[Utils] Add filters for spoiler markdown (#2401)

This also wraps some fields of the modlog with the same sanitization, as well as the `[p]names` command.

redbot/core/utils/common_filters.py

@@ -9,6 +9,8 @@ __all__ = [
     "filter_mass_mentions",
     "filter_various_mentions",
     "normalize_smartquotes",
+    "escape_spoilers",
+    "escape_spoilers_and_mass_mentions",
 ]
 
 # regexes
@@ -29,6 +31,10 @@ SMART_QUOTE_REPLACEMENT_DICT = {
 
 SMART_QUOTE_REPLACE_RE = re.compile("|".join(SMART_QUOTE_REPLACEMENT_DICT.keys()))
 
+SPOILER_CONTENT_RE = re.compile(
+    r"(?s)(?<!\\)(?P<OPEN>\|{2})(?P<SPOILERED>.*?)(?<!\\)(?P<CLOSE>\|{2})"
+)
+
 
 # convenience wrappers
 def filter_urls(to_filter: str) -> str:
@@ -133,3 +139,37 @@ def normalize_smartquotes(to_normalize: str) -> str:
         return SMART_QUOTE_REPLACEMENT_DICT.get(obj.group(0), "")
 
     return SMART_QUOTE_REPLACE_RE.sub(replacement_for, to_normalize)
+
+
+def escape_spoilers(content: str) -> str:
+    """
+    Get a string with spoiler syntax escaped.
+
+    Parameters
+    ----------
+    content : str
+        The string to escape.
+
+    Returns
+    -------
+    str
+        The escaped string.
+    """
+    return SPOILER_CONTENT_RE.sub(r"\\\g<OPEN>\g<SPOILERED>\\\g<CLOSE>", content)
+
+
+def escape_spoilers_and_mass_mentions(content: str) -> str:
+    """
+    Get a string with spoiler syntax and mass mentions escaped
+
+    Parameters
+    ----------
+    content : str
+        The string to escape.
+
+    Returns
+    -------
+    str
+        The escaped string.
+    """
+    return escape_spoilers(filter_mass_mentions(content))