feat: support optional inject (#254)

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##### Checklist
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[x]. -->

- [x] `npm test` passes
- [x] tests and/or benchmarks are included
- [x] documentation is changed or added
- [x] commit message follows commit guidelines

##### Affected core subsystem(s)
<!-- Provide affected core subsystem(s). -->


##### Description of change
<!-- Provide a description of the change below this comment. -->

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- any feature?
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<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

## Release Notes

- **New Features**
- Introduced optional dependency injection capabilities, allowing
services to be injected as optional.
- Added a new `InjectOptional` decorator for marking parameters as
optional.

- **Improvements**
- Enhanced error handling in the `EggPrototypeBuilder` for optional
inject objects.
  - Streamlined logic for parameter handling in the `Inject` decorator.
- Improved flexibility in service management by allowing optional
dependencies in various services.

- **Tests**
  - Expanded test coverage for optional injections in various scenarios.
- Added new test cases to validate the functionality of optional
dependencies.

- **Documentation**
- Updated documentation to include detailed sections on optional
dependency injection and lifecycle hooks, enhancing clarity and
usability.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Author: gxkl

README.md

@@ -474,6 +474,25 @@ Proto 中可以依赖其他的 Proto，或者 egg 中的对象。
   // 在某些情况不希望注入的原型和属性使用一个名称
   // 默认为属性名称
   proto?: string;
+  // 注入对象是否为可选，默认为 false
+  // 若为 false，当不存在该对象时，启动阶段将会抛出异常
+  // 若为 true，且未找到对象时，该属性值为 undefined
+  optional?: boolean;
+})
+```
+
+对于 optional 为 true 的情况，也提供了 InjectOptional 的 alias 装饰器
+```typescript
+// 等价于 @Inject({ ...params, optional: true })
+@InjectOptional(params: {
+  // 注入对象的名称，在某些情况下一个原型可能有多个实例
+  // 比如说 egg 的 logger
+  // 默认为属性名称
+  name?: string;
+  // 注入原型的名称
+  // 在某些情况不希望注入的原型和属性使用一个名称
+  // 默认为属性名称
+  proto?: string;
 })
 ```
 
@@ -489,9 +508,17 @@ import { Inject } from '@eggjs/tegg';
 export class HelloService {
   @Inject()
   logger: EggLogger;
+  
+  // 等价于 @Inject({ optional: true })
+  @InjectOptional()
+  maybeUndefinedLogger?: EggLogger;
 
   async hello(user: User): Promise<string> {
     this.logger.info(`[HelloService] hello ${user.name}`);
+    // optional inject 使用时，需要判断是否有值
+    if (this.maybeUndefinedLogger) {
+      this.maybeUndefinedLogger.info(`[HelloService] hello ${user.name}`);
+    }
     const echoResponse = await this.echoAdapter.echo({ name: user.name });
     return `hello, ${echoResponse.name}`;
   }
@@ -506,11 +533,17 @@ import { Inject } from '@eggjs/tegg';
 
 @ContextProto()
 export class HelloService {
-  constructor(@Inject() readonly logger: EggLogger) {
-  }
+  constructor(
+    @Inject() readonly logger: EggLogger,
+    @InjectOptional() readonly maybeUndefinedLogger?: EggLogger,
+  ) {}
 
   async hello(user: User): Promise<string> {
     this.logger.info(`[HelloService] hello ${user.name}`);
+    // optional inject 使用时，需要判断是否有值
+    if (this.maybeUndefinedLogger) {
+      this.maybeUndefinedLogger.info(`[HelloService] hello ${user.name}`);
+    }
     const echoResponse = await this.echoAdapter.echo({ name: user.name });
     return `hello, ${echoResponse.name}`;
   }

core/core-decorator/src/decorator/Inject.ts

@@ -3,9 +3,11 @@ import { PrototypeUtil } from '../util/PrototypeUtil';
 import { ObjectUtils } from '@eggjs/tegg-common-util';
 
 export function Inject(param?: InjectParams | string) {
+  const injectParam = typeof param === 'string' ? { name: param } : param;
+
   function propertyInject(target: any, propertyKey: PropertyKey) {
     let objName: PropertyKey | undefined;
-    if (!param) {
+    if (!injectParam) {
       // try to read design:type from proto
       const proto = PrototypeUtil.getDesignType(target, propertyKey);
       if (typeof proto === 'function' && proto !== Object) {
@@ -15,29 +17,36 @@ export function Inject(param?: InjectParams | string) {
       }
     } else {
       // params allow string or object
-      objName = typeof param === 'string' ? param : param?.name;
+      objName = injectParam?.name;
     }
 
     const injectObject: InjectObjectInfo = {
       refName: propertyKey,
       objName: objName || propertyKey,
     };
 
+    if (injectParam?.optional) {
+      injectObject.optional = true;
+    }
+
     PrototypeUtil.setInjectType(target.constructor, InjectType.PROPERTY);
     PrototypeUtil.addInjectObject(target.constructor as EggProtoImplClass, injectObject);
   }
 
   function constructorInject(target: any, parameterIndex: number) {
