Syntax-highlight Edit, Write, and Read tool calls (#1218)

Highlighting reuses the existing code-block tokenizer and LRU cache, runs lazily on expand, and falls back to plain text above a size cap so a large Read can't stall the main thread. The diff highlighter reconstructs the old and new file text by position rather than from @@ line ranges, so diffs that arrive without real hunk headers still highlight. Read content is normalized server-side: the cat -n line-number gutter some providers emit is stripped so content is uniformly raw source, with the first line number surfaced as offset for the client to rebuild the gutter.
2026-05-29 14:51:14 +08:00
parent 25d6fc8515
commit 38f0560f9b
12 changed files with 661 additions and 77 deletions
@@ -0,0 +1,65 @@
+import { describe, expect, it } from "vitest";
+import {
+  extensionFromPath,
+  highlightToKeyedLines,
+  MAX_HIGHLIGHT_CHARS,
+  tokenizeToLines,
+} from "./highlight-cache";
+
+describe("extensionFromPath", () => {
+  it("extracts a lowercased extension regardless of absolute/relative path", () => {
+    expect(extensionFromPath("/repo/src/Index.TS")).toBe("ts");
+    expect(extensionFromPath("src/index.ts")).toBe("ts");
+    expect(extensionFromPath("a.b/c.tsx")).toBe("tsx");
+  });
+
+  it("returns null for paths without a usable extension", () => {
+    expect(extensionFromPath(null)).toBeNull();
+    expect(extensionFromPath(undefined)).toBeNull();
+    expect(extensionFromPath("Makefile")).toBeNull();
+    expect(extensionFromPath(".gitignore")).toBeNull();
+    expect(extensionFromPath("trailingdot.")).toBeNull();
+  });
+});
+
+describe("tokenizeToLines", () => {
+  it("returns one token array per line for a supported language", () => {
+    const lines = tokenizeToLines("const a = 1;\nconst b = 2;", "ts");
+    expect(lines).not.toBeNull();
+    expect(lines).toHaveLength(2);
+    expect(lines?.[0].some((token) => token.style === "keyword")).toBe(true);
+  });
+
+  it("returns null when there is no extension", () => {
+    expect(tokenizeToLines("whatever", null)).toBeNull();
+  });
+
+  it("falls back to style-less per-line tokens for an unknown extension", () => {
+    const lines = tokenizeToLines("line one\nline two", "unknownext");
+    expect(lines).toHaveLength(2);
+    expect(lines?.[0]).toEqual([{ text: "line one", style: null }]);
+  });
+
+  it("returns null above the size cap so callers fall back to plain text", () => {
+    const huge = "x".repeat(MAX_HIGHLIGHT_CHARS + 1);
+    expect(tokenizeToLines(huge, "ts")).toBeNull();
+  });
+
+  it("serves a cached result on repeat calls (identity-stable)", () => {
+    const first = tokenizeToLines("const cached = true;", "ts");
+    const second = tokenizeToLines("const cached = true;", "ts");
+    expect(first).toBe(second);
+  });
+});
+
+describe("highlightToKeyedLines", () => {
+  it("produces stable keys for lines and tokens", () => {
+    const keyed = highlightToKeyedLines("const a = 1;", "ts");
+    expect(keyed?.[0].key).toBe("line-0");
+    expect(keyed?.[0].tokens[0].key).toBe("0-0");
+  });
+
+  it("returns null when highlighting is unavailable", () => {
+    expect(highlightToKeyedLines("text", null)).toBeNull();
+  });
+});