Add VFS handling logic to mj_openResource.

PiperOrigin-RevId: 653124909
Change-Id: I4d031eb0bfb0070f8493753d2aeaac60ac283b85

src/xml/xml.cc

@@ -173,27 +173,23 @@ static void mjIncludeXML(mjXReader& reader, XMLElement* elem,
   } else {
     fullname = filename;
   }
-  mjResource *resource = mju_openVfsResource(fullname.c_str(), vfs);
-  if (!resource) {
-    // load from provider or OS filesystem
-    std::array<char, 1024> error;
-    resource = mju_openResource(fullname.c_str(), error.data(), error.size());
-    if (!resource) {
-      if (!mjuu_isabspath(filename)) {
-        fullname = std::string(dir) + filename;
-      } else {
-        fullname = filename;
-      }
 
-      // load from provider or OS filesystem
-      std::array<char, 1024> error;
-      resource = mju_openResource(fullname.c_str(), error.data(), error.size());
-      if (!resource) {
-        throw mjXError(elem, "%s", error.data());
-      }
+  // legacy behavior: try to load in top level directory
+  std::array<char, 1024> error;
+  mjResource *resource = mju_openResource(fullname.c_str(), vfs,
+                                          error.data(), error.size());
+  if (resource == nullptr) {
+    // new behavior: try to load in relative directory
+    if (!mjuu_isabspath(filename)) {
+      fullname = std::string(dir) + filename;
+      resource = mju_openResource(fullname.c_str(), vfs, error.data(), error.size());
     }
   }
 
+  if (resource == nullptr) {
+    throw mjXError(elem, "%s", error.data());
+  }
+
   if (!mjuu_isabspath(filename)) {
     filename = std::string(dir) + filename;
   }
@@ -293,16 +289,12 @@ mjSpec* mjParseXML(const char* filename, const mjVFS* vfs,
 
   // get data source
   const char* xmlstring = nullptr;
-  mjResource* resource = mju_openVfsResource(filename, vfs);
-
-  if (!resource) {
-    // load from provider or fallback to OS filesystem
-    std::array<char, 1024> rerror;
-    resource = mju_openResource(filename, rerror.data(), rerror.size());
-    if (!resource) {
-      std::snprintf(error, error_sz, "mjParseXML: %s", rerror.data());
-      return nullptr;
-    }
+  std::array<char, 1024> rerror;
+  mjResource* resource = mju_openResource(filename, vfs,
+                                          rerror.data(), rerror.size());
+  if (resource == nullptr) {
+    std::snprintf(error, error_sz, "mjParseXML: %s", rerror.data());
+    return nullptr;
   }
 
   int buffer_size = mju_readResource(resource, (const void**) &xmlstring);

src/xml/xml_api.cc

@@ -14,6 +14,7 @@
 
 #include "xml/xml_api.h"
 
+#include <array>
 #include <cstdio>
 #include <cstring>
 #include <fstream>
@@ -186,15 +187,12 @@ int mj_printSchema(const char* filename, char* buffer, int buffer_sz, int flg_ht
 
 // load model from binary MJB resource
 mjModel* mj_loadModel(const char* filename, const mjVFS* vfs) {
-  mjResource* resource = nullptr;
-
-  // first try vfs, otherwise try a provider or OS filesystem
-  if (!(resource = mju_openVfsResource(filename, vfs))) {
-    char error[1024];
-    if (!(resource = mju_openResource(filename, error, 1024))) {
-       mju_warning("%s", error);
-      return nullptr;
-    }
+  std::array<char, 1024> error;
+  mjResource* resource = mju_openResource(filename, vfs,
+                                          error.data(), error.size());
+  if (resource == nullptr) {
+    mju_warning("%s", error.data());
+    return nullptr;
   }
 
   const void* buffer = NULL;

src/xml/xml_util.cc

@@ -169,7 +169,8 @@ static std::string ResolveFilePath(XMLElement* e, std::string filename,
   // TODO(kylebayes): We first look in the base model directory for files to
   // remain backwards compatible.
   std::string full_filename = mjuu_combinePaths(dir, filename);
-  mjResource *resource = mju_openResource(full_filename.c_str(), nullptr, 0);
+  mjResource *resource = mju_openResource(full_filename.c_str(), nullptr,
+                                          nullptr, 0);
   if (resource != nullptr) {
     mju_closeResource(resource);
     return filename;