add marks feature

Author: keithamus

src/mark.ts

@@ -0,0 +1,35 @@
+type PropertyType = 'field' | 'getter' | 'setter' | 'method'
+type PropertyDecorator = (proto: object, key: PropertyKey) => void
+type GetMarks = (instance: object) => Set<PropertyKey>
+export function createMark(validate: (key: PropertyKey, type: PropertyType) => void): [PropertyDecorator, GetMarks] {
+  const marks = new WeakMap<object, Set<PropertyKey>>()
+  const sym = Symbol()
+  function get(proto: object): Set<PropertyKey> {
+    if (!marks.has(proto)) {
+      const parent = Object.getPrototypeOf(proto)
+      marks.set(proto, new Set(marks.get(parent) || []))
+    }
+    return marks.get(proto)!
+  }
+  const marker = (proto: object, key: PropertyKey, descriptor?: PropertyDescriptor): void => {
+    if (get(proto).has(key)) return
+    let type: PropertyType = 'field'
+    if (descriptor) {
+      if (typeof descriptor.value === 'function') type = 'method'
+      if (typeof descriptor.get === 'function') type = 'getter'
+      if (typeof descriptor.set === 'function') type = 'setter'
+    }
+    validate(key, type)
+    get(proto).add(key)
+  }
+  marker.static = sym
+
+  return [
+    marker,
+    (instance: object): Set<PropertyKey> => {
+      const proto = Object.getPrototypeOf(instance)
+      for (const key of proto.constructor[sym] || []) marker(proto, key, Object.getOwnPropertyDescriptor(proto, key))
+      return new Set(get(proto))
+    }
+  ]
+}

test/mark.ts

@@ -0,0 +1,158 @@
+import {expect} from '@open-wc/testing'
+import {fake} from 'sinon'
+import {createMark} from '../src/mark.js'
+
+describe('createMark', () => {
+  it('returns a tuple of functions: a mark and getMarks', () => {
+    const mark = createMark(() => {})
+    expect(mark).to.be.an('array').with.lengthOf(2)
+    expect(mark).to.have.property(0).a('function')
+    expect(mark).to.have.property(1).a('function')
+  })
+
+  it('attaches a `static` unique symbol to the first function', () => {
+    const mark = createMark(() => {})
+    expect(mark).to.have.nested.property('0.static').a('symbol')
+    const otherMark = createMark(() => {})
+    expect(otherMark).to.have.nested.property('0.static').a('symbol').not.equal(mark[0].static)
+  })
+
+  it('can be added to class fields without errors', () => {
+    const [mark] = createMark(() => {})
+    class FooBar {
+      @mark foo
+      @mark bar = 1
+      @mark baz = 'hi'
+    }
+    new FooBar()
+  })
+
+  it('can be added to getters or setters without errors', () => {
+    const [mark] = createMark(() => {})
+    class FooBar {
+      @mark get foo() {}
+      set foo(v) {}
+
+      @mark get bar() {}
+      @mark set baz(v) {}
+    }
+    new FooBar()
+  })
+
+  it('can be added to methods without errors', () => {
+    const [mark] = createMark(() => {})
+    class Foo {
+      @mark foo() {}
+    }
+    new Foo()
+  })
+
+  it('retrieves all marked fields with the get mark function', () => {
+    const [mark, getMark] = createMark(() => {})
+    class FooBar {
+      @mark foo
+      @mark bar = 1
+      @mark baz = 'hi'
+      @mark get bing() {}
+      @mark get qux() {}
+      @mark set quuz(v) {}
+      @mark set corge(v) {}
+      @mark grault() {}
+    }
+    expect(getMark(new FooBar())).to.eql(new Set(['foo', 'bar', 'baz', 'bing', 'qux', 'quuz', 'corge', 'grault']))
+  })
+
+  it('retrieves marked symbol methods correctly', () => {
+    const [mark, getMark] = createMark(() => {})
+    const sym = Symbol('foo')
+    class FooBar {
+      @mark [sym]() {}
+    }
+    expect(getMark(new FooBar()).has(sym)).to.equal(true)
+  })
+
+  it('retrieves fields declared using the `mark.static` symbol as a static class field', () => {
+    const [mark, getMark] = createMark(() => {})
+    class FooBar {
+      static [mark.static] = ['bar', 'bing', 'quuz', 'grault']
+      @mark foo
+      bar = 1
+      @mark baz = 'hi'
+      get bing() {}
+      @mark get qux() {}
+      set quuz(v) {}
+      @mark set corge(v) {}
+      grault() {}
+    }
+    const instance = new FooBar()
+    expect(getMark(instance)).to.eql(new Set(['foo', 'baz', 'qux', 'corge', 'bar', 'bing', 'quuz', 'grault']))
+  })
+
+  it('will not contain duplicates', () => {
+    const [mark, getMark] = createMark(() => {})
+    class FooBar {
+      static [mark.static] = ['bar', 'bing', 'quuz', 'grault']
+      @mark foo
+      @mark bar = 1
+      @mark baz = 'hi'
+      @mark get bing() {}
+      @mark get qux() {}
+      @mark set quuz(v) {}
+      @mark set corge(v) {}
+      @mark grault() {}
+    }
+    expect(getMark(new FooBar())).to.eql(new Set(['foo', 'bar', 'baz', 'bing', 'qux', 'quuz', 'corge', 'grault']))
+  })
+
+  it('calls the given function for each field, with name and type', () => {
+    const validate = fake()
+    const [mark] = createMark(validate)
+    const sym = Symbol('garply')
+    class FooBar {
+      @mark foo
+      @mark bar = 1
+      @mark baz = 'hi'
+      @mark get bing() {}
+      @mark get qux() {}
+      @mark set quuz(v) {}
+      @mark set corge(v) {}
+      @mark grault() {}
+      @mark [sym]() {}
+    }
+    expect(validate).to.be.calledWith('foo', 'field')
+    expect(validate).to.be.calledWith('bar', 'field')
+    expect(validate).to.be.calledWith('baz', 'field')
+    expect(validate).to.be.calledWith('bing', 'getter')
+    expect(validate).to.be.calledWith('qux', 'getter')
+    expect(validate).to.be.calledWith('quuz', 'setter')
+    expect(validate).to.be.calledWith('corge', 'setter')
+    expect(validate).to.be.calledWith('grault', 'method')
+    expect(validate).to.be.calledWith(sym, 'method')
+    return new FooBar()
+  })
+
+  it('calls the given function for each static defined field once initialized, with name and type', () => {
+    const validate = fake()
+    const [mark, getMark] = createMark(validate)
+    class FooBar {
+      static [mark.static] = ['foo', 'bar', 'baz', 'bing', 'qux', 'quuz', 'corge', 'grault']
+      foo
+      bar = 1
+      baz = 'hi'
+      get bing() {}
+      get qux() {}
+      set quuz(v) {}
+      set corge(v) {}
+      grault() {}
+    }
+    getMark(new FooBar())
+    expect(validate).to.be.calledWith('foo', 'field')
+    expect(validate).to.be.calledWith('bar', 'field')
+    expect(validate).to.be.calledWith('baz', 'field')
+    expect(validate).to.be.calledWith('bing', 'getter')
+    expect(validate).to.be.calledWith('qux', 'getter')
+    expect(validate).to.be.calledWith('quuz', 'setter')
+    expect(validate).to.be.calledWith('corge', 'setter')
+    expect(validate).to.be.calledWith('grault', 'method')
+  })
+})