refactor(engine): Locker Service related refactor

packages/lwc-engine/src/framework/__tests__/def.spec.ts

@@ -32,10 +32,7 @@ describe('def', () => {
                 bar() {}
             }
             MyComponent.publicMethods = ['foo', 'bar'];
-            expect(target.getComponentDef(MyComponent).methods).toEqual({
-                foo: 1,
-                bar: 1,
-            });
+            expect(Object.keys(target.getComponentDef(MyComponent).methods)).toEqual(['foo', 'bar']);
         });
 
         it('should understand static wire', () => {
@@ -255,12 +252,12 @@ describe('def', () => {
 
             MySubComponent.publicMethods = ['fizz', 'buzz'];
 
-            expect(target.getComponentDef(MySubComponent).methods).toEqual({
-                foo: 1,
-                bar: 1,
-                fizz: 1,
-                buzz: 1
-            });
+            expect(Object.keys(target.getComponentDef(MySubComponent).methods)).toEqual([
+                'foo',
+                'bar',
+                'fizz',
+                'buzz'
+            ]);
         });
 
         it('should inherit static wire properly', () => {

packages/lwc-engine/src/framework/api.ts

@@ -1,5 +1,5 @@
 import assert from "./assert";
-import { freeze, isArray, isUndefined, isNull, isFunction, isObject, isString, ArrayPush, assign, create, forEach, StringSlice, StringCharCodeAt, isNumber } from "./language";
+import { freeze, isArray, isUndefined, isNull, isFunction, isObject, isString, ArrayPush, assign, create, forEach, StringSlice, StringCharCodeAt, isNumber, hasOwnProperty } from "./language";
 import { vmBeingRendered, invokeComponentCallback } from "./invoker";
 import { EmptyArray, SPACE_CHAR } from "./utils";
 import { renderVM, createVM, appendVM, removeVM, VM } from "./vm";
@@ -181,7 +181,7 @@ export function c(sel: string, Ctor: ComponentConstructor, data: VNodeData): VEl
     // The compiler produce AMD modules that do not support circular dependencies
     // We need to create an indirection to circumvent those cases.
     // We could potentially move this check to the definition
-    if (Ctor.__circular__) {
+    if (hasOwnProperty.call(Ctor, '__circular__')) {
         Ctor = Ctor();
     }
 

packages/lwc-engine/src/framework/component.ts

@@ -5,7 +5,7 @@ import {
     isRendering,
     vmBeingRendered,
 } from "./invoker";
-import { isArray, ArrayIndexOf, ArraySplice } from "./language";
+import { isArray, ArrayIndexOf, ArraySplice, isObject } from "./language";
 import { invokeServiceHook, Services } from "./services";
 import { getComponentDef, PropsDef, WireHash, TrackDef, ViewModelReflection } from './def';
 import { VM } from "./vm";
@@ -19,7 +19,7 @@ export interface Component {
     [ViewModelReflection]: VM;
     readonly classList: DOMTokenList;
     readonly root: ShadowRoot;
-    render?: () => void | Template;
+    render?: () => (void | Template);
     connectedCallback?: () => void;
     disconnectedCallback?: () => void;
     renderedCallback?: () => void;
@@ -48,13 +48,13 @@ export function createComponent(vm: VM, Ctor: ComponentConstructor) {
         assert.vm(vm);
     }
     // create the component instance
-    const component = invokeComponentConstructor(vm, Ctor);
+    invokeComponentConstructor(vm, Ctor);
 
     if (process.env.NODE_ENV !== 'production') {
-        assert.isTrue(vm.component === component, `Invalid construction for ${vm}, maybe you are missing the call to super() on classes extending Element.`);
+        assert.isTrue(isObject(vm.component), `Invalid construction for ${vm}, maybe you are missing the call to super() on classes extending Element.`);
         const { track } = getComponentDef(Ctor);
-        if ('state' in component && (!track || !track.state)) {
-            assert.logWarning(`Non-trackable component state detected in ${component}. Updates to state property will not be reactive. To make state reactive, add @track decorator.`);
+        if ('state' in (vm.component as Component) && (!track || !track.state)) {
+            assert.logWarning(`Non-trackable component state detected in ${vm.component}. Updates to state property will not be reactive. To make state reactive, add @track decorator.`);
         }
     }
 }

packages/lwc-engine/src/framework/decorators/__tests__/api.spec.ts

@@ -363,18 +363,4 @@ describe('decorators/api.ts', () => {
         });
     });
 
