feat(context): Add toJSON() for Context & Binding

Provide customization to serialize Context and Binding objects to JSON

Author: Raymond Feng

packages/context/src/binding.ts

@@ -34,7 +34,7 @@ export enum BindingScope {
    * req2.get('b1') ==> 3
    * app.get('b1') ==> 4
    */
-  TRANSIENT,
+  TRANSIENT = 'Transient',
 
   /**
    * The binding provides a value as a singleton within each local context. The
@@ -59,7 +59,7 @@ export enum BindingScope {
    * // 2 is the singleton for req2 afterward
    * req2.get('b1') ==> 2
    */
-  CONTEXT,
+  CONTEXT = 'Context',
 
   /**
    * The binding provides a value as a singleton within the context hierarchy
@@ -82,7 +82,14 @@ export enum BindingScope {
    * // 'b1' is found in app, reuse it
    * req2.get('b1') ==> 0
    */
-  SINGLETON,
+  SINGLETON = 'Singleton',
+}
+
+export enum BindingType {
+  CONSTANT = 'Constant',
+  DYNAMIC_VALUE = 'DynamicValue',
+  CLASS = 'Class',
+  PROVIDER = 'Provider',
 }
 
 // FIXME(bajtos) The binding class should be parameterized by the value
@@ -127,6 +134,7 @@ export class Binding {
   public readonly key: string;
   public readonly tags: Set<string> = new Set();
   public scope: BindingScope = BindingScope.TRANSIENT;
+  public type: BindingType;
 
   private _cache: BoundValue;
   private _getValue: (ctx?: Context) => BoundValue | Promise<BoundValue>;
@@ -243,8 +251,9 @@ export class Binding {
     return this;
   }
 
-  inScope(scope: BindingScope) {
+  inScope(scope: BindingScope): this {
     this.scope = scope;
+    return this;
   }
 
   /**
@@ -259,6 +268,7 @@ export class Binding {
    * ```
    */
   to(value: BoundValue): this {
+    this.type = BindingType.CONSTANT;
     this._getValue = () => value;
     return this;
   }
@@ -282,7 +292,7 @@ export class Binding {
    * ```
    */
   toDynamicValue(factoryFn: () => BoundValue | Promise<BoundValue>): this {
-    // TODO(bajtos) allow factoryFn with @inject arguments
+    this.type = BindingType.DYNAMIC_VALUE;
     this._getValue = ctx => factoryFn();
     return this;
   }
@@ -304,6 +314,7 @@ export class Binding {
    * @param provider The value provider to use.
    */
   public toProvider<T>(providerClass: Constructor<Provider<T>>): this {
+    this.type = BindingType.PROVIDER;
     this._getValue = ctx => {
       const providerOrPromise = instantiateClass<Provider<T>>(
         providerClass,
@@ -326,6 +337,7 @@ export class Binding {
    *   we can resolve them from the context.
    */
   toClass<T>(ctor: Constructor<T>): this {
+    this.type = BindingType.CLASS;
     this._getValue = ctx => instantiateClass(ctor, ctx!);
     this.valueConstructor = ctor;
     return this;
@@ -335,4 +347,18 @@ export class Binding {
     this.isLocked = false;
     return this;
   }
+
+  toJSON(): Object {
+    // tslint:disable-next-line:no-any
+    const json: {[name: string]: any} = {
+      key: this.key,
+      scope: this.scope,
+      tags: Array.from(this.tags),
+      isLocked: this.isLocked,
+    };
+    if (this.type != null) {
+      json.type = this.type;
+    }
+    return json;
+  }
 }

packages/context/src/context.ts

@@ -192,6 +192,17 @@ export class Context {
 
     return getDeepProperty(boundValue, path);
   }
+
+  /**
+   * Create a plain JSON object for the context
+   */
+  toJSON(): Object {
+    const json: {[key: string]: Object} = {};
+    for (const [k, v] of this.registry) {
+      json[k] = v.toJSON();
+    }
+    return json;
+  }
 }
 
 function getDeepProperty(value: BoundValue, path: string) {

packages/context/src/index.ts

@@ -3,7 +3,14 @@
 // This file is licensed under the MIT License.
 // License text available at https://opensource.org/licenses/MIT
 
-export {Binding, BindingScope, BoundValue, ValueOrPromise} from './binding';
+export {
+  Binding,
+  BindingScope,
+  BindingType,
+  BoundValue,
+  ValueOrPromise,
+} from './binding';
+
 export {Context} from './context';
 export {Constructor} from './resolver';
 export {inject, Setter, Getter} from './inject';

packages/context/test/unit/binding.ts

@@ -4,7 +4,14 @@
 // License text available at https://opensource.org/licenses/MIT
 
 import {expect} from '@loopback/testlab';
-import {Binding, BindingScope, Context, inject, Provider} from '../..';
+import {
+  Binding,
+  BindingScope,
+  BindingType,
+  Context,
+  inject,
+  Provider,
+} from '../..';
 
 const key = 'foo';
 
