Add deprecation warning for the Rope Composite type.

PiperOrigin-RevId: 494985209
Change-Id: I6ce7ca2aeae6f1e798bd4bda9b755852add26a36

model/composite/rope.xml

@@ -1,32 +0,0 @@
-<!-- Copyright 2021 DeepMind Technologies Limited
-
-     Licensed under the Apache License, Version 2.0 (the "License");
-     you may not use this file except in compliance with the License.
-     You may obtain a copy of the License at
-
-         http://www.apache.org/licenses/LICENSE-2.0
-
-     Unless required by applicable law or agreed to in writing, software
-     distributed under the License is distributed on an "AS IS" BASIS,
-     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-     See the License for the specific language governing permissions and
-     limitations under the License.
--->
-
-<mujoco model="Rope">
-  <include file="scene.xml"/>
-
-  <option timestep="0.002" jacobian="dense"/>
-
-  <size memory="2M"/>
-
-  <worldbody>
-    <body name="B10" pos="0 0 1">
-      <freejoint/>
-      <composite type="rope" count="21 1 1" spacing="0.04" offset="0 0 2">
-        <joint kind="main" damping="0.005"/>
-        <geom type="capsule" size=".01 .015" rgba=".8 .2 .1 1"/>
-      </composite>
-    </body>
-  </worldbody>
-</mujoco>

src/user/user_composite.cc

@@ -297,6 +297,8 @@ bool mjCComposite::Make(mjCModel* model, mjCBody* body, char* error, int error_s
     return MakeGrid(model, body, error, error_sz);
 
   case mjCOMPTYPE_ROPE:
+    mju_warning("The \"rope\" composite type is deprecated. Please use \"cable\" instead.");
+    [[fallthrough]];
   case mjCOMPTYPE_LOOP:
     return MakeRope(model, body, error, error_sz);
 

test/user/user_composite_test.cc

@@ -20,6 +20,7 @@
 #include <gmock/gmock.h>
 #include <gtest/gtest.h>
 #include <absl/strings/str_format.h>
+#include "src/cc/array_safety.h"
 #include <mujoco/mjdata.h>
 #include <mujoco/mjmodel.h>
 #include <mujoco/mujoco.h>
@@ -72,9 +73,15 @@ TEST_F(UserCompositeTest, StretchAndTwistAllowed) {
   </worldbody>
   </mujoco>
   )";
+  static char warning[1024];
+  warning[0] = '\0';
+  mju_user_warning = [](const char* msg) {
+    util::strcpy_arr(warning, msg);
+  };
   std::array<char, 1024> error;
   mjModel* m = LoadModelFromString(xml, error.data(), error.size());
   EXPECT_THAT(m, NotNull());
+  EXPECT_THAT(warning, HasSubstr("deprecated"));
   mj_deleteModel(m);
 }