-    describe('@api misuse', () => {
-        it('should throw when invoking api as a function', () => {
-            class MyComponent extends Element {
-                constructor() {
-                    super();
-                    api();
-                }
-            }
-            expect(() => {
-                createElement('x-foo', { is: MyComponent });
-            }).toThrow('@api may only be used as a decorator.');
-        });
-    });
-
 });

packages/lwc-engine/src/framework/decorators/__tests__/decorate.spec.ts

@@ -0,0 +1,63 @@
+import decorate from "../decorate";
+
+describe('decorate.ts', () => {
+    describe('decorate() api', () => {
+        it('should throw when invoking it with no arguments', () => {
+            expect(() => {
+                decorate();
+            }).toThrow();
+        });
+
+        it('should throw when invoking it with a non-function', () => {
+            expect(() => {
+                decorate({}, {});
+            }).toThrow();
+        });
+
+        it('should throw when invoking it with an invalid decorator descriptor', () => {
+            expect(() => {
+                class f {}
+                decorate(f, undefined);
+            }).toThrow();
+        });
+
+        it('should throw when passed an invalid decorator', () => {
+            expect(() => {
+                class f {}
+                decorate(f, {
+                    x: undefined
+                });
+            }).toThrow();
+        });
+    });
+    describe('decorate()', () => {
+        it('can be chained', () => {
+            class f {}
+            expect(decorate(f, {})).toBe(f);
+        });
+        it('should throw when invoking it with no arguments', () => {
+            expect.assertions(7);
+            class f {
+                get y() { return 1; }
+                set y(v) { }
+            }
+            decorate(f, {
+                x: function (Ctor, key, descriptor) {
+                    expect(Ctor).toBe(f);
+                    expect(key).toBe('x');
+                    expect(descriptor).toBe(undefined);
+                    return {
+                        value: 1
+                    };
+                },
+                y: function (Ctor, key, descriptor) {
+                    expect(Ctor).toBe(f);
+                    expect(key).toBe('y');
+                    expect(descriptor.configurable).toBe(true);
+                    return descriptor;
+                }
+            });
+            expect(new f().x).toBe(1);
+        });
+    });
+});

packages/lwc-engine/src/framework/decorators/__tests__/track.spec.ts

@@ -248,12 +248,6 @@ describe('track.ts', () => {
     });
 
     describe('track()', () => {
-        it('should throw when invoking it with no arguments', () => {
-            expect(() => {
-                track();
-            }).toThrow();
-        });
-
         it('should throw when invoking it with more than one argument', () => {
             expect(() => {
                 track({}, {});

packages/lwc-engine/src/framework/decorators/__tests__/wire.spec.ts

@@ -200,7 +200,7 @@ describe('wire.ts', () => {
     });
 
     describe('@wire misuse', () => {
-        it('should throw when invoking wire as a function', () => {
+        it('should throw when invoking wire without adapter', () => {
             class MyComponent extends Element {
                 constructor() {
                     super();
@@ -209,7 +209,7 @@ describe('wire.ts', () => {
             }
             expect(() => {
                 createElement('x-foo', { is: MyComponent });
-            }).toThrow('@wire may only be used as a decorator.');
+            }).toThrow('@wire(adapter, config?) may only be used as a decorator.');
         });
     });
 

packages/lwc-engine/src/framework/decorators/api.ts

@@ -1,17 +1,42 @@
 import assert from "../assert";
-import { defineProperty, isObject, isNull, isTrue } from "../language";
 import { isRendering, vmBeingRendered, isBeingConstructed } from "../invoker";
+import { isObject, isNull, isTrue, hasOwnProperty } from "../language";
 import { observeMutation, notifyMutation } from "../watcher";
 import { Component } from "../component";
 import { VM } from "../vm";
 import { getCustomElementVM } from "../html-element";
 import { isUndefined, isFunction } from "../language";
 import { reactiveMembrane } from "../membrane";
 
