Fix property injection prototype hoisting bug

src/di/decorator/getPropertyInjectionMetadata.ts

@@ -0,0 +1,9 @@
+import {Instantiable, PropertyDependency} from '../types'
+import {Collection, logIfDebugging} from '../../util'
+import {propertyInjectionMetadata} from './propertyInjectionMetadata'
+
+export function getPropertyInjectionMetadata(token: Instantiable<any>): Collection<PropertyDependency> {
+    const loadedMeta = ((token as any)[propertyInjectionMetadata] || new Collection()) as Collection<PropertyDependency>
+    logIfDebugging('extollo.di.injection', 'getPropertyInjectionMetadata() target:', token, 'loaded:', loadedMeta)
+    return loadedMeta
+}

src/di/decorator/injection.ts

@@ -2,16 +2,16 @@ import 'reflect-metadata'
 import {collect, Collection} from '../../util'
 import {logIfDebugging} from '../../util/support/debug'
 import {
+    DEPENDENCY_KEYS_METADATA_KEY,
+    DEPENDENCY_KEYS_SERVICE_TYPE_KEY,
     DependencyKey,
     DependencyRequirement,
-    DEPENDENCY_KEYS_METADATA_KEY,
-    DEPENDENCY_KEYS_PROPERTY_METADATA_KEY,
-    isInstantiable,
     InjectionType,
-    DEPENDENCY_KEYS_SERVICE_TYPE_KEY,
+    isInstantiable,
     PropertyDependency,
 } from '../types'
 import {ContainerBlueprint} from '../ContainerBlueprint'
+import {propertyInjectionMetadata} from './propertyInjectionMetadata'
 
 /**
  * Get a collection of dependency requirements for the given target object.
@@ -67,6 +67,7 @@ export const Injectable = (): ClassDecorator => {
     }
 }
 
+
 /**
  * Mark the given class property to be injected by the container.
  * If a `key` is specified, that DependencyKey will be injected.
@@ -77,10 +78,27 @@ export const Injectable = (): ClassDecorator => {
  */
 export const Inject = (key?: DependencyKey, { debug = false } = {}): PropertyDecorator => {
     return (target, property) => {
-        let propertyMetadata = Reflect.getMetadata(DEPENDENCY_KEYS_PROPERTY_METADATA_KEY, target?.constructor || target) as Collection<PropertyDependency>
+        if ( !target?.constructor ) {
+            logIfDebugging('extollo.di.decoration', '[DEBUG] @Inject(): target has no constructor', target)
+            throw new Error('Unable to define property injection: target has no constructor. Enable `extollo.di.decoration` logging to debug')
+        }
+
+        const propertyTarget = target.constructor
+
+        // let propertyMetadata = Reflect.getMetadata(DEPENDENCY_KEYS_PROPERTY_METADATA_KEY, propertyTarget) as Collection<PropertyDependency>
+        // Okay, this is a little fucky. We can't use Reflect's metadata capabilities because we need to write the metadata to
+        // the constructor, not the `target`. Because Reflect is using the prototype to store data, defining a metadata key on the constructor
+        // will define it for its parent constructors as well.
+        // So, if you have class A, class B extends A, and class C extends A, the properties for B and C will be defined on A, causing
+        // BOTH B and C's properties to be injected on any class extending A.
+        // To get around this, we instead define a custom property on the constructor itself, then use hasOwnProperty to make sure we're not
+        // getting the one for the parent class via the prototype chain.
+        let propertyMetadata = Object.prototype.hasOwnProperty.call(propertyTarget, propertyInjectionMetadata) ?
+            (propertyTarget as any)[propertyInjectionMetadata] as Collection<PropertyDependency> : undefined
+
         if ( !propertyMetadata ) {
             propertyMetadata = new Collection<PropertyDependency>()
-            Reflect.defineMetadata(DEPENDENCY_KEYS_PROPERTY_METADATA_KEY, propertyMetadata, target?.constructor || target)
+            ;(propertyTarget as any)[propertyInjectionMetadata] = propertyMetadata
         }
 
         const type = Reflect.getMetadata('design:type', target, property)
@@ -103,7 +121,7 @@ export const Inject = (key?: DependencyKey, { debug = false } = {}): PropertyDec
 
         logIfDebugging('extollo.di.decoration', '[DEBUG] @Inject() - key:', key, 'property:', property, 'target:', target, 'target constructor:', target?.constructor, 'type:', type)
 
-        Reflect.defineMetadata(DEPENDENCY_KEYS_PROPERTY_METADATA_KEY, propertyMetadata, target?.constructor || target)
+        ;(propertyTarget as any)[propertyInjectionMetadata] = propertyMetadata
     }
 }
 

src/di/decorator/propertyInjectionMetadata.ts

@@ -0,0 +1,2 @@
+
+export const propertyInjectionMetadata = Symbol('@extollo/lib:propertyInjectionMetadata')

src/di/factory/Factory.ts

@@ -1,13 +1,13 @@
 import {AbstractFactory} from './AbstractFactory'
 import {
     DEPENDENCY_KEYS_METADATA_KEY,
-    DEPENDENCY_KEYS_PROPERTY_METADATA_KEY,
     DependencyRequirement,
     Instantiable,
     PropertyDependency,
 } from '../types'
 import {Collection, logIfDebugging} from '../../util'
 import 'reflect-metadata'
+import {getPropertyInjectionMetadata} from '../decorator/getPropertyInjectionMetadata'
 
 /**
  * Standard static-class factory. The token of this factory is a reference to a
@@ -57,7 +57,7 @@ export class Factory<T> extends AbstractFactory<T> {
         let currentToken = this.token
 
         do {
-            const loadedMeta = Reflect.getMetadata(DEPENDENCY_KEYS_PROPERTY_METADATA_KEY, currentToken)
+            const loadedMeta = getPropertyInjectionMetadata(currentToken)
             logIfDebugging('extollo.di.injection', 'Factory.getInjectedProperties() target:', currentToken, 'loaded:', loadedMeta)
             if ( loadedMeta ) {
                 meta.concat(loadedMeta)

src/di/index.ts

@@ -13,5 +13,6 @@ export * from './ScopedContainer'
 export * from './types'
 
 export * from './decorator/injection'
+export * from './decorator/getPropertyInjectionMetadata'
 export * from './InjectionAware'
 export * from './constructable'