Add mj_parseXML and mj_saveXML to xml_api.

PiperOrigin-RevId: 640099466
Change-Id: I75f763523c5bc8f6f7c2f2de6806d82ba37ebd4e

test/user/user_api_test.cc

@@ -25,7 +25,7 @@
 #include <absl/strings/match.h>
 #include <mujoco/mujoco.h>
 #include "src/user/user_api.h"
-#include "src/xml/xml.h"
+#include "src/xml/xml_api.h"
 #include "src/xml/xml_numeric_format.h"
 #include "test/fixture.h"
 
@@ -125,7 +125,7 @@ TEST_F(PluginTest, RecompileCompare) {
 
         // load spec
         std::array<char, 1000> err;
-        mjSpec* s = mjParseXML(xml.c_str(), nullptr, err.data(), err.size());
+        mjSpec* s = mj_parseXML(xml.c_str(), 0, err.data(), err.size());
 
         ASSERT_THAT(s, NotNull())
             << "Failed to load " << xml << ": " << err.data();
@@ -417,7 +417,7 @@ TEST_F(MujocoTest, AttachSame) {
   </mujoco>)";
 
   // create parent
-  mjSpec* parent = ParseSpecFromString(xml_child, er.data(), er.size());
+  mjSpec* parent = mj_parseXMLString(xml_child, 0, er.data(), er.size());
   EXPECT_THAT(parent, NotNull()) << er.data();
 
   // get frame
@@ -530,7 +530,7 @@ TEST_F(MujocoTest, AttachDifferent) {
   </mujoco>)";
 
   // model with one free sphere and a frame
-  mjSpec* parent = ParseSpecFromString(xml_parent, er.data(), er.size());
+  mjSpec* parent = mj_parseXMLString(xml_parent, 0, er.data(), er.size());
   EXPECT_THAT(parent, NotNull()) << er.data();
 
   // get frame
@@ -538,7 +538,7 @@ TEST_F(MujocoTest, AttachDifferent) {
   EXPECT_THAT(frame, NotNull());
 
   // model with one cylinder and a hinge
-  mjSpec* child = ParseSpecFromString(xml_child, er.data(), er.size());
+  mjSpec* child = mj_parseXMLString(xml_child, 0, er.data(), er.size());
   EXPECT_THAT(child, NotNull()) << er.data();
 
   // get subtree
@@ -642,7 +642,7 @@ TEST_F(MujocoTest, AttachFrame) {
   </mujoco>)";
 
   // model with one free sphere and a frame
-  mjSpec* parent = ParseSpecFromString(xml_parent, er.data(), er.size());
+  mjSpec* parent = mj_parseXMLString(xml_parent, 0, er.data(), er.size());
   EXPECT_THAT(parent, NotNull()) << er.data();
 
   // get frame
@@ -650,7 +650,7 @@ TEST_F(MujocoTest, AttachFrame) {
   EXPECT_THAT(body, NotNull());
 
   // model with one cylinder and a hinge
-  mjSpec* child = ParseSpecFromString(xml_child, er.data(), er.size());
+  mjSpec* child = mj_parseXMLString(xml_child, 0, er.data(), er.size());
   EXPECT_THAT(child, NotNull()) << er.data();
 
   // get subtree
@@ -711,7 +711,7 @@ void TestDetachBody(bool compile) {
   </mujoco>)";
 
   // model with one cylinder and a hinge
-  mjSpec* child = ParseSpecFromString(xml_child, er.data(), er.size());
+  mjSpec* child = mj_parseXMLString(xml_child, 0, er.data(), er.size());
   EXPECT_THAT(child, NotNull()) << er.data();
 
   // compile model (for testing double compilation)

test/xml/xml_api_test.cc

@@ -24,6 +24,8 @@
 #include <mujoco/mjdata.h>
 #include <mujoco/mjmodel.h>
 #include <mujoco/mujoco.h>
+#include "src/user/user_api.h"
+#include "src/xml/xml_api.h"
 #include "test/fixture.h"
 
 namespace mujoco {
@@ -33,6 +35,21 @@ using ::testing::IsNull;
 using ::testing::NotNull;
 using ::testing::StartsWith;
 
