feat(review): toggle unchanged context inline

Let the review controller own gap state and source-load lifecycles so keyboard, mouse, reload invalidation, and visible loading/error rows stay in one review flow.

Author: adit-chandra

CHANGELOG.md

@@ -6,6 +6,8 @@ All notable user-visible changes to Hunk are documented in this file.
 
 ### Added
 
+- Added inline expansion for collapsed unchanged file content. Click an unchanged-context row (`▾ N unchanged lines` when expandable, otherwise the static `··· N unchanged lines ···` form) or press `e` while a hunk is selected to reveal surrounding and trailing file lines without leaving the review. The affordance is shown only for input modes that have reachable source content (`hunk diff`, `show`, `stash show`, file-pair `diff` and `difftool`, untracked files); raw `hunk patch` input still renders as before. Failed and in-flight loads surface a one-line status ("Loading…", "Could not load N unchanged lines") on the gap row. Expanded context rows use the same syntax highlighting as the surrounding diff.
+
 ### Changed
 
 ### Fixed

src/ui/App.tsx

@@ -562,6 +562,7 @@ export function App({
     switchMenu,
     toggleAgentNotes,
     toggleFocusArea,
+    toggleGapForSelectedHunk: review.toggleSelectedHunkGap,
     toggleHelp,
     toggleHunkHeaders,
     toggleLineNumbers,
@@ -702,6 +703,7 @@ export function App({
         <DiffPane
           codeHorizontalOffset={codeHorizontalOffset}
           diffContentWidth={diffContentWidth}
+          expandedGapsByFileId={review.expandedGapsByFileId}
           files={filteredFiles}
           pagerMode={pagerMode}
           headerLabelWidth={diffHeaderLabelWidth}
@@ -715,6 +717,7 @@ export function App({
           showAgentNotes={showAgentNotes}
           showLineNumbers={showLineNumbers}
           showHunkHeaders={showHunkHeaders}
+          sourceStatusByFileId={review.sourceStatusByFileId}
           wrapLines={wrapLines}
           wrapToggleScrollTop={wrapToggleScrollTopRef.current}
           layoutToggleScrollTop={layoutToggleScrollTopRef.current}
@@ -728,6 +731,7 @@ export function App({
             scrollCodeHorizontally(delta * FAST_CODE_HORIZONTAL_SCROLL_COLUMNS);
           }}
           onSelectFile={jumpToFile}
+          onToggleGap={review.toggleGap}
           onViewportCenteredHunkChange={(fileId, hunkIndex) =>
             review.selectHunk(fileId, hunkIndex, { preserveViewport: true })
           }

src/ui/components/chrome/HelpDialog.tsx

@@ -44,6 +44,7 @@ export function HelpDialog({
         ["1 / 2 / 0", "split / stack / auto"],
         ["s / t", "sidebar / theme"],
         ["a", "toggle AI notes"],
+        ["e", "toggle unchanged context"],
         ["l / w / m", "lines / wrap / metadata"],
       ],
     },

src/ui/components/panes/DiffPane.tsx

@@ -10,6 +10,7 @@ import {
   type RefObject,
 } from "react";
 import type { DiffFile, LayoutMode } from "../../../core/types";
+import type { FileSourceStatus } from "../../diff/expandCollapsedRows";
 import type { VisibleAgentNote } from "../../lib/agentAnnotations";
 import { computeHunkRevealScrollTop } from "../../lib/hunkScroll";
 import {
@@ -125,10 +126,16 @@ function buildHighlightPrefetchFileIds({
   return next;
 }
 
