join: report the field number the user gave

[MsfPablo]

Fixes #13376.

Both halves of the issue come down to the reported field number not matching the input.

The k + 1 overflow. parse_field_number deliberately clamps an out-of-range field to usize::MAX, and get_field_number then renders it one-based with k + 1. That aborts under overflow-checks and wraps to 0 in a normal build. Now saturates.

The rounding. This one is not join-specific, so I fixed it where it lives. translate! stringifies a value, re-parses it as i64 or f64, and sets it on Fluent as a number — but FluentNumber is f64-backed, so anything past 2^53 rounds. Note that taking the i64 branch is not enough to stay exact; -j 9007199254740993 parses fine as i64 and still comes out as …992. So the check is whether f64 can hold the value exactly, not whether i64 can:

• exactly representable → still set as a number, so plural rules and number formatting are untouched
• an integer past that → passed through as its exact decimal string
• anything else → unchanged

That also fixes the csplit case you mentioned:

$ printf 'a\nb\nc\n' | csplit - 9007199254740995 9007199254740995
csplit: warning: line number '9007199254740995' is the same as preceding line number

All the values from the issue now match GNU, including 18446744073709551615 for the clamped case.

Tests: unit tests in locale.rs for the representability boundary, and an integration test in test_join.rs covering the four field values above.

Since this touches uucore, I ran the suites for csplit, nl, split, head, expr, seq, tail, wc, fold and sort as well as join — 982 tests, all passing.

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/date/date-locale-hour (fails in this run but passes in the 'main' branch)
Skip an intermittent issue tests/tail/tail-n0f (fails in this run but passes in the 'main' branch)
Skipping an intermittent issue tests/cut/bounded-memory (passes in this run but fails in the 'main' branch)
Skipping an intermittent issue tests/date/resolution (passes in this run but fails in the 'main' branch)

[codspeed-hq]

Merging this PR will regress 2 benchmarks

⚠️ Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

⚡ 5 improved benchmarks
❌ 2 regressed benchmarks
✅ 349 untouched benchmarks
⏩ 51 skipped benchmarks¹

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
❌	Simulation	numfmt_large_numbers_si[10000]	93.2 ms	98.4 ms	-5.34%
❌	Simulation	ptx_input_references_long_lines[1000]	1.9 s	2 s	-4.31%
⚡	Simulation	shuf_lines[100000]	72.1 ms	54.7 ms	+31.77%
⚡	Simulation	shuf_repeat_sampling[50000]	14 ms	12.3 ms	+14.18%
⚡	Simulation	expand_many_lines[100000]	116.4 ms	107.3 ms	+8.55%
⚡	Simulation	numfmt_stream_to_si_precision	390.9 ms	361.1 ms	+8.25%
⚡	Simulation	expand_custom_tabstops[50000]	31.5 ms	29.2 ms	+7.93%

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.

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_{Comparing MsfPablo:join-exact-field-numbers (a7b3dee) with main (9504124)}

Footnotes

1. 51 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