Add default value for info argument of ClassDescription (#3017)

* Closes #2924

Two changes:
* You can now easily specify the `info` without having to also specify
label and color, using `info=0`.
* The default info is one with `id=0`, matching 0.7.0 behavior and how
`log_points` work


(This took me over an hour to figure out 😭)

### Checklist
* [x] I have read and agree to [Contributor
Guide](https://github.com/rerun-io/rerun/blob/main/CONTRIBUTING.md) and
the [Code of
Conduct](https://github.com/rerun-io/rerun/blob/main/CODE_OF_CONDUCT.md)
* [x] I've included a screenshot or gif (if applicable)
* [x] I have tested [demo.rerun.io](https://demo.rerun.io/pr/3017) (if
applicable)

- [PR Build Summary](https://build.rerun.io/pr/3017)
- [Docs
preview](https://rerun.io/preview/pr%3Aemilk%2Ffix-annotation-context-default/docs)
- [Examples
preview](https://rerun.io/preview/pr%3Aemilk%2Ffix-annotation-context-default/examples)

crates/re_types/definitions/rerun/datatypes/annotation_info.fbs

@@ -12,7 +12,7 @@ namespace rerun.datatypes;
 /// Color and label will be used to annotate entities/keypoints which reference the id.
 /// The id refers either to a class or key-point id
 table AnnotationInfo (
-  "attr.python.aliases": "Tuple[int, str], Tuple[int, str, datatypes.ColorLike]",
+  "attr.python.aliases": "int, Tuple[int, str], Tuple[int, str, datatypes.ColorLike]",
   "attr.rust.derive": "Default, Eq, PartialEq",
   order: 500
 ) {

crates/re_types/definitions/rerun/datatypes/class_description.fbs

@@ -21,6 +21,8 @@ namespace rerun.datatypes;
 /// defined, and both keypoints exist within the instance of the class, then the
 /// keypoints should be connected with an edge. The edge should be labeled and
 /// colored as described by the class's `AnnotationInfo`.
+///
+/// The default `info` is an `id=0` with no label or color.
 table ClassDescription (
   "attr.python.aliases": "datatypes.AnnotationInfoLike",
   "attr.rust.derive": "Default, Eq, PartialEq",

rerun_py/rerun_sdk/rerun/_rerun2/datatypes/_overrides/annotation_context.py

@@ -29,7 +29,8 @@
 
 def classdescription_init(
     self: ClassDescription,
-    info: AnnotationInfoLike,
+    info: AnnotationInfoLike = 0,
+    *,
     keypoint_annotations: Sequence[AnnotationInfoLike] = [],
     keypoint_connections: Sequence[KeypointPairLike] = [],
 ) -> None:
@@ -89,6 +90,8 @@ def classdescription_info_converter(
 
     if isinstance(data, AnnotationInfo):
         return data
+    elif isinstance(data, int):
+        return AnnotationInfo(id=data)
     else:
         return AnnotationInfo(*data)
 

tests/python/roundtrips/annotation_context/main.py

@@ -16,7 +16,7 @@ def main() -> None:
         [
             (1, "hello"),
             rrd.ClassDescription(
-                (2, "world", [3, 4, 5]),
+                info=(2, "world", [3, 4, 5]),
                 keypoint_annotations=[(17, "head"), (42, "shoulders")],
                 keypoint_connections=[(1, 2), (3, 4)],
             ),