Generate the MJCF grammar table and enforce its constraints.

The hand-written MJCF[] table in xml_native_reader.cc is replaced by
mjcf_table.inc, emitted from mjcf.schema by generate_mjcf_table.py and
checked for freshness by doc_test. nMJCF is now self-sizing. The two
tables are identical as trees of (tag, cardinality, attribute-set);
within-row attribute order changes where the schema factors shared
groups and projects default-context rows, and top-level rows follow
the schema's dependency order -- neither affects validation, which is
set-based, nor XMLschema.rst, whose generator orders sections itself
(regenerated here, reading the .inc instead of the reader source).

The schema's constraint declarations become enforcement: the emitter
writes a companion MJCF_constraints[] array (row-indexed into MJCF[]),
and mjXSchema::Check evaluates each element's constraints after its
attribute check, with uniform messages derived from the declaration:
"at most one of 'fovy', 'sensorsize' can be specified", "attributes
'reftype', 'refname' must be specified together", and so on.
Multi-attribute bundles render as ('site1', 'site2').

Fifteen hand-written co-occurrence checks across fourteen elements are
deleted -- connect/weld semantics mixing and completeness, the actuator
transmission mutex, camera fovy/sensorsize, light directional/type,
inertial fullinertia-versus-orientation, rangefinder and the distance
family, contact's matching criteria, user-sensor pairing, the frame
family's reftype/refname, size memory exclusivities, mesh builtin
exclusions, and attach body/frame (newly declared). Tests assert the
uniform messages.

Two findings along the way: sensorsize-requires-resolution is a
value-level compiler rule (positive resolution), not a presence rule --
a presence constraint would be wrong and is not declared; and Size()'s
nstack/njmax range checks tested the spec value before assignment, so
they never validated the parsed value -- now they do.

Verified by compiling all 81 models in the model/ corpus.

PiperOrigin-RevId: 958064622
Change-Id: I802cf5c0aee08a62926e36a281320ff9e34c0668

test/doc/doc_test.py

@@ -24,7 +24,9 @@ _REPO_ROOT = os.path.dirname(os.path.dirname(_SCRIPT_DIR))
 sys.path.insert(0, os.path.join(_REPO_ROOT, 'doc', 'generate'))
 import generate_api_header
 import generate_functions
+import generate_mjcf_table
 import generate_schema
+import mjcf_schema
 
 # Functions in headers that are intentionally not in functions.rst.
 _FUNCTIONS_TO_SKIP = set()
@@ -81,6 +83,14 @@ class DocTest(googletest.TestCase):
       if source != file.read():
         self.fail("The file 'references.h' needs to be updated.")
 
+  def test_mjcf_table(self):
+    """Checks that mjcf_table.inc matches the schema-generated output."""
+    table_file = os.path.join(_REPO_ROOT, 'src', 'xml', 'mjcf_table.inc')
+    source = generate_mjcf_table.generate()
+    with open(table_file, 'r', encoding='utf-8') as file:
+      if source != file.read():
+        self.fail("The file 'mjcf_table.inc' needs to be updated.")
+
   def test_schema(self):
     """Checks that XMLschema.rst matches the generated output."""
     schema_file = os.path.join(_REPO_ROOT, 'doc', 'XMLschema.rst')
@@ -91,7 +101,9 @@ class DocTest(googletest.TestCase):
 
   def test_functions(self):
     """Checks that functions.rst matches the generated output."""
-    functions_file = os.path.join(_REPO_ROOT, 'doc', 'APIreference', 'functions.rst')
+    functions_file = os.path.join(
+        _REPO_ROOT, 'doc', 'APIreference', 'functions.rst'
+    )
     source = generate_functions.generate()
     with open(functions_file, 'r', encoding='utf-8') as file:
       if source != file.read():
@@ -100,7 +112,9 @@ class DocTest(googletest.TestCase):
   def test_all_functions_included(self):
     """Checks that every public C function has an entry in functions.rst."""
 
-    functions_file = os.path.join(_REPO_ROOT, 'doc', 'APIreference', 'functions.rst')
+    functions_file = os.path.join(
+        _REPO_ROOT, 'doc', 'APIreference', 'functions.rst'
+    )
     with open(functions_file, 'r', encoding='utf-8') as file:
       content = file.read()
 
@@ -125,7 +139,9 @@ class DocTest(googletest.TestCase):
   def test_all_types_included(self):
     """Checks that every public struct and enum has an entry in APItypes.rst."""
 
