fix: skip asterisks inside math blocks in remend (#306)

* fix: skip asterisks inside math blocks in remend

* chore: add changeset for remend asterisk fix

Author: lihuaabcder

.changeset/tidy-cases-cut.md

@@ -0,0 +1,5 @@
+---
+"remend": patch
+---
+
+Fix asterisks inside math blocks being incorrectly treated as italic markers

packages/remend/__tests__/katex.test.ts

@@ -178,3 +178,26 @@ describe("math blocks with underscores", () => {
     expect(remend(str)).toBe("$$formula$$ and code `$$` and $$incomplete$$");
   });
 });
+
+describe("math blocks with asterisks", () => {
+  it("should not complete asterisks within block math", () => {
+    const text = "$$\\mathbf{w}^{*}$$";
+    expect(remend(text)).toBe(text);
+  });
+
+  it("should not complete asterisks in complex math expressions", () => {
+    const text =
+      "$$\n\\mathbf{w}^{*} = \\underset{\\|\\mathbf{w}\\|=1}{\\arg\\max} \\;\\; \\mathbf{w}^T S \\mathbf{w}\n$$";
+    expect(remend(text)).toBe(text);
+  });
+
+  it("should handle asterisks outside math blocks normally", () => {
+    const text = "Text with *italic* and math $$x^{*}$$";
+    expect(remend(text)).toBe(text);
+  });
+
+  it("should complete italic asterisk outside math but not inside", () => {
+    const text = "Start *italic with $$x^{*}$$";
+    expect(remend(text)).toBe("Start *italic with $$x^{*}$$*");
+  });
+});

packages/remend/src/emphasis-handlers.ts

@@ -57,6 +57,12 @@ const shouldSkipAsterisk = (
     return true;
   }
 
+  // Skip if within math block (only check if text has dollar signs)
+  const hasMathBlocks = text.includes("$");
+  if (hasMathBlocks && isWithinMathBlock(text, index)) {
+    return true;
+  }
+
   // Special handling for *** sequences
   // If this is the first * in ***, don't skip it - it can close a single * italic
   // Example: **bold and *italic*** should count the first * of *** as closing the italic
@@ -313,7 +319,8 @@ const findFirstSingleAsteriskIndex = (text: string): number => {
       text[i] === "*" &&
       text[i - 1] !== "*" &&
       text[i + 1] !== "*" &&
-      text[i - 1] !== "\\"
+      text[i - 1] !== "\\" &&
+      !isWithinMathBlock(text, i)
     ) {
       // Check if asterisk is word-internal (between word characters)
       const prevChar = i > 0 ? text[i - 1] : "";