Detect More Faulty Codeblocks (#3514)

* enhanced codeblock regex and made stricter requirements for valid codeblocks

* added empty newline for readability

* minor code cleanup

Author: SamuelRoettgermann

bot/exts/info/codeblock/_parsing.py

@@ -35,11 +35,11 @@
     fr"""
     (?P<ticks>
         (?P<tick>[{''.join(_TICKS)}]) # Put all ticks into a character class within a group.
-        \2{{2}}                       # Match previous group 2 more times to ensure the same char.
+        \2*                           # Match previous group up to N more times to ensure the same char.
     )
-    (?P<lang>[A-Za-z0-9\+\-\.]+\n)?   # Optionally match a language specifier followed by a newline.
+    (?P<lang>[A-Za-z0-9+\-.]+\s)?     # Optionally match a language specifier followed by a whitespace.
     (?P<code>.+?)                     # Match the actual code within the block.
-    \1                                # Match the same 3 ticks used at the start of the block.
+    \1                                # Match the same N ticks used at the start of the block.
     """,
     re.DOTALL | re.VERBOSE
 )
@@ -86,11 +86,12 @@ def find_code_blocks(message: str) -> Sequence[CodeBlock] | None:
     for match in _RE_CODE_BLOCK.finditer(message):
         # Used to ensure non-matched groups have an empty string as the default value.
         groups = match.groupdict("")
-        language = groups["lang"].strip()  # Strip the newline cause it's included in the group.
+        language = groups["lang"].strip()  # Strip the whitespace cause it's included in the group.
 
-        if groups["tick"] == BACKTICK and language:
+        if groups["tick"] == BACKTICK and len(groups["ticks"]) == 3 and language and ("\n" in groups["lang"]):
             log.trace("Message has a valid code block with a language; returning None.")
             return None
+
         if has_lines(groups["code"], constants.CodeBlock.minimum_lines):
             code_block = CodeBlock(groups["code"], language, groups["tick"])
             code_blocks.append(code_block)
@@ -181,14 +182,15 @@ def parse_bad_language(content: str) -> BadLanguage | None:
     )
 
 
-def _get_leading_spaces(content: str) -> int:
+def _get_leading_spaces(content: str) -> int | None:
     """Return the number of spaces at the start of the first line in `content`."""
     leading_spaces = 0
     for char in content:
         if char == " ":
             leading_spaces += 1
         else:
             return leading_spaces
+
     return None