Babel plugin to emit decorator metadata like typescript compiler. 

Babel plugin to emit decorator metadata like typescript compiler

leonardfactory

babel-plugin-transform-typescript-metadata

## [0.2.1](https://github.com/leonardfactory/babel-plugin-transform-typescript-metadata/compare/v0.2.0...v0.2.1) (2019-03-24)

* Add current pitfalls to README ([2f2b888](https://github.com/leonardfactory/babel-plugin-transform-typescript-metadata/commit/2f2b888))

* Add package.json keywords ([97690ca](https://github.com/leonardfactory/babel-plugin-transform-typescript-metadata/commit/97690ca))

# [0.2.0](https://github.com/leonardfactory/babel-plugin-transform-typescript-metadata/compare/v0.1.1...v0.2.0) (2019-03-24)

* Enhance type serialization following TSC [#1](https://github.com/leonardfactory/babel-plugin-transform-typescript-metadata/issues/1) ([5a76db1](https://github.com/leonardfactory/babel-plugin-transform-typescript-metadata/commit/5a76db1))

* Fix parameter assignments type serialization ([0eb91bb](https://github.com/leonardfactory/babel-plugin-transform-typescript-metadata/commit/0eb91bb))

* Add motivation to README ([f59c802](https://github.com/leonardfactory/babel-plugin-transform-typescript-metadata/commit/f59c802))

## [0.1.1](https://github.com/leonardfactory/babel-plugin-transform-typescript-metadata/compare/v0.1.0...v0.1.1) (2019-03-24)

* Add CHANGELOG ([880b618](https://github.com/leonardfactory/babel-plugin-transform-typescript-metadata/commit/880b618))

* Add decorators metadata support ([9cb1e8f](https://github.com/leonardfactory/babel-plugin-transform-typescript-metadata/commit/9cb1e8f))

* Add installation and usage in README ([8d31825](https://github.com/leonardfactory/babel-plugin-transform-typescript-metadata/commit/8d31825))

* Use babel-plugin-utils to assert babel version ([bbf626a](https://github.com/leonardfactory/babel-plugin-transform-typescript-metadata/commit/bbf626a))

  "name": "babel-plugin-transform-typescript-metadata",

  "description": "Babel plugin to emit decorator metadata like typescript compiler",

  "repository": "https://github.com/leonardfactory/babel-plugin-transform-typescript-metadata.git",

  "author": "Leonardo Ascione <leonardo.ascione@gmail.com>",

    "dev": "babel src -w -d lib -x '.ts,.tsx'",

    "build": "yarn build:lib && yarn build:types",

    "build:lib": "babel src -d lib -x '.ts,.tsx'",

    "build:types": "tsc --emitDeclarationOnly",

    "release": "yarn test && yarn build && release-it",

    "test:ci": "jest --ci --runInBand --coverage"

      "commitMessage": "🔖 v${version}"

    "increment": "conventional:@favoloso/emoji",

      "changelog": "./node_modules/.bin/conventional-changelog -p @favoloso/emoji | tail -n +3",

      "beforeStage": "./node_modules/.bin/conventional-changelog -p @favoloso/emoji -i CHANGELOG.md -s"

    "registry": "https://registry.npmjs.org/"

    "@babel/plugin-proposal-class-properties": "^7.4.0",

    "@babel/plugin-proposal-decorators": "^7.4.0",

    "@babel/preset-typescript": "^7.3.3",

    "@favoloso/conventional-changelog-emoji": "^0.9.0",

    "conventional-changelog-cli": "^2.0.12",

    "@babel/helper-plugin-utils": "^7.0.0"

# babel-plugin-transform-typescript-metadata

[![Travis (.com)](https://img.shields.io/travis/com/leonardfactory/babel-plugin-transform-typescript-metadata.svg)](https://travis-ci.com/leonardfactory/babel-plugin-transform-typescript-metadata)

[![Codecov](https://img.shields.io/codecov/c/github/leonardfactory/babel-plugin-transform-typescript-metadata.svg)](https://codecov.io/gh/leonardfactory/babel-plugin-transform-typescript-metadata)

[![npm](https://img.shields.io/npm/v/babel-plugin-transform-typescript-metadata.svg?style=popout)](https://www.npmjs.com/package/babel-plugin-transform-typescript-metadata)

TypeScript _Decorators_ allows advanced reflection patterns when combined

with [`Reflect.metadata`](https://rbuckton.github.io/reflect-metadata/) output.

Current `@babel/preset-typescript` implementation however just strips all types and

_does not_ emit the relative Metadata in the output code.

Since this kind of information is used extensively in libraries like

[Nest](https://docs.nestjs.com/providers) and [TypeORM](https://typeorm.io/#/)

to implement advanced features like **Dependency Injection**, I've thought it would

be awesome to be able to provide the same functionality that [TypeScript

compiler `experimentalDecorators` and `emitDecoratorMetadata`

flags](https://www.typescriptlang.org/docs/handbook/decorators.html) provide.

import { Configuration } from './Configuration';

  constructor(private service: MyService) {}

@Reflect.metadata('design:paramtypes', [MyService])

  @Reflect.metadata('design:type', Configuration)

Since decorators in typescript supports also _Parameters_, this plugin

also provides support for them, enabling the following syntax:

  constructor(@Inject() private: SomeService);

npm install --dev --save babel-plugin-transform-typescript-metadata

yarn add --dev babel-plugin-transform-typescript-metadata

> **Note:** should be placed **before** `@babel/plugin-proposal-decorators`.

    "babel-plugin-transform-typescript-metadata",

    ["@babel/plugin-proposal-decorators", { "legacy": true }],

    ["@babel/plugin-proposal-class-properties", { "loose": true }],

- We cannot know if type annotations are just types (i.e. `IMyInterface`) or

  concrete values (like classes, etc.). In order to resolve this, we emit the

  following: `typeof Type === 'undefined' ? Object : Type`. The code has the

  advantage of not throwing If you know a better

- Parameter decorators are emitted right _after_ the `ClassDeclaration` node,

  Inject()(A.prototype, 'methodName', 1);

  I'm not sure if this can cause issue with scoping, if you get in troubles with

  this kind of decorators, please open an issue.

		{
		"name": "babel-plugin-transform-typescript-metadata",
		"version": "0.2.0",
		"version": "0.2.1",
		"description": "Babel plugin to emit decorator metadata like typescript compiler",
		@@ -12,2 +12,9 @@ "main": "lib/plugin.js",
		],
		"keywords": [
		"babel",
		"babel-plugin",
		"babel-typescript",
		"decorators",
		"reflect-metadata"
		],
		"scripts": {
		@@ -14,0 +21,0 @@ "dev": "babel src -w -d lib -x '.ts,.tsx'",

		@@ -0,1 +1,14 @@
		## [0.2.1](https://github.com/leonardfactory/babel-plugin-transform-typescript-metadata/compare/v0.2.0...v0.2.1) (2019-03-24)


		### 📚 Documentation

		* Add current pitfalls to README ([2f2b888](https://github.com/leonardfactory/babel-plugin-transform-typescript-metadata/commit/2f2b888))


		### 🏗 Chore

		* Add package.json keywords ([97690ca](https://github.com/leonardfactory/babel-plugin-transform-typescript-metadata/commit/97690ca))


		# [0.2.0](https://github.com/leonardfactory/babel-plugin-transform-typescript-metadata/compare/v0.1.1...v0.2.0) (2019-03-24)
		@@ -2,0 +15,0 @@

		@@ -107,1 +107,19 @@ # babel-plugin-transform-typescript-metadata
		```

		## Current Pitfalls

		- We cannot know if type annotations are just types (i.e. `IMyInterface`) or
		concrete values (like classes, etc.). In order to resolve this, we emit the
		following: `typeof Type === 'undefined' ? Object : Type`. The code has the
		advantage of not throwing If you know a better
		way to do this, let me know!
		- Parameter decorators are emitted right _after_ the `ClassDeclaration` node,
		like:

		```js
		let A = (/* ... */)
		Inject()(A.prototype, 'methodName', 1);
		```

		I'm not sure if this can cause issue with scoping, if you get in troubles with
		this kind of decorators, please open an issue.

Improved metrics