feat: allow specifying handlers as config

demo.citty.ts

@@ -60,63 +60,68 @@ main.subCommands = {
   lint: lintCommand,
 } as Record<string, CommandDef<any>>;
 
-const completion = await tab(main);
-
-for (const command of completion.commands.values()) {
-  if (command.name === 'lint') {
-    command.handler = () => {
-      return [
-        { value: 'main.ts', description: 'Main file' },
-        { value: 'index.ts', description: 'Index file' },
-      ];
-    };
-  }
-
-  for (const [o, config] of command.options.entries()) {
-    if (o === '--port') {
-      config.handler = () => {
-        return [
-          { value: '3000', description: 'Development server port' },
-          { value: '8080', description: 'Alternative port' },
-        ];
-      };
-    }
-    if (o === '--host') {
-      config.handler = () => {
+const completion = await tab(main, {
+  subCommands: {
+    lint: {
+      handler() {
         return [
-          { value: 'localhost', description: 'Localhost' },
-          { value: '0.0.0.0', description: 'All interfaces' },
+          { value: 'main.ts', description: 'Main file' },
+          { value: 'index.ts', description: 'Index file' },
         ];
-      };
-    }
-    if (o === '--config') {
-      config.handler = () => {
+      },
+    },
+    dev: {
+      options: {
+        port: {
+          handler() {
+            return [
+              { value: '3000', description: 'Development server port' },
+              { value: '8080', description: 'Alternative port' },
+            ];
+          },
+        },
+        host: {
+          handler() {
+            return [
+              { value: 'localhost', description: 'Localhost' },
+              { value: '0.0.0.0', description: 'All interfaces' },
+            ];
+          },
+        },
+      },
+    },
+  },
+  options: {
+    config: {
+      handler() {
         return [
           { value: 'vite.config.ts', description: 'Vite config file' },
           { value: 'vite.config.js', description: 'Vite config file' },
         ];
-      };
-    }
-    if (o === '--mode') {
-      config.handler = () => {
+      },
+    },
+    mode: {
+      handler() {
         return [
           { value: 'development', description: 'Development mode' },
           { value: 'production', description: 'Production mode' },
         ];
-      };
-    }
-    if (o === '--logLevel') {
-      config.handler = () => {
+      },
+    },
+    logLevel: {
+      handler() {
         return [
           { value: 'info', description: 'Info level' },
           { value: 'warn', description: 'Warn level' },
           { value: 'error', description: 'Error level' },
           { value: 'silent', description: 'Silent level' },
         ];
-      };
-    }
-  }
-}
+      },
+    },
+  },
+});
+
+completion;
 
 const cli = createMain(main);
 

src/citty.ts

@@ -3,7 +3,7 @@ import * as zsh from './zsh';
 import * as bash from './bash';
 import * as fish from './fish';
 import * as powershell from './powershell';
-import { Completion } from '.';
+import { Completion, type Handler } from '.';
 import type {
   ArgsDef,
   CommandDef,
@@ -29,15 +29,34 @@ function isConfigPositional<T extends ArgsDef>(config: CommandDef<T>) {
   );
 }
 
-async function handleSubCommands<T extends ArgsDef = ArgsDef>(
+// TODO (43081j): use type inference some day, so we can type-check
+// that the sub commands exist, the options exist, etc.
+interface CompletionConfig {
+  handler?: Handler;
+  subCommands?: Record<string, CompletionConfig>;
+  options?: Record<
+    string,
+    {
+      handler: Handler;
+    }
+  >;
+}
+
+const noopHandler: Handler = () => {
+  return [];
+};
+
+async function handleSubCommands(
   completion: Completion,
   subCommands: SubCommandsDef,
-  parentCmd?: string
+  parentCmd?: string,
+  completionConfig?: Record<string, CompletionConfig>
 ) {
   for (const [cmd, resolvableConfig] of Object.entries(subCommands)) {
     const config = await resolve(resolvableConfig);
     const meta = await resolve(config.meta);
     const subCommands = await resolve(config.subCommands);
+    const subCompletionConfig = completionConfig?.[cmd];
 
     if (!meta || typeof meta?.description !== 'string') {
       throw new Error('Invalid meta or missing description.');
@@ -47,15 +66,18 @@ async function handleSubCommands<T extends ArgsDef = ArgsDef>(
       cmd,
       meta.description,
       isPositional ? [false] : [],
-      async (previousArgs, toComplete, endsWithSpace) => {
-        return [];
-      },
+      subCompletionConfig?.handler ?? noopHandler,
       parentCmd
     );
 
     // Handle nested subcommands recursively
     if (subCommands) {
-      await handleSubCommands(completion, subCommands, name);
+      await handleSubCommands(
+        completion,
+        subCommands,
+        name,
+        subCompletionConfig?.subCommands
+      );
     }
 
     // Handle arguments
@@ -77,18 +99,17 @@ async function handleSubCommands<T extends ArgsDef = ArgsDef>(
           name,
           `--${argName}`,
           conf.description ?? '',
-          async (previousArgs, toComplete, endsWithSpace) => {
-            return [];
-          },
+          subCompletionConfig?.options?.[argName]?.handler ?? noopHandler,
           shortFlag
         );
       }
     }
   }
 }
 
-export default async function tab<T extends ArgsDef = ArgsDef>(
-  instance: CommandDef<T>
+export default async function tab<TArgs extends ArgsDef>(
+  instance: CommandDef<TArgs>,
+  completionConfig?: CompletionConfig
 ) {
   const completion = new Completion();
 
@@ -113,12 +134,15 @@ export default async function tab<T extends ArgsDef = ArgsDef>(
     root,
     meta?.description ?? '',
     isPositional ? [false] : [],
-    async (previousArgs, toComplete, endsWithSpace) => {
-      return [];
-    }
+    completionConfig?.handler ?? noopHandler
   );
 
-  await handleSubCommands(completion, subCommands);
+  await handleSubCommands(
+    completion,
+    subCommands,
+    undefined,
+    completionConfig?.subCommands
+  );
 
   if (instance.args) {
     for (const [argName, argConfig] of Object.entries(instance.args)) {
@@ -127,9 +151,7 @@ export default async function tab<T extends ArgsDef = ArgsDef>(
         root,
         `--${argName}`,
         conf.description ?? '',
-        async (previousArgs, toComplete, endsWithSpace) => {
-          return [];
-        }
+        completionConfig?.options?.[argName]?.handler ?? noopHandler
       );
     }
   }

src/index.ts

@@ -66,7 +66,7 @@ type Item = {
   value: string;
 };
 
-type Handler = (
+export type Handler = (
   previousArgs: string[],
   toComplete: string,
   endsWithSpace: boolean