Extract shared raw CLI hint scanner (#342)

[leynos]

Summary

Closes #342

locale_hint_from_args and diag_json_hint_from_args in src/cli_l10n.rs duplicated the raw argument grammar (-- terminator, --flag value, --flag=value, last-wins). This extracts a single lexical scanner so the locale and diagnostic-mode startup paths cannot diverge.

Changes

• src/cli_l10n.rs: add scan_raw_hints(args, value_flags, bare_flags) -> RawArgHints plus small scan_value_flags/consume_flag_value helpers (flattened to satisfy the nesting threshold). Both public hint functions now delegate to it; value interpretation stays at the call sites as the issue suggests.
• tests/cli_tests/locale.rs: five new edge-case tests — trailing valueless flag keeps the earlier value, -- after a value flag stops scanning without discarding state, a value flag greedily consumes a flag-like token (--output-format --diag-json → None), the last --output-format wins even when unrecognised, and a bare --diag-json survives an unrecognised format value.

All existing locale/diag-json hint tests pass unchanged, pinning behavioural equivalence.

Validation

• make check-fmt / make lint / make test — pass (37 suites)

🤖 Generated with Claude Code

Summary by Sourcery

Extract a shared raw CLI argument scanner used by locale and diagnostic JSON hint detection to keep their startup parsing behavior consistent.

Enhancements:

• Introduce a reusable lexical scanner for raw CLI hints that supports value flags, bare flags, and terminator handling, and use it in both locale and diagnostic-mode hint extraction.

Tests:

• Add edge-case tests for locale and diagnostic JSON hint parsing to pin behavior around missing values, -- terminators, value precedence, and interaction between output format and diag-json flags.

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[sourcery-ai]

Reviewer's Guide

Refactors CLI startup hint parsing by extracting a shared raw argument scanner for locale and diagnostic JSON detection, preserving existing behaviour while adding targeted edge-case tests to pin the new grammar.

File-Level Changes

Change	Details	Files
Introduce a shared raw argument scanning utility and data structure used by both locale and diagnostic JSON hint extraction.	Add RawArgHints struct holding last-seen values for value flags and presence of bare flags, with helper accessors Implement scan_raw_hints to walk OsString args with support for -- terminator, value flags, inline --flag=value, last-wins semantics, and bare flags Factor out scan_value_flags and consume_flag_value helpers plus ScanStep enum and RawArgIter alias to keep scanning logic flat and readable	src/cli_l10n.rs
Change locale and diag-json hint functions to use the shared scanner while keeping value interpretation at call sites.	Refactor locale_hint_from_args to delegate to scan_raw_hints with --locale as a value flag and return the captured value Refactor diag_json_hint_from_args to delegate to scan_raw_hints with --output-format as a value flag and --diag-json as a bare flag, then compute the final bool via diag_json_hint_from_output_format and flag presence	src/cli_l10n.rs
Add regression and edge-case tests to pin the new raw scanning behaviour for locale and diag-json hints.	Add tests ensuring a trailing valueless --locale or --locale followed by -- does not discard earlier valid locale values Add tests verifying a value flag greedily consumes following flag-like tokens as values, last --output-format wins even with invalid values, and a bare --diag-json flag still takes effect after an invalid output format	tests/cli_tests/locale.rs

Assessment against linked issues

Issue	Objective	Addressed	Explanation
#342	Extract shared raw CLI hint scanning logic used by locale_hint_from_args and diag_json_hint_from_args into a small internal helper, while keeping value interpretation at the call sites.	✅
#342	Ensure shared scanning logic consistently handles -- terminator, --flag value, and --flag=value forms, preserving existing behaviour for locale and diagnostic hints so existing tests continue to pass.	✅
#342	Add focused tests for the shared scanner edge cases and ensure the test/lint/format suite passes.	✅

Possibly linked issues

• Extract shared raw CLI hint scanning logic #342: PR implements the shared raw CLI hint scanner, updates locale/diag-json hint functions, and adds edge-case tests as requested.

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