fix(mobile): reject partially numeric line params in the comment composer

apps/mobile/src/components/pr-review/discussion/comment-row.tsx

@@ -162,11 +162,10 @@ export function CommentRow({
           {relative}
         </Text>
         {/* `gap-3` (10.5pt at NativeWind's 14pt rem) exceeds the pill's 2pt
-            right hitSlop plus the overflow's 3pt left slop, leaving
-            commentTrailingControlsClearanceDp() dp between the two tap areas,
-            so a tap anywhere on the pill — including its right edge — opens the
-            session and never the moderation sheet (vr1). See
-            comment-trailing-controls.ts. */}
+            right hitSlop plus the overflow's 3pt left slop, leaving 5.5pt
+            between the two tap areas, so a tap anywhere on the pill — including
+            its right edge — opens the session and never the moderation sheet
+            (vr1). See comment-trailing-controls.ts and its test. */}
         <View className="ml-auto flex-row items-center gap-3">
           <PrCommentFixWithKilo
             owner={owner}

apps/mobile/src/lib/pr-review/comment-composer-params.test.ts

@@ -61,6 +61,16 @@ describe('parseComposerParams', () => {
     expect(parseComposerParams(valid({ line: 'abc' }))).toBeNull();
   });
 
+  it('rejects a partially numeric line or startLine instead of truncating it', () => {
+    // `Number.parseInt` stops at the first non-digit, so these used to resolve
+    // to lines 1, 12 and 9 and post an inline comment to a line the deep link
+    // never named.
+    expect(parseComposerParams(valid({ line: '1.5' }))).toBeNull();
+    expect(parseComposerParams(valid({ line: '12abc' }))).toBeNull();
+    expect(parseComposerParams(valid({ line: '9x', startLine: '2' }))).toBeNull();
+    expect(parseComposerParams(valid({ line: '9', startLine: '9x' }))).toBeNull();
+  });
+
   it('rejects startLine greater than line', () => {
     expect(parseComposerParams(valid({ line: '5', startLine: '6' }))).toBeNull();
   });

apps/mobile/src/lib/pr-review/comment-composer-params.ts

@@ -1,4 +1,4 @@
-import { parseParam } from '@/lib/route-params';
+import { parseParam, parsePositiveIntParam } from '@/lib/route-params';
 
 type RawComposerParams = {
   owner?: string | string[] | undefined;
@@ -24,32 +24,23 @@ type ParsedComposerParams = {
   pendingId?: string;
 };
 
-function parsePositiveInt(value: string | string[] | undefined): number | null {
-  const text = parseParam(value);
-  if (!text) {
-    return null;
-  }
-  const parsed = Number.parseInt(text, 10);
-  if (!Number.isInteger(parsed) || parsed <= 0) {
-    return null;
-  }
-  return parsed;
-}
-
 /**
  * Runtime-validates the comment-composer route params before the screen
  * queries or renders the composer. Returns `null` for any invalid
  * combination (missing owner/repo/number, empty path, invalid side,
- * non-positive line, or startLine greater than line).
+ * non-positive or partially numeric line or startLine, or startLine greater
+ * than line). The numeric params go through `parsePositiveIntParam` so a
+ * segment like `1.5` or `12abc` is rejected rather than silently truncated to
+ * a line the user never selected.
  */
 export function parseComposerParams(raw: RawComposerParams): ParsedComposerParams | null {
   const owner = parseParam(raw.owner);
   const repo = parseParam(raw.repo);
-  const number = parsePositiveInt(raw.number);
+  const number = parsePositiveIntParam(raw.number);
   const path = parseParam(raw.path);
   const side = parseParam(raw.side, ['LEFT', 'RIGHT'] as const);
-  const line = parsePositiveInt(raw.line);
-  const startLine = parsePositiveInt(raw.startLine);
+  const line = parsePositiveIntParam(raw.line);
+  const startLine = parsePositiveIntParam(raw.startLine);
   const hasStartLine = parseParam(raw.startLine) !== null;
   // Optional edit-mode id: absent → undefined; present non-empty string
   // passes through. Empty/array values are treated as absent (not a hard

