Detect mismatch between maxNodes and Nodes in a gmsh block. Fixes #2342

PiperOrigin-RevId: 745967745
Change-Id: If1b5fcd71079a0e6a6def9b442758678e31a5828

src/user/user_flexcomp.cc

@@ -1167,6 +1167,11 @@ void mjCFlexcomp::LoadGMSH41(char* buffer, int binary, int nodeend,
       throw mjCError(NULL, "All nodes must be in single block");
     }
 
+    // require maximum number of nodes be equal to maximum number of nodes in a block
+    if (maxNodeTag != numNodesInBlock){
+      throw mjCError(NULL, "Maximum number of nodes must be equal to number of nodes in a block");
+    }
+
     // check dimensionality and save
     if (entityDim < 1 || entityDim > 3) {
       throw mjCError(NULL, "Entity must be 1D, 2D or 3D");

test/user/testdata/malformed_cube_41_ascii_mismatch_between_max_nodes_and_nodes_in_block.msh

@@ -0,0 +1,67 @@
+$MeshFormat
+4.1 0 8
+$EndMeshFormat
+$Entities
+0 0 0 1
+1 -0.5 -0.5 0 0.5 0.5 1 0 0
+$EndEntities
+$Nodes
+1 14 1 100
+3 1 0 14
+1
+2
+3
+4
+5
+6
+7
+8
+9
+10
+11
+12
+13
+14
+-0.5 -0.5 0
+0.5 -0.5 0
+0.5 0.5 0
+-0.5 0.5 0
+-0.5 -0.5 1
+0.5 -0.5 1
+0.5 0.5 1
+-0.5 0.5 1
+0 0 0
+0 -0.5 0.5
+0.5 0 0.5
+0 0.5 0.5
+-0.5 0 0.5
+0 0 1
+$EndNodes
+$Elements
+1 24 1 24
+3 1 4 24
+1 10 9 12 11
+2 10 12 13 14
+3 9 10 12 13
+4 10 12 14 11
+5 9 10 1 2
+6 7 11 12 3
+7 4 1 9 13
+8 13 12 4 8
+9 1 10 13 5
+10 13 8 5 14
+11 12 8 14 7
+12 14 5 10 6
+13 14 6 11 7
+14 9 4 12 3
+15 3 11 9 2
+16 11 6 10 2
+17 6 10 14 11
+18 1 10 9 13
+19 12 4 9 13
+20 5 10 13 14
+21 8 13 12 14
+22 12 14 11 7
+23 9 12 11 3
+24 10 9 11 2
+$EndElements

test/user/testdata/malformed_cube_41_ascii_mismatch_between_max_nodes_and_nodes_in_block.xml

@@ -0,0 +1,27 @@
+<mujoco model="gmsh">
+  <option timestep="0.01" integrator="implicitfast" solver="CG" />
+
+  <asset>
+    <texture type="skybox" builtin="gradient" rgb1=".3 .5 .7" rgb2="0 0 0" width="512" height="512" />
+    <texture name="grid" type="2d" builtin="checker" width="512" height="512" rgb1=".1 .2 .3"
+      rgb2=".2 .3 .4" />
+    <material name="grid" texture="grid" texrepeat="1 1" texuniform="true" reflectance=".2" />
+  </asset>
+
+  <visual>
+    <headlight diffuse="0.9 0.9 0.9" ambient="0.3 0.3 0.3" specular="0 0 0" />
+    <map force="0.1" zfar="30" />
+    <rgba haze="0.15 0.25 0.35 1" />
+    <quality shadowsize="4096" />
+    <global offwidth="800" offheight="800" />
+  </visual>
+
+  <worldbody>
+    <geom name="floor" size="20 20 .05" type="plane" material="grid" condim="3" />
+    <light directional="false" diffuse=".2 .2 .2" specular="0 0 0" pos="0 0 5" dir="0 0 -1" />
+    <flexcomp name="cube" type="gmsh" dim="3" rgba=".8 .2 .2 1" radius="0.001" pos="0 0 4" mass="10"
+              scale="1 1 1" file="malformed_cube_41_ascii_mismatch_between_max_nodes_and_nodes_in_block.msh">
+      <edge equality="true" />
+    </flexcomp>
+  </worldbody>
+</mujoco>

test/user/user_flex_test.cc

@@ -697,6 +697,18 @@ TEST_F(UserFlexTest, LoadMSHASCII_41_MissingElement_Fail) {
   mj_deleteModel(m);
 }
 
+TEST_F(UserFlexTest,
+       LoadMSHASCII_41_MismatchBetweenMaxNodesAndNodesInBlock_Fail) {
+  const std::string xml_path =
+      GetTestDataFilePath(
+          "user/testdata/malformed_cube_41_ascii_mismatch_between_max_nodes_and_nodes_in_block.xml");
+  std::array<char, 1024> error;
+  mjModel* m = mj_loadXML(xml_path.c_str(), 0, error.data(), error.size());
+  EXPECT_THAT(error.data(), HasSubstr(
+        "XML Error: Error: Maximum number of nodes must be equal to number of nodes in a block\nElement 'flexcomp', line 22\n"));
+  mj_deleteModel(m);
+}
+
 TEST_F(UserFlexTest, LoadMSHASCII_22_MissingNumNodes_Fail) {
   const std::string xml_path =
       GetTestDataFilePath(