Update markdown detection to avoid regex

Signed-off-by: Émile Ré <emile@getprobo.com>

packages/prosemirror/src/hasMarkdown.ts

@@ -0,0 +1,109 @@
+// Copyright (c) 2026 Probo Inc <hello@getprobo.com>.
+// Use of this source code is governed by the ISC license
+// that can be found in the LICENSE file.
+
+function isTableSeparatorCell(cell: string): boolean {
+  const trimmed = cell.trim();
+  if (trimmed.length < 3) return false;
+
+  let start = 0;
+  let end = trimmed.length;
+  if (trimmed[0] === ":") start = 1;
+  if (trimmed[end - 1] === ":") end -= 1;
+  if (end - start < 3) return false;
+
+  for (let i = start; i < end; i++) {
+    if (trimmed[i] !== "-") return false;
+  }
+  return true;
+}
+
+function isTableSeparatorLine(line: string): boolean {
+  const trimmed = line.trim();
+  if (trimmed.length < 3) return false;
+
+  let s = trimmed;
+  if (s[0] === "|") s = s.slice(1);
+  if (s[s.length - 1] === "|") s = s.slice(0, -1);
+  if (s.trim().length === 0) return false;
+
+  const cells = s.split("|");
+  for (const cell of cells) {
+    if (!isTableSeparatorCell(cell)) return false;
+  }
+  return true;
+}
+
+function isWordChar(c: number): boolean {
+  return (
+    (c >= 48 && c <= 57) ||
+    (c >= 65 && c <= 90) ||
+    (c >= 97 && c <= 122) ||
+    c === 95
+  );
+}
+
+function hasMarkdownLine(line: string): boolean {
+  if (line.length === 0) return false;
+  const ch = line[0];
+
+  if (ch === "`" && line.startsWith("```")) {
+    for (let i = 3; i < line.length; i++) {
+      if (!isWordChar(line.charCodeAt(i))) return false;
+    }
+    return true;
+  }
+
+  if (ch === "#") {
+    let i = 1;
+    while (i < line.length && i < 6 && line[i] === "#") i++;
+    return i <= 6 && i < line.length && (line[i] === " " || line[i] === "\t");
+  }
+
+  if (ch === ">" && line.length > 1 && (line[1] === " " || line[1] === "\t")) {
+    return true;
+  }
+
+  if (
+    (ch === "-" || ch === "+" || ch === "*") &&
+    line.length > 1 &&
+    (line[1] === " " || line[1] === "\t")
+  ) {
+    return true;
+  }
+
+  if (ch >= "0" && ch <= "9") {
+    let i = 1;
+    while (i < line.length && line[i] >= "0" && line[i] <= "9") i++;
+    if (
+      i < line.length &&
+      line[i] === "." &&
+      i + 1 < line.length &&
+      (line[i + 1] === " " || line[i + 1] === "\t")
+    ) {
+      return true;
+    }
+  }
+
+  if (
+    line.length >= 3 &&
+    (ch === "-" || ch === "_" || ch === "*") &&
+    line[1] === ch &&
+    line[2] === ch
+  ) {
+    for (let i = 3; i < line.length; i++) {
+      if (line[i] !== " " && line[i] !== "\t") return false;
+    }
+    return true;
+  }
+
+  return false;
+}
+
+export function hasMarkdown(text: string): boolean {
+  const lines = text.split("\n");
+  for (const line of lines) {
+    if (hasMarkdownLine(line) || isTableSeparatorLine(line)) return true;
+  }
+  return false;
+}

packages/prosemirror/src/index.ts

@@ -2,4 +2,5 @@
 // Use of this source code is governed by the ISC license
 // that can be found in the LICENSE file.
 
-export { hasMarkdown, parseInlineContent, parseMarkdown } from "./markdown";
+export { hasMarkdown } from "./hasMarkdown";
+export { parseInlineContent, parseMarkdown } from "./markdown";

packages/prosemirror/src/markdown.ts

@@ -15,11 +15,6 @@ import {
   safeLinkHref,
 } from "./htmlBlock";
 
-const tableSeparatorPattern =
-  /^\|?\s*:?-{3,}:?\s*(\|\s*:?-{3,}:?\s*)*\|?\s*$/m;
-const markdownLinePattern =
-  /(?:^```\w*$|^#{1,6}\s|^>\s|^[-+*]\s|^\d+\.\s|^(?:---|___|\*\*\*)\s*$)/m;
-
 function unescapeHtml(html: string): string {
   return html
     .replace(/&lt;/g, "<")
@@ -412,10 +407,6 @@ class Converter {
   }
 }
 
-export function hasMarkdown(text: string): boolean {
-  return markdownLinePattern.test(text) || tableSeparatorPattern.test(text);
-}
-
 export function parseInlineContent(
   schema: Schema,
   text: string,