-// stub function to prevent misuse of the @api decorator
-export default function api() {
+const COMPUTED_GETTER_MASK = 1;
+const COMPUTED_SETTER_MASK = 2;
+
+export default function api(target: any, propName: PropertyKey, descriptor: PropertyDescriptor | undefined): PropertyDescriptor {
     if (process.env.NODE_ENV !== 'production') {
-        assert.fail("@api may only be used as a decorator.");
+        if (arguments.length !== 3) {
+            assert.fail(`@api decorator can only be used as a decorator function.`);
+        }
+    }
+    const meta = target.publicProps;
+    const config = (hasOwnProperty.call(target, 'publicProps') && hasOwnProperty.call(meta, propName)) ? meta[propName].config : 0;
+    // initializing getters and setters for each public prop on the target prototype
+    if (COMPUTED_SETTER_MASK & config || COMPUTED_GETTER_MASK & config) {
+        if (process.env.NODE_ENV !== 'production') {
+            assert.invariant(!descriptor || (isFunction(descriptor.get) || isFunction(descriptor.set)), `Invalid property ${propName} definition in ${target}, it cannot be a prototype definition if it is a public property. Instead use the constructor to define it.`);
+            const mustHaveGetter = COMPUTED_GETTER_MASK & config;
+            const mustHaveSetter = COMPUTED_SETTER_MASK & config;
+            if (mustHaveGetter) {
+                assert.isTrue(isObject(descriptor) && isFunction(descriptor.get), `Missing getter for property ${propName} decorated with @api in ${target}`);
+            }
+            if (mustHaveSetter) {
+                assert.isTrue(isObject(descriptor) && isFunction(descriptor.set), `Missing setter for property ${propName} decorated with @api in ${target}`);
+                assert.isTrue(mustHaveGetter, `Missing getter for property ${propName} decorated with @api in ${target}. You cannot have a setter without the corresponding getter.`);
+            }
+        }
+        // if it is configured as an accessor it must have a descriptor
+        return createPublicAccessorDescriptor(target, propName, descriptor as PropertyDescriptor);
+    } else {
+        return createPublicPropertyDescriptor(target, propName, descriptor);
     }
 }
 
@@ -23,9 +48,8 @@ export function prepareForPropUpdate(vm: VM) {
     vmBeingUpdated = vm;
 }
 
-// TODO: how to allow symbols as property keys?
-export function createPublicPropertyDescriptor(proto: object, key: string, descriptor: PropertyDescriptor | undefined) {
-    defineProperty(proto, key, {
+export function createPublicPropertyDescriptor(proto: object, key: PropertyKey, descriptor: PropertyDescriptor | undefined): PropertyDescriptor {
+    return {
         get(this: Component): any {
             const vm = getCustomElementVM(this);
             if (process.env.NODE_ENV !== 'production') {
@@ -74,18 +98,18 @@ export function createPublicPropertyDescriptor(proto: object, key: string, descr
             }
         },
         enumerable: isUndefined(descriptor) ? true : descriptor.enumerable,
-    });
+    };
 }
 
-export function createPublicAccessorDescriptor(proto: object, key: string, descriptor: PropertyDescriptor) {
+export function createPublicAccessorDescriptor(Ctor: any, key: PropertyKey, descriptor: PropertyDescriptor): PropertyDescriptor {
     const { get, set, enumerable } = descriptor;
     if (!isFunction(get)) {
         if (process.env.NODE_ENV !== 'production') {
-            assert.fail(`Invalid attempt to create public property descriptor ${key} in ${proto}. It is missing the getter declaration with @api get ${key}() {} syntax.`);
+            assert.fail(`Invalid attempt to create public property descriptor ${key} in ${Ctor}. It is missing the getter declaration with @api get ${key}() {} syntax.`);
         }
         throw new TypeError();
     }
-    defineProperty(proto, key, {
+    return {
         get(this: Component): any {
             if (process.env.NODE_ENV !== 'production') {
                 const vm = getCustomElementVM(this);
@@ -125,5 +149,5 @@ export function createPublicAccessorDescriptor(proto: object, key: string, descr
             }
         },
         enumerable,
-    });
+    };
 }

