From db28c31f05b00f933e581defa1cd8d328484cca2 Mon Sep 17 00:00:00 2001
From: Saran Tunyasuvunakool <stunya@google.com>
Date: Mon, 13 Feb 2023 08:41:06 -0800
Subject: [PATCH] Rename `<required>` tag to `<plugin>`.

PiperOrigin-RevId: 509237786
Change-Id: I35e812830b479004ac5025cbd9477888f51fb43e
---
 doc/XMLschema.rst                         |  2 +-
 model/plugin/belt.xml                     |  4 ++--
 model/plugin/cable.xml                    |  2 +-
 model/plugin/coil.xml                     |  4 ++--
 model/plugin/floppy.xml                   |  2 +-
 model/plugin/jelly.xml                    |  2 +-
 model/plugin/press.xml                    |  2 +-
 python/mujoco/bindings_test.py            |  2 +-
 src/xml/xml_native_reader.cc              |  6 +++---
 src/xml/xml_native_writer.cc              | 18 +++++++++---------
 test/engine/engine_plugin_test.cc         | 10 +++++-----
 test/plugin/elasticity/elasticity_test.cc | 16 ++++++++--------
 12 files changed, 35 insertions(+), 35 deletions(-)

diff --git a/doc/XMLschema.rst b/doc/XMLschema.rst
index 11cdb6b4..ec61223a 100644
--- a/doc/XMLschema.rst
+++ b/doc/XMLschema.rst
@@ -446,7 +446,7 @@
 | |_|:el:`extension`       | \* | *no attribute*                                                                     |
 |                          |    |                                                                                    |
 +--------------------------+----+------------------------------------------------------------------------------------+
-| |_2|:el:`required`       | \* | .. table::                                                                         |
+| |_2|:el:`plugin`         | \* | .. table::                                                                         |
 |                          |    |    :class: mjcf-attributes                                                         |
 |                          |    |                                                                                    |
 |                          |    |    +-------------------------+-------------------------+-------------------------+ |
diff --git a/model/plugin/belt.xml b/model/plugin/belt.xml
index cdb4d181..e1f0db65 100644
--- a/model/plugin/belt.xml
+++ b/model/plugin/belt.xml
@@ -17,7 +17,7 @@
   <include file="scene.xml"/>
 
   <extension>
-    <required plugin="mujoco.elasticity.cable"/>
+    <plugin plugin="mujoco.elasticity.cable"/>
   </extension>
 
   <statistic center="0 0 .2" extent="1"/>
@@ -74,4 +74,4 @@
   <actuator>
     <motor site="S_last" gear="0 0 0 1 0 0" ctrlrange="-.2 .2"/>
   </actuator>
-</mujoco>
\ No newline at end of file
+</mujoco>
diff --git a/model/plugin/cable.xml b/model/plugin/cable.xml
index 4d1337ff..2db16b57 100644
--- a/model/plugin/cable.xml
+++ b/model/plugin/cable.xml
@@ -17,7 +17,7 @@
   <include file="scene.xml"/>
 
   <extension>
-    <required plugin="mujoco.elasticity.cable"/>
+    <plugin plugin="mujoco.elasticity.cable"/>
   </extension>
 
   <statistic center="0 0 .3" extent="1"/>
diff --git a/model/plugin/coil.xml b/model/plugin/coil.xml
index 2709cc9a..dff6464f 100644
--- a/model/plugin/coil.xml
+++ b/model/plugin/coil.xml
@@ -17,7 +17,7 @@
   <include file="scene.xml"/>
 
   <extension>
-    <required plugin="mujoco.elasticity.cable"/>
+    <plugin plugin="mujoco.elasticity.cable"/>
   </extension>
 
   <statistic center="0 0 .2" extent="1"/>
@@ -103,4 +103,4 @@
   <actuator>
     <position joint="slide" name="extend" gear="1 0 0 0 0 0" ctrlrange="-.25 1" kp="100"/>
   </actuator>
-</mujoco>
\ No newline at end of file
+</mujoco>
diff --git a/model/plugin/floppy.xml b/model/plugin/floppy.xml
index 748b19a9..5819451f 100644
--- a/model/plugin/floppy.xml
+++ b/model/plugin/floppy.xml
@@ -17,7 +17,7 @@
   <include file="scene.xml"/>
 
   <extension>
-    <required plugin="mujoco.elasticity.solid"/>
+    <plugin plugin="mujoco.elasticity.solid"/>
   </extension>
 
