feat(dispatcher): dependency injection

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 +199,26 @@ 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 {
+        if (this._parent) {
+            throw new MtArgumentError('Cannot inject dependencies to child dispatchers')
+        }
+
+        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 +704,7 @@ 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 +800,9 @@ 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/src/filters/bots.test.ts

@@ -12,6 +12,7 @@ peers.chats.set(1, createStub('channel', { id: 1 }))
 const createMessageContext = (partial: Partial<tl.RawMessage>) =>
     new MessageContext(
         StubTelegramClient.full(), // eslint-disable-line
+        {},
         new Message(createStub('message', partial), peers, false),
     )
 

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)',
+            ])
+        })
+    })
 })

packages/i18n/tests/i18n.test.ts

@@ -85,6 +85,7 @@ describe('i18n', () => {
     it('should parse language from a message', () => {
         const message = new MessageContext(
             null as never,
+            {},
             new Message(
                 { _: 'message', peerId: { _: 'peerUser', userId: 1 } } as never,
                 PeersIndex.from({