apps/mobile/src/lib/pr-review/comment-trailing-controls.test.ts

@@ -1,24 +1,82 @@
+// The clearance arithmetic only keeps the pill's and the overflow's tap areas
+// apart if the row lays them out the way this reads it. `comment-row.tsx`
+// spells the trailing group's gap as a literal `gap-3` class (NativeWind reads
+// the class at build time, so the component cannot import a number) and hands
+// each control its shared hit-slop object. This guards those actual values by
+// reading the row and the pill source and pairing them with the two slop
+// objects, instead of re-deriving a helper the row never calls.
+
+// eslint-disable-next-line import/no-nodejs-modules -- vitest-only guard, runs in node, never bundled into the app
+import { readFileSync } from 'node:fs';
+// eslint-disable-next-line import/no-nodejs-modules -- vitest-only guard, runs in node, never bundled into the app
+import { fileURLToPath } from 'node:url';
+
 import { describe, expect, it, vi } from 'vitest';
 
-import { MIN_TAP_TARGET_DP } from '@/lib/a11y/tap-target';
+import { MIN_TAP_TARGET_DP, TOUCH_TARGET_DP } from '@/lib/a11y/tap-target';
 import {
   COMMENT_ACTIONS_FRAME_DP,
   COMMENT_ACTIONS_HIT_SLOP,
   COMMENT_ACTIONS_VISUAL_DP,
   COMMENT_TRAILING_CONTROLS_GAP_DP,
-  commentTrailingControlsClearanceDp,
   FIX_WITH_KILO_HIT_SLOP,
   FIX_WITH_KILO_VISUAL_DP,
 } from '@/lib/pr-review/comment-trailing-controls';
 
 vi.mock('react-native', () => ({ I18nManager: { isRTL: false } }));
 
+// Removes `//` line comments and `/* */` block comments, preserving line
+// breaks, so a comment that merely names a class or a hit-slop object cannot
+// satisfy the guards below.
+function stripComments(source: string): string {
+  return source
+    .replaceAll(/\/\*[\s\S]*?\*\//g, match => match.replaceAll(/[^\n]/g, ''))
+    .replaceAll(/\/\/[^\n]*/g, '');
+}
+
+const discussionDir = fileURLToPath(
+  new URL('../../components/pr-review/discussion', import.meta.url)
+);
+const rowSource = stripComments(readFileSync(`${discussionDir}/comment-row.tsx`, 'utf8'));
+const pillSource = stripComments(
+  readFileSync(`${discussionDir}/pr-comment-fix-with-kilo.tsx`, 'utf8')
+);
+
 describe('comment trailing controls tap areas', () => {
+  it('finds the row and the pill it guards', () => {
+    // A renamed control or a moved file would make the assertions below pass
+    // vacuously.
+    expect(rowSource).toContain('PrCommentFixWithKilo');
+    expect(pillSource).toContain('FIX_WITH_KILO_HIT_SLOP');
+  });
+
+  it('lays the two controls out with the gap the clearance assumes', () => {
+    // The regression this guards: a change to the row's actual gap class would
+    // leave COMMENT_TRAILING_CONTROLS_GAP_DP stating a spacing the row no
+    // longer renders.
+    const groupClassName = /className="([^"]*ml-auto[^"]*)"/.exec(rowSource)?.[1] ?? '';
+    const classes = groupClassName.split(/\s+/);
+    expect(classes).toContain('flex-row');
+    expect(classes).toContain('items-center');
+    expect(classes).toContain('gap-3');
+  });
+
+  it('wires the shared hit slop objects into the row and the pill', () => {
+    expect(rowSource).toContain('hitSlop={COMMENT_ACTIONS_HIT_SLOP}');
+    expect(pillSource).toContain('hitSlop={FIX_WITH_KILO_HIT_SLOP}');
+  });
+
   it('keeps the pill and the overflow hit areas apart', () => {
-    // The regression this guards: the overflow's 8pt left hitleed used to
-    // reach into the pill's right edge, so a tap on the pill opened the
-    // moderation sheet instead of the session.
-    expect(commentTrailingControlsClearanceDp()).toBeGreaterThan(0);
+    // The overflow's 3pt left slop used to reach into the pill's right edge, so
+    // a tap on the pill opened the moderation sheet instead of the session. The
+    // gap and both slops are measured from the frames, so the overflow frame's
+    // inset around its visible circle does not enter here.
+    const clearance =
+      COMMENT_TRAILING_CONTROLS_GAP_DP -
+      FIX_WITH_KILO_HIT_SLOP.right -
+      COMMENT_ACTIONS_HIT_SLOP.left;
+    expect(clearance).toBeGreaterThan(0);
+    expect(clearance).toBe(5.5);
   });
 
