Add pydrake bindings for model directives.

* Weld error support omitted for simplicity.
* Follow-up to RobotLocomotion#14038
* Completes RobotLocomotion#13282

bindings/pydrake/multibody/BUILD.bazel

@@ -220,6 +220,7 @@ drake_py_unittest(
     data = [
         "//examples/atlas:models",
         "//multibody/benchmarks/acrobot:models",
+        "//multibody/parsing:process_model_directives_test_models",
     ],
     deps = [
         ":parsing_py",

bindings/pydrake/multibody/parsing_py.cc

@@ -5,6 +5,7 @@
 #include "drake/bindings/pydrake/pydrake_pybind.h"
 #include "drake/multibody/parsing/package_map.h"
 #include "drake/multibody/parsing/parser.h"
+#include "drake/multibody/parsing/process_model_directives.h"
 
 using drake::geometry::SceneGraph;
 using drake::multibody::MultibodyPlant;
@@ -57,6 +58,38 @@ PYBIND11_MODULE(parsing, m) {
             py::arg("file_contents"), py::arg("file_type"),
             py::arg("model_name") = "", cls_doc.AddModelFromString.doc);
   }
+
+  // Model Directives
+  {
+    constexpr auto& parsing_doc = doc.parsing;
+    py::class_<parsing::ModelDirectives>(
+        m, "ModelDirectives", parsing_doc.ModelDirectives.doc);
+    m.def("LoadModelDirectives", &parsing::LoadModelDirectives,
+        py::arg("filename"));
+    py::class_<parsing::ModelInstanceInfo>(m, "ModelInstanceInfo")
+        .def_readonly("model_name", &parsing::ModelInstanceInfo::model_name)
+        .def_readonly("model_path", &parsing::ModelInstanceInfo::model_path)
+        .def_readonly(
+            "parent_frame_name", &parsing::ModelInstanceInfo::parent_frame_name)
+        .def_readonly(
+            "child_frame_name", &parsing::ModelInstanceInfo::child_frame_name)
+        .def_readonly("X_PC", &parsing::ModelInstanceInfo::X_PC)
+        .def_readonly(
+            "model_instance", &parsing::ModelInstanceInfo::model_instance);
+    m.def(
+        "ProcessModelDirectives",
+        [](const parsing::ModelDirectives& directives,
+            MultibodyPlant<double>* plant, Parser* parser = nullptr) {
+          std::vector<parsing::ModelInstanceInfo> added_models;
+          parsing::ProcessModelDirectives(
+              directives, plant, &added_models, parser);
+          return added_models;
+        },
+        py::arg("directives"), py::arg("plant"), py::arg("parser"),
+        (std::string(parsing_doc.ProcessModelDirectives.doc) +
+            "\nNOTE:  pydrake does not support `ModelWeldErrorFunction`.")
+            .c_str());
+  }
 }
 
 }  // namespace pydrake

bindings/pydrake/multibody/test/parsing_test.py

@@ -3,6 +3,8 @@
 from pydrake.multibody.parsing import (
     Parser,
     PackageMap,
+    LoadModelDirectives,
+    ProcessModelDirectives,
 )
 
 import os
@@ -82,3 +84,23 @@ def test_parser_string(self):
         result = parser.AddModelFromString(
             file_contents=sdf_contents, file_type="sdf")
         self.assertIsInstance(result, ModelInstanceIndex)
+
+    def test_model_directives(self):
+        model_dir = os.path.dirname(FindResourceOrThrow(
+            "drake/multibody/parsing/test/"
+            "process_model_directives_test/package.xml"))
+        plant = MultibodyPlant(time_step=0.01)
+        parser = Parser(plant=plant)
+        parser.package_map().PopulateFromFolder(model_dir)
+        directives_file = model_dir + "/add_scoped_top.yaml"
+        directives = LoadModelDirectives(directives_file)
+        added_models = ProcessModelDirectives(
+            directives=directives, plant=plant, parser=parser)
+        # Check for an instance.
+        model_names = [model.model_name for model in added_models]
+        self.assertIn("extra_model", model_names)
+        plant.GetModelInstanceByName("extra_model")
+
+    def test_model_directives_doc(self):
+        """Check that the warning note in the docstring was added."""
+        self.assertIn("NOTE:", ProcessModelDirectives.__doc__)

multibody/parsing/BUILD.bazel

@@ -268,6 +268,9 @@ filegroup(
     name = "process_model_directives_test_models",
     testonly = True,
     data = glob(["test/process_model_directives_test/**"]),
+    visibility = [
+        "//visibility:public",
+    ],
 )
 
 drake_cc_googletest(