3 people 5f7b001cbe Fix: measure gradient body grounds instead of assuming white (low-contrast false positives) (#557) ...

* Fix: measure gradient body grounds instead of assuming white (browser mode)

A page whose ground is set via background: linear-gradient(...) on body
leaves backgroundColor transparent, and resolveBackground assumed white
for any body/html-level gradient. In a real browser that assumption is
wrong: the shorthand is always decomposed there, so reaching that branch
means the ground truly is the gradient. On a dark oklch gradient ground
(impeccable.style's lacquer) this turned every light-on-dark text into a
~1.3:1 "on #ffffff" low-contrast finding, ~120 false positives on one
site. Browser mode now returns null so the caller measures against the
actual gradient stops; the white assumption stays for jsdom, where the
undecomposed-shorthand rationale still holds.

Gradient stops also now parse modern color syntax: computed
backgroundImage keeps oklch()/oklab()/hsl()/hwb() stops as authored, and
parseGradientColors only read rgb()/hex, so a token-driven gradient
ground was invisible even once the walk deferred to it. New
parseGradientColorsModern routes those stops through parseAnyColor.

Covered by a Puppeteer fixture (dark oklch body gradient): light text on
the ground must not flag, muted dark-gray ink must, proving the stops
are measured rather than the checks silently skipping.

Prepared with AI assistance (Claude Code), on maintainer instruction.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* Composite translucent layers over gradient stops; parse modern glow stops

Review fixes from PR #557's automated reviews, applied with AI
assistance (Claude Code):

- Cursor Bugbot found the new browser-mode early return discarded the
  translucent ancestors resolveBackground had collected: text on a
  frosted wash over a body gradient was measured against raw stops.
  resolveGradientStops now collects translucent layers during its own
  walk (through readCascadeBackgroundColor, extracted so both walks
  read surfaces identically) and composites every stop under them.
- Copilot flagged the other legacy parseGradientColors call sites. The
  glow-context fallback now uses parseGradientColorsModern, since body
  gradients reach it more often after this change. The AI-palette rule
  and the injected analytic sampler stay on the legacy parser
  deliberately: the former is a rule-behavior expansion deserving its
  own fixtures, the latter degrades to pixel sampling or a skip.
- Greptile asked for standard fixture structure: the fixture now has
  labeled flag/pass cases (3 flag, 5 pass) including the frosted-wash
  pair that locks the overlay compositing in both directions and a
  legacy hex-stop gradient guarding the original parser path.

The test scopes itself to the DOM path via visualContrast: false, the
suite's established pattern; the screenshot sampler is a separate
subsystem with its own coverage.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* Pin gradient-ground flag cases to their snippet signatures

Bugbot follow-up: a count-only assertion let an offsetting miss and
false positive cancel, especially the frosted pair. Each flag case now
asserts its full text-on-background signature, so the frosted case must
measure against the composited wash and the count guard excludes any
pass case flagging in its place. Applied with AI assistance (Claude
Code).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* Comments: the static path is the custom engine now, not jsdom

jsdom left the dependency tree when the static-html engine (StaticElement
+ css-cascade.mjs) replaced it, and that engine does decompose the
background shorthand, so the comments this PR added were dated in both
name and rationale. Only comments touched by this PR are renamed; the
~40 legacy jsdom mentions elsewhere in checks.mjs are a separate sweep.
Applied with AI assistance (Claude Code).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* Static engine: measure body gradients too, dropping the white assumption

Follow-up to the browser-mode fix: the white assumption for body/html
gradients was a jsdom guard, and jsdom is gone. The static cascade
decomposes the background shorthand (expandStaticDeclaration) and
preserves var() colors for later resolution, so a missing solid under a
body gradient is now as real in static mode as in a browser — and the
static engine had the identical false-positive class (light text on a
dark gradient ground flagged "on #ffffff") while missing the muted-ink
true positives on the same page.

The old catastrophic case cannot recur: opaque stops fully cover any
hidden solid (they are the ground), alpha stops composite over the
resolved base or the white canvas default, and unresolvable stops drop
rather than guess.

Static twin of the browser test added over the same fixture; the full
suite, the url()-ancestor guard, and a source scan of impeccable.style
(0 low-contrast findings) all stay clean. Applied with AI assistance
(Claude Code).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

2026-08-10 12:35:55 -07:00

..

checks.mjs

Fix: measure gradient body grounds instead of assuming white (low-contrast false positives) (#557)

2026-08-10 12:35:55 -07:00