test(ui): tighten UTF-16 truncation coverage

steipete · steipete · commit ed138d7b03ed · 2026-07-09T04:15:22.000+01:00
diff --git a/ui/src/lib/format.test.ts b/ui/src/lib/format.test.ts
@@ -274,81 +274,30 @@ describe("formatTokens", () => {
   });
 });
 
-describe("clampText surrogate-safe truncation", () => {
-  it("does not split an emoji across the truncation boundary", () => {
-    // 121 UTF-16 units: 119 'a's then an emoji (surrogate pair at 119-120).
-    // With max = 120, naive slice(0, 119) keeps only the emoji's high surrogate.
-    const value = `${"a".repeat(119)}\u{1F600}`;
-    expect(value.length).toBe(121);
-
-    const result = clampText(value, 120);
-
-    // The emoji should be entirely dropped, leaving the 119 'a's + "…"
-    expect(result).toBe(`${"a".repeat(119)}…`);
-    // No dangling surrogates
-    for (let i = 0; i < result.length; i++) {
-      const cu = result.charCodeAt(i);
-      if (cu >= 0xd800 && cu <= 0xdbff) {
-        expect(result.charCodeAt(i + 1) >= 0xdc00 && result.charCodeAt(i + 1) <= 0xdfff).toBe(true);
-      }
-      if (cu >= 0xdc00 && cu <= 0xdfff) {
-        expect(
-          i > 0 && result.charCodeAt(i - 1) >= 0xd800 && result.charCodeAt(i - 1) <= 0xdbff,
-        ).toBe(true);
-      }
-    }
+describe("text truncation", () => {
+  it("keeps clampText output valid when the ellipsis boundary bisects an emoji", () => {
+    expect(clampText(`${"a".repeat(118)}😀x`, 120)).toBe(`${"a".repeat(118)}…`);
   });
 
-  it("leaves short text unchanged", () => {
-    expect(clampText("hello", 120)).toBe("hello");
-  });
-
-  it("appends ellipsis when truncated", () => {
-    expect(clampText("x".repeat(200), 120)).toMatch(/…$/);
+  it("keeps truncateText output valid when the boundary bisects an emoji", () => {
+    expect(truncateText(`${"a".repeat(120)}😀`, 121)).toEqual({
+      text: "a".repeat(120),
+      truncated: true,
+      total: 122,
+    });
   });
-});
 
-describe("truncateText surrogate-safe truncation", () => {
-  it("does not split an emoji across the truncation boundary", () => {
-    // 121 UTF-16 units: 120 'a's then an emoji at index 120.
-    const value = `${"a".repeat(120)}\u{1F600}`;
-    expect(value.length).toBe(122);
-
-    const result = truncateText(value, 121);
-
-    expect(result.truncated).toBe(true);
-    // The emoji should be dropped entirely
-    expect(result.text).not.toContain("\u{1F600}");
-    // No dangling surrogates
-    for (let i = 0; i < result.text.length; i++) {
-      const cu = result.text.charCodeAt(i);
-      if (cu >= 0xd800 && cu <= 0xdbff) {
-        expect(
-          result.text.charCodeAt(i + 1) >= 0xdc00 && result.text.charCodeAt(i + 1) <= 0xdfff,
-        ).toBe(true);
-      }
-      if (cu >= 0xdc00 && cu <= 0xdfff) {
-        expect(
-          i > 0 &&
-            result.text.charCodeAt(i - 1) >= 0xd800 &&
-            result.text.charCodeAt(i - 1) <= 0xdbff,
-        ).toBe(true);
-      }
-    }
-  });
-
-  it("returns truncated: false for short text", () => {
+  it("leaves short text unchanged", () => {
+    expect(clampText("hello", 120)).toBe("hello");
     expect(truncateText("hello", 120)).toEqual({
       text: "hello",
       truncated: false,
       total: 5,
     });
   });
 
-  it("reports correct total for truncated text", () => {
-    const result = truncateText("x".repeat(200), 120);
-    expect(result.truncated).toBe(true);
-    expect(result.total).toBe(200);
-    expect(result.text.length).toBeLessThan(200);
+  it("preserves ordinary truncation behavior", () => {
+    expect(clampText("abc", 2)).toBe("a…");
+    expect(truncateText("abc", 2)).toEqual({ text: "ab", truncated: true, total: 3 });
   });
 });
