fix(generator): emit .msg syntax in _fields_and_field_types for bounded types#262
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fix(generator): emit .msg syntax in _fields_and_field_types for bounded types#262vik-shah-ai wants to merge 1 commit into
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…ed types
_fields_and_field_types / get_fields_and_field_types() is documented as a
Python introspection API for message field types. However it was emitting
OMG IDL 4.2 syntax for bounded strings and sequences:
sequence<string<256>, 32> (IDL)
instead of the canonical ROS 2 .msg syntax:
string<=256[<=32] (.msg)
This breaks any consumer that passes the output directly to the MCAP
ros2msg schema encoder (e.g. mcap_utils _build_ros2_schema()), because
the ros2msg schema encoding requires .msg syntax per the MCAP registry
spec (https://mcap.dev/spec/registry#ros2msg). Foxglove and other
ros2msg-aware tools reject the IDL form.
Changes:
- Remove IDL-style sequence<> prefix/suffix generation in the
_fields_and_field_types dict template.
- Emit bounded string bound with <= (string<=N) instead of <N>.
- Emit bounded sequence bound as [<=N], unbounded sequence as [],
fixed-size array as [N] -- all matching .msg syntax.
- Update test_interfaces.py expected values accordingly.
The SLOT_TYPES tuple (rosidl_parser.definition objects) is unchanged
and remains the correct API for programmatic type inspection.
Signed-off-by: Vikrant Shah <vikrant.shah@applied.co>
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Problem
_fields_and_field_types/get_fields_and_field_types()currently emits OMG IDL 4.2 syntax for bounded strings and sequences:The canonical ROS 2
.msgsyntax for these is:This matters because
get_fields_and_field_types()is used by tools that buildros2msg-encoded MCAP schemas (e.g.rosbag2-to-MCAP converters,mcap_utilsin downstream tooling). The MCAP registry spec requiresros2msgschema data to contain.msg-syntax definitions. Consumers such as Foxglove reject the IDL form and silently fail to decode topics with bounded string arrays.Changes
sequence<>prefix/suffix from_fields_and_field_typestemplate.<=(string<=N) instead of<N>..msgsyntax:[<=N](bounded),[](unbounded),[N](fixed).test_interfaces.pyexpected values to match.SLOT_TYPES(which holdsrosidl_parser.definitionobjects) is unchanged and remains the correct API for programmatic type inspection.Relation to issue #99
Issue #99 proposes deprecating
get_fields_and_field_types()in favour ofSLOT_TYPES. This fix is complementary: until that deprecation lands and all consumers have migrated, the string API should emit valid.msgsyntax rather than leaking IDL internals.