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Allow self-attach in MJCF

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PiperOrigin-RevId: 941676717
Change-Id: I9ff8fc89716bc14b438a41e2b4075bbe5fdb83cf
This commit is contained in:
Yuval Tassa
2026-07-02 06:51:04 -07:00
committed by Copybara-Service
parent cdc35dec38
commit 2d283b5e9d
4 changed files with 178 additions and 37 deletions
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src/xml/xml_native_reader.cc
+49 -19
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@@ -3942,7 +3942,7 @@ void mjXReader::Body(XMLElement* section, mjsBody* body, mjsFrame* frame,
// attachment
else if (name == "attach") {
string model_name, child_name, prefix;
ReadAttrTxt(elem, "model", model_name, /*required=*/true);
bool has_model = ReadAttrTxt(elem, "model", model_name, /*required=*/false);
bool has_body = ReadAttrTxt(elem, "body", child_name, /*required=*/false);
bool has_frame = ReadAttrTxt(elem, "frame", child_name, /*required=*/false);
ReadAttrTxt(elem, "prefix", prefix, /*required=*/true);
@@ -3950,31 +3950,61 @@ void mjXReader::Body(XMLElement* section, mjsBody* body, mjsFrame* frame,
if (has_body && has_frame) {
throw mjXError(elem, "only one of body or frame can be specified in attach");
}
mjtObj type = has_body ? mjOBJ_BODY : mjOBJ_FRAME;
mjtObj type = mjOBJ_UNKNOWN;
if (has_body) type = mjOBJ_BODY;
else if (has_frame) type = mjOBJ_FRAME;
string full_name = prefix+child_name;
if (mjs_findElement(spec, type, full_name.c_str())) {
throw mjXError(elem, "cannot attach: element %s already exists", full_name.c_str());
}
mjsElement* source_elem = nullptr;
if (!has_model) { // Self-attach
if (type == mjOBJ_UNKNOWN) {
throw mjXError(elem, "either 'body' or 'frame' attribute must be specified for self-attach");
}
mjSpec* asset = mjs_findSpec(spec, model_name.c_str());
if (!asset) {
throw mjXError(elem, "could not find model '%s'", model_name.c_str());
}
// check for name collision in the current spec
string full_name = prefix + child_name;
if (mjs_findElement(spec, type, full_name.c_str())) {
throw mjXError(elem, "cannot self-attach: element %s already exists", full_name.c_str());
}
source_elem = mjs_findElement(spec, type, child_name.c_str());
if (!source_elem) {
throw mjXError(elem, "%s",
(string("could not find ") + mju_type2Str(type) + " '" + child_name +
"' in the current model for self-attachment").c_str());
}
} else { // Attach from external model asset
// Check for name collision in the current spec
if (!child_name.empty()) {
string full_name = prefix + child_name;
if (mjs_findElement(spec, type, full_name.c_str())) {
throw mjXError(elem, "%s",
(string("cannot attach: element ") + child_name +
" already exists with prefix " + prefix).c_str());
}
}
mjsElement* child;
if (child_name.empty()) {
child = asset->element;
} else {
child = mjs_findElement(asset, type, child_name.c_str());
if (!child) {
throw mjXError(elem, "could not find %s",
(string(mju_type2Str(type)) + " '" + child_name + "'").c_str());
mjSpec* asset = mjs_findSpec(spec, model_name.c_str());
if (!asset) {
throw mjXError(elem, "could not find model '%s'", model_name.c_str());
}
if (type == mjOBJ_UNKNOWN) { // Attach world body contents
source_elem = asset->element;
} else { // Attach specific body or frame
source_elem = mjs_findElement(asset, type, child_name.c_str());
if (!source_elem) {
throw mjXError(elem, "%s",
(string("could not find ") + mju_type2Str(type) + " '" + child_name +
"' in model asset '" + model_name + "'").c_str());
}
}
}
mjsFrame* pframe = frame ? frame : mjs_addFrame(body, nullptr);
if (!mjs_attach(pframe->element, child, prefix.c_str(), "")) {
// Set default for the new frame from the current context
mjs_setDefault(pframe->element, mjs_getDefault(frame ? frame->element : body->element));
mjs_setString(pframe->info, ("line = " + std::to_string(elem->GetLineNum())).c_str());
if (!mjs_attach(pframe->element, source_elem, prefix.c_str(), "")) {
throw mjXError(elem, "%s", stripError(mjs_getError(spec)));
}
}