Limit recursion with nesting Ruby heredocs

fixes #1638

CHANGES

@@ -18,6 +18,7 @@ Version 2.7.4
 
 - Fixed infinite loop in SML lexer (#1625)
 - Fixed backtracking string regexes in JavaScript/TypeScript lexers (#1637)
+- Limit recursion with nesting Ruby heredocs (#1638)
 
 
 Version 2.7.3

pygments/lexers/crystal.py

@@ -57,8 +57,11 @@ def heredoc_callback(self, match, ctx):
 
         ctx.pos = match.start(5)
         ctx.end = match.end(5)
-        # this may find other heredocs
-        yield from self.get_tokens_unprocessed(context=ctx)
+        # this may find other heredocs, so limit the recursion depth
+        if len(heredocstack) < 100:
+            yield from self.get_tokens_unprocessed(context=ctx)
+        else:
+            yield ctx.pos, String.Heredoc, match.group(5)
         ctx.pos = match.end()
 
         if outermost:

pygments/lexers/ruby.py

@@ -57,8 +57,11 @@ def heredoc_callback(self, match, ctx):
 
         ctx.pos = match.start(5)
         ctx.end = match.end(5)
-        # this may find other heredocs
-        yield from self.get_tokens_unprocessed(context=ctx)
+        # this may find other heredocs, so limit the recursion depth
+        if len(heredocstack) < 100:
+            yield from self.get_tokens_unprocessed(context=ctx)
+        else:
+            yield ctx.pos, String.Heredoc, match.group(5)
         ctx.pos = match.end()
 
         if outermost: