From c6be50ca83ce8ceaf9fa99d71aa098edfd41fbfa Mon Sep 17 00:00:00 2001
From: sapphi-red <green@sapphi.red>
Date: Fri, 11 Mar 2022 19:41:08 +0900
Subject: [PATCH 1/2] feat: throw error on unused args

---
 src/CAC.ts                 |  8 +++++++-
 src/Command.ts             | 16 ++++++++++++++++
 src/__test__/index.test.ts | 10 ++++++++++
 3 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/src/CAC.ts b/src/CAC.ts
index 7a3df11a..c4c4e987 100644
--- a/src/CAC.ts
+++ b/src/CAC.ts
@@ -220,7 +220,11 @@ class CAC extends EventEmitter {
       this.unsetMatchedCommand()
     }
 
-    if (this.options.version && this.showVersionOnExit && this.matchedCommandName == null) {
+    if (
+      this.options.version &&
+      this.showVersionOnExit &&
+      this.matchedCommandName == null
+    ) {
       this.outputVersion()
       run = false
       this.unsetMatchedCommand()
@@ -328,6 +332,8 @@ class CAC extends EventEmitter {
 
     command.checkRequiredArgs()
 
+    command.checkUnusedArgs()
+
     const actionArgs: any[] = []
     command.args.forEach((arg, index) => {
       if (arg.variadic) {
diff --git a/src/Command.ts b/src/Command.ts
index 93027972..d7f1aeac 100644
--- a/src/Command.ts
+++ b/src/Command.ts
@@ -295,6 +295,22 @@ class Command {
       }
     }
   }
+
+  /**
+   * Check if the number of args is more than expected
+   */
+  checkUnusedArgs() {
+    const hasVariadicArg = this.args.some((arg) => arg.variadic)
+    const maximumArgsCount = hasVariadicArg ? Infinity : this.args.length
+
+    if (maximumArgsCount < this.cli.args.length) {
+      const argsString = this.cli.args
+        .slice(maximumArgsCount)
+        .map((arg) => `\`${arg}\``)
+        .join(', ')
+      throw new CACError(`Unused args: ${argsString}`)
+    }
+  }
 }
 
 class GlobalCommand extends Command {
diff --git a/src/__test__/index.test.ts b/src/__test__/index.test.ts
index 6cb84069..7bbd5905 100644
--- a/src/__test__/index.test.ts
+++ b/src/__test__/index.test.ts
@@ -165,6 +165,16 @@ test('throw on unknown options', () => {
   }).toThrowError('Unknown option `--xx`')
 })
 
+test('throw on unused args', () => {
+  const cli = cac()
+
+  cli.command('build [entry]', 'Build your app').action(() => {})
+
+  expect(() => {
+    cli.parse(`node bin build app.js foo bar`.split(' '))
+  }).toThrowError('Unused args: `foo`, `bar`')
+})
+
 describe('--version in help message', () => {
   test('sub command', async () => {
     const output = await getOutput('help.js', ['lint', '--help'])

From 92051f26e86edd02b858b5b6e17c605a34fcc96e Mon Sep 17 00:00:00 2001
From: sapphi-red <49056869+sapphi-red@users.noreply.github.com>
Date: Wed, 25 Feb 2026 14:35:26 +0900
Subject: [PATCH 2/2] chore: fix build

---
 src/command.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/command.ts b/src/command.ts
index 9f2a1dcb..33058597 100644
--- a/src/command.ts
+++ b/src/command.ts
@@ -311,7 +311,7 @@ export class Command {
   /**
    * Check if the number of args is more than expected
    */
-  checkUnusedArgs() {
+  checkUnusedArgs(): void {
     const hasVariadicArg = this.args.some((arg) => arg.variadic)
     const maximumArgsCount = hasVariadicArg ? Infinity : this.args.length