "eslint-plugin-standard": "^4.0.0",
        "jest": "^23.6.0",
        "nodemon": "^1.18.5",
        "npm-run-all": "^4.1.3",
        "regenerator-runtime": "^0.12.1",
        "source-map-loader": "^0.2.4",
        "ts-jest": "^23.10.4",
        "typescript": "^3.1.3",
        "webpack": "^4.23.0",
        "webpack-cli": "^3.1.2"
    }
}

Answer 1

不支持开箱即用，如另一个答案中所述。但是，我们可以编写一个babel插件使其工作。

编写代码不是很复杂，问题来自babel内部信息的局限性。 Babel不对打字稿进行类型检查。这意味着我们没有任何语义信息，我们只有类型注释以及可以从中得到什么信息。这意味着我们的解决方案必不可少

限制：

如果没有类型注释，我们就没有类型可以写
如果有类型引用，则只能使用类型名称，而不能检查引用是针对接口的，如类型别名，类或枚举。实际上，这意味着：
- 如果类型是接口或类型别名，则在运行时类型名称将为undefined，为避免未定义，我们可以type || Object将默认值设置为对象，如果类型不具有关联的运行时值
- 如果类型是枚举，则Typescript会根据枚举的类型在元数据中写入Number或String。由于我们将类型名称写入元数据，因此这意味着您将获得元数据内枚举的容器对象。

类型序列化可以从类型脚本编译器本身进行复制，而只需进行很少的更改（实际上，这两个函数serializeTypeNode和serializeTypeList大约有150行代码）。

对于此示例类，我们得到的结果是：

declare var decorator: any;

interface ISampleInterface {

}

enum Flags { One }
class OtherClass {}


type ArrayAlias = number[]

class Test {
    @decorator
    untypedProp; // no design:type
    @decorator
    nrProp: number // Number as expected
    @decorator
    strProp: string // String as expected
    @decorator
    boolProp: boolean // Boolean as expected

    @decorator
    nrPropUndefined: number | undefined // Number as expected
    @decorator
    strPropUndefined: string | undefined // String as expected
    @decorator
    boolPropUndefined: boolean | undefined // Boolean as expected

    @decorator
    arrayProp: number[]

    // Type references
    @decorator
    classRefProp: OtherClass; // OtherClass || Object  = Object since OtherClass is still a class at runtime

    @decorator
    interfaceRefProp: ISampleInterface;  // ISampleInterface || Object  = Object since ISampleInterface is undefined at runtime

    @decorator
    enumRefProp: Flags; // Flags || Object = Flags since Flags exists as a value at runtime, here TS would have written Number/String

    @decorator
    typeAliasProp: ArrayAlias; // ArrayAlias || Object = Object since ArrayAlias does not exist t runtime and in Babel swe have no idea ArrayAlias is actually an array

    @decorator
    selfClassRefProp: Test; // Test || Object  = Object since Babel puts decorators instantiation before class definition, this is a quirk, this may be fixable
}

实际的插件代码不是很大（减去从TS版本复制过来的方法）：

export default declare((api: typeof import('@babel/core'), { jsxPragma = "React" }): PluginObj => {
  api.assertVersion(7);

  return {
    name: "transform-typescript-decorator-metadata",
    inherits: syntaxTypeScript,

    visitor: {
      ClassDeclaration(path) {
        var node = path.node;
        for (const field of node.body.body) {
          if (field.type !== "ClassProperty") continue;

          if (field.typeAnnotation && field.typeAnnotation.type === "TSTypeAnnotation" && field.decorators && field.decorators.length > 0) {
            const key = field.key as t.Identifier;
            const serializedType = serializeTypeNode(field.typeAnnotation.typeAnnotation);
            field.decorators.push(decorator(
              t.callExpression(
                t.memberExpression(t.identifier("Reflect"), t.identifier("metadata")), [
                  t.stringLiteral("design:type"),
                  t.logicalExpression("||", serializedType, createIdentifier("Object"))
                ])
            ))
          }
        }
      },
    }
  };
});

您可以找到完整的插件代码和有效的示例here

从另一方面来说，插件的顺序很重要，如果@babel/plugin-proposal-class-properties出现在我们的插件之前，它将删除所有属性，并且我们的插件将不再具有发出装饰器的信息。这是我测试过的.babelrc，它可以正常工作，但我在其他任何配置下都无法使用它（但是我不能说我尝试了那么多）

  {
    "env": {},
    "ignore": [],
    "plugins": [
      "../plugin/plugin.js",
      ["@babel/plugin-proposal-decorators", { "legacy": true }],
      ["@babel/plugin-proposal-class-properties", { "loose": true }],
      "babel-plugin-transform-es2015-modules-commonjs"
    ],
    "presets": [
      "@babel/preset-typescript"
    ]
  }

Answer 2

不幸的是，我有理由确定这是将Babel与Typescript结合使用的限制。 Babel所做的只是剥离Typescript类型and then treats the code as JavaScript。这意味着babel不在乎您的tsconfig.json at all，也不在乎emitDecoratorMetadata。

不幸的是，如果您需要装饰器元数据，则必须坚持使用tsc

使用Typescript，Babel 7，Decorators保留元数据

2 个答案: