feat(Metadata): Add the metadata package

packages/Metadata/createMetadataDecorator.test.ts

@@ -0,0 +1,71 @@
+import { createMetadataDecorator } from './createMetadataDecorator.js'
+import { type } from './type.js'
+
+const meta = createMetadataDecorator(Symbol('meta'))
+
+describe('createMetadata', () => {
+	class TestClassZero { }
+	@meta('Test #1') class TestClassOne { }
+	class TestClassTwo extends TestClassOne { }
+	@meta('Test #3') class TestClassThree extends TestClassTwo { }
+
+	describe('on class', () => {
+		it('should return undefined for a class without the metadata', () => {
+			expect(meta.get(TestClassZero)).toBe(undefined)
+		})
+
+		it('should attach the metadata onto a class', () => {
+			expect(meta.get(TestClassOne)).toBe('Test #1')
+		})
+
+		it('should inherit the metadata from a parent class', () => {
+			expect(meta.get(TestClassTwo)).toBe('Test #1')
+		})
+
+		it('should override the metadata from a parent class', () => {
+			expect(meta.get(TestClassThree)).toBe('Test #3')
+		})
+	})
+
+	describe('on properties', () => {
+		class TestPropertyOne {
+			@meta('Some property') prop?: string
+		}
+
+		class TestPropertyTwo extends TestPropertyOne {
+			override prop = ''
+		}
+
+		class TestPropertyThree extends TestPropertyTwo {
+			@meta('Overridden property') override prop = ''
+			nested = new TestPropertyOne()
+		}
+
+		it('should attach the metadata onto a property', () => {
+			expect(meta.get(TestPropertyOne, 'prop')).toBe('Some property')
+		})
+
+		it('should inherit the metadata from a parent property', () => {
+			expect(meta.get(TestPropertyTwo, 'prop')).toBe('Some property')
+		})
+
+		it('should override the metadata from a parent property', () => {
+			expect(meta.get(TestPropertyThree, 'prop')).toBe('Overridden property')
+		})
+	})
+
+	describe('by key path', () => {
+		class TestKeyPathOne {
+			@meta('Some property') property?: string
+		}
+
+		class TestKeyPathTwo {
+			@type(TestKeyPathOne)
+			@meta('Property One') one?: TestKeyPathOne
+		}
+
+		it('should return the metadata by key path', () => {
+			expect(meta.getByKeyPath(TestKeyPathTwo, 'one.property')).toBe('Some property')
+		})
+	})
+})

packages/Metadata/createMetadataDecorator.ts

@@ -0,0 +1,31 @@
+/**
+ * Creates a metadata decorator with the given key supporting both class and property metadata.
+ * It also provides a getter for retrieving metadata by key and key-path (e.g. 'property.subProperty').
+ * The key-path getter needs the property to be decorated with `@type(SubPropertyType)`
+ * for the generated decorator to be able to resolve the metadata.
+ */
+export function createMetadataDecorator(key: symbol) {
+	function metadata(value: unknown) {
+		return (target: any, propertyKey?: string) => {
+			Reflect.defineMetadata(key, value, target, propertyKey!)
+		}
+	}
+
+	metadata.get = function (constructor: Constructor<any>, propertyKey?: string) {
+		return propertyKey === undefined
+			? Reflect.getMetadata(key, constructor)
+			: Reflect.getMetadata(key, constructor.prototype, propertyKey)
+	}
+
+	metadata.getByKeyPath = function <T>(constructor: Constructor<T>, keyPath: KeyPathOf<T>) {
+		const keys = keyPath.split('.')
+		const key = keys.pop() as string
+		const parent = keys.reduce((previousType, key) => type.get(previousType, key), constructor)
+		if (!parent) {
+			throw new Error(`Could not resolve type for key path "${keyPath}". Ensure nested properties are decorated with @type(SubPropertyType)`)
+		}
+		return metadata.get(parent, key)
+	}
+
+	return metadata
+}

packages/Metadata/description.ts

@@ -0,0 +1,9 @@
+import { createMetadataDecorator } from './createMetadataDecorator.js'
+
+export const description = createMetadataDecorator(Symbol('description'))
+globalThis.description = description
+
+declare global {
+	// eslint-disable-next-line no-var
+	var description: typeof import('./description.js').description
+}

packages/Metadata/index.ts

@@ -0,0 +1,10 @@
+import 'reflect-metadata'
+import '@a11d/constructor'
+import '@a11d/key-path'
+export * from './createMetadataDecorator.js'
+export * from './type.js'
+import './type.js'
+export * from './label.js'
+import './label.js'
+export * from './description.js'
+import './description.js'

packages/Metadata/label.ts

@@ -0,0 +1,9 @@
+import { createMetadataDecorator } from './createMetadataDecorator.js'
+
+export const label = createMetadataDecorator(Symbol('label'))
+globalThis.label = label
+
+declare global {
+	// eslint-disable-next-line no-var
+	var label: typeof import('./label.js').label
+}

packages/Metadata/package.json

@@ -0,0 +1,37 @@
+{
+	"name": "@a11d/metadata",
+	"version": "0.1.0",
+	"description": "A set of behavior-less metadata decorators.",
+	"repository": {
+		"type": "git",
+		"url": "git+https://github.com/a11delavar/lit-application.git"
+	},
+	"keywords": [
+		"metadata",
+		"decorator",
+		"attribute",
+		"reflect",
+		"reflect-metadata"
+	],
+	"author": "a11delavar",
+	"license": "MIT",
+	"bugs": {
+		"url": "https://github.com/a11delavar/lit-application/issues"
+	},
+	"homepage": "https://github.com/a11delavar/lit-application#readme",
+	"type": "module",
+	"main": "dist/index.js",
+	"types": "dist/index.d.ts",
+	"files": [
+		"dist"
+	],
+	"scripts": {
+		"build": "tsc"
+	},
+	"dependencies": {
+		"tslib": "x",
+		"reflect-metadata": "0.x",
+		"@a11d/key-path": "1.x",
+		"@a11d/constructor": "x"
+	}
+}

packages/Metadata/tsconfig.json

@@ -0,0 +1,11 @@
+{
+	"extends": "../../tsconfig.base.json",
+	"exclude": [
+		"./dist",
+		"*.test.ts"
+	],
+	"compilerOptions": {
+		"baseUrl": ".",
+		"outDir": "./dist"
+	}
+}

packages/Metadata/type.ts

@@ -0,0 +1,23 @@
+const key = 'design:type'
+
+/**
+ * A general-purpose metadata decorator to store the type of a property in runtime.
+ */
+export function type<Target, TKey extends keyof Target>(type: Constructor<Target[TKey]>) {
+	return (target: Target, propertyKey?: TKey) => {
+		Reflect.defineMetadata(key, type, target as any, propertyKey as any)
+	}
+}
+
+type.get = function (constructor: Constructor<any>, propertyKey: string) {
+	return Reflect.getMetadata(key, constructor.prototype, propertyKey)
+}
+
+globalThis.type = type
+
+declare global {
+	// eslint-disable-next-line no-var
+	var type: typeof import('./type.js').type & {
+		get: typeof import('./type.js').type.get
+	}
+}

tsconfig.json

@@ -5,9 +5,8 @@
 		"incremental": true,
 		"declaration": true,
 		"declarationMap": true,
-		"target": "ES2020",
+		"target": "ES2022",
 		"lib": [
-			"ES2021",
 			"DOM",
 			"DOM.Iterable"
 		],