fix(ffi): report the producer's C stream error message, don't unwrap it - #10844
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`get_stream_schema` discarded the producer's message entirely, reporting only the numeric return code. `Iterator::next` did the opposite, unwrapping the producer's message without checking there was one. The C Stream Interface lets `get_last_error` return NULL when no detailed description is available, so a conforming producer that reported a failure without a message made the consumer panic instead of returning an error. Signed-off-by: Fredrik Fornwall <fredrik@fornwall.net>
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Jefffrey
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Aug 26, 2026
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makes sense, just a minor comment (applies for both unsafe usages)
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Aug 26, 2026
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thanks @fornwall |
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Which issue does this PR close?
No issue filed (this is a minor fix).
Rationale for this change
get_stream_schemadiscarded the producer's message entirely, reporting only the numeric return code, so a failed import left the consumer with nothing but an errno.Iterator::nextdid the opposite, unwrapping the producer's message without checking there was one. The C stream interface letsget_last_errorreturnNULLwhen no detailed description is available, so a conforming producer that reported a failure without a message made the consumer panic across an FFI boundary instead of returning an error.What changes are included in this PR?
get_stream_schemaandIterator::nextnow includes the producer's error message when there is one.Are these changes tested?
Yes.
test_error_importnow asserts the full message that a failing Rust producer surfaces through a round trip. New tests drive a hand-written producer through both the schema and thenextpath, covering: a producer message,get_last_errorreturning NULL, and a NULLget_last_errorcallback. The NULL-message case panicked before this change.Are there any user-facing changes?
No API changes; error messages change:
Cannot get schema from input stream. Error code: 5, and now appends. Producer error: <message>when the producer supplies one.next()previously surfaced the producer's message alone (e.g.Memory error: out of memory), and now readsCannot get next batch from input stream. Error code: 12. Producer error: Memory error: out of memory.AI usage: Created with claude code and opus 5. I have reviewed the code and iterated on it.