pybricks._common.Motor: Fix nested attributes.

Now we can use relative paths, which should help when sharing the motor class contents.

doc/common/extensions/nestedmethod.py

@@ -0,0 +1,41 @@
+"""Provides the ``autonestedmethod`` directive.
+
+Like ``automethod``, but resolves dotted names such as ``control.limits``
+relative to the class documented by the enclosing ``autoclass`` directive.
+Plain ``automethod`` treats everything before the last dot as a module/class
+path, so ``control.limits`` would be looked up as an attribute of the current
+*module* instead of the current class. Resolving the class here keeps shared
+include fragments module-neutral.
+"""
+
+from sphinx.util import logging
+from sphinx.util.docutils import SphinxDirective
+
+logger = logging.getLogger(__name__)
+
+
+class AutoNestedMethodDirective(SphinxDirective):
+    required_arguments = 1
+    has_content = False
+
+    def run(self):
+        current = self.env.current_document
+        module = current.autodoc_module or self.env.ref_context.get("py:module")
+        cls = current.autodoc_class or self.env.ref_context.get("py:class")
+
+        if not module or not cls:
+            logger.warning(
+                "autonestedmethod:: %s used outside of an autoclass context",
+                self.arguments[0],
+                location=self.get_location(),
+            )
+            return []
+
+        return self.parse_text_to_nodes(
+            f".. automethod:: {module}::{cls}.{self.arguments[0]}"
+        )
+
+
+def setup(app):
+    app.add_directive("autonestedmethod", AutoNestedMethodDirective)
+    return {"parallel_read_safe": True}