packages/lwc-engine/src/framework/decorators/decorate.ts

@@ -0,0 +1,26 @@
+import { getOwnPropertyNames, getOwnPropertyDescriptor, defineProperty, isFunction, isUndefined } from "../language";
+
+export type DecoratorFunction = (Ctor: any, key: PropertyKey, descriptor: PropertyDescriptor | undefined) => PropertyDescriptor;
+export type DecoratorMap = Record<string, DecoratorFunction>;
+
+export default function decorate(Ctor: any, decorators: DecoratorMap): any {
+    if (!isFunction(Ctor) || decorators == null) {
+        throw new TypeError();
+    }
+    const props = getOwnPropertyNames(decorators);
+    // intentionally allowing decoration of classes only for now
+    const target = Ctor.prototype;
+    for (let i = 0, len = props.length; i < len; i += 1) {
+        const prop = props[i];
+        const decorator = decorators[prop];
+        if (!isFunction(decorator)) {
+            throw new TypeError();
+        }
+        const originalDescriptor = getOwnPropertyDescriptor(target, prop);
+        const descriptor = decorator(Ctor, prop, originalDescriptor);
+        if (!isUndefined(descriptor)) {
+            defineProperty(target, prop, descriptor);
+        }
+    }
+    return Ctor; // chaining
+}

packages/lwc-engine/src/framework/decorators/track.ts

@@ -1,24 +1,31 @@
 import assert from "../assert";
-import { isArray, isObject, defineProperty, isUndefined } from "../language";
+import { isArray, isObject, isUndefined } from "../language";
 import { isRendering, vmBeingRendered } from "../invoker";
 import { observeMutation, notifyMutation } from "../watcher";
 import { VMElement } from "../vm";
 import { getCustomElementVM } from "../html-element";
 import { reactiveMembrane } from '../membrane';
 
-// stub function to prevent misuse of the @track decorator
-export default function track(obj: any): any {
+export default function track(target: any, prop: PropertyKey, descriptor: PropertyDescriptor | undefined): PropertyDescriptor | any {
+    if (arguments.length === 1) {
+        return reactiveMembrane.getProxy(target);
+    }
     if (process.env.NODE_ENV !== 'production') {
-        if (arguments.length !== 1) {
-            assert.fail("@track can be used as a decorator or as a function with one argument to produce a trackable version of the provided value.");
+        if (arguments.length !== 3) {
+            assert.fail(`@track decorator can only be used with one argument to return a trackable object, or as a decorator function.`);
+        }
+        if (!isUndefined(descriptor)) {
+            const { get, set, configurable, writable } = descriptor;
+            assert.isTrue(!get && !set, `Compiler Error: A @track decorator can only be applied to a public field.`);
+            assert.isTrue(configurable !== false, `Compiler Error: A @track decorator can only be applied to a configurable property.`);
+            assert.isTrue(writable !== false, `Compiler Error: A @track decorator can only be applied to a writable property.`);
         }
     }
-    return reactiveMembrane.getProxy(obj);
+    return createTrackedPropertyDescriptor(target, prop, isObject(descriptor) ? descriptor.enumerable === true : true);
 }
 
-// TODO: how to allow symbols as property keys?
-export function createTrackedPropertyDescriptor(proto: object, key: string, descriptor: PropertyDescriptor | undefined) {
-    defineProperty(proto, key, {
+export function createTrackedPropertyDescriptor(Ctor: any, key: PropertyKey, enumerable: boolean): PropertyDescriptor {
+    return {
         get(this: VMElement): any {
             const vm = getCustomElementVM(this);
             if (process.env.NODE_ENV !== 'production') {
@@ -50,7 +57,7 @@ export function createTrackedPropertyDescriptor(proto: object, key: string, desc
                 }
             }
         },
-        enumerable: isUndefined(descriptor) ? true : descriptor.enumerable,
-        configurable: false,
-    });
+        enumerable,
+        configurable: true,
+    };
 }