Python: preserve PEP 695 type-alias type parameters across RPC#8331
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Python: preserve PEP 695 type-alias type parameters across RPC#8331shanman190 wants to merge 2 commits into
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Py.TypeAlias had no typeParameters field on the Java side, so all four RPC codecs (Python + Java, sender + receiver) dropped it. `type X[T] = ...` was silently narrowed to `type X = ...` once the tree crossed the RPC boundary — a print-fidelity loss invisible to the in-process printer suite and baked into every serialized LST. Add the field to Py.TypeAlias (JContainer<J.TypeParameter>, mirroring J.ClassDeclaration) and send/receive it between name and value in all four codecs. Both serialization formats (V2 Jackson-reflection, V3 reflective field walk) discover the new field automatically, so no moderne-cli change is needed. Verified: Python and Java RPC round-trip tests preserve simple, bound, variadic and ParamSpec parameters; numpy (3 -> 0) and home-assistant (15 -> 0) TypeAlias round-trip mismatches resolved; existing type-alias parser/printer suite green.
Space out the type parameters (before `[`, inside the brackets, around the `:` bound and the commas) so the round-trip also asserts JContainer.before and the element padding survive, not just the parameters' presence.
shanman190
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July 26, 2026 02:31
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Py.TypeAliashad notypeParametersfield on the Java side, so all four RPC codecs (Python + Java, sender + receiver) dropped it.type X[T] = ...was silently narrowed totype X = ...once the tree crossed the RPC boundary — a print-fidelity loss invisible to the in-process printer suite and baked into every serialized LST.Change
Py.TypeAlias— add@Nullable JContainer<J.TypeParameter> typeParameters(mirroringJ.ClassDeclaration), with the unwrapped getter,withTypeParameters, andPaddingaccessors.PythonSender/PythonReceiver.visitTypeAliasand_visit_type_aliason both Python sides send/receive the container betweennameandvalue.Both serialization formats (V2 Jackson-reflection, V3 reflective field walk) discover the new field automatically, so no moderne-cli change is needed.
Verification
Python RPC round-trip test (
tests/rpc/test_type_alias_roundtrip.py) and a JavaPythonSenderReceiverRoundTripTestcase cover simple, bound (T: int), variadic (*Ts) and ParamSpec (**P) parameters, plus the no-params regression.Serialize→deserialize→print corpus: numpy 3 → 0 and home-assistant 15 → 0
TypeAliasround-trip mismatches; existing type-alias parser/printer suite green.Draft: independent of the
match-parser fix (Python: fix match-statement parse desync that corrupts trees over RPC #8330). Optional follow-up: a Java assertion for the null (no-params) path — currently covered by thegetAndSendnull-guard and the Python test.