test: `interface_ipc.py` might start skipping if installed capnp version changes #34016

Noticed this on a Fedora (Rawhide) Box that has capnp 1.2.0 (recently updated from 1.1.0) and pycapnp 2.1.0 installed, but was skipping interface_ipc.py as if the Python module was not available. The failure was that pycanp 2.1.0 tries to load an older shared lib, and fails:

Remaining jobs: [interface_ipc.py]
1/1 - interface_ipc.py failed, Duration: 0 s

stdout:


stderr:
Traceback (most recent call last):
  File "/root/ci_scratch/build/test/functional/interface_ipc.py", line 20, in <module>
    import capnp  # type: ignore[import] # noqa: F401
    ^^^^^^^^^^^^
  File "/usr/local/lib64/python3.14/site-packages/capnp/__init__.py", line 36, in <module>
    from .version import version as __version__
  File "/usr/local/lib64/python3.14/site-packages/capnp/version.py", line 1, in <module>
    from .lib.capnp import _CAPNP_VERSION_MAJOR as LIBCAPNP_VERSION_MAJOR  # noqa: F401
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
ImportError: libcapnpc.so.1.0.1: cannot open shared object file: No such file or directory

We catch this and skip as if the module isn't available. Updating to pycapnp 2.2.1 solved the issue.

Maybe this would get the failure to be reported properly:

--- a/test/functional/interface_ipc.py
+++ b/test/functional/interface_ipc.py
@@ -19,7 +19,7 @@ from test_framework.wallet import MiniWallet
 # Test may be skipped and not have capnp installed
 try:
     import capnp  # type: ignore[import] # noqa: F401
-except ImportError:
+except ModuleNotFoundError:
     pass [@asynccontextmanager](/bitcoin-bitcoin/contributor/asynccontextmanager/)

@ryanofsky yes, that works.

Noticed this on a Fedora (Rawhide) Box that has capnp 1.2.0 (recently updated from 1.1.0) and pycapnp 2.1.0 installed, but was skipping interface_ipc.py as if the Python module was not available. The failure was that pycanp 2.1.0 tries to load an older shared lib, and fails:

Remaining jobs: [interface_ipc.py]
1/1 - interface_ipc.py failed, Duration: 0 s

stdout:


stderr:
Traceback (most recent call last):
  File "/root/ci_scratch/build/test/functional/interface_ipc.py", line 20, in <module>
    import capnp  # type: ignore[import] # noqa: F401
    ^^^^^^^^^^^^
  File "/usr/local/lib64/python3.14/site-packages/capnp/__init__.py", line 36, in <module>
    from .version import version as __version__
  File "/usr/local/lib64/python3.14/site-packages/capnp/version.py", line 1, in <module>
    from .lib.capnp import _CAPNP_VERSION_MAJOR as LIBCAPNP_VERSION_MAJOR  # noqa: F401
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
ImportError: libcapnpc.so.1.0.1: cannot open shared object file: No such file or directory

We catch this and skip as if the module isn't available. Updating to pycapnp 2.2.1 solved the issue.

I can't reproduce the issue:

# dnf info capnproto 2>&1 | grep Version
Version         : 1.3.0
# pip show pycapnp | grep Version
Version: 2.1.0
# ./build/test/functional/test_runner.py interface_ipc
Temporary test directory at /tmp/test_runner_₿_🏃_20260126_130625
Remaining jobs: [interface_ipc.py]
1/1 - interface_ipc.py passed, Duration: 7 s

TEST             | STATUS    | DURATION

interface_ipc.py | ✓ Passed  | 7 s

ALL              | ✓ Passed  | 7 s (accumulated) 
Runtime: 7 s

I can't reproduce the issue:

It's not clear what you tested here. You need to test the capnp shared libs being updated, without updating pycapnp.

I can't reproduce the issue:

It's not clear what you tested here.

I've tested this claim: "The failure was that pycanp 2.1.0 tries to load an older shared lib, and fails:". It wasn't clear that updating capnp is necessary for observing the issue.

You need to test the capnp shared libs being updated, without updating pycapnp.

Well, this could be tricky as the Rawhide repository doesn't keep the previous capnproto version.