fix(completion): stop emitting empty switch blocks that break the PowerShell script

An empty switch body is a parse error in PowerShell, and the generator
emitted one for every command whose positionals are all path-typed
(18 in the current registry). PowerShell parses the entire file before
execution, so the whole completion script failed to load. Skip the
positional-index block when no positional produces completions.

Fixes #1293

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: clay-good

.changeset/fix-powershell-empty-switch.md

@@ -0,0 +1,7 @@
+---
+"@fission-ai/openspec": patch
+---
+
+fix(completion): make the PowerShell completion script parse and load again
+
+The generated `OpenSpecCompletion.ps1` contained 18 empty `switch ($positionalIndex) { }` blocks — emitted for commands whose positionals are all `path`-typed (PowerShell completes paths natively, so those cases produce no clauses). A switch with no clauses is a PowerShell parse error ("Missing condition in switch statement clause"), and PowerShell parses the whole file before running it, so the script never loaded and completions never registered. The generator now skips the positional-index block entirely when no positional produces completions, so the script parses clean (18 → 0 errors) and tab completion works.

src/core/completions/generators/powershell-generator.ts

@@ -196,6 +196,20 @@ Register-ArgumentCompleter -CommandName openspec -ScriptBlock $openspecCompleter
     firstPositionalTokenIndex: number,
     indent: string
   ): string[] {
+    const caseLines: string[] = [];
+    for (const [index, positional] of positionals.entries()) {
+      const completion = this.generatePositionalCompletion(positional.type, indent + '    ');
+      if (completion.length === 0) continue;
+      caseLines.push(`${indent}    ${index} {`);
+      caseLines.push(...completion);
+      caseLines.push(`${indent}    }`);
+    }
+
+    // A switch with no clauses is a PowerShell parse error, so when no
+    // positional produces completions skip the whole block (it would only
+    // feed the empty switch anyway).
+    if (caseLines.length === 0) return [];
+
     const lines: string[] = [];
     const valueFlags = this.generateValueFlags(flags);
 
@@ -228,15 +242,7 @@ Register-ArgumentCompleter -CommandName openspec -ScriptBlock $openspecCompleter
     lines.push(`${indent}}`);
     lines.push('');
     lines.push(`${indent}switch ($positionalIndex) {`);
-
-    for (const [index, positional] of positionals.entries()) {
-      const completion = this.generatePositionalCompletion(positional.type, indent + '    ');
-      if (completion.length === 0) continue;
-      lines.push(`${indent}    ${index} {`);
-      lines.push(...completion);
-      lines.push(`${indent}    }`);
-    }
-
+    lines.push(...caseLines);
     lines.push(`${indent}}`);
 
     return lines;

test/core/completions/generators/powershell-generator.test.ts

@@ -1,5 +1,6 @@
 import { describe, it, expect, beforeEach } from 'vitest';
 import { PowerShellGenerator } from '../../../../src/core/completions/generators/powershell-generator.js';
+import { COMMAND_REGISTRY } from '../../../../src/core/completions/command-registry.js';
 import { CommandDefinition } from '../../../../src/core/completions/types.js';
 
 describe('PowerShellGenerator', () => {
@@ -461,6 +462,36 @@ describe('PowerShellGenerator', () => {
 			expect(script).toContain('Get-OpenSpecSpecs');
 		});
 
+		it('should not emit an empty switch when no positional produces completions', () => {
+			const commands: CommandDefinition[] = [
+				{
+					name: 'init',
+					description: 'Initialize OpenSpec',
+					flags: [
+						{
+							name: 'tools',
+							description: 'AI tools to configure',
+							takesValue: true,
+						},
+					],
+					positionals: [{ name: 'path', type: 'path', optional: true }],
+				},
+			];
+
+			const script = generator.generate(commands);
+
+			// An empty switch body is a PowerShell parse error that aborts the
+			// entire completion script ("Missing condition in switch statement clause").
+			expect(script).not.toMatch(/switch \(\$positionalIndex\) \{\s*\}/);
+			expect(script).not.toContain('$positionalIndex');
+		});
+
+		it('should not emit empty switch blocks for the real command registry', () => {
+			const script = generator.generate(COMMAND_REGISTRY);
+
+			expect(script).not.toMatch(/switch \(\$positionalIndex\) \{\s*\}/);
+		});
+
 		it('should not emit trailing commas in @() arrays', () => {
 			const commands: CommandDefinition[] = [
 				{