Add collapsedContextThreshold #298

fat · 2026-01-27T03:48:22Z

🏄

vercel · 2026-01-27T03:48:26Z

The latest updates on your projects. Learn more about Vercel for GitHub.

Project	Deployment	Review	Updated (UTC)
pierrejs-diff-demo	Ready	Preview	Jan 29, 2026 0:45am
pierrejs-docs	Ready	Preview	Jan 29, 2026 0:45am
pierrejs-solid-diff-demo	Ready	Preview	Jan 29, 2026 0:45am

l

Copilot

Pull request overview

Adds a new collapsedContextThreshold option to automatically expand small collapsed context regions (defaulting to 2), updating diff iteration/rendering, documentation examples, and virtualization tests/snapshots accordingly.

Changes:

Introduce collapsedContextThreshold (default 2) and thread it through diff rendering/iteration paths.
Auto-expand collapsed context regions at/below the threshold to reduce “1 unmodified line” separators.
Update docs examples and adjust virtualization tests/snapshots to the new rendered output.

Reviewed changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
packages/diffs/src/constants.ts	Adds `DEFAULT_COLLAPSED_CONTEXT_THRESHOLD`.
packages/diffs/src/types.ts	Exposes `collapsedContextThreshold` in public option types.
packages/diffs/src/utils/iterateOverDiff.ts	Implements threshold-based auto-expansion for collapsed context regions.
packages/diffs/src/utils/renderDiffWithHighlighter.ts	Plumbs `collapsedContextThreshold` into iteration used for highlighted/plain diff rendering.
packages/diffs/src/renderers/DiffHunksRenderer.ts	Defaults and forwards `collapsedContextThreshold` through renderer + worker plain-AST path.
packages/diffs/src/components/SimpleVirtualizedFileDiff.ts	Applies threshold in virtualization sizing/expansion logic and passes it into iteration.
packages/diffs/src/worker/WorkerPoolManager.ts	Passes `collapsedContextThreshold` to plain diff rendering in worker manager.
packages/diffs/src/style.css	Removes styling hooks for `context-expanded` lines.
packages/diffs/test/DiffHunksRendererVirtualization.test.ts	Updates expected counts/indices to match new auto-expanded rendering.
packages/diffs/test/snapshots/DiffHunksRendererVirtualization.test.ts.snap	Updates snapshots for new DOM/line-type output.
apps/docs/app/docs/VanillaAPI/constants.ts	Documents the new option in the Vanilla API example.
apps/docs/app/docs/ReactAPI/constants.ts	Documents the new option in the React API example.

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

Copilot · 2026-01-27T06:30:55Z

packages/diffs/src/utils/renderDiffWithHighlighter.ts

    startingLine,
    totalLines,
    expandedHunks,
+    collapsedContextThreshold,


collapsedContextThreshold is destructured from ForcePlainTextOptions without any default. Callers that omit the 4th arg to renderDiffWithHighlighter (e.g. the worker render path) will end up passing undefined into iterateOverDiff, effectively disabling the “default: 2” behavior and potentially causing the plain pre-render and highlighted render to disagree.

Consider defaulting collapsedContextThreshold here (e.g. via destructuring default or by including it in DEFAULT_PLAIN_TEXT_OPTIONS) so the default behavior is consistent for all call sites.

Suggested change

collapsedContextThreshold,

collapsedContextThreshold = 2,

Probably akin to one of my other comments, but obvi use the constant

packages/diffs/src/style.css

amadeus · 2026-01-27T06:23:08Z

packages/diffs/src/components/SimpleVirtualizedFileDiff.ts

        : this.hunksRenderer.getExpandedHunksMap(),
+      collapsedContextThreshold:
+        this.options.collapsedContextThreshold ??
+        DEFAULT_COLLAPSED_CONTEXT_THRESHOLD,


kind of a nit, but can we pull this value out above from this.options on line 190? Since we do that with a couple of other props out of options already?

amadeus · 2026-01-27T06:26:12Z

packages/diffs/src/components/SimpleVirtualizedFileDiff.ts

        renderAll: false,
      };
    }
+    const threshold = Math.max(


Why do we need Math.max for this? The value check on threshold and rangeSize should be sufficient?