     const argNames = ObjectUtils.getConstructorArgNameList(target);
     const argName = argNames[parameterIndex];
-    // TODO get objName from design:type
-    const objName = typeof param === 'string' ? param : param?.name;
     const injectObject: InjectConstructorInfo = {
       refIndex: parameterIndex,
       refName: argName,
-      objName: objName || argName,
+      // TODO get objName from design:type
+      objName: injectParam?.name || argName,
     };
 
+    if (injectParam?.optional) {
+      injectObject.optional = true;
+    }
+
     PrototypeUtil.setInjectType(target, InjectType.CONSTRUCTOR);
     PrototypeUtil.addInjectConstructor(target as EggProtoImplClass, injectObject);
   }
@@ -50,3 +59,12 @@ export function Inject(param?: InjectParams | string) {
     }
   };
 }
+
+export function InjectOptional(param?: Omit<InjectParams, 'optional'> | string) {
+  const injectParam = typeof param === 'string' ? { name: param } : param;
+
+  return Inject({
+    ...injectParam,
+    optional: true,
+  });
+}

core/core-decorator/test/decorators.test.ts

@@ -73,6 +73,14 @@ describe('test/decorator.test.ts', () => {
       }, {
         objName: 'testService4',
         refName: 'testService4',
+      }, {
+        objName: 'optionalService1',
+        refName: 'optionalService1',
+        optional: true,
+      }, {
+        objName: 'optionalService2',
+        refName: 'optionalService2',
+        optional: true,
       }];
       assert.deepStrictEqual(PrototypeUtil.getInjectObjects(CacheService), expectInjectInfo);
     });
@@ -82,6 +90,8 @@ describe('test/decorator.test.ts', () => {
       assert.deepStrictEqual(injectConstructors, [
         { refIndex: 0, refName: 'xCache', objName: 'fooCache' },
         { refIndex: 1, refName: 'cache', objName: 'cache' },
+        { refIndex: 2, refName: 'optional1', objName: 'optional1', optional: true },
+        { refIndex: 3, refName: 'optional2', objName: 'optional2', optional: true },
       ]);
     });
   });

core/core-decorator/test/fixtures/decators/CacheService.ts

@@ -1,4 +1,5 @@
-import { ContextProto, Inject } from '../../..';
+import { ContextProto } from '../../../src/decorator/ContextProto';
+import { Inject, InjectOptional } from '../../../src/decorator/Inject';
 import { ICache } from './ICache';
 import { TestService, TestService2 } from './OtherService';
 
@@ -37,4 +38,10 @@ export default class CacheService {
 
   @Inject()
   testService4: any;
+
+  @Inject({ optional: true })
+  optionalService1?: any;
+
+  @InjectOptional()
+  optionalService2?: any;
 }

core/core-decorator/test/fixtures/decators/ConstructorObject.ts

@@ -1,6 +1,6 @@
 import { SingletonProto } from '../../../src/decorator/SingletonProto';
 import { ICache } from './ICache';
-import { Inject } from '../../../src/decorator/Inject';
+import { Inject, InjectOptional } from '../../../src/decorator/Inject';
 import { InitTypeQualifier } from '../../../src/decorator/InitTypeQualifier';
 import { ObjectInitType } from '@eggjs/tegg-types';
 import { ModuleQualifier } from '../../../src/decorator/ModuleQualifier';
@@ -12,6 +12,8 @@ export class ConstructorObject {
       @ModuleQualifier('foo')
       @Inject({ name: 'fooCache'}) readonly xCache: ICache,
       @Inject() readonly cache: ICache,
+      @Inject({ optional: true }) readonly optional1?: ICache,
+      @InjectOptional() readonly optional2?: ICache,
     ) {
     }
 }

core/metadata/src/impl/EggPrototypeBuilder.ts

@@ -63,7 +63,7 @@ export class EggPrototypeBuilder {
     return builder.build();
   }
 
-  private tryFindDefaultPrototype(injectObject: InjectObject): EggPrototype {
+  private tryFindDefaultPrototype(injectObject: InjectObject | InjectConstructor): EggPrototype {
     const propertyQualifiers = QualifierUtil.getProperQualifiers(this.clazz, injectObject.refName);
     const multiInstancePropertyQualifiers = this.properQualifiers[injectObject.refName as string] ?? [];
     return EggPrototypeFactory.instance.getPrototype(injectObject.objName, this.loadUnit, QualifierUtil.mergeQualifiers(
@@ -72,7 +72,7 @@ export class EggPrototypeBuilder {
     ));
   }
 
-  private tryFindContextPrototype(injectObject: InjectObject): EggPrototype {
+  private tryFindContextPrototype(injectObject: InjectObject | InjectConstructor): EggPrototype {
     const propertyQualifiers = QualifierUtil.getProperQualifiers(this.clazz, injectObject.refName);
     const multiInstancePropertyQualifiers = this.properQualifiers[injectObject.refName as string] ?? [];
     return EggPrototypeFactory.instance.getPrototype(injectObject.objName, this.loadUnit, QualifierUtil.mergeQualifiers(
@@ -85,7 +85,7 @@ export class EggPrototypeBuilder {
     ));
   }
 
-  private tryFindSelfInitTypePrototype(injectObject: InjectObject): EggPrototype {
