Fat/merge conflict diff

[fat]

Merge conflict built on top of diff primitive…

VSCODE (note the syntax highlighting failure)

Pierre (note the correct highlighting)

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Project	Deployment	Actions	Updated (UTC)
pierrejs-diff-demo	Ready	Preview	Mar 10, 2026 3:33am
pierrejs-docs	Ready	Preview	Mar 10, 2026 3:33am

[amadeus]

in prog review

[Copilot]

Pull request overview

Adds a dedicated “unresolved merge conflict” diff primitive on top of the existing diffs renderer, including parsing conflict markers into a structured diff, rendering conflict-aware UI rows, and providing utilities + docs/SSR support to resolve conflicts while preserving syntax highlighting.

Changes:

• Introduces merge-conflict parsing and resolution utilities (getMergeConflictLineTypes, parseMergeConflictDiffFromFile, resolveMergeConflict) with test coverage.
• Adds UnresolvedFile (vanilla + React) and UnresolvedFileHunksRenderer to render conflict markers/sections with built-in action controls and optional custom utilities via slots.
• Extends renderer infrastructure (line decorations, custom <pre> properties) and updates docs + SSR preloading (preloadUnresolvedFile) to demo/hydrate the new UI.

Reviewed changes

Copilot reviewed 41 out of 41 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
packages/diffs/test/resolveMergeConflict.test.ts	Adds tests for applying merge-conflict resolutions to raw contents.
packages/diffs/test/parseMergeConflictDiffFromFile.test.ts	Adds tests ensuring conflict files are split into current/incoming views + diff metadata/actions.
packages/diffs/test/getMergeConflictLineTypes.test.ts	Adds tests for marker/body classification, nested handling, and region extraction.
packages/diffs/src/utils/setWrapperNodeProps.ts	Adds support for custom <pre> attributes during DOM application.
packages/diffs/src/utils/resolveMergeConflict.ts	New utility to apply a merge-conflict resolution payload to file contents.
packages/diffs/src/utils/parseMergeConflictDiffFromFile.ts	New utility to convert conflict-marked file contents into a synthetic diff + action metadata.
packages/diffs/src/utils/hast_utils.ts	Extends gutter item creation to accept additional properties.
packages/diffs/src/utils/getMergeConflictLineTypes.ts	New parser for conflict markers/stages + region extraction.
packages/diffs/src/utils/getMergeConflictActionSlotName.ts	New helper to generate stable slot names for action rows.
packages/diffs/src/utils/createPreElement.ts	Adds custom <pre> properties for SSR/HAST-rendered output.
packages/diffs/src/utils/arePrePropertiesEqual.ts	Updates equality check to include custom <pre> properties.
packages/diffs/src/utils/areMergeConflictActionsEqual.ts	Adds equality helper for merge-conflict action metadata caching.
packages/diffs/src/types.ts	Introduces merge-conflict types, CustomPreProperties, and BaseDiffOptionsWithDefaults.
packages/diffs/src/style.css	Adds conflict-marker/section styling and action-row UI styling.
packages/diffs/src/ssr/preloadDiffs.ts	Adds SSR preload APIs for unresolved merge-conflict files and refactors common rendering flow.
packages/diffs/src/renderers/UnresolvedFileHunksRenderer.ts	New renderer that decorates conflict lines and injects action rows/slots.
packages/diffs/src/renderers/DiffHunksRenderer.ts	Adds line decoration hooks + custom pre properties support to enable conflict rendering overlays.
packages/diffs/src/react/utils/useUnresolvedFileInstance.ts	New hook to manage UnresolvedFile instance + sequential conflict resolutions in React.
packages/diffs/src/react/utils/useFileDiffInstance.ts	Minor refactor to reduce repeated ref reads.
packages/diffs/src/react/utils/renderDiffChildren.tsx	Adds rendering of merge-conflict utility slot children in React.
packages/diffs/src/react/index.ts	Exports React UnresolvedFile.
packages/diffs/src/react/constants.ts	Adds styling constant for merge-conflict slot wrappers.
packages/diffs/src/react/UnresolvedFile.tsx	New React component wrapper for unresolved merge-conflict rendering.
packages/diffs/src/managers/InteractionManager.ts	Adds click targeting + dispatch for merge-conflict action buttons and accounts for action rows in layout logic.
packages/diffs/src/index.ts	Exports vanilla UnresolvedFile and resolveMergeConflict.
packages/diffs/src/components/UnresolvedFile.ts	New vanilla component handling uncontrolled/controlled conflict resolution flows and optional custom action rendering.
packages/diffs/src/components/FileDiff.ts	Refactors renderer construction for extensibility and allows custom separator renderers to return undefined.
apps/docs/app/page.tsx	Adds a merge-conflict demo section to the homepage.
apps/docs/app/docs/page.tsx	Integrates merge-conflict demo + adds docs/examples for new APIs.
apps/docs/app/docs/VanillaAPI/content.mdx	Documents UnresolvedFile in vanilla API docs.
apps/docs/app/docs/VanillaAPI/constants.ts	Adds vanilla unresolved-file example snippet.
apps/docs/app/docs/VanillaAPI/ComponentTabs.tsx	Adds an “UnresolvedFile” tab in vanilla API example UI.
apps/docs/app/docs/Utilities/content.mdx	Documents resolveMergeConflict utility usage.
apps/docs/app/docs/Utilities/constants.ts	Adds resolveMergeConflict example snippet.
apps/docs/app/docs/SSR/content.mdx	Documents preloadUnresolvedFile.
apps/docs/app/docs/SSR/constants.ts	Adds SSR preload unresolved-file example snippet.
apps/docs/app/docs/ReactAPI/content.mdx	Documents React UnresolvedFile and its uncontrolled behavior.
apps/docs/app/docs/ReactAPI/constants.ts	Adds React unresolved-file example snippet.
apps/docs/app/docs/ReactAPI/ComponentTabs.tsx	Adds an “UnresolvedFile” tab in React API example UI.
apps/docs/app/diff-examples/MergeConflict/constants.ts	Adds merge-conflict demo fixture/options.
apps/docs/app/diff-examples/MergeConflict/MergeConflict.tsx	Adds client-side demo UI for resetting/toggling theme while testing the conflict renderer.

Comments suppressed due to low confidence (1)

packages/diffs/src/style.css:38

• The "Available CSS Color Overrides" list now mentions --diffs-fg-conflict-marker-override, but the stylesheet also introduces several new conflict-related override variables (e.g. --diffs-bg-conflict-marker-override, --diffs-bg-conflict-current-override, etc.) that aren't documented in this list. To keep the inline docs accurate/discoverable, consider adding the rest of the conflict override vars that are actually supported below.

    /*
    // Available CSS Color Overrides
    --diffs-bg-buffer-override
    --diffs-bg-hover-override
    --diffs-bg-context-override
    --diffs-bg-separator-override

    --diffs-fg-number-override
    --diffs-fg-number-addition-override
    --diffs-fg-number-deletion-override
    --diffs-fg-conflict-marker-override

    --diffs-deletion-color-override
    --diffs-addition-color-override
    --diffs-modified-color-override

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