   <compiler autolimits="true"/>
diff --git a/model/plugin/jelly.xml b/model/plugin/jelly.xml
index be583020..7ee3cb04 100644
--- a/model/plugin/jelly.xml
+++ b/model/plugin/jelly.xml
@@ -17,7 +17,7 @@
   <include file="scene.xml"/>
 
   <extension>
-    <required plugin="mujoco.elasticity.solid"/>
+    <plugin plugin="mujoco.elasticity.solid"/>
   </extension>
 
   <option solver="CG" tolerance="1e-6" timestep=".001"/>
diff --git a/model/plugin/press.xml b/model/plugin/press.xml
index b55bf40b..81a86574 100644
--- a/model/plugin/press.xml
+++ b/model/plugin/press.xml
@@ -17,7 +17,7 @@
   <include file="scene.xml"/>
 
   <extension>
-    <required plugin="mujoco.elasticity.solid"/>
+    <plugin plugin="mujoco.elasticity.solid"/>
   </extension>
 
   <compiler autolimits="true"/>
diff --git a/python/mujoco/bindings_test.py b/python/mujoco/bindings_test.py
index 16b56546..d5d90a90 100644
--- a/python/mujoco/bindings_test.py
+++ b/python/mujoco/bindings_test.py
@@ -72,7 +72,7 @@ TEST_XML_SENSOR = r"""
 TEST_XML_PLUGIN = r"""
 <mujoco model="test">
   <extension>
-    <required plugin="mujoco.elasticity.cable"/>
+    <plugin plugin="mujoco.elasticity.cable"/>
   </extension>
 </mujoco>
 """
diff --git a/src/xml/xml_native_reader.cc b/src/xml/xml_native_reader.cc
index 9e998e8d..174e2ece 100644
--- a/src/xml/xml_native_reader.cc
+++ b/src/xml/xml_native_reader.cc
@@ -190,11 +190,11 @@ static const char* MJCF[nMJCF][mjXATTRNUM] = {
 
     {"extension", "*", "0"},
     {"<"},
-        {"required", "*", "1", "plugin"},
+        {"plugin", "*", "1", "plugin"},
         {"<"},
             {"instance", "*", "1", "name"},
             {"<"},
-              {"config", "*", "2", "key", "value"},
+                {"config", "*", "2", "key", "value"},
             {">"},
         {">"},
     {">"},
@@ -2196,7 +2196,7 @@ void mjXReader::Extension(XMLElement* section) {
     // get sub-element name
     std::string_view name = elem->Value();
 
-    if (name == "required") {
+    if (name == "plugin") {
       std::string plugin_name;
       int plugin_slot = -1;
       ReadAttrTxt(elem, "plugin", plugin_name, /* required = */ true);
diff --git a/src/xml/xml_native_writer.cc b/src/xml/xml_native_writer.cc
index dfc8a4a2..77934565 100644
--- a/src/xml/xml_native_writer.cc
+++ b/src/xml/xml_native_writer.cc
@@ -1081,12 +1081,12 @@ void mjXWriter::Extension(XMLElement* root) {
   // create section
   XMLElement* section = InsertEnd(root, "extension");
 
-  // keep track of plugins whose <required> section have been created
+  // keep track of plugins whose <plugin> section have been created
   std::unordered_set<const mjpPlugin*> seen_plugins;
 
   // write all plugins
   const mjpPlugin* last_plugin = nullptr;
-  XMLElement* required_elem = nullptr;
+  XMLElement* plugin_elem = nullptr;
   for (int i = 0; i < model->plugins.size(); ++i) {
     mjCPlugin* pp = static_cast<mjCPlugin*>(model->GetObject(mjOBJ_PLUGIN, i));
 
@@ -1096,17 +1096,17 @@ void mjXWriter::Extension(XMLElement* root) {
       break;
     }
 
-    // check if we need to open a new <required> section
+    // check if we need to open a new <plugin> section
     const mjpPlugin* plugin = mjp_getPluginAtSlot(pp->plugin_slot);
     if (plugin != last_plugin) {
-      required_elem = InsertEnd(section, "required");
-      WriteAttrTxt(required_elem, "plugin", plugin->name);
+      plugin_elem = InsertEnd(section, "plugin");
+      WriteAttrTxt(plugin_elem, "plugin", plugin->name);
       seen_plugins.insert(plugin);
       last_plugin = plugin;
     }
 
     // write instance element
-    XMLElement* elem = InsertEnd(required_elem, "instance");
+    XMLElement* elem = InsertEnd(plugin_elem, "instance");
     WriteAttrTxt(elem, "name", pp->name);
 
