chore: make context flavor transformative

.github/workflows/build.yml

@@ -14,7 +14,7 @@ jobs:
 
       - uses: denoland/setup-deno@v1
         with:
-          deno-version: v1.x
+          deno-version: v2.x
 
       - name: Format
         run: deno fmt --check
@@ -23,7 +23,7 @@ jobs:
         run: deno lint
 
       - name: Check
-        run: deno check src/mod.ts
+        run: deno check --allow-import src/mod.ts
 
       - name: Test
         run: deno task test

deno.jsonc

@@ -9,7 +9,7 @@
   },
   "tasks": {
     "example": "cd examples && deno run --allow-net --allow-read deno.ts",
-    "test": "deno test --allow-read --allow-run --allow-write",
+    "test": "deno test --allow-import --allow-read --allow-run --allow-write",
     "dnt": "deno run --allow-env --allow-net --allow-read --allow-run --allow-write scripts/dnt.ts"
   },
   "test": {

src/i18n.ts

@@ -110,7 +110,7 @@ export class I18n<C extends Context = Context> {
   }
 
   /** Returns a middleware to .use on the `Bot` instance. */
-  middleware(): MiddlewareFn<C & I18nFlavor> {
+  middleware(): MiddlewareFn<I18nFlavor<C>> {
     return middleware(this.fluent, this.config);
   }
 }
@@ -123,7 +123,7 @@ function middleware<C extends Context = Context>(
     useSession,
     globalTranslationContext,
   }: I18nConfig<C>,
-): MiddlewareFn<C & I18nFlavor> {
+): MiddlewareFn<I18nFlavor<C>> {
   return async function (ctx, next): Promise<void> {
     let translate: TranslateFunction;
 
@@ -201,10 +201,10 @@ should either enable sessions or use `ctx.i18n.useLocale()` instead.",
  *
  * @param key Key of the message to listen for.
  */
-export function hears(key: string) {
-  return function <C extends Context & I18nFlavor>(
-    ctx: C,
-  ): ctx is HearsContext<C> {
+export function hears<C extends Context>(key: string) {
+  return function <TContext extends I18nFlavor<C>>(
+    ctx: TContext,
+  ): ctx is HearsContext<TContext> {
     const expected = ctx.t(key);
     return ctx.hasText(expected);
   };

src/types.ts

@@ -42,7 +42,7 @@ export type TranslateFunction = <K extends string>(
   variables?: TranslationVariables<K>,
 ) => string;
 
-export interface I18nFlavor {
+export type I18nFlavor<C extends Context> = C & {
   /** I18n context namespace object */
   i18n: {
     /** Fluent instance used internally. */
@@ -76,7 +76,7 @@ export interface I18nFlavor {
   translate: TranslateFunction;
   /** Translation function bound to the current locale. */
   t: TranslateFunction;
-}
+};
 
 export interface I18nConfig<C extends Context = Context> {
   /**

tests/bot.ts

@@ -1,14 +1,13 @@
-import { Bot, Context, session, SessionFlavor } from "./deps.ts";
 import { hears, I18n, I18nFlavor } from "../src/mod.ts";
+import { Bot, Context, session, SessionFlavor } from "./deps.ts";
 import { makeTempLocalesDir } from "./utils.ts";
 
 interface SessionData {
   apples: number;
 }
 
 type MyContext =
-  & Context
-  & I18nFlavor
+  & I18nFlavor<Context>
   & SessionFlavor<SessionData>;
 
 export const bot = new Bot<MyContext>("TOKEN");

tests/session_bot.ts

@@ -1,11 +1,10 @@
-import { Bot, Context, session, SessionFlavor } from "./deps.ts";
 import { I18n, I18nFlavor } from "../src/mod.ts";
+import { Bot, Context, session, SessionFlavor } from "./deps.ts";
 import { makeTempLocalesDir } from "./utils.ts";
 
 type SessionData = Record<never, never>;
 type MyContext =
-  & Context
-  & I18nFlavor
+  & I18nFlavor<Context>
   & SessionFlavor<SessionData>;
 
 export const bot = new Bot<MyContext>("TOKEN");