-    types_file = os.path.join(_REPO_ROOT, 'doc', 'APIreference', 'APItypes.rst')
+    types_file = os.path.join(
+        _REPO_ROOT, 'doc', 'APIreference', 'APItypes.rst'
+    )
     with open(types_file, 'r', encoding='utf-8') as file:
       content = file.read()
 
@@ -151,6 +167,30 @@ class DocTest(googletest.TestCase):
       msg = 'APItypes.rst mismatches:\n' + '\n'.join(errors)
       self.fail(msg)
 
+  def test_element_constraints_diamond_inheritance(self):
+    con = mjcf_schema.Constraint(
+        kind='exclusive', bundles=(('a',), ('b',)), doc=None, line=1)
+    common_group = mjcf_schema.Group(
+        name='common', variant=False, members=[con], doc=None, line=1)
+    group1 = mjcf_schema.Group(
+        name='group1', variant=False,
+        members=[mjcf_schema.Use(group='common', line=1)], doc=None, line=1)
+    group2 = mjcf_schema.Group(
+        name='group2', variant=False,
+        members=[mjcf_schema.Use(group='common', line=1)], doc=None, line=1)
+    elem = mjcf_schema.Element(
+        name='elem', spec=None, facets={},
+        members=[mjcf_schema.Use(group='group1', line=1),
+                 mjcf_schema.Use(group='group2', line=1)],
+        doc=None, line=1)
+    schema = mjcf_schema.Schema(
+        enums={},
+        groups={'common': common_group, 'group1': group1, 'group2': group2},
+        elements={'elem': elem},
+        path='<test>')
+    cons = generate_mjcf_table._element_constraints(schema, elem)
+    self.assertEqual(len(cons), 1)  # pylint: disable=g-generic-assert
+
 
 if __name__ == '__main__':
   googletest.main()

test/engine/engine_sensor_test.cc

@@ -698,9 +698,9 @@ TEST_F(SensorTest, BadContact) {
       {"geom1='sphere1' geom2='sphere2' num='-3'",
        "'num' must be positive in sensor"},
       {"geom1='sphere1' geom2='sphere2' site='site'",
-       "at most one of (geom1, body1, subtree1, site) can be specified"},
+       "at most one of 'geom1', 'body1', 'subtree1', 'site' can be specified"},
       {"geom2='sphere1' body2='body'",
-       "at most one of (geom2, body2, subtree2) can be specified"},
+       "at most one of 'geom2', 'body2', 'subtree2' can be specified"},
   };
 
   for (const auto& test : test_cases) {

test/user/user_objects_test.cc

@@ -2461,8 +2461,8 @@ TEST_F(UserObjectsTest, BadConnect) {
   EXPECT_THAT(AsVector(m->eq_data, 6), ElementsAre(0, 0, 0, 0, 0, 0));
 
   char error_missing[] =
-      "either both body1 and anchor must be defined,"
-      " or both site1 and site2 must be defined\nElement 'connect', line 12";
+      "one of ('site1', 'site2'), ('body1', 'anchor') must be specified"
+      "\nElement 'connect', line 12";
 
   // bad model (missing anchor)
   xml = base.replace(pos, len, "<connect body1='1'/>");
@@ -2471,8 +2471,8 @@ TEST_F(UserObjectsTest, BadConnect) {
   EXPECT_THAT(error, HasSubstr(error_missing));
 
   char error_mixed[] =
-      "body and site semantics cannot be mixed"
-      "\nElement 'connect', line 12";
+      "at most one of ('site1', 'site2'), ('body1', 'body2', 'anchor')"
+      " can be specified\nElement 'connect', line 12";
 
   // bad model (mixing body and site)
   xml = base.replace(pos, len, "<connect body1='1' site1='1'/>");
@@ -2540,8 +2540,8 @@ TEST_F(UserObjectsTest, BadWeld) {
               ElementsAre(0, 1, 0, 0, 0, 0, 0, 0, 0, 0));
 
   char error_mixed[] =
-      "body and site semantics cannot be mixed"
-      "\nElement 'weld', line 12";
+      "at most one of ('site1', 'site2'), ('body1', 'body2', 'anchor', "
+      "'relpose') can be specified\nElement 'weld', line 12";
 
   // bad model (mixing body and site)
   xml = base.replace(pos, len, "<weld body1='1' site1='1'/>");
@@ -2568,8 +2568,8 @@ TEST_F(UserObjectsTest, BadWeld) {
   EXPECT_THAT(error, HasSubstr(error_mixed));
 
   char error_underspecified[] =
-      "either body1 must be defined and optionally {body2, anchor, "
-      "relpose}, or site1 and site2 must be defined\nElement 'weld', line 12";
+      "one of ('site1', 'site2'), 'body1' must be specified"
+      "\nElement 'weld', line 12";
 