     // write plugin config attributes
@@ -1123,11 +1123,11 @@ void mjXWriter::Extension(XMLElement* root) {
     }
   }
 
-  // write <required> elements for plugins without explicit instances
+  // write <plugin> elements for plugins without explicit instances
   for (const auto& [plugin, slot] : model->active_plugins) {
     if (seen_plugins.find(plugin) == seen_plugins.end()) {
-      required_elem = InsertEnd(section, "required");
-      WriteAttrTxt(required_elem, "plugin", plugin->name);
+      plugin_elem = InsertEnd(section, "plugin");
+      WriteAttrTxt(plugin_elem, "plugin", plugin->name);
     }
   }
 }
diff --git a/test/engine/engine_plugin_test.cc b/test/engine/engine_plugin_test.cc
index a0091c2c..3d7e6960 100644
--- a/test/engine/engine_plugin_test.cc
+++ b/test/engine/engine_plugin_test.cc
@@ -343,19 +343,19 @@ class PluginTest : public MujocoTest {
 constexpr char xml[] = R"(
 <mujoco>
   <extension>
-    <required plugin="mujoco.test.sensor">
+    <plugin plugin="mujoco.test.sensor">
       <instance name="twosensors"/>
       <instance name="threesensors">
         <config key="stride" value="3"/>
       </instance>
-    </required>
-    <required plugin="mujoco.test.actuator">
+    </plugin>
+    <plugin plugin="mujoco.test.actuator">
       <instance name="actuator2">
         <config key="stride" value="2"/>
         <config key="multiplier" value="0.125"/>
       </instance>
-    </required>
-    <required plugin="mujoco.test.passive"/>
+    </plugin>
+    <plugin plugin="mujoco.test.passive"/>
   </extension>
   <worldbody>
     <body>
diff --git a/test/plugin/elasticity/elasticity_test.cc b/test/plugin/elasticity/elasticity_test.cc
index 206aba5a..2c72dc06 100644
--- a/test/plugin/elasticity/elasticity_test.cc
+++ b/test/plugin/elasticity/elasticity_test.cc
@@ -56,7 +56,7 @@ TEST_F(PluginTest, ElasticEnergy) {
   static constexpr char cantilever_xml[] = R"(
   <mujoco>
   <extension>
-    <required plugin="mujoco.elasticity.solid"/>
+    <plugin plugin="mujoco.elasticity.solid"/>
   </extension>
 
   <worldbody>
@@ -114,7 +114,7 @@ TEST_F(PluginTest, CantileverIntoCircle) {
   <mujoco>
     <option gravity="0 0 0"/>
     <extension>
-      <required plugin="mujoco.elasticity.cable"/>
+      <plugin plugin="mujoco.elasticity.cable"/>
     </extension>
     <worldbody>
       <geom type="plane" size="0 0 1" quat="1 0 0 0"/>
@@ -167,12 +167,12 @@ TEST_F(PluginTest, InvalidTxtAttribute) {
   static constexpr char cantilever_xml[] = R"(
   <mujoco>
     <extension>
-      <required plugin="mujoco.elasticity.cable">
+      <plugin plugin="mujoco.elasticity.cable">
         <instance name="invalid">
           <config key="twist" value="one"/>
           <config key="bend" value="1"/>
         </instance>
-      </required>
+      </plugin>
     </extension>
     <worldbody>
       <geom type="plane" size="0 0 1" quat="1 0 0 0"/>
@@ -190,12 +190,12 @@ TEST_F(PluginTest, InvalidMixedAttribute) {
   static constexpr char cantilever_xml[] = R"(
   <mujoco>
     <extension>
-      <required plugin="mujoco.elasticity.cable">
+      <plugin plugin="mujoco.elasticity.cable">
         <instance name="invalid">
           <config key="twist" value="1"/>
           <config key="bend" value="1 is not a number"/>
         </instance>
-      </required>
+      </plugin>
     </extension>
     <worldbody>
       <geom type="plane" size="0 0 1" quat="1 0 0 0"/>
@@ -213,12 +213,12 @@ TEST_F(PluginTest, ValidAttributes) {
   static constexpr char cantilever_xml[] = R"(
   <mujoco>
     <extension>
-      <required plugin="mujoco.elasticity.cable">
+      <plugin plugin="mujoco.elasticity.cable">
         <instance name="invalid">
           <config key="twist" value="0.0"/>
           <config key="bend" value=" 0  "/>
         </instance>
-      </required>
+      </plugin>
     </extension>
     <worldbody>
       <geom type="plane" size="0 0 1" quat="1 0 0 0"/>