fix(ui): prevent over-eager slash subcommand completion (#20136)

packages/cli/src/ui/hooks/useCommandCompletion.test.tsx

@@ -1,6 +1,6 @@
 /**
  * @license
- * Copyright 2025 Google LLC
+ * Copyright 2026 Google LLC
  * SPDX-License-Identifier: Apache-2.0
  */
 
@@ -20,7 +20,7 @@ import {
   useCommandCompletion,
   CompletionMode,
 } from './useCommandCompletion.js';
-import type { CommandContext } from '../commands/types.js';
+import type { CommandContext, SlashCommand } from '../commands/types.js';
 import type { Config } from '@google/gemini-cli-core';
 import { useTextBuffer } from '../components/shared/text-buffer.js';
 import type { Suggestion } from '../components/SuggestionsDisplay.js';
@@ -72,7 +72,11 @@ const setupMocks = ({
   shellSuggestions = [],
   isLoading = false,
   isPerfectMatch = false,
-  slashCompletionRange = { completionStart: 0, completionEnd: 0 },
+  slashCompletionRange = {
+    completionStart: 0,
+    completionEnd: 0,
+    getCommandFromSuggestion: () => undefined,
+  },
   shellCompletionRange = {
     completionStart: 0,
     completionEnd: 0,
@@ -85,7 +89,13 @@ const setupMocks = ({
   shellSuggestions?: Suggestion[];
   isLoading?: boolean;
   isPerfectMatch?: boolean;
-  slashCompletionRange?: { completionStart: number; completionEnd: number };
+  slashCompletionRange?: {
+    completionStart: number;
+    completionEnd: number;
+    getCommandFromSuggestion: (
+      suggestion: Suggestion,
+    ) => SlashCommand | undefined;
+  };
   shellCompletionRange?: {
     completionStart: number;
     completionEnd: number;
@@ -471,10 +481,15 @@ describe('useCommandCompletion', () => {
   });
 
   describe('handleAutocomplete', () => {
-    it('should complete a partial command', async () => {
+    it('should complete a partial command and NOT add a space if it has an action', async () => {
       setupMocks({
         slashSuggestions: [{ label: 'memory', value: 'memory' }],
-        slashCompletionRange: { completionStart: 1, completionEnd: 4 },
+        slashCompletionRange: {
+          completionStart: 1,
+          completionEnd: 4,
+          getCommandFromSuggestion: () =>
+            ({ action: vi.fn() }) as unknown as SlashCommand,
+        },
       });
 
       const { result } = await renderCommandCompletionHook('/mem');
@@ -487,12 +502,40 @@ describe('useCommandCompletion', () => {
         result.current.handleAutocomplete(0);
       });
 
-      expect(result.current.textBuffer.text).toBe('/memory ');
+      expect(result.current.textBuffer.text).toBe('/memory');
+    });
+
+    it('should complete a partial command and ADD a space if it has NO action (e.g. just a parent)', async () => {
+      setupMocks({
+        slashSuggestions: [{ label: 'chat', value: 'chat' }],
+        slashCompletionRange: {
+          completionStart: 1,
+          completionEnd: 5,
+          getCommandFromSuggestion: () => ({}) as unknown as SlashCommand, // No action
+        },
+      });
+
+      const { result } = await renderCommandCompletionHook('/chat');
+
+      await waitFor(() => {
+        expect(result.current.suggestions.length).toBe(1);
+      });
+
+      act(() => {
+        result.current.handleAutocomplete(0);
+      });
+
+      expect(result.current.textBuffer.text).toBe('/chat ');
     });
 
     it('should complete a file path', async () => {
       setupMocks({
         atSuggestions: [{ label: 'src/file1.txt', value: 'src/file1.txt' }],
+        slashCompletionRange: {
+          completionStart: 0,
+          completionEnd: 0,
+          getCommandFromSuggestion: () => undefined,
+        },
       });
 
       const { result } = await renderCommandCompletionHook('@src/fi');
@@ -517,7 +560,11 @@ describe('useCommandCompletion', () => {
             insertValue: 'resume list',
           },
         ],
-        slashCompletionRange: { completionStart: 1, completionEnd: 5 },
+        slashCompletionRange: {
+          completionStart: 1,
+          completionEnd: 5,
+          getCommandFromSuggestion: () => undefined,
+        },
       });
 
       const { result } = await renderCommandCompletionHook('/resu');
@@ -539,6 +586,11 @@ describe('useCommandCompletion', () => {
 
       setupMocks({
         atSuggestions: [{ label: 'src/file1.txt', value: 'src/file1.txt' }],
+        slashCompletionRange: {
+          completionStart: 0,
+          completionEnd: 0,
+          getCommandFromSuggestion: () => undefined,
+        },
       });
 
       const { result } = await renderCommandCompletionHook(text, cursorOffset);
@@ -559,6 +611,11 @@ describe('useCommandCompletion', () => {
     it('should complete a directory path ending with / without a trailing space', async () => {
       setupMocks({
         atSuggestions: [{ label: 'src/components/', value: 'src/components/' }],
+        slashCompletionRange: {
+          completionStart: 0,
+          completionEnd: 0,
+          getCommandFromSuggestion: () => undefined,
+        },
       });
 
       const { result } = await renderCommandCompletionHook('@src/comp');
@@ -579,6 +636,11 @@ describe('useCommandCompletion', () => {
         atSuggestions: [
           { label: 'src\\components\\', value: 'src\\components\\' },
         ],
+        slashCompletionRange: {
+          completionStart: 0,
+          completionEnd: 0,
+          getCommandFromSuggestion: () => undefined,
+        },
       });
 
       const { result } = await renderCommandCompletionHook('@src\\comp');
@@ -594,6 +656,33 @@ describe('useCommandCompletion', () => {
       expect(result.current.textBuffer.text).toBe('@src\\components\\');
     });
 
+    it('should ADD a space for AT completion even if name matches a command with an action', async () => {
+      // Setup a mock where getCommandFromSuggestion WOULD return a command with an action
+      // if it were in SLASH mode.
+      setupMocks({
+        atSuggestions: [{ label: 'memory', value: 'memory' }],
+        slashCompletionRange: {
+          completionStart: 0,
+          completionEnd: 0,
+          getCommandFromSuggestion: () =>
+            ({ action: vi.fn() }) as unknown as SlashCommand,
+        },
+      });
+
+      const { result } = await renderCommandCompletionHook('@mem');
+
+      await waitFor(() => {
+        expect(result.current.suggestions.length).toBe(1);
+      });
+
+      act(() => {
+        result.current.handleAutocomplete(0);
+      });
+
+      // Should have a space because it's AT mode, not SLASH mode
+      expect(result.current.textBuffer.text).toBe('@memory ');
+    });
+
     it('should show ghost text for a single shell completion', async () => {
       const text = 'l';
       setupMocks({
@@ -905,6 +994,11 @@ describe('useCommandCompletion', () => {
     it('should complete file path and add trailing space', async () => {
       setupMocks({
         atSuggestions: [{ label: 'src/file.txt', value: 'src/file.txt' }],
+        slashCompletionRange: {
+          completionStart: 0,
+          completionEnd: 0,
+          getCommandFromSuggestion: () => undefined,
+        },
       });
 
       const { result } = await renderCommandCompletionHook('/cmd @src/fi');