[pengpengyi92]

Summary

Addresses the remaining legacy-resolver behavior in #181. On current main, with CSP_PYDANTIC set to the empty string before importing CSP, passing an int list/dict basket to a float-basket input still replaces entries in the caller's container with float-cast edges. Reusing that basket as int input can then fail. The Pydantic path already preserves these inputs and is unchanged.

Make a shallow copy on the first required cast, update the resolved basket instead of the original, and reuse that copy for subsequent casts. Baskets that require no cast do not incur a copy in this path. No C++ or public API changes.

Regression tests

• The graph reproducer from Casting of ts[int] to ts[float] as part of type checking will mutate input baskets in-place, which can lead to downstream errors. #181 asserts the original int edges remain available for downstream casts.
• A node runtime test covers multiple int entries mixed with existing float entries in both list and dict baskets, original-edge identity, and a real float output of 11.0.
• Both tests run under both validators; they are not skipped in legacy mode.
• Against unchanged main c7d0aded32cf9b6c969490a9a7a55376476e7464, the exact two new tests fail under legacy validation due to mutated edge identity. With this patch both pass; under Pydantic they pass before and after.

This branch is based directly on upstream main and does not include #779.

Verification

Windows x64; Python 3.12.14; Pydantic 2.14.1; pytest 9.1.1.

python -m pytest csp/tests/test_type_checking.py csp/tests/test_parsing.py csp/tests/test_typing.py csp/tests/impl/wiring csp/tests/impl/types csp/tests/impl/test_pushadapter.py csp/tests/impl/test_pulladapter.py csp/tests/impl/test_outputadapter.py csp/tests/impl/test_pushpulladapter.py -q -p no:cacheprovider --tb=short

145 passed, 2 skipped, exit 0 (plus 5 passing unittest subtests).

Legacy mode must be selected before importing CSP, for example:

import os
os.environ["CSP_PYDANTIC"] = ""
import pytest
raise SystemExit(pytest.main([
    "csp/tests/test_type_checking.py", "csp/tests/test_parsing.py",
    "csp/tests/test_typing.py", "csp/tests/test_baskets.py",
    "csp/tests/test_basketlib.py", "-k", "not test_literal_typing", "-q",
]))

61 passed, 1 explicitly deselected, exit 0. Without excluding the known Literal case, the three typing/parsing files give 48 passed, 1 failed. Unmodified upstream in the same environment gives 46 passed, 1 failed, with the identical test_literal_typing failure. That pre-existing failure is not fixed or hidden by this PR.

Ruff check/format on the changed files and git diff --check: PASS.

Local runs use checked-out Python source with official CSP 0.19.1 Windows wheel native libraries. No native source rebuild, Linux/macOS matrix or full service-dependent suite was run. Runtime/memory performance has not been benchmarked. Maintainer CI and review remain required; no upstream acceptance is implied.