@@ -73,40 +80,105 @@ describe('Binding', () => {
       binding.to('value');
       expect(binding.getValue(ctx)).to.equal('value');
     });
+
+    it('sets the type to CONSTANT', () => {
+      binding.to('value');
+      expect(binding.type).to.equal(BindingType.CONSTANT);
+    });
+  });
+
+  describe('toDynamicValue(dynamicValueFn)', () => {
+    it('support a factory', async () => {
+      const b = ctx.bind('msg').toDynamicValue(() => Promise.resolve('hello'));
+      const value: string = await ctx.get('msg');
+      expect(value).to.equal('hello');
+      expect(b.type).to.equal(BindingType.DYNAMIC_VALUE);
+    });
+  });
+
+  describe('toClass(cls)', () => {
+    it('support a class', async () => {
+      ctx.bind('msg').toDynamicValue(() => Promise.resolve('world'));
+      const b = ctx.bind('myService').toClass(MyService);
+      expect(b.type).to.equal(BindingType.CLASS);
+      const myService: MyService = await ctx.get('myService');
+      expect(myService.getMessage()).to.equal('hello world');
+    });
   });
 
   describe('toProvider(provider)', () => {
     it('binding returns the expected value', async () => {
       ctx.bind('msg').to('hello');
       ctx.bind('provider_key').toProvider(MyProvider);
-      const value: String = await ctx.get('provider_key');
+      const value: string = await ctx.get('provider_key');
       expect(value).to.equal('hello world');
     });
 
     it('can resolve provided value synchronously', () => {
       ctx.bind('msg').to('hello');
       ctx.bind('provider_key').toProvider(MyProvider);
-      const value: String = ctx.getSync('provider_key');
+      const value: string = ctx.getSync('provider_key');
       expect(value).to.equal('hello world');
     });
 
     it('support asynchronous dependencies of provider class', async () => {
       ctx.bind('msg').toDynamicValue(() => Promise.resolve('hello'));
       ctx.bind('provider_key').toProvider(MyProvider);
-      const value: String = await ctx.get('provider_key');
+      const value: string = await ctx.get('provider_key');
       expect(value).to.equal('hello world');
     });
+
+    it('sets the type to PROVIDER', () => {
+      ctx.bind('msg').to('hello');
+      const b = ctx.bind('provider_key').toProvider(MyProvider);
+      expect(b.type).to.equal(BindingType.PROVIDER);
+    });
+  });
+
+  describe('toJSON()', () => {
+    it('converts a keyed binding to plain JSON object', () => {
+      const json = binding.toJSON();
+      expect(json).to.eql({
+        key: key,
+        scope: BindingScope.TRANSIENT,
+        tags: [],
+        isLocked: false,
+      });
+    });
+
+    it('converts a binding with more attributes to plain JSON object', () => {
+      const myBinding = new Binding(key, true)
+        .inScope(BindingScope.CONTEXT)
+        .tag('model')
+        .to('a');
+      const json = myBinding.toJSON();
+      expect(json).to.eql({
+        key: key,
+        scope: BindingScope.CONTEXT,
+        tags: ['model'],
+        isLocked: true,
+        type: BindingType.CONSTANT,
+      });
+    });
   });
 
   function givenBinding() {
     ctx = new Context();
     binding = new Binding(key);
   }
 
-  class MyProvider implements Provider<String> {
+  class MyProvider implements Provider<string> {
     constructor(@inject('msg') private _msg: string) {}
-    value(): String {
+    value(): string {
       return this._msg + ' world';
     }
   }
+
+  class MyService {
+    constructor(@inject('msg') private _msg: string) {}
+
+    getMessage(): string {
+      return 'hello ' + this._msg;
+    }
+  }
 });

packages/context/test/unit/context.ts

@@ -4,7 +4,7 @@
 // License text available at https://opensource.org/licenses/MIT
 
 import {expect} from '@loopback/testlab';
-import {Context, Binding, BindingScope, isPromise} from '../..';
+import {Context, Binding, BindingScope, BindingType, isPromise} from '../..';
 
 describe('Context', () => {
   let ctx: Context;
@@ -375,6 +375,47 @@ describe('Context', () => {
     });
   });
 
+  describe('toJSON()', () => {
+    it('converts to plain JSON object', () => {
+      ctx
+        .bind('a')
+        .to('1')
+        .lock();
+      ctx
+        .bind('b')
+        .toDynamicValue(() => 2)
+        .inScope(BindingScope.SINGLETON)
+        .tag(['X', 'Y']);
+      ctx
+        .bind('c')
+        .to(3)
+        .tag('Z');
+      expect(ctx.toJSON()).to.eql({
+        a: {
+          key: 'a',
+          scope: BindingScope.TRANSIENT,
+          tags: [],
+          isLocked: true,
+          type: BindingType.CONSTANT,
+        },
+        b: {
+          key: 'b',
+          scope: BindingScope.SINGLETON,
+          tags: ['X', 'Y'],
+          isLocked: false,
+          type: BindingType.DYNAMIC_VALUE,
+        },
+        c: {
+          key: 'c',
+          scope: BindingScope.TRANSIENT,
+          tags: ['Z'],
+          isLocked: false,
+          type: BindingType.CONSTANT,
+        },
+      });
+    });
+  });
+
   function createContext() {
     ctx = new Context();
   }