Slightly different approach.

tools/roslaunch/resources/example.launch

@@ -59,7 +59,14 @@
   <!-- more compact import syntax -->
   <include ns="included2" file="$(find roslaunch)/resources/example-include.launch" />
 
-  <!-- Pass over an include with an if-attribute that evaluates to false. -->
-  <arg name="dont_include_me" value="false" />
-  <include if="$(arg dont_include_me)" file="does/not/exist.launch" />
+  <!-- Pass over an include and node with if-attributes that evaluate to false. -->
+  <arg name="false_arg" value="false" />
+  <include if="$(arg false_arg)" file="does/not/exist.launch" />
+  <node if="$(arg false_arg)" pkg="doesnt_exit" type="nope" name="nope" />
+
+  <arg name="true_arg" value="true" />
+  <group unless="$(arg true_arg)">
+      <include file="does/not/exist.launch" />
+      <node pkg="doesnt_exit" type="nope" name="nope" />
+  </group>
 </launch>

tools/roslaunch/src/roslaunch/depends.py

@@ -95,20 +95,16 @@ def _get_arg_value(tag, context):
     else:
         raise RoslaunchDepsException("No value for arg [%s]"%(name))
 
-def _parse_arg(tag, context):
-    name = tag.attributes['name'].value
+def _check_ifunless(tag, context):
     if tag.attributes.has_key('if'):
         val = resolve_args(tag.attributes['if'].value, context)
-        if convert_value(val, 'bool'):
-            return (name, _get_arg_value(tag, context))
-    elif tag.attributes.has_key('unless'):
-        val = resolve_args(tag.attributes['unless'].value, context)
         if not convert_value(val, 'bool'):
-            return (name, _get_arg_value(tag, context))
-    else:
-        return (name, _get_arg_value(tag, context))
-    # nothing to return (no value, or conditional wasn't satisfied)
-    return None
+            return False
+    if tag.attributes.has_key('unless'):
+        val = resolve_args(tag.attributes['unless'].value, context)
+        if convert_value(val, 'bool'):
+            return False
+    return True
 
 def _parse_subcontext(tags, context):
     subcontext = {'arg': {}}
@@ -117,12 +113,8 @@ def _parse_subcontext(tags, context):
        return subcontext
 
     for tag in [t for t in tags if t.nodeType == DomNode.ELEMENT_NODE]:
-        if tag.tagName == 'arg':
-            # None is returned for args with if/unless that evaluate to false
-            ret = _parse_arg(tag, context)
-            if ret is not None:
-                (name, val) = ret
-                subcontext['arg'][name] = val
+        if tag.tagName == 'arg' and _check_ifunless(tag, context):
+            subcontext['arg'][tag.attributes['name'].value] = _get_arg_value(tag, context)
     return subcontext
 
 def _parse_launch(tags, launch_file, file_deps, verbose, context):
@@ -131,17 +123,17 @@ def _parse_launch(tags, launch_file, file_deps, verbose, context):
 
     # process group, include, node, and test tags from launch file
     for tag in [t for t in tags if t.nodeType == DomNode.ELEMENT_NODE]:
+        if not _check_ifunless(tag, context):
+            continue
 
         if tag.tagName == 'group':
 
             #descend group tags as they can contain node tags
             _parse_launch(tag.childNodes, launch_file, file_deps, verbose, context)
 
         elif tag.tagName == 'arg':
-            v = _parse_arg(tag, context)
-            if v:
-                (name, val) = v
-                context['arg'][name] = val
+            context['arg'][tag.attributes['name'].value] = _get_arg_value(tag, context)
+
         elif tag.tagName == 'include':
             if tag.attributes.has_key('if'):
                 val = resolve_args(tag.attributes['if'].value, context)
@@ -174,7 +166,7 @@ def _parse_launch(tags, launch_file, file_deps, verbose, context):
 
             if sub_launch_file not in file_deps[launch_file].includes:
                 file_deps[launch_file].includes.append(sub_launch_file)
-            if launch_file_pkg != sub_pkg:            
+            if launch_file_pkg != sub_pkg:
                 file_deps[launch_file].pkgs.append(sub_pkg)
 
             # recurse