Fix bug with absolute meshdirs in included XML files. Fixes #1772.

PiperOrigin-RevId: 649150979
Change-Id: I5df08c689afc4f5bc625e989a8c0b9733fcfa3c2

src/user/user_flexcomp.cc

@@ -900,7 +900,7 @@ bool mjCFlexcomp::MakeMesh(mjCModel* model, char* error, int error_sz) {
   }
 
   // load resource
-  std::string filename = mjuu_makefullname(mjs_getString(model->spec.modelfiledir),
+  std::string filename = mjuu_combinePaths(mjs_getString(model->spec.modelfiledir),
                                            mjs_getString(model->spec.meshdir), file);
   mjResource* resource = nullptr;
 
@@ -999,7 +999,7 @@ bool mjCFlexcomp::MakeGMSH(mjCModel* model, char* error, int error_sz) {
   }
 
   // open resource
-  std::string filename = mjuu_makefullname(mjs_getString(model->spec.modelfiledir),
+  std::string filename = mjuu_combinePaths(mjs_getString(model->spec.modelfiledir),
                                            mjs_getString(model->spec.meshdir), file);
   mjResource* resource = nullptr;
 

src/user/user_mesh.cc

@@ -368,7 +368,7 @@ void mjCMesh::Compile(const mjVFS* vfs) {
       throw mjCError(this, "unsupported content type: '%s'", asset_type.c_str());
     }
 
-    string filename = mjuu_makefullname(model->modelfiledir_, model->meshdir_, file_);
+    string filename = mjuu_combinePaths(model->modelfiledir_, model->meshdir_, file_);
     mjResource* resource = LoadResource(filename, vfs);
 
     try {
@@ -2091,7 +2091,7 @@ void mjCSkin::Compile(const mjVFS* vfs) {
       throw mjCError(this, "Unknown skin file type: %s", file_.c_str());
     }
 
-    string filename = mjuu_makefullname(model->modelfiledir_, model->meshdir_, file_);
+    string filename = mjuu_combinePaths(model->modelfiledir_, model->meshdir_, file_);
     mjResource* resource = LoadResource(filename, vfs);
 
     try {

src/user/user_objects.cc

@@ -3105,7 +3105,7 @@ void mjCHField::Compile(const mjVFS* vfs) {
       throw mjCError(this, "unsupported content type: '%s'", asset_type.c_str());
     }
 
-    string filename = mjuu_makefullname(model->modelfiledir_, model->meshdir_, file_);
+    string filename = mjuu_combinePaths(model->modelfiledir_, model->meshdir_, file_);
     mjResource* resource = LoadResource(filename, vfs);
 
     try {
@@ -3723,7 +3723,7 @@ void mjCTexture::LoadCubeSeparate(const mjVFS* vfs) {
       }
 
       // make filename
-      string filename = mjuu_makefullname(model->modelfiledir_, model->texturedir_, cubefiles_[i]);
+      string filename = mjuu_combinePaths(model->modelfiledir_, model->texturedir_, cubefiles_[i]);
 
       // load PNG or custom
       unsigned int w, h;
@@ -3821,7 +3821,7 @@ void mjCTexture::Compile(const mjVFS* vfs) {
     }
 
     // make filename
-    string filename = mjuu_makefullname(model->modelfiledir_, model->texturedir_, file_);
+    string filename = mjuu_combinePaths(model->modelfiledir_, model->texturedir_, file_);
 
     // dispatch
     if (type==mjTEXTURE_2D) {

src/user/user_util.cc

@@ -837,23 +837,30 @@ bool mjuu_isabspath(string path) {
 
 
 
-// assemble full filename
-string mjuu_makefullname(string filedir, string meshdir, string filename) {
-  // filename has absolute path: filename
-  if (mjuu_isabspath(filename)) {
-    return filename;
+// assemble two file paths
+std::string mjuu_combinePaths(const string& path1, const string& path2) {
+  // path2 has absolute path
+  if (mjuu_isabspath(path2)) {
+    return path2;
   }
 
-  // meshdir has absolute path: meshdir + filename
-  if (mjuu_isabspath(meshdir)) {
-    return meshdir + filename;
+  std::size_t n = path1.size();
+  if (n > 0 && path1[n - 1] != '\\' && path1[n - 1] != '/') {
+    return path1 + "/" + path2;
   }
-
-  // default
-  return filedir + meshdir + filename;
+  return path1 + path2;
 }
 
 
+
+// assemble three file paths
+std::string mjuu_combinePaths(const string& path1, const string& path2,
+                              const string& path3) {
+  return mjuu_combinePaths(path1, mjuu_combinePaths(path2, path3));
+}
+
+
+
 // return true if the text is in a valid content type format:
 // {type}/{subtype}[;{parameter}={value}]
 static bool mjuu_isValidContentType(std::string_view text) {

src/user/user_util.h

@@ -167,8 +167,10 @@ std::string mjuu_getext(std::string_view filename);
 // check if path is absolute
 bool mjuu_isabspath(std::string path);
 
-// assemble full filename
-std::string mjuu_makefullname(std::string filedir, std::string meshdir, std::string filename);
+// assemble file paths
+std::string mjuu_combinePaths(const std::string& path1, const std::string& path2);
+std::string mjuu_combinePaths(const std::string& path1, const std::string& path2,
+                              const std::string& path3);
 
 // return type from content_type format {type}/{subtype}[;{parameter}={value}]
 std::optional<std::string_view> mjuu_parseContentTypeAttrType(std::string_view text);