fix: allow strikethrough inside strong and em to follow gfm (#3569)

UziTech · web-flow · commit 8a01658cac12 · 2025-01-02T08:34:55.000-07:00
diff --git a/src/rules.ts b/src/rules.ts
@@ -249,27 +249,40 @@ const _notPunctuationOrSpace = /[^\s\p{P}\p{S}]/u;
 const punctuation = edit(/^((?![*_])punctSpace)/, 'u')
   .replace(/punctSpace/g, _punctuationOrSpace).getRegex();
 
+// GFM allows ~ inside strong and em for strikethrough
+const _punctuationGfmStrongEm = /(?!~)[\p{P}\p{S}]/u;
+const _punctuationOrSpaceGfmStrongEm = /(?!~)[\s\p{P}\p{S}]/u;
+const _notPunctuationOrSpaceGfmStrongEm = /(?:[^\s\p{P}\p{S}]|~)/u;
+
 // sequences em should skip over [title](link), `code`, <html>
 const blockSkip = /\[[^[\]]*?\]\((?:\\.|[^\\\(\)]|\((?:\\.|[^\\\(\)])*\))*\)|`[^`]*?`|<[^<>]*?>/g;
 
 const emStrongLDelim = edit(/^(?:\*+(?:((?!\*)punct)|[^\s*]))|^_+(?:((?!_)punct)|([^\s_]))/, 'u')
   .replace(/punct/g, _punctuation)
   .getRegex();
 
-const emStrongRDelimAst = edit(
+const emStrongRDelimAstCore =
   '^[^_*]*?__[^_*]*?\\*[^_*]*?(?=__)' // Skip orphan inside strong
 + '|[^*]+(?=[^*])' // Consume to delim
 + '|(?!\\*)punct(\\*+)(?=[\\s]|$)' // (1) #*** can only be a Right Delimiter
 + '|notPunctSpace(\\*+)(?!\\*)(?=punctSpace|$)' // (2) a***#, a*** can only be a Right Delimiter
 + '|(?!\\*)punctSpace(\\*+)(?=notPunctSpace)' // (3) #***a, ***a can only be Left Delimiter
 + '|[\\s](\\*+)(?!\\*)(?=punct)' // (4) ***# can only be Left Delimiter
 + '|(?!\\*)punct(\\*+)(?!\\*)(?=punct)' // (5) #***# can be either Left or Right Delimiter
-+ '|notPunctSpace(\\*+)(?=notPunctSpace)', 'gu') // (6) a***a can be either Left or Right Delimiter
++ '|notPunctSpace(\\*+)(?=notPunctSpace)'; // (6) a***a can be either Left or Right Delimiter
+
+const emStrongRDelimAst = edit(emStrongRDelimAstCore, 'gu')
   .replace(/notPunctSpace/g, _notPunctuationOrSpace)
   .replace(/punctSpace/g, _punctuationOrSpace)
   .replace(/punct/g, _punctuation)
   .getRegex();
 
+const emStrongRDelimAstGfm = edit(emStrongRDelimAstCore, 'gu')
+  .replace(/notPunctSpace/g, _notPunctuationOrSpaceGfmStrongEm)
+  .replace(/punctSpace/g, _punctuationOrSpaceGfmStrongEm)
+  .replace(/punct/g, _punctuationGfmStrongEm)
+  .getRegex();
+
 // (6) Not allowed for _
 const emStrongRDelimUnd = edit(
   '^[^_*]*?\\*\\*[^_*]*?_[^_*]*?(?=\\*\\*)' // Skip orphan inside strong
@@ -375,7 +388,7 @@ const inlinePedantic: Record<InlineKeys, RegExp> = {
 
 const inlineGfm: Record<InlineKeys, RegExp> = {
   ...inlineNormal,
-  escape: edit(escape).replace('])', '~|])').getRegex(),
+  emStrongRDelimAst: emStrongRDelimAstGfm,
   url: edit(/^((?:ftp|https?):\/\/|www\.)(?:[a-zA-Z0-9\-]+\.?)+[^\s<]*|^email/, 'i')
     .replace('email', /[A-Za-z0-9._+-]+(@)[a-zA-Z0-9-_]+(?:\.[a-zA-Z0-9-_]*[a-zA-Z0-9])+(?![-_])/)
     .getRegex(),
diff --git a/test/specs/new/strikethrough_in_em_strong.html b/test/specs/new/strikethrough_in_em_strong.html
@@ -0,0 +1,15 @@
+<p><em><del>a</del></em>b</p>
+
+<p><em><del>a</del></em>b</p>
+
+<p><strong><del>a</del></strong>b</p>
+
+<p><strong><del>a</del></strong>b</p>
+
+<p>_<del>a</del>_b</p>
+
+<p>_<del>a</del>_b</p>
+
+<p>__<del>a</del>__b</p>
+
+<p>__<del>a</del>__b</p>
diff --git a/test/specs/new/strikethrough_in_em_strong.md b/test/specs/new/strikethrough_in_em_strong.md
@@ -0,0 +1,15 @@
+*~a~*b
+
+*~~a~~*b
+
+**~a~**b
+
+**~~a~~**b
+
+_~a~_b
+
+_~~a~~_b
+
+__~a~__b
+
+__~~a~~__b
