Lazy full file hydration

[samhh]

Closes GB-1836.

[Copilot]

Pull request overview

Adds “lazy full file hydration” for the Lite workspace diff viewer by wiring CodeView’s loadDiffFiles callback to fetch full file contents on demand via TanStack Query, rather than eagerly hydrating full files up front.

Changes:

• Plumbs loadDiffFiles into the CodeView options to enable on-demand loading of full file contents for diffs.
• Introduces blob/workspace file query usage (via blobFileQueryOptions / workspaceFileQueryOptions) and uses useQueryClient().fetchQuery() for imperative fetching.

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[Copilot]

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated no new comments.

Suppressed comments (1)

apps/lite/ui/src/routes/project/$id/workspace/Details.tsx:1352

• loadDiffFiles treats only UncommittedChanges as workspace-backed. In this codebase FileParent can also be Branch, and branch diffs are applied to the workspace (see apps/lite/ui/src/operands.ts + existing ImageDiff logic). As written, branch diffs will incorrectly hydrate the “new” file from getBlobFile instead of the workspace state.

			// Don't await yet, retain prospective parallelisation.
			const asyncNewFile =
				fileParent._tag === "UncommittedChanges"
					? loadWorkspaceFile(change.path)
					: loadBlobFile(change.path, change.status.subject.state.id);

[Copilot]

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated no new comments.

[linear-code]

GB-1836

[Copilot]

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated no new comments.

Suppressed comments (3)

apps/lite/ui/src/routes/project/$id/workspace/Details.tsx:1336

• fileByPath.get(fileDiff.name) can return undefined (e.g., CodeView holds a stale snapshot or the name doesn’t match the map key). In that case the current file?.patch?.type !== "Patch" branch throws a misleading "Cannot expand non-patch diff" error. Add an explicit not-found check so failures are diagnosable.

			const file = fileByPath.get(fileDiff.name);
			if (file?.patch?.type !== "Patch") throw new Error("Cannot expand non-patch diff");

apps/lite/ui/src/routes/project/$id/workspace/Details.tsx:1375

• After allowing additions/deletions, the asyncNewFile computation still assumes change.status.subject.state.id exists, which will crash for deletions. Also, for pure renames it’s more consistent to return both old/new contents (they’re identical) so split views don’t look like an addition. Handle Addition/Deletion explicitly before building asyncNewFile, and load the old file for rename-pure renames.

			// Don't await yet, retain prospective parallelisation.
			const asyncNewFile =
				fileParent._tag === "UncommittedChanges"
					? loadWorkspaceFile(change.path)
					: loadBlobFile(change.path, change.status.subject.state.id);

apps/lite/ui/src/routes/project/$id/workspace/Details.tsx:1345

• loadDiffFiles currently only allows Modification and Rename, but CodeView can request full-file hydration for additions/deletions as well (and synthesizeFilePatch already produces patch headers for those statuses). If this guard stays as-is, expanding full-file views for added/deleted files will always throw.

This issue also appears on line 1371 of the same file.

			if (change.status.type !== "Modification" && change.status.type !== "Rename")
				throw new Error(`Cannot load full files for ${fileDiff.name}`);