+static constexpr char xml[] = R"(
+  <mujoco>
+    <worldbody>
+      <body>
+        <joint/>
+        <geom size="1"/>
+      </body>
+      <body>
+        <joint/>
+        <geom size="0.5"/>
+      </body>
+    </worldbody>
+  </mujoco>
+  )";
+
 // ---------------------------- test mj_loadXML --------------------------------
 
 using LoadXmlTest = MujocoTest;
@@ -66,20 +83,6 @@ TEST_F(LoadXmlTest, InvalidXmlFailsToLoad) {
 }
 
 TEST_F(LoadXmlTest, MultipleBodies) {
-  static constexpr char xml[] = R"(
-  <mujoco>
-    <worldbody>
-      <body>
-        <joint/>
-        <geom size="1"/>
-      </body>
-      <body>
-        <joint/>
-        <geom size="0.5"/>
-      </body>
-    </worldbody>
-  </mujoco>
-  )";
   std::array<char, 1000> error;
   mjModel* model = LoadModelFromString(xml, error.data(), error.size());
 
@@ -92,7 +95,6 @@ TEST_F(LoadXmlTest, MultipleBodies) {
   mj_deleteData(data);
   mj_deleteModel(model);
 }
-
 using SaveLastXmlTest = MujocoTest;
 
 TEST_F(SaveLastXmlTest, EmptyModel) {
@@ -112,5 +114,51 @@ TEST_F(SaveLastXmlTest, EmptyModel) {
   mj_deleteModel(model);
 }
 
+TEST_F(MujocoTest, SaveXmlShortString) {
+  std::array<char, 1000> error;
+
+  mjSpec* spec = mj_parseXMLString(xml, 0, error.data(), error.size());
+  EXPECT_THAT(spec, NotNull()) << "Failed to parse spec: " << error.data();
+  mjModel* model = mjs_compile(spec, 0);
+  EXPECT_THAT(model, NotNull()) << "Failed to compile model: " << error.data();
+
+  std::array<char, 10> out;
+  EXPECT_THAT(mj_saveXMLString(spec, out.data(), out.size(),
+                               error.data(), error.size()), 0);
+  EXPECT_STREQ(error.data(), "Output string too short, should be at least 273");
+
+  mjs_deleteSpec(spec);
+  mj_deleteModel(model);
+}
+
+TEST_F(MujocoTest, SaveXml) {
+  std::array<char, 1000> error;
+
+  mjSpec* spec = mj_parseXMLString(xml, 0, error.data(), error.size());
+  EXPECT_THAT(spec, NotNull()) << "Failed to parse spec: " << error.data();
+  mjModel* model = mjs_compile(spec, 0);
+  EXPECT_THAT(model, NotNull()) << "Failed to compile model: " << error.data();
+
+  std::array<char, 273> out;
+  EXPECT_THAT(mj_saveXMLString(spec, out.data(), out.size(), error.data(),
+                               error.size()), 1) << error.data();
+
+  mjSpec* saved_spec = mj_parseXMLString(xml, 0, error.data(), error.size());
+  EXPECT_THAT(saved_spec, NotNull()) << "Invalid saved spec: " << error.data();
+  mjModel* saved_model = mjs_compile(saved_spec, 0);
+  EXPECT_THAT(saved_model, NotNull()) << "Invalid model: " << error.data();
+
+  mjtNum tol = 0;
+  std::string field = "";
+  EXPECT_LE(CompareModel(model, saved_model, field), tol)
+            << "Expected and attached models are different!\n"
+            << "Different field: " << field << '\n';
+
+  mjs_deleteSpec(spec);
+  mjs_deleteSpec(saved_spec);
+  mj_deleteModel(model);
+  mj_deleteModel(saved_model);
+}
+
 }  // namespace
 }  // namespace mujoco

test/xml/xml_native_reader_test.cc

@@ -28,7 +28,7 @@
 #include "src/cc/array_safety.h"
 #include "src/engine/engine_util_errmem.h"
 #include "src/user/user_api.h"
-#include "src/xml/xml.h"
+#include "src/xml/xml_api.h"
 #include "test/fixture.h"
 
 namespace mujoco {
@@ -1084,7 +1084,7 @@ TEST_F(XMLReaderTest, ParseReplicateDefaultPropagate) {
   </mujoco>
   )";
   std::array<char, 1024> error;
-  mjSpec* spec = ParseSpecFromString(xml, error.data(), error.size());
+  mjSpec* spec = mj_parseXMLString(xml, 0, error.data(), error.size());
   EXPECT_THAT(spec, NotNull()) << error.data();
 
   mjsBody* torso = mjs_findBody(spec, "torso-0");