Merge pull request 'fix(search): the mobile hero search was indented by a card's padding' (#130) from fix/mobile-hero-search into main

Reviewed-on: #130

nextjs-app/__tests__/components/filterBarScoping.test.ts

@@ -0,0 +1,108 @@
+import fs from 'fs';
+import path from 'path';
+
+/**
+ * The hero search and the results filter bar are the same component in two
+ * costumes. `.filterBar` is the card — background, border, shadow, padding —
+ * and `.heroMode` strips all of it so the search sits directly on the hero
+ * panel.
+ *
+ * Both selectors have specificity (0,1,0), so **source order decides**, and
+ * `.heroMode` only wins because it is declared immediately after. Any later
+ * bare `.filterBar` rule — which in practice means one inside a media query —
+ * silently wins instead, and the hero grows a card's padding back.
+ *
+ * That is exactly what happened: `@media (max-width: 768px) { .filterBar {
+ * padding: 0.875rem } }` re-added 14px in hero mode, indenting the search box,
+ * the hint and the location link 14px past the headline above them and costing
+ * the search field 28px of width on a 390px screen. The two rules directly
+ * below it in the same block were correctly written as
+ * `.filterBar:not(.heroMode)`; this one was missed, and nothing caught it
+ * because the result is a plausible-looking layout rather than a broken one.
+ */
+
+const CSS = path.join(__dirname, '..', '..', 'components', 'FilterBar.module.css');
+
+/** Properties `.heroMode` resets. A later bare `.filterBar` rule setting any
+ *  of these puts the card back on the hero. */
+const RESET_BY_HERO_MODE = [
+  'background', 'border', 'border-radius', 'box-shadow', 'padding',
+];
+
+/**
+ * Comments are stripped before anything is parsed.
+ *
+ * A `{` or `}` inside a comment would otherwise desynchronise the brace walk
+ * below and the rule regex alike, and the selector text captured for each rule
+ * would carry the preceding comment along with it.
+ */
+function withoutComments(css: string): string {
+  return css.replace(/\/\*[\s\S]*?\*\//g, '');
+}
+
+/**
+ * The individual selectors in a rule's prelude.
+ *
+ * Split on commas, because a selector list is a list: `.filterBar, .other { }`
+ * applies to `.filterBar` just as surely as `.filterBar { }` does, and an
+ * earlier version of this guard compared the whole prelude against the literal
+ * string '.filterBar' — so writing the regression as a comma list, or across
+ * two lines, would have walked straight past it.
+ */
+function selectorsOf(prelude: string): string[] {
+  return prelude.split(',').map((sel) => sel.trim().replace(/\s+/g, ' '))
+    .filter(Boolean);
+}
+
+function mediaQueryBodies(css: string): string[] {
+  const bodies: string[] = [];
+  const re = /@media[^{]*\{/g;
+  let m: RegExpExecArray | null;
+  while ((m = re.exec(css)) !== null) {
+    // Walk braces from the opening one to find this at-rule's whole body.
+    let depth = 1;
+    let i = m.index + m[0].length;
+    const start = i;
+    while (i < css.length && depth > 0) {
+      if (css[i] === '{') depth++;
+      else if (css[i] === '}') depth--;
+      i++;
+    }
+    bodies.push(css.slice(start, i - 1));
+  }
+  return bodies;
+}
+
+describe('FilterBar hero-mode scoping', () => {
+  const css = withoutComments(fs.readFileSync(CSS, 'utf8'));
+
+  it('confirms heroMode still resets the card, which is what makes this matter', () => {
+    const hero = css.match(/\.heroMode\s*\{([^}]*)\}/);
+    expect(hero).not.toBeNull();
+    expect(hero![1]).toMatch(/padding:\s*0/);
+  });
+
+  it('never re-applies card styling to the hero from inside a media query', () => {
+    const offenders: string[] = [];
+
+    for (const body of mediaQueryBodies(css)) {
+      for (const rule of body.matchAll(/([^{}]+)\{([^{}]*)\}/g)) {
+        // Only a *bare* .filterBar is dangerous, and it is dangerous wherever
+        // it appears in a selector list. Scoped variants
+        // (`.filterBar:not(.heroMode)`) and descendants are fine.
+        const selectors = selectorsOf(rule[1]);
+        if (!selectors.includes('.filterBar')) continue;
+
+        for (const prop of RESET_BY_HERO_MODE) {
+          if (new RegExp(`(^|[;\\s])${prop}\\s*:`).test(rule[2])) {
+            offenders.push(`${rule[1].trim()} sets ${prop}`);
+          }
+        }
+      }
+    }
+
+    // Fix by scoping the rule as `.filterBar:not(.heroMode)`, the way the
+    // neighbouring rules in the same block already are.
+    expect(offenders).toEqual([]);
+  });
+});