feat(dispatcher): dependency injection (#55)

packages/dispatcher/src/dispatcher.ts

@@ -90,6 +90,10 @@ export interface DispatcherParams {
     key?: StateKeyDelegate
 }
 
+export interface DispatcherDependencies {
+    // intentionally empty, to be extended by consumers
+}
+
 /**
  * Updates dispatcher
  */
@@ -112,6 +116,8 @@ export class Dispatcher<State extends object = never> {
     private _customStateKeyDelegate?: StateKeyDelegate
     private _customStorage?: StateService
 
+    private _deps: DispatcherDependencies = {}
+
     private _errorHandler?: <T = {}>(
         err: Error,
         update: ParsedUpdate & T,
@@ -193,6 +199,42 @@ export class Dispatcher<State extends object = never> {
         return this._scene
     }
 
+    /**
+     * Inject a dependency to be available in this dispatcher and all its children.
+     *
+     * **Note**: This is only available for the root dispatcher.
+     */
+    inject<Name extends keyof DispatcherDependencies>(name: Name, value: DispatcherDependencies[Name]): void
+    /**
+     * Inject dependencies to be available in this dispatcher and all its children.
+     *
+     * **Note**: This is only available for the root dispatcher.
+     */
+    inject(deps: Partial<DispatcherDependencies>): void
+    inject<Name extends keyof DispatcherDependencies>(
+        name: Name | Partial<DispatcherDependencies>,
+        value?: DispatcherDependencies[Name],
+    ): void {
+        if (this._parent) {
+            throw new MtArgumentError('Cannot inject dependencies to child dispatchers')
+        }
+
+        if (typeof name === 'object') {
+            for (const [k, v] of Object.entries(name)) {
+                (this._deps as any)[k] = v
+            }
+        } else {
+            this._deps[name] = value!
+        }
+    }
+
+    /**
+     * Get the dependencies injected into this dispatcher.
+     */
+    get deps(): DispatcherDependencies {
+        return this._deps
+    }
+
     /**
      * Bind the dispatcher to the client.
      * Called by the constructor automatically if
@@ -678,6 +720,7 @@ export class Dispatcher<State extends object = never> {
         child._parent = this as any
         child._client = this._client
         child._storage = this._storage
+        child._deps = this._deps
         child._stateKeyDelegate = this._stateKeyDelegate
         child._customStorage ??= this._customStorage
         child._customStateKeyDelegate ??= this._customStateKeyDelegate
@@ -773,8 +816,9 @@ export class Dispatcher<State extends object = never> {
 
     private _unparent(): void {
         this._parent = this._client = undefined
-        ;(this as any)._stateKeyDelegate = undefined
-        ;(this as any)._storage = undefined
+        this._deps = {} // to avoid dangling references
+        this._stateKeyDelegate = undefined
+        this._storage = undefined
     }
 
     /**

packages/dispatcher/tests/dispatcher.test.ts

@@ -1,8 +1,8 @@
 import { describe, expect, it } from 'vitest'
 
-import { PeersIndex } from '@mtcute/core'
+import { Message, PeersIndex } from '@mtcute/core'
 import { TelegramClient } from '@mtcute/core/client.js'
-import { StubTelegramClient } from '@mtcute/test'
+import { createStub, StubTelegramClient } from '@mtcute/test'
 
 import { Dispatcher, PropagationAction } from '../src/index.js'
 
@@ -237,4 +237,41 @@ describe('Dispatcher', () => {
             ])
         })
     })
+
+    describe('Dependency injection', () => {
+        it('should inject dependencies into update contexts', async () => {
+            const dp = Dispatcher.for(client)
+
+            dp.inject('foo' as never, 'foo' as never)
+
+            const log: string[] = []
+
+            dp.onNewMessage(() => {
+                // eslint-disable-next-line
+                log.push(`received ${(dp.deps as any).foo}`)
+            })
+
+            const dp2 = Dispatcher.child()
+
+            dp2.onNewMessage(() => {
+                // eslint-disable-next-line
+                log.push(`received ${(dp.deps as any).foo} (child)`)
+            })
+
+            dp.addChild(dp2)
+
+            await dp.dispatchUpdateNow({
+                name: 'new_message',
+                data: new Message(
+                    createStub('message'),
+                    emptyPeers,
+                ),
+            })
+
+            expect(log).eql([
+                'received foo',
+                'received foo (child)',
+            ])
+        })
+    })
 })

tsconfig.json

@@ -14,7 +14,7 @@
         "noImplicitAny": true,
         "noImplicitThis": true,
         "incremental": true,
-        "stripInternal": true,
+        "stripInternal": false,
         "skipLibCheck": true,
         "composite": true,
         "types": [