+const EMPTY_EXPANDED_GAP_KEYS: ReadonlySet<string> = new Set();
+const EMPTY_EXPANDED_GAPS_BY_FILE_ID: Record<string, ReadonlySet<string>> = {};
+const EMPTY_SOURCE_STATUS_BY_FILE_ID: Record<string, FileSourceStatus> = {};
+const NOOP_TOGGLE_GAP = () => {};
+
 /** Render the main multi-file review stream. */
 export function DiffPane({
   codeHorizontalOffset = 0,
   diffContentWidth,
+  expandedGapsByFileId = EMPTY_EXPANDED_GAPS_BY_FILE_ID,
   files,
   headerLabelWidth,
   headerStatsWidth,
@@ -142,6 +149,7 @@ export function DiffPane({
   showAgentNotes,
   showLineNumbers,
   showHunkHeaders,
+  sourceStatusByFileId = EMPTY_SOURCE_STATUS_BY_FILE_ID,
   wrapLines,
   wrapToggleScrollTop,
   layoutToggleScrollTop = null,
@@ -153,10 +161,12 @@ export function DiffPane({
   onOpenAgentNotesAtHunk,
   onScrollCodeHorizontally = () => {},
   onSelectFile,
+  onToggleGap = NOOP_TOGGLE_GAP,
   onViewportCenteredHunkChange,
 }: {
   codeHorizontalOffset?: number;
   diffContentWidth: number;
+  expandedGapsByFileId?: Record<string, ReadonlySet<string>>;
   files: DiffFile[];
   headerLabelWidth: number;
   headerStatsWidth: number;
@@ -170,6 +180,7 @@ export function DiffPane({
   showAgentNotes: boolean;
   showLineNumbers: boolean;
   showHunkHeaders: boolean;
+  sourceStatusByFileId?: Record<string, FileSourceStatus>;
   wrapLines: boolean;
   wrapToggleScrollTop: number | null;
   layoutToggleScrollTop?: number | null;
@@ -181,6 +192,7 @@ export function DiffPane({
   onOpenAgentNotesAtHunk: (fileId: string, hunkIndex: number) => void;
   onScrollCodeHorizontally?: (delta: number) => void;
   onSelectFile: (fileId: string) => void;
+  onToggleGap?: (fileId: string, gapKey: string) => void;
   onViewportCenteredHunkChange?: (fileId: string, hunkIndex: number) => void;
 }) {
   const renderer = useRenderer();
@@ -398,9 +410,21 @@ export function DiffPane({
           diffContentWidth,
           showLineNumbers,
           wrapLines,
+          expandedGapsByFileId[file.id] ?? EMPTY_EXPANDED_GAP_KEYS,
+          sourceStatusByFileId[file.id],
         ),
       ),
-    [diffContentWidth, files, layout, showHunkHeaders, showLineNumbers, theme, wrapLines],
+    [
+      diffContentWidth,
+      expandedGapsByFileId,
+      files,
+      layout,
+      showHunkHeaders,
+      showLineNumbers,
+      sourceStatusByFileId,
+      theme,
+      wrapLines,
+    ],
   );
   const baseEstimatedBodyHeights = useMemo(
     () => baseSectionGeometry.map((metrics) => metrics.bodyHeight),
@@ -466,16 +490,20 @@ export function DiffPane({
           diffContentWidth,
           showLineNumbers,
           wrapLines,
+          expandedGapsByFileId[file.id] ?? EMPTY_EXPANDED_GAP_KEYS,
+          sourceStatusByFileId[file.id],
         );
       }),
     [
       allAgentNotesByFile,
       baseSectionGeometry,
       diffContentWidth,
+      expandedGapsByFileId,
       files,
       layout,
       showHunkHeaders,
       showLineNumbers,
+      sourceStatusByFileId,
       theme,
       wrapLines,
     ],
@@ -1163,6 +1191,7 @@ export function DiffPane({
                     <DiffSection
                       key={file.id}
                       codeHorizontalOffset={codeHorizontalOffset}
+                      expandedGapKeys={expandedGapsByFileId[file.id] ?? EMPTY_EXPANDED_GAP_KEYS}
                       file={file}
                       headerLabelWidth={headerLabelWidth}
                       headerStatsWidth={headerStatsWidth}
@@ -1175,6 +1204,7 @@ export function DiffPane({
                       showSeparator={index > 0}
                       showLineNumbers={showLineNumbers}
                       showHunkHeaders={showHunkHeaders}
+                      sourceStatus={sourceStatusByFileId[file.id]}
                       wrapLines={wrapLines}
                       theme={theme}
                       viewWidth={diffContentWidth}
@@ -1186,6 +1216,7 @@ export function DiffPane({
                         onOpenAgentNotesAtHunk(file.id, hunkIndex)
                       }
                       onSelect={() => onSelectFile(file.id)}
+                      onToggleGap={(gapKey) => onToggleGap(file.id, gapKey)}
                     />
                   );
                 })}