amadeus · 2026-01-27T06:28:16Z

packages/diffs/src/components/SimpleVirtualizedFileDiff.ts

+        DEFAULT_COLLAPSED_CONTEXT_THRESHOLD,
+      0
+    );
+    if (threshold > 0 && rangeSize <= threshold) {


Also since this line is essentially the same return as expandUnchanged, can we just combine this if statement with the one below?

if (expandUnchanged || rangeSize <= collapsedContextThreshold)

Might also be a nice opportunity to destruct both expandUnchanged and collapsedContextThreshold out at the same time with default values.

amadeus · 2026-01-27T06:29:56Z

packages/diffs/src/components/SimpleVirtualizedFileDiff.ts

        : this.hunksRenderer.getExpandedHunksMap(),
+      collapsedContextThreshold:
+        this.options.collapsedContextThreshold ??
+        DEFAULT_COLLAPSED_CONTEXT_THRESHOLD,


Small nit to destruct this higher up with the other this.options above

amadeus · 2026-01-27T06:31:48Z

packages/diffs/src/renderers/DiffHunksRenderer.ts

              ? true
-              : this.expandedHunks
+              : this.expandedHunks,
+          this.getOptionsWithDefaults().collapsedContextThreshold


This a good spot where i did a dumb. On line 325, i use this.options, I should've used this.getOptionsWithDefaults(). then can you destruct both this value and expandUnchanged up there?

amadeus · 2026-01-27T06:34:01Z

packages/diffs/src/utils/iterateOverDiff.ts

  startingLine = 0,
  totalLines = Infinity,
  expandedHunks,
+  collapsedContextThreshold,


Question here -- if 2 is our default, should we default prop this to that constant?

collapsedContextThreshold = 2

That or imo we should default arg it to 0. Kinda thinking if we go all in on 2, then everywhere we default arg it to 2 for consistency?

Then the rest of the functions internally here should just require a number, and this should satisfy them. Then the call sites to use it are cleaner.

Ahh yeah -- codex code review brought up a good point that we should probably default this arg in renderDiffWithHighlighter as well

amadeus · 2026-01-27T06:34:18Z

packages/diffs/src/utils/iterateOverDiff.ts

  expandedHunks: Map<number, HunkExpansionRegion> | true | undefined,
-  hunkIndex: number
+  hunkIndex: number,
+  collapsedContextThreshold: number | undefined


This becomes just collapsedContextThreshold: number

amadeus · 2026-01-27T06:36:04Z

packages/diffs/src/utils/iterateOverDiff.ts

+      collapsedLines: 0,
+    };
+  }
  if (expandedHunks === true) {


Similar comment from before, i don't think we need a max here, and if it's a : number then we can just do the:

if (expandedHunks === true || rangeSize <= collapsedContextThreshold)

amadeus · 2026-01-27T06:39:11Z

packages/diffs/test/DiffHunksRendererVirtualization.test.ts

      // to figure out, so mostly a good reference if tests change these
      // assumptions
-      expect(unifiedIndices[0]).toBe(186);
+      expect(unifiedIndices[0]).toBe(184);


weird that this number went down... 🤔

all the rest went up, which is what you would expect if they are rendering a few more lines...

The number going down makes sense. Previously, collapsedContextThreshold was not being defaulted in the rendering path (it was undefined), so small collapsed regions (1-2 lines) stayed collapsed and were rendered as a single hunk separator. Now with the default threshold of 2, those small regions are expanded into actual lines. When a 1-2 line collapsed region expands, it takes up more rendered lines (1-2 lines instead of 1 separator). So when iterating to find line index 100 (the startingLine), the iteration reaches 100 rendered lines sooner — meaning the first rendered line corresponds to an earlier source line index. That's why 186 dropped to 184: the expanded small regions before line 100 cause the window to start at an earlier point in the file. The other values going up follows the same logic — more total source lines are being rendered within the same window because previously-collapsed lines are now visible.

fat · 2026-01-29T00:43:54Z

apps/docs/app/docs/ReactAPI/constants.ts

  expansionLineCount: 100,

+  // Auto-expand collapsed context regions at or below this size
+  // (default: 1)


