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pxf.bind_row promises (pxf.default) and (pxf.required) but applies neither #24
Description
Problem
The bind_row docstring promises something the code does not do. It says an absent cell takes (pxf.default) and that (pxf.required) errors. Neither happens, so a dataset row can silently lose its default or skip a required field.
Evidence
Measured with a one-field schema on protowire-cpp main (8d0867a):
| Call | (pxf.required), field absent |
(pxf.default) = "x", field absent |
|---|---|---|
pxf.unmarshal |
accepted | not tested |
pxf.bind_row |
accepted | f == "" |
pxf.unmarshal_full |
required field "f" is absent |
f == "x" |
The cause is upstream. protowire-cpp applies both options only in UnmarshalFull (src/pxf/decode_fast.cc), and bind_row and cpp's BindRow both go through plain Unmarshal. cpp's comment in BindRow makes the same promise.
Open question
Should bind_row apply the options, or should the docstring change? Going through unmarshal_full would make it match the text but would change what existing rows decode to. That choice belongs to the owner, and I have not made it.
Done when
bind_row's behavior and its docstring agree, with a test for an absent required field and an absent default.
Activity
bfrancojr commentedon Nov 7, 2026
This adds to what this issue decides. protowire-go is changing
DatasetReader.Scan(trendvidia/protowire-go#280, PR trendvidia/protowire-go#281; decided in trendvidia/protowire-cpp#166). A streamed row will be bound under all the caller's options exceptMaxMessageSize, as the options-takingBindRowbinds it. Only a decode error gets the row's position. A schema violation and a validator's error come back with no position. protowire-cpp'sScanandBindRowalready do this (PR trendvidia/protowire-cpp#174).From reading this port's code at df004ec (not run):
scanandbind_rowhave nodiscard_unknown, so it is always False for a streamed row.skip_validatedefaults to True. Go validates by default.If this issue settles on calling cpp's
BindRow, all three come with it once the cpp pin moves past #174. The test cases to copy are in protowire-go'sencoding/pxf/dataset_scan_options_test.goon #281.bfrancojr commentedon Nov 7, 2026
Unblocked: trendvidia/protowire-go#281 merged (8894b7b), which closed #280. The reference tests are in
encoding/pxf/dataset_scan_options_test.goon protowire-go main.