[00129] Replace the Four Hardcoded Barrel Guard Tests With an Eager Graph Reachability Assertion

[rorychatt]

00129 - Replace the Four Hardcoded Barrel Guard Tests With an Eager Graph Reachability Assertion

What landed

One new test replaces four hardcoded string tests, and the README stops pointing at a file that no
longer exists.

src/frontend/src/widgets/__tests__/lazyWidgetBarrels.test.ts (103 lines, 2 cases, 11 ms) indexes the
static import edges of every first-party non-test file, walks them breadth-first from src/index.tsx,
and fails if any module named in a widgetMap.ts import("@/...") is reachable that way. A reachable
lazy module is one whose import() no longer splits anything. The failure message is the whole import
chain, e.g.

@/widgets/lists/ListWidget is eagerly reachable: index.tsx -> components/App.tsx ->
widgets/widgetRenderer.tsx -> widgets/lists/index.ts -> widgets/lists/ListWidget.tsx

Deleted, each an 11-line read-the-barrel-and-regex test covering one barrel and one widget name:
src/widgets/lists/index.test.ts, src/widgets/chunkSplitting.test.ts,
src/widgets/inputs/ContentInputWidget/index.test.ts,
src/widgets/inputs/DateTimeInputWidget/index.test.ts.

src/frontend/README.md gains a pointer to the new test in place of the dangling reference, plus four
lines naming the build gate's one real blind spot.

Net: 6 files changed, 113 insertions(+), 51 deletions(-).

Commits

Hash	What
8e498df	Add the test, delete the four string tests; mutation matrix in the message
08407c3	Both README edits
9e425d5	Resolve the README conflict with main's rewrite of the same section
a385b1f	Recalibrate the test for main's 55-widget lazification
b4a50a7	Merge origin/main 9b7c764 (clean, no conflicts)

Branch tendril/00129-..., 5 commits ahead of origin/main, merged up to 9b7c764. main moved four
times during execution: df4e685 -> 7bd1fdc -> 6e7664c -> e6c4398 -> 9b7c764.

Why this shape

The four deleted tests were the same idea copied four times, and two of the four could not fail for a
structural reason: inputs/ContentInputWidget/index.ts and inputs/DateTimeInputWidget/index.ts
are the import() target, so a re-export inside them can never create an eager edge. The new test
asserts reachability instead of names, so barrels are just edges - which removes the name matching, the
inert-barrel filter, and the carve-out those two files needed.

It is deliberately redundant with the build-time assert-lazy-chunks gate. It reads source only, so it
needs no build and runs in 11 ms rather than 2 s plus a toolchain; it names the import chain rather than
a chunk filename; and it survives a change to the bundler's graph API. The README now says explicitly
that it is a complement to the build gate, not a replacement.

Mutation matrix (re-measured on the merged tree)

Eleven rows, each reverted after, exit codes read unpiped, git diff --stat confirmed empty between
rows. Full table with evidence in Verification/CheckResult.md. The three rows the plan requires (2, 6,
8) were all reproduced. Headlines:

• The test fires on all four ways an eager edge gets created: bare side-effect import "x", a used
  named import, an unused named import, and a barrel re-export reached through either
  widgetMap.ts (row 6b) or widgetRenderer.tsx (row 11).
• It stays silent where the build stays silent: import type (row 5) and an inert barrel (row 7).
• The anti-vacuity assertion works: stubbing src/index.tsx to export {}; fails with "the eager walk
  from index.tsx never reached widgets/widgetMap.ts" instead of passing trivially.
• Row 4 is the one place the test is stricter than the build, as the plan predicted. New finding: that
  only holds for a plainly named binding - with an underscore-prefixed alias, pnpm lint and tsc -b
  both stay green by design and this test is the only gate that catches it.

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Created using Ivy Tendril.