   it('keeps the overflow frame at or above the 28dp the size audit measures', () => {
@@ -35,22 +93,9 @@ describe('comment trailing controls tap areas', () => {
     // the pill needs its own vertical slop to get there.
     expect(
       COMMENT_ACTIONS_FRAME_DP + COMMENT_ACTIONS_HIT_SLOP.top + COMMENT_ACTIONS_HIT_SLOP.bottom
-    ).toBeGreaterThanOrEqual(44);
+    ).toBeGreaterThanOrEqual(TOUCH_TARGET_DP);
     expect(
       FIX_WITH_KILO_HIT_SLOP.top + FIX_WITH_KILO_HIT_SLOP.bottom + FIX_WITH_KILO_VISUAL_DP
-    ).toBeGreaterThanOrEqual(44);
-  });
-
-  it('derives the clearance from the gap and the two facing slops', () => {
-    // The gap and both tap areas are measured from the frames, so the overflow
-    // frame's inset around its visible circle does not enter here. `gap-3` is
-    // 0.75rem, which is 10.5dp at NativeWind's 14pt rem, so the pill's 2pt
-    // right slop and the overflow's 3pt left slop leave 5.5dp.
-    expect(commentTrailingControlsClearanceDp()).toBe(
-      COMMENT_TRAILING_CONTROLS_GAP_DP -
-        FIX_WITH_KILO_HIT_SLOP.right -
-        COMMENT_ACTIONS_HIT_SLOP.left
-    );
-    expect(commentTrailingControlsClearanceDp()).toBe(5.5);
+    ).toBeGreaterThanOrEqual(TOUCH_TARGET_DP);
   });
 });

apps/mobile/src/lib/pr-review/comment-trailing-controls.ts

@@ -9,8 +9,10 @@
 // that same rem, so its own vertical slop, not its frame, is what reaches the
 // minimum. The pill's expanded right edge and the overflow's expanded left edge
 // must never meet: a tap on the pill — including its right edge — must open the
-// session, never the moderation sheet. Keeping the arithmetic in one place lets
-// the row's gap and the two tap areas be checked together (vr1, 2026-09-16).
+// session, never the moderation sheet. The row keeps the literal classes and
+// the slop objects below; `comment-trailing-controls.test.ts` reads the row's
+// source and these two slop objects together so the gap and the two tap areas
+// are checked against what the row actually renders (vr1, 2026-09-16).
 
 import { COMPACT_H11_FRAME_DP, COMPACT_H11_HIT_SLOP_DP } from '@/lib/a11y/tap-target';
 
@@ -48,17 +50,3 @@ export const COMMENT_ACTIONS_HIT_SLOP = {
 
 /** The trailing group's `gap-3` class, in dp: 0.75rem at NativeWind's 14pt rem. */
 export const COMMENT_TRAILING_CONTROLS_GAP_DP = 10.5;
-
-/**
- * Horizontal dp between the pill's expanded right edge and the overflow's
- * expanded left edge: the gap between the two frames less each control's slop
- * on the facing side. The overflow's frame is wider than its visible circle,
- * but the gap and both slops are measured from the frame, so the frame's inset
- * does not enter here. A positive value means the two tap areas never overlap,
- * so each control keeps every tap that lands on it.
- */
-export function commentTrailingControlsClearanceDp(): number {
-  return (
-    COMMENT_TRAILING_CONTROLS_GAP_DP - FIX_WITH_KILO_HIT_SLOP.right - COMMENT_ACTIONS_HIT_SLOP.left
-  );
-}