   // bad model (underspecified body semantics)
   xml = base.replace(pos, len, "<weld anchor='0 0 1'/>");
@@ -2663,7 +2663,7 @@ TEST_F(UserObjectsTest, Inertial) {
   )";
   m = LoadModelFromString(bad_xml2.c_str(), error, sizeof(error));
   ASSERT_THAT(m.get(), IsNull());
-  EXPECT_THAT(error, HasSubstr("fullinertia and inertial orientation cannot"));
+  EXPECT_THAT(error, HasSubstr("at most one of 'fullinertia', 'quat'"));
 }
 
 // Merged COM must be correct when a fused-static child has a non-identity

test/xml/xml_native_reader_test.cc

@@ -2024,7 +2024,7 @@ TEST_F(XMLReaderTest, CameraInvalidFovyAndSensorsize) {
   std::array<char, 1024> error;
   MjModelPtr m = LoadModelFromString(xml, error.data(), error.size());
   EXPECT_THAT(m.get(), IsNull());
-  EXPECT_THAT(error.data(), HasSubstr("either 'fovy' or 'sensorsize'"));
+  EXPECT_THAT(error.data(), HasSubstr("at most one of 'fovy', 'sensorsize'"));
   EXPECT_THAT(error.data(), HasSubstr("line 6"));
 }
 
@@ -2081,8 +2081,8 @@ TEST_F(XMLReaderTest, InvalidInertialOrientation) {
   ASSERT_THAT(model.get(), IsNull());
   EXPECT_THAT(
       error.data(),
-      HasSubstr(
-          "fullinertia and inertial orientation cannot both be specified"));
+      HasSubstr("at most one of 'fullinertia', 'quat', 'axisangle', "
+                "'xyaxes', 'zaxis', 'euler' can be specified"));
 }
 
 TEST_F(XMLReaderTest, ReadShellParameter) {
@@ -2137,7 +2137,7 @@ TEST_F(XMLReaderTest, BuiltinAndFile) {
   MjModelPtr model = LoadModelFromString(xml, error.data(), error.size());
   ASSERT_THAT(model.get(), IsNull());
   EXPECT_THAT(error.data(),
-              HasSubstr("builtin mesh cannot be used with user vertex data"));
+              HasSubstr("at most one of 'builtin', 'vertex' can be specified"));
 }
 
 TEST_F(XMLReaderTest, MakePlateNoParameters) {
@@ -2422,7 +2422,9 @@ TEST_F(RelativeFrameSensorParsingTest, RefNameButNoType) {
   )";
   std::array<char, 1024> error;
   LoadModelFromString(xml, error.data(), error.size());
-  EXPECT_THAT(error.data(), HasSubstr("but reftype is missing"));
+  EXPECT_THAT(
+      error.data(),
+      HasSubstr("attributes 'reftype', 'refname' must be specified together"));
   EXPECT_THAT(error.data(), HasSubstr("line 8"));
 }
 
@@ -2440,7 +2442,9 @@ TEST_F(RelativeFrameSensorParsingTest, RefTypeButNoName) {
   )";
   std::array<char, 1024> error;
   LoadModelFromString(xml, error.data(), error.size());
-  EXPECT_THAT(error.data(), HasSubstr("attribute missing: 'refname'"));
+  EXPECT_THAT(
+      error.data(),
+      HasSubstr("attributes 'reftype', 'refname' must be specified together"));
   EXPECT_THAT(error.data(), HasSubstr("line 8"));
 }
 
@@ -3563,7 +3567,9 @@ TEST_F(SensorParseTest, UserObjTypeNoName) {
   std::array<char, 1024> error;
   MjModelPtr model = LoadModelFromString(xml, error.data(), error.size());
   ASSERT_THAT(model.get(), IsNull());
-  EXPECT_THAT(error.data(), HasSubstr("objtype 'site' given but"));
+  EXPECT_THAT(
+      error.data(),
+      HasSubstr("attributes 'objtype', 'objname' must be specified together"));
   EXPECT_THAT(error.data(), HasSubstr("line 4"));
 }
 
@@ -3578,7 +3584,9 @@ TEST_F(SensorParseTest, UserObjNameNoType) {
   std::array<char, 1024> error;
   MjModelPtr model = LoadModelFromString(xml, error.data(), error.size());
   ASSERT_THAT(model.get(), IsNull());
-  EXPECT_THAT(error.data(), HasSubstr("objname 'kevin' given but"));
+  EXPECT_THAT(
+      error.data(),
+      HasSubstr("attributes 'objtype', 'objname' must be specified together"));
   EXPECT_THAT(error.data(), HasSubstr("line 4"));
 }