fix(toolbar): apply heading levels across multiline selections (#1901)

Co-authored-by: sunsonliu <sunsonliu@tencent.com>

Author: SomSamantray

.changeset/bright-headings-smile.md

@@ -0,0 +1,5 @@
+---
+'cherry-markdown': patch
+---
+
+fix: apply heading levels consistently across multiline selections

packages/cherry-markdown/src/toolbars/hooks/Header.js

@@ -71,7 +71,7 @@ export default class Header extends MenuBase {
   }
 
   $testIsHead(selection) {
-    return /^\s*(#+)\s*.+/.test(selection);
+    return /^[ \t]*#+[ \t]*.+/m.test(selection);
   }
 
   /**
@@ -99,9 +99,9 @@ export default class Header extends MenuBase {
       // 如果选中的内容里有标题语法，并且标记级别与目标一致，则去掉标题语法
       // 反之，修改标题级别与目标一致
       let needClean = true;
-      const tmp = $selection.replace(/(^\s*)(#+)(\s*)(.+$)/gm, (w, m1, m2, m3, m4) => {
-        needClean = needClean ? m2.length === header.length : false;
-        return `${m1}${header}${m3}${m4}`;
+      const tmp = $selection.replace(/^([ \t]*)(#+)?([ \t]*)(.+)$/gm, (w, m1, m2, m3, m4) => {
+        needClean = needClean && !!m2 && m2.length === header.length;
+        return `${m1}${header}${m2 ? m3 : ' '}${m4}`;
       });
       if (needClean) {
         return $selection.replace(/(^\s*)(#+)(\s*)(.+$)/gm, '$1$4');

packages/cherry-markdown/test/toolbars/hooks/formatting.spec.ts

@@ -108,6 +108,13 @@ describe('toolbars/hooks formatting', () => {
     expect(createHook(Hook, input).hook.onClick(input)).toBe(expected);
   });
 
+  it('replaces an existing heading after ordinary text in a multiline selection', () => {
+    const input = 'ordinary text\n##   existing heading';
+    const header = createHook(Header, input).hook;
+
+    expect(header.onClick(input, '1')).toBe('# ordinary text\n#   existing heading');
+  });
+
   it.each([
     [H1, '# h1'],
     [H2, '## h2'],