From 56c67381df71ecf805b811051c880da531c62e78 Mon Sep 17 00:00:00 2001
From: Martin Pecka <peckama2@fel.cvut.cz>
Date: Mon, 30 Mar 2026 17:42:47 +0200
Subject: [PATCH] feat(args): Allow specifying dynamic arg

Signed-off-by: Martin Pecka <peckama2@fel.cvut.cz>
---
 test/test_xacro.py | 28 ++++++++++++++++++++++++++++
 xacro/__init__.py  |  1 +
 2 files changed, 29 insertions(+)

diff --git a/test/test_xacro.py b/test/test_xacro.py
index 6ee89f8..699934f 100644
--- a/test/test_xacro.py
+++ b/test/test_xacro.py
@@ -1110,6 +1110,34 @@ def test_arg_function(self):
 <a xmlns:xacro="http://www.ros.org/wiki/xacro">
 <xacro:arg name="foo" default="bar"/>${xacro.arg('foo')}</a>'''), '<a>bar</a>')
 
+    def test_dynamic_arg_default(self):
+        self.assert_matches(self.quick_xacro('''
+<a xmlns:xacro="http://www.ros.org/wiki/xacro">
+    <xacro:macro name="dyn_arg" params="name">
+        <xacro:arg name="${name}_test" default="test" />
+        <link name="$(arg ${name}_test)" />
+    </xacro:macro>
+    <xacro:dyn_arg name="a" />
+    <xacro:dyn_arg name="b" />
+</a>'''), '''<a>
+  <link name="test"/>
+  <link name="test"/>
+</a>''')
+
+    def test_dynamic_arg_specified(self):
+        self.assert_matches(self.quick_xacro('''
+<a xmlns:xacro="http://www.ros.org/wiki/xacro">
+    <xacro:macro name="dyn_arg" params="name">
+        <xacro:arg name="${name}_test" default="test" />
+        <link name="$(arg ${name}_test)" />
+    </xacro:macro>
+    <xacro:dyn_arg name="a" />
+    <xacro:dyn_arg name="b" />
+</a>''', cli=['a_test:=test1', 'b_test:=test2']), '''<a>
+  <link name="test1"/>
+  <link name="test2"/>
+</a>''')
+
     def test_broken_include_error_reporting(self):
         self.assertRaises(xml.parsers.expat.ExpatError, self.quick_xacro,
         '''<a xmlns:xacro="http://www.ros.org/wiki/xacro">
diff --git a/xacro/__init__.py b/xacro/__init__.py
index ef224df..f924928 100644
--- a/xacro/__init__.py
+++ b/xacro/__init__.py
@@ -952,6 +952,7 @@ def eval_all(node, macros, symbols):
 
             elif node.tagName == 'xacro:arg':
                 name, default = check_attrs(node, ['name', 'default'], [])
+                name = str(eval_text(name, symbols))
                 if name not in substitution_args_context['arg']:
                     substitution_args_context['arg'][name] = str(eval_text(default, symbols))