GeezerVison

LLM Description written by Claude Code:claude-opus-5-5

Refs #815. This is slice 1 of 2; the issue stays open for slice 2.

Summary

Writers that insert lines into a user's file each hand-wrote "if the text contains any \r\n, use CRLF". This PR adds one rule, utils::line_endings::terminator(text), and routes the 7 copies outside open-PR files through it:

• CRLF file → \r\n;
• LF file, or no break at all → \n;
• mixed file → the existing majority_terminator.

Why (leverage)

• B 0. U 1: slice 2 and children 2–4 of tracking Tracking: classify line endings in one place instead of five drifting rules #814 build on this helper. D 7 hand-written copies of one rule collapse into one. S 0. R L. Score ≈ 16, the best eligible candidate this run. The higher-ranked Finish every vendored revert through one shared helper with an explicit keep policy instead of 12 copied finish blocks #990, Build npm-family vendor ledger entries through one constructor instead of seven literal VendorEntry blocks #922, apply, apply --check and vendor report noManifest (exit 0) when .socket/manifest.json exists but can't be stat'd #998 and Stage prebuilt service archives through one shared helper instead of four per-backend service-copy pipelines #906 all change files that other open PRs change.
• Register row E16 and the living document's {{E16}} passages in doc/04-js-lockfiles.md and doc/05-vendored.md (discussion #560).

What changed

Deleted: the 6 inline copies and both go_mod_edit calls to detect_eol. Production: about +25 / −12 lines. Tests: about +100 lines. Goldens: about 240 lines re-blessed.

Left for slice 2 (every site sits in a file another open PR changes): vendor::common::detect_eol and its callers (go.sum, requirements, yarn classic), pypi_uv::newline_of, maven_reactor.rs ×2, redirect/mod.rs, the crlf flags in upstream/cargo.rs, npmrc.rs and pypi_pipenv.rs, and Gradle's first-line newline_of. Upstream gem's restore_manifest is deliberately left out too: manifest_blocks_restore_in_place pins CRLF output for a CRLF Gemfile that holds an older rewriter's LF block, so it has to move together with its forward Gemfile writer in redirect/mod.rs.

Behavior

• LF-only and CRLF-only files: none. terminator agrees with the old rule whenever the file isn't mixed.
• Mixed-ending files (the change Pick the line terminator for spliced lines through one line_endings::terminator #815 asks for): inserted lines now take the majority style. Before, a single \r\n anywhere made every inserted line CRLF. The two rules differ only on a mixed file whose majority is LF. A mixed LF-majority composer.lock now unwinds byte for byte; before, its restored dist block came back CRLF.
• Goldens: the go and uv equivalence generators turn one input in five into a mixed file (every 4th line CRLF), so those cases moved: 194 of 300 golang_rewrite chunks (plus 13 more from the follow-up below) and 19 of 300 python_lock_rewrite chunks (20 cases per chunk). No LF-only or CRLF-only case can move, per the rule above.
• No change to JSON output, error codes, exit codes or the CLI contract.

Test evidence

• New tests, all on mixed inputs:
  • unit tests: terminator_follows_the_file_and_the_majority_when_mixed, formatted_entry_takes_the_majority_line_ending, replaced_metadata_takes_the_majority_line_ending, mixed_go_mod_append_takes_the_majority_line_ending, restored_hash_continuation_takes_the_majority_line_ending;
  • tests/upstream_restore_golden.rs: composer_mixed_line_endings_restore_in_the_majority_style (byte-exact round trip) and gem_lock_pin_on_a_mixed_lock_takes_the_majority_terminator.
• Red → green: with terminator temporarily given the old "any CRLF" rule, all 6 per-site tests fail (4 lib + 2 integration). With the new rule, all pass.
• cargo test -p socket-patch-core --lib: 5667 passed, 4 failed. All 4 are the known root-only sandbox failures that also fail on main: relax_loop_must_not_traverse_symlinked_root, an_unremovable_hidden_lock_keeps_every_store_entry, wire_write_failure_maps_error_and_leaves_lock_untouched, wire_failure_rolls_back_already_written_files. After the follow-up, the go/golden/equivalence subset passes 248/248.
• cargo test -p socket-patch-core --test upstream_restore_golden: 50 passed.
• cargo clippy --workspace --all-features -- -D warnings: clean, before and after the follow-up.
• rustfmt: every touched file is rustfmt-clean.
• Not run locally: cargo test --workspace --all-features, because linking all ~235 CLI test binaries filled the sandbox disk. CI covers the CLI suites.

Review follow-up

• Bugbot (311462c): on an LF-majority go.mod whose trailing blank line is CRLF, the append missed the blank and wrote a second one. Fixed in 6b72d7f: the append detects a trailing blank whichever break spells it. Covered by an extra case in mixed_go_mod_append_takes_the_majority_line_ending. Bugbot is clean on 6b72d7f.
• CI on 6b72d7f: 415 of 416 checks passing or skipped at hand-off, with one Gradle e2e leg still running. The ci-ok failure on 311462c is the aggregator of runs cancelled by the 6b72d7f push.

Risk

Low. Seven one-line call-site swaps behind a 6-line pure function. The only behavior change is on mixed-ending files, as #815 specifies. The wrappers (npm/, pypi/, gem/) are unaffected.

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