Do not write nameless frames whose class is "main".

quagla · copybara-github · commit 5f42078dc149 · 2025-06-10T10:15:43.000-07:00
PiperOrigin-RevId: 769685151
Change-Id: I3d993d7521db2b2adbf611c3e4eb5b4b293bdc30
diff --git a/src/xml/xml_native_writer.cc b/src/xml/xml_native_writer.cc
@@ -1595,7 +1595,8 @@ XMLElement* mjXWriter::OneFrame(XMLElement* elem, mjCFrame* frame) {
     return elem;
   }
 
-  if (frame->name.empty() && frame->classname.empty()) {
+  // TODO: empty classname should not occur (but does)
+  if (frame->name.empty() && (frame->classname.empty() || frame->classname == "main")) {
     return elem;
   }
 
diff --git a/test/xml/xml_native_writer_test.cc b/test/xml/xml_native_writer_test.cc
@@ -762,7 +762,7 @@ TEST_F(XMLWriterTest, WritesFrameDefaults) {
         <frame pos="0 1 0" name="f2" childclass="dframe">
           <geom pos="0 1 0"/>
           <frame pos="0 1 0" name="f3">
-            <frame pos="0 1 0" name="f4">
+            <frame pos="0 1 0">
               <body pos="1 0 0">
                 <geom pos="0 0 1"/>
               </body>
@@ -791,16 +791,14 @@ TEST_F(XMLWriterTest, WritesFrameDefaults) {
       <frame name="f2" childclass="dframe">
         <geom pos="0 2 0"/>
         <frame name="f3" childclass="dframe">
-          <frame name="f4" childclass="dframe">
+          <frame childclass="dframe">
             <body pos="1 3 0">
               <geom pos="0 0 1"/>
             </body>
           </frame>
         </frame>
       </frame>
-      <frame>
-        <light pos="0 0 1" dir="0 0 -1"/>
-      </frame>
+      <light pos="0 0 1" dir="0 0 -1"/>
     </body>
     <frame name="f1">
       <geom size="0.5" quat="0.906308 0 0 0.422618"/>

Original file line number	Diff line number	Diff line change
`@@ -1595,7 +1595,8 @@ XMLElement* mjXWriter::OneFrame(XMLElement* elem, mjCFrame* frame) {`
`1595`	`1595`	`return elem;`
`1596`	`1596`	`}`
`1597`	`1597`
`1598`		`- if (frame->name.empty() && frame->classname.empty()) {`
	`1598`	`+ // TODO: empty classname should not occur (but does)`
	`1599`	`+ if (frame->name.empty() && (frame->classname.empty() \|\| frame->classname == "main")) {`
`1599`	`1600`	`return elem;`
`1600`	`1601`	`}`
`1601`	`1602`