From 6c01f86540e8e8b134c231882507aef9a9b46e36 Mon Sep 17 00:00:00 2001
From: John Gee <john@ruru.gen.nz>
Date: Sun, 17 Aug 2025 11:40:57 +1200
Subject: [PATCH] Collect variadic with push, add tests

---
 lib/argument.js                 |  7 ++++---
 lib/command.js                  |  2 +-
 lib/option.js                   |  7 ++++---
 tests/argument.variadic.test.js | 13 +++++++++++++
 tests/options.variadic.test.js  |  8 ++++++++
 5 files changed, 30 insertions(+), 7 deletions(-)

diff --git a/lib/argument.js b/lib/argument.js
index 33493d44a..2c2f840e3 100644
--- a/lib/argument.js
+++ b/lib/argument.js
@@ -53,12 +53,13 @@ class Argument {
    * @package
    */
 
-  _concatValue(value, previous) {
+  _collectValue(value, previous) {
     if (previous === this.defaultValue || !Array.isArray(previous)) {
       return [value];
     }
 
-    return previous.concat(value);
+    previous.push(value);
+    return previous;
   }
 
   /**
@@ -103,7 +104,7 @@ class Argument {
         );
       }
       if (this.variadic) {
-        return this._concatValue(arg, previous);
+        return this._collectValue(arg, previous);
       }
       return arg;
     };
diff --git a/lib/command.js b/lib/command.js
index bb6529e49..a176dfbb9 100644
--- a/lib/command.js
+++ b/lib/command.js
@@ -701,7 +701,7 @@ Expecting one of '${allowedValues.join("', '")}'`);
       if (val !== null && option.parseArg) {
         val = this._callParseArg(option, val, oldValue, invalidValueMessage);
       } else if (val !== null && option.variadic) {
-        val = option._concatValue(val, oldValue);
+        val = option._collectValue(val, oldValue);
       }
 
       // Fill-in appropriate missing values. Long winded but easy to follow.
diff --git a/lib/option.js b/lib/option.js
index 715c6cf08..4a0bd7fac 100644
--- a/lib/option.js
+++ b/lib/option.js
@@ -162,12 +162,13 @@ class Option {
    * @package
    */
 
-  _concatValue(value, previous) {
+  _collectValue(value, previous) {
     if (previous === this.defaultValue || !Array.isArray(previous)) {
       return [value];
     }
 
-    return previous.concat(value);
+    previous.push(value);
+    return previous;
   }
 
   /**
@@ -186,7 +187,7 @@ class Option {
         );
       }
       if (this.variadic) {
-        return this._concatValue(arg, previous);
+        return this._collectValue(arg, previous);
       }
       return arg;
     };
diff --git a/tests/argument.variadic.test.js b/tests/argument.variadic.test.js
index 07732e54b..a74c9be0e 100644
--- a/tests/argument.variadic.test.js
+++ b/tests/argument.variadic.test.js
@@ -101,4 +101,17 @@ describe('variadic argument', () => {
     program.parse(['one', 'two'], { from: 'user' });
     expect(passedArg).toEqual(['one', 'two']);
   });
+
+  test('when variadic has default array then specified value is used instead of default (not appended)', () => {
+    const program = new commander.Command();
+    let passedArg;
+    program
+      .addArgument(new commander.Argument('[value...]').default(['DEFAULT']))
+      .action((value) => {
+        passedArg = value;
+      });
+
+    program.parse(['one', 'two'], { from: 'user' });
+    expect(passedArg).toEqual(['one', 'two']);
+  });
 });
diff --git a/tests/options.variadic.test.js b/tests/options.variadic.test.js
index de2f18c1b..0fe419465 100644
--- a/tests/options.variadic.test.js
+++ b/tests/options.variadic.test.js
@@ -162,4 +162,12 @@ describe('variadic special cases', () => {
 
     expect(program.options[0].variadic).toBeFalsy();
   });
+
+  test('when option has default array then specified value is used instead of default (not appended)', () => {
+    const program = new commander.Command();
+    program.option('-c,--comma [value...]', 'values', ['default']);
+    program.parse(['--comma', 'CCC'], { from: 'user' });
+
+    expect(program.opts().comma).toEqual(['CCC']);
+  });
 });