fix(context): clear binding cache upon scope or value getter changes

Author: raymondfeng

packages/context/src/__tests__/unit/binding.unit.ts

@@ -3,7 +3,7 @@
 // This file is licensed under the MIT License.
 // License text available at https://opensource.org/licenses/MIT
 
-import {expect} from '@loopback/testlab';
+import {expect, sinon, SinonSpy} from '@loopback/testlab';
 import {
   Binding,
   BindingScope,
@@ -214,6 +214,68 @@ describe('Binding', () => {
     });
   });
 
+  describe('cache', () => {
+    let spy: SinonSpy;
+    beforeEach(() => {
+      spy = sinon.spy();
+    });
+
+    it('clears cache if scope changes', () => {
+      const indexBinding = ctx
+        .bind<number>('index')
+        .toDynamicValue(spy)
+        .inScope(BindingScope.SINGLETON);
+
+      ctx.getSync(indexBinding.key);
+      sinon.assert.calledOnce(spy);
+      spy.resetHistory();
+
+      // Singleton
+      ctx.getSync(indexBinding.key);
+      sinon.assert.notCalled(spy);
+      spy.resetHistory();
+
+      indexBinding.inScope(BindingScope.CONTEXT);
+      ctx.getSync(indexBinding.key);
+      sinon.assert.calledOnce(spy);
+    });
+
+    it('clears cache if _getValue changes', () => {
+      const providerSpy = sinon.spy();
+      class IndexProvider implements Provider<number> {
+        value() {
+          return providerSpy();
+        }
+      }
+      const indexBinding = ctx
+        .bind<number>('index')
+        .toDynamicValue(spy)
+        .inScope(BindingScope.SINGLETON);
+
+      ctx.getSync(indexBinding.key);
+      sinon.assert.calledOnce(spy);
+      spy.resetHistory();
+
+      // Singleton
+      ctx.getSync(indexBinding.key);
+      sinon.assert.notCalled(spy);
+      spy.resetHistory();
+
+      // Now change the value getter
+      indexBinding.toProvider(IndexProvider);
+      ctx.getSync(indexBinding.key);
+      sinon.assert.notCalled(spy);
+      sinon.assert.calledOnce(providerSpy);
+      spy.resetHistory();
+      providerSpy.resetHistory();
+
+      // Singleton
+      ctx.getSync(indexBinding.key);
+      sinon.assert.notCalled(spy);
+      sinon.assert.notCalled(providerSpy);
+    });
+  });
+
   describe('toJSON()', () => {
     it('converts a keyed binding to plain JSON object', () => {
       const json = binding.toJSON();

packages/context/src/binding.ts

@@ -211,6 +211,15 @@ export class Binding<T = BoundValue> {
     });
   }
 
+  /**
+   * Clear the cache
+   */
+  private _clearCache() {
+    if (!this._cache) return;
+    // WeakMap does not have a `clear` method
+    this._cache = new WeakMap();
+  }
+
   /**
    * This is an internal function optimized for performance.
    * Users should use `@inject(key)` or `ctx.get(key)` instead.
@@ -346,6 +355,7 @@ export class Binding<T = BoundValue> {
    * @param scope Binding scope
    */
   inScope(scope: BindingScope): this {
+    if (this._scope !== scope) this._clearCache();
     this._scope = scope;
     return this;
   }
@@ -357,7 +367,7 @@ export class Binding<T = BoundValue> {
    */
   applyDefaultScope(scope: BindingScope): this {
     if (!this._scope) {
-      this._scope = scope;
+      this.inScope(scope);
     }
     return this;
   }
@@ -367,6 +377,8 @@ export class Binding<T = BoundValue> {
    * @param getValue getValue function
    */
   private _setValueGetter(getValue: ValueGetter<T>) {
+    // Clear the cache
+    this._clearCache();
     this._getValue = getValue;
   }