CLI compat (phase E): byte-for-byte junit + Rust unit tests + JS integration tests

[bokuweb]

Summary

Follow-up to merged #586.
Fixes a junit-format compat bug that snuck into phase D and adds a real
test suite (Rust unit + JS integration) so we can keep catching drift
like this before release.

Fix: junit XML is now byte-identical to classic reg-cli

Phase D shipped a simplified JUnit schema (<testsuites> bare,
classname="reg-cli", message="changed|new|deleted") that diverged
from what classic reg-cli produces via xmlbuilder2 — which is exactly
what downstream CI parsers and test/cli.test.mjs snapshot-check.

Corrected to the classic schema:

• <?xml version="1.0"?> (no encoding attr)
• <testsuites name="reg-cli tests" tests=N failures=M> (attrs on both
  testsuites and testsuite)
• <testcase name="..."> (no classname)
• <failure message="failed"/> for failed items; "newItem" /
  "deletedItem" only when -E/--extendedErrors is set, otherwise
  new/deleted are counted as passed testcases (classic behaviour)

To make that last branch possible, extended_errors is now plumbed through
Options → reg_cli clap (-E/--extendedErrors) → compare() library
forwarding → build_junit_xml. The JS CLI wrapper still owns exit-code
semantics for -E, but the flag is now dual-forwarded so Rust can also
see it.

New tests

Rust — cargo test -p reg_core --lib, 6 new cases in
crates/reg_core/src/report.rs:

• single failure
• passed + failed mix
• new/deleted with and without extended_errors (both branches)
• XML attribute escaping (&, <, >, ")
• empty report → self-closing <testsuite/>

JS — node --test, 19 tests across two files (no new deps):

• js/test/cli.test.mjs (13) — spawns the built CLI, asserts exit codes
  (-I, -E), reg.json schema keys, JUnit XML byte-for-byte vs
  classic, -R, -X client, -F (verifies source reg.json is immutable
  and no diff dir is recreated), stdout formatting, -D custom trailer.
• js/test/library.test.mjs (6) — compare() EventEmitter lifecycle
  (start→compare×N→complete), junit/reg.json via Rust,
  update: true file copy + update event,
  additionalDetection: 'client', and the legacy
  enableClientAdditionalDetection: true alias.

CI

New wasm-test job runs cargo test -p reg_core --lib, then builds the
js dist (using the committed js/reg.wasm — no wasi-sdk needed) and runs
pnpm --filter ./js test. The classic test job is unchanged.

Notable compat finding

Documented in the library test header: wasm32-wasip1-threads libstd's
prestat enumeration only honours the first path segment of a preopen
name. computeWasiSandbox collapses every touched dir into a single
common ancestor, so when all paths live under one scratch (update mode),
that scratch must itself be one segment deep at the repo root. The
lib-test scaffolding uses .libtest-<pid>-<n>-<rand> at the repo root
for exactly this reason. This is a pre-existing limitation worth a
follow-up (multi-segment preopen support) — not something introduced by
this PR.

Test plan

• cargo test -p reg_core --lib — 10/10 pass.
• bash scripts/build-wasm.sh + pnpm --filter ./js build — clean.
• pnpm --filter ./js test — 19/19 pass (13 CLI + 6 library).
• JUnit XML byte-equal to classic reg-cli's xmlbuilder2 output.
• -F regenerates HTML/JUnit without creating diff/; reg.json
  unchanged afterwards.
• -X client flips ximgdiffConfig.enabled in HTML.
• CI green on otel base.

🤖 Generated with Claude Code