Fix diff line range normalization

Author: maskdotdev

apps/web/src/components/DiffPanel.logic.test.ts

@@ -1,6 +1,6 @@
 import { describe, expect, it } from "vitest";
 import type { FileDiffMetadata } from "@pierre/diffs/react";
-import { buildFileKeyByPathIndex } from "./DiffPanel.logic";
+import { areSelectedLineRangesEqual, buildFileKeyByPathIndex } from "./DiffPanel.logic";
 
 function makeFileDiff(
   input: Partial<Pick<FileDiffMetadata, "name" | "prevName" | "cacheKey">>,
@@ -38,3 +38,14 @@ describe("buildFileKeyByPathIndex", () => {
     expect([...fileKeyByPath.entries()]).toEqual([["src/example.ts", "same-cache-key"]]);
   });
 });
+
+describe("areSelectedLineRangesEqual", () => {
+  it("treats forward and backward single-side selections as equal", () => {
+    expect(
+      areSelectedLineRangesEqual(
+        { start: 5, end: 10, side: "additions" },
+        { start: 10, end: 5, side: "additions" },
+      ),
+    ).toBe(true);
+  });
+});

apps/web/src/components/DiffPanel.logic.ts

@@ -80,7 +80,7 @@ function toNormalizedLineRange(range: SelectedLineRange): SelectedLineRange {
     start: range.end,
     end: range.start,
     ...((range.endSide ?? range.side) ? { side: range.endSide ?? range.side } : {}),
-    ...(range.side ? { endSide: range.side } : {}),
+    ...(range.endSide ? { endSide: range.side } : {}),
   };
 }
 
@@ -92,7 +92,7 @@ function toLineRange(range: SelectedLineRange): { start: number; end: number } {
   };
 }
 
-function areSelectedLineRangesEqual(
+export function areSelectedLineRangesEqual(
   left: SelectedLineRange | null,
   right: SelectedLineRange | null,
 ): boolean {