I changed it to 1 i think that's better than 2

vercel bot deployed to Preview – pierrejs-docs January 27, 2026 03:48 View deployment

vercel bot deployed to Preview – pierrejs-solid-diff-demo January 27, 2026 03:48 View deployment

update constants and styles

21d7448

fat force-pushed the fat/expanded-v2 branch from 64e458a to 21d7448 Compare January 27, 2026 04:03

vercel bot deployed to Preview – pierrejs-diff-demo January 27, 2026 04:04 View deployment

vercel bot deployed to Preview – pierrejs-docs January 27, 2026 04:04 View deployment

vercel bot deployed to Preview – pierrejs-solid-diff-demo January 27, 2026 04:05 View deployment

okay col

453a911

l

vercel bot deployed to Preview – pierrejs-diff-demo January 27, 2026 04:09 View deployment

vercel bot deployed to Preview – pierrejs-docs January 27, 2026 04:10 View deployment

vercel bot deployed to Preview – pierrejs-solid-diff-demo January 27, 2026 04:10 View deployment

oksy

f437f28

vercel bot deployed to Preview – pierrejs-diff-demo January 27, 2026 04:19 View deployment

fat changed the title ~~Add collpaseHunkThreshold~~ Add collapsedContextThreshold Jan 27, 2026

vercel bot deployed to Preview – pierrejs-docs January 27, 2026 04:20 View deployment

vercel bot deployed to Preview – pierrejs-solid-diff-demo January 27, 2026 04:20 View deployment

toaksdfjl

a63e225

vercel bot deployed to Preview – pierrejs-diff-demo January 27, 2026 05:04 View deployment

vercel bot deployed to Preview – pierrejs-docs January 27, 2026 05:05 View deployment

vercel bot deployed to Preview – pierrejs-solid-diff-demo January 27, 2026 05:05 View deployment

amadeus requested a review from Copilot January 27, 2026 06:22

Copilot started reviewing on behalf of amadeus January 27, 2026 06:22 View session

Copilot AI reviewed Jan 27, 2026

View reviewed changes

amadeus reviewed Jan 27, 2026

View reviewed changes

fat added 5 commits January 28, 2026 16:21

amadeus nit #1

ecbd716

nit 2

5b419d3

nit 4

34cc8fe

more nits

f143161

NITITITT

df8af2d

vercel bot deployed to Preview – pierrejs-diff-demo January 29, 2026 00:31 View deployment

vercel bot deployed to Preview – pierrejs-docs January 29, 2026 00:32 View deployment

vercel bot deployed to Preview – pierrejs-solid-diff-demo January 29, 2026 00:32 View deployment

okay sick

e697089

vercel bot deployed to Preview – pierrejs-diff-demo January 29, 2026 00:37 View deployment

vercel bot deployed to Preview – pierrejs-docs January 29, 2026 00:38 View deployment

vercel bot deployed to Preview – pierrejs-solid-diff-demo January 29, 2026 00:38 View deployment

okay

5bdf024

vercel bot deployed to Preview – pierrejs-diff-demo January 29, 2026 00:43 View deployment

sure

90b3672

vercel bot deployed to Preview – pierrejs-diff-demo January 29, 2026 00:43 View deployment

fat commented Jan 29, 2026

View reviewed changes

lame

8eb1bf5

vercel bot deployed to Preview – pierrejs-diff-demo January 29, 2026 00:44 View deployment

vercel bot deployed to Preview – pierrejs-docs January 29, 2026 00:45 View deployment

vercel bot deployed to Preview – pierrejs-solid-diff-demo January 29, 2026 00:45 View deployment

amadeus approved these changes Jan 29, 2026

View reviewed changes

fat merged commit 03d26df into main Jan 29, 2026
9 checks passed

fat deleted the fat/expanded-v2 branch January 29, 2026 02:11

Add collapsedContextThreshold #298

Add collapsedContextThreshold #298

Uh oh!

Conversation

fat commented Jan 27, 2026

Uh oh!

vercel bot commented Jan 27, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull request overview

Reviewed changes

Uh oh!

Copilot AI Jan 27, 2026

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

3 participants

vercel bot commented Jan 27, 2026 •

edited

Loading