Fix circular dependencies in migrator

src/di/Container.ts

@@ -1,4 +1,4 @@
-import {DependencyKey, InstanceRef, Instantiable, isInstantiable, StaticClass} from './types'
+import {DependencyKey, InstanceRef, Instantiable, isInstantiable, StaticClass, TypedDependencyKey} from './types'
 import {AbstractFactory} from './factory/AbstractFactory'
 import {collect, Collection, globalRegistry, logIfDebugging} from '../util'
 import {Factory} from './factory/Factory'
@@ -7,7 +7,7 @@ import {ClosureFactory} from './factory/ClosureFactory'
 import NamedFactory from './factory/NamedFactory'
 import SingletonFactory from './factory/SingletonFactory'
 import {InvalidDependencyKeyError} from './error/InvalidDependencyKeyError'
-import {ContainerBlueprint} from './ContainerBlueprint'
+import {ContainerBlueprint, ContainerResolutionCallback} from './ContainerBlueprint'
 
 export type MaybeFactory<T> = AbstractFactory<T> | undefined
 export type MaybeDependency = any | undefined
@@ -17,18 +17,36 @@ export type ResolvedDependency = { paramIndex: number, key: DependencyKey, resol
  * A container of resolve-able dependencies that are created via inversion-of-control.
  */
 export class Container {
+    /**
+     * Given a Container instance, apply the ContainerBlueprint to it.
+     * @param container
+     */
+    public static realizeContainer<T extends Container>(container: T): T {
+        ContainerBlueprint.getContainerBlueprint()
+            .resolve()
+            .map(factory => container.registerFactory(factory))
+
+        ContainerBlueprint.getContainerBlueprint()
+            .resolveConstructable()
+            .map((factory: StaticClass<AbstractFactory<any>, any>) => container.registerFactory(container.make(factory)))
+
+        ContainerBlueprint.getContainerBlueprint()
+            .resolveResolutionCallbacks()
+            .map((listener: {key: TypedDependencyKey<any>, callback: ContainerResolutionCallback<any>}) => {
+                container.onResolve(listener.key)
+                    .then(value => listener.callback(value))
+            })
+
+        return container
+    }
+
     /**
      * Get the global instance of this container.
      */
     public static getContainer(): Container {
         const existing = <Container | undefined> globalRegistry.getGlobal('extollo/injector')
         if ( !existing ) {
-            const container = new Container()
-
-            ContainerBlueprint.getContainerBlueprint()
-                .resolve()
-                .map(factory => container.registerFactory(factory))
-
+            const container = Container.realizeContainer(new Container())
             globalRegistry.setGlobal('extollo/injector', container)
             return container
         }
@@ -48,6 +66,12 @@ export class Container {
      */
     protected instances: Collection<InstanceRef> = new Collection<InstanceRef>()
 
+    /**
+     * Collection of callbacks waiting for a dependency key to be resolved.
+     * @protected
+     */
+    protected waitingResolveCallbacks: Collection<{ key: DependencyKey, callback: (t: unknown) => unknown }> = new Collection<{key: DependencyKey; callback:(t: unknown) => unknown}>();
+
     constructor() {
         this.registerSingletonInstance<Container>(Container, this)
         this.registerSingleton('injector', this)
@@ -172,6 +196,26 @@ export class Container {
         return this.instances.where('key', '=', key).isNotEmpty()
     }
 
+    /**
+     * Get a Promise that resolves the first time the given dependency key is resolved
+     * by the application. If it has already been resolved, the Promise will resolve immediately.
+     * @param key
+     */
+    onResolve<T>(key: TypedDependencyKey<T>): Promise<T> {
+        if ( this.hasInstance(key) ) {
+            return new Promise<T>(res => res(this.make<T>(key)))
+        }
+
+        // Otherwise, we haven't instantiated an instance with this key yet,
+        // so put it onto the waitlist.
+        return new Promise<T>(res => {
+            this.waitingResolveCallbacks.push({
+                key,
+                callback: (res as (t: unknown) => unknown),
+            })
+        })
+    }
+
     /**
      * Returns true if the container has a factory for the given key.
      * @param {DependencyKey} key
@@ -234,6 +278,15 @@ export class Container {
             value: newInstance,
         })
 
+        this.waitingResolveCallbacks = this.waitingResolveCallbacks.filter(waiter => {
+            if ( waiter.key === key ) {
+                waiter.callback(newInstance)
+                return false
+            }
+
+            return true
+        })
+
         return newInstance
     }