src/ui/components/panes/DiffSection.tsx

@@ -1,6 +1,7 @@
 import { memo } from "react";
 import type { DiffFile, LayoutMode } from "../../../core/types";
 import { PierreDiffView } from "../../diff/PierreDiffView";
+import type { FileSourceStatus } from "../../diff/expandCollapsedRows";
 import type { VisibleBodyBounds } from "../../diff/rowWindowing";
 import type { DiffSectionGeometry } from "../../lib/diffSectionGeometry";
 import { getAnnotatedHunkIndices, type VisibleAgentNote } from "../../lib/agentAnnotations";
@@ -11,6 +12,7 @@ import { DiffFileHeaderRow } from "./DiffFileHeaderRow";
 
 interface DiffSectionProps {
   codeHorizontalOffset: number;
+  expandedGapKeys: ReadonlySet<string>;
   file: DiffFile;
   headerLabelWidth: number;
   headerStatsWidth: number;
@@ -21,6 +23,7 @@ interface DiffSectionProps {
   separatorWidth: number;
   showLineNumbers: boolean;
   showHunkHeaders: boolean;
+  sourceStatus: FileSourceStatus | undefined;
   wrapLines: boolean;
   showHeader: boolean;
   showSeparator: boolean;
@@ -30,11 +33,13 @@ interface DiffSectionProps {
   viewWidth: number;
   onOpenAgentNotesAtHunk: (hunkIndex: number) => void;
   onSelect: () => void;
+  onToggleGap: (gapKey: string) => void;
 }
 
 /** Render one file section in the main review stream. */
 function DiffSectionComponent({
   codeHorizontalOffset,
+  expandedGapKeys,
   file,
   headerLabelWidth,
   headerStatsWidth,
@@ -45,6 +50,7 @@ function DiffSectionComponent({
   separatorWidth,
   showLineNumbers,
   showHunkHeaders,
+  sourceStatus,
   wrapLines,
   showHeader,
   showSeparator,
@@ -54,6 +60,7 @@ function DiffSectionComponent({
   viewWidth,
   onOpenAgentNotesAtHunk,
   onSelect,
+  onToggleGap,
 }: DiffSectionProps) {
   const annotatedHunkIndices = getAnnotatedHunkIndices(file);
 
@@ -92,17 +99,20 @@ function DiffSectionComponent({
       ) : null}
 
       <PierreDiffView
+        expandedGapKeys={expandedGapKeys}
         file={file}
         layout={layout}
         showLineNumbers={showLineNumbers}
         showHunkHeaders={showHunkHeaders}
+        sourceStatus={sourceStatus}
         wrapLines={wrapLines}
         codeHorizontalOffset={codeHorizontalOffset}
         theme={theme}
         width={viewWidth}
         annotatedHunkIndices={annotatedHunkIndices}
         visibleAgentNotes={visibleAgentNotes}
         onOpenAgentNotesAtHunk={onOpenAgentNotesAtHunk}
+        onToggleGap={onToggleGap}
         selectedHunkIndex={selectedHunkIndex}
         sectionGeometry={sectionGeometry}
         shouldLoadHighlight={shouldLoadHighlight}
@@ -119,6 +129,7 @@ export const DiffSection = memo(DiffSectionComponent, (previous, next) => {
   // This comparator relies on stable upstream object identity for files and visible-note arrays.
   return (
     previous.codeHorizontalOffset === next.codeHorizontalOffset &&
+    previous.expandedGapKeys === next.expandedGapKeys &&
     previous.file === next.file &&
     previous.headerLabelWidth === next.headerLabelWidth &&
     previous.headerStatsWidth === next.headerStatsWidth &&
@@ -129,6 +140,7 @@ export const DiffSection = memo(DiffSectionComponent, (previous, next) => {
     previous.separatorWidth === next.separatorWidth &&
     previous.showLineNumbers === next.showLineNumbers &&
     previous.showHunkHeaders === next.showHunkHeaders &&
+    previous.sourceStatus === next.sourceStatus &&
     previous.wrapLines === next.wrapLines &&
     previous.showHeader === next.showHeader &&
     previous.showSeparator === next.showSeparator &&