UI: add description methods for `wm.context_*` operators

Generic context operators now look-up the RNA properties to extract
their description (when it's available).

Add `bl_rna_utils.data_path.property_definition_from_data_path()`
to handle the details of accessing the RNA property definition.

2 files changed, 80 insertions, 0 deletions

diff --git a/release/scripts/modules/bl_rna_utils/__init__.py b/release/scripts/modules/bl_rna_utils/__init__.py
new file mode 100644
index 00000000000..e69de29bb2d
--- /dev/null
+++ b/release/scripts/modules/bl_rna_utils/__init__.py
diff --git a/release/scripts/modules/bl_rna_utils/data_path.py b/release/scripts/modules/bl_rna_utils/data_path.py
new file mode 100644
index 00000000000..76306e379f0
--- /dev/null
+++ b/release/scripts/modules/bl_rna_utils/data_path.py
@@ -0,0 +1,80 @@
+# ##### BEGIN GPL LICENSE BLOCK #####
+#
+#  This program is free software; you can redistribute it and/or
+#  modify it under the terms of the GNU General Public License
+#  as published by the Free Software Foundation; either version 2
+#  of the License, or (at your option) any later version.
+#
+#  This program is distributed in the hope that it will be useful,
+#  but WITHOUT ANY WARRANTY; without even the implied warranty of
+#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#  GNU General Public License for more details.
+#
+#  You should have received a copy of the GNU General Public License
+#  along with this program; if not, write to the Free Software Foundation,
+#  Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+#
+# ##### END GPL LICENSE BLOCK #####
+
+# <pep8 compliant>
+
+__all__ = (
+    "property_definition_from_data_path",
+)
+
+class _TokenizeDataPath:
+    """Class to split up tokens of a data-path."""
+    __slots__ = (
+        "data_path",
+    )
+
+    def __init__(self, attrs):
+        self.data_path = attrs
+
+    def __getattr__(self, attr):
+        return _TokenizeDataPath(self.data_path + ((".%s" % attr),))
+
+    def __getitem__(self, key):
+        return _TokenizeDataPath(self.data_path + (("[%r]" % (key,)),))
+
+    def __call__(self, *args, **kw):
+        value_str = ", ".join([
+            val for val in (
+                repr(args)[1:-1],
+                ", ".join(["%s=%r" % (key, value) for key, value in kw.items()])
+            ) if val])
+        return _TokenizeDataPath(self.data_path + ('(%s)' % value_str, ))
+
+    def __iter__(self):
+        return iter(self.data_path)
+
+
+def property_definition_from_data_path(base, data_path):
+    """
+    Return an RNA property definition from an object and a data path.
+
+    In Blender this is often used with ``context`` as the base and a
+    path that it references, for example ``.space_data.lock_camera``.
+    """
+    base_tokenize = _TokenizeDataPath(())
+    data = list(eval("base_tokenize" + data_path))
+    del base_tokenize
+    while data and (not data[-1].startswith(".")):
+        data.pop()
+
+    if (not data) or (not data[-1].startswith(".")) or (len(data) < 2):
+        return None
+
+    data_path_head = "".join(data[:-1])
+    data_path_tail = data[-1]
+
+    value_head = eval("base" + data_path_head)
+    value_head_rna = getattr(value_head, "bl_rna", None)
+    if value_head_rna is None:
+        return None
+
+    value_tail = value_head.bl_rna.properties.get(data_path_tail[1:])
+    if not value_tail:
+        return None
+
+    return value_tail