+  private tryFindSelfInitTypePrototype(injectObject: InjectObject | InjectConstructor): EggPrototype {
     const propertyQualifiers = QualifierUtil.getProperQualifiers(this.clazz, injectObject.refName);
     const multiInstancePropertyQualifiers = this.properQualifiers[injectObject.refName as string] ?? [];
     return EggPrototypeFactory.instance.getPrototype(injectObject.objName, this.loadUnit, QualifierUtil.mergeQualifiers(
@@ -98,7 +98,7 @@ export class EggPrototypeBuilder {
     ));
   }
 
-  private findInjectObjectPrototype(injectObject: InjectObject): EggPrototype {
+  private findInjectObjectPrototype(injectObject: InjectObject | InjectConstructor): EggPrototype {
     const propertyQualifiers = QualifierUtil.getProperQualifiers(this.clazz, injectObject.refName);
     try {
       return this.tryFindDefaultPrototype(injectObject);
@@ -121,22 +121,34 @@ export class EggPrototypeBuilder {
     const injectObjectProtos: Array<InjectObjectProto | InjectConstructorProto> = [];
     for (const injectObject of this.injectObjects) {
       const propertyQualifiers = QualifierUtil.getProperQualifiers(this.clazz, injectObject.refName);
-      const proto = this.findInjectObjectPrototype(injectObject);
-      if (this.injectType === InjectType.PROPERTY) {
-        injectObjectProtos.push({
-          refName: injectObject.refName,
-          objName: injectObject.objName,
-          qualifiers: propertyQualifiers,
-          proto,
-        });
-      } else {
-        injectObjectProtos.push({
-          refIndex: (injectObject as InjectConstructor).refIndex,
-          refName: injectObject.refName,
-          objName: injectObject.objName,
-          qualifiers: propertyQualifiers,
-          proto,
-        });
+      try {
+        const proto = this.findInjectObjectPrototype(injectObject);
+        let injectObjectProto: InjectObjectProto | InjectConstructorProto;
+        if (this.injectType === InjectType.PROPERTY) {
+          injectObjectProto = {
+            refName: injectObject.refName,
+            objName: injectObject.objName,
+            qualifiers: propertyQualifiers,
+            proto,
+          };
+        } else {
+          injectObjectProto = {
+            refIndex: (injectObject as InjectConstructor).refIndex,
+            refName: injectObject.refName,
+            objName: injectObject.objName,
+            qualifiers: propertyQualifiers,
+            proto,
+          };
+        }
+        if (injectObject.optional) {
+          injectObject.optional = true;
+        }
+        injectObjectProtos.push(injectObjectProto);
+      } catch (e) {
+        if (e instanceof EggPrototypeNotFound && injectObject.optional) {
+          continue;
+        }
+        throw e;
       }
     }
     const id = IdenticalUtil.createProtoId(this.loadUnit.id, this.name);

core/metadata/test/LoadUnit.test.ts

@@ -75,6 +75,18 @@ describe('test/LoadUnit/LoadUnit.test.ts', () => {
     });
   });
 
+  describe('optional inject', () => {
+    it('should success', async () => {
+      const optionalInjectModulePath = path.join(__dirname, './fixtures/modules/optional-inject-module');
+      const loader = new TestLoader(optionalInjectModulePath);
+      buildGlobalGraph([ optionalInjectModulePath ], [ loader ]);
+
+      const loadUnit = await LoadUnitFactory.createLoadUnit(optionalInjectModulePath, EggLoadUnitType.MODULE, loader);
+      const optionalInjectServiceProto = loadUnit.getEggPrototype('optionalInjectService', [{ attribute: InitTypeQualifierAttribute, value: ObjectInitType.SINGLETON }]);
+      assert.deepStrictEqual(optionalInjectServiceProto[0].injectObjects, []);
+    });
+  });
+
   describe('invalidate load unit', () => {
     it('should init failed', async () => {
       const invalidateModulePath = path.join(__dirname, './fixtures/modules/invalidate-module');

core/metadata/test/fixtures/modules/optional-inject-module/OptionalInjectService.ts

@@ -0,0 +1,13 @@
+import { Inject, InjectOptional, SingletonProto } from '@eggjs/core-decorator';
+
+interface PersistenceService {
+}
+
+@SingletonProto()
+export default class OptionalInjectService {
+  @Inject({ optional: true })
+  persistenceService?: PersistenceService;
+
+  @InjectOptional()
+  persistenceService2?: PersistenceService;
+}

core/metadata/test/fixtures/modules/optional-inject-module/package.json

@@ -0,0 +1,6 @@
+{
+  "name": "optional-inject-service",
+  "eggModule": {
+    "name": "optionalInjectService"
+  }
+}

core/types/core-decorator/Inject.ts

@@ -1,4 +1,6 @@
 export interface InjectParams {
   // obj instance name, default is property name
   name?: string;
+  // optional inject, default is false which means it will throw error when there is no relative object
+  optional?: boolean;
 }