fix!: gathered_filter to process regex correctly (#583)

Removed backslash(\) escape char from shlex to avoid escaping
and properly processing regex expressions.

BREAKING CHANGE: `gathered_filter` in 'gathered' state now accepts valid regex
expressions, the previous syntax with extra escape characters is not valid anymore.

docs/source/gatheredfilter.rst

@@ -125,6 +125,31 @@ These all do the same thing, listed from fastest to slowest.
     gathered_filter: 'name matches-regex .*?'
 
 
+Example - Matching a Regex
+--------------------------
+
+It is possible to write regex in the following formats;
+
+* Standard regex in single quotation marks(`'`)
+* Escaped backslash in double quotation marks(`"`)
+* Using folded block scalar followed by a dash (`>-`) without any quotation marks
+
+See examples below which correspond to the same regex:
+
+.. code-block:: yaml
+
+    gathered_filter: 'name matches-regex \sPAN\s'
+
+.. code-block:: yaml
+
+    gathered_filter: "name matches-regex \\sPAN\\s"
+
+.. code-block:: yaml
+
+    gathered_filter: >-
+      name matches-regex \sPAN\s
+
+
 Example - Matching a Suffix
 ---------------------------
 

plugins/module_utils/panos.py

@@ -1200,6 +1200,18 @@ def _get_default_value(self, obj, key):
 
         return default_value
 
+    def _shlex_split(self, logic):
+        """Split string using shlex.split without escape char
+
+        Escape char '\' is removed from shlex class to correctly process regex.
+        """
+        lex = shlex.shlex(logic, posix=True)
+        lex.whitespace_split = True
+        lex.commenters = ""
+        lex.escape = ""
+
+        return list(lex)
+
     def matches_gathered_filter(self, item, logic):
         """Returns True if the item and its contents matches the logic given.
 
@@ -1223,7 +1235,7 @@ def matches_gathered_filter(self, item, logic):
         evaler = []
 
         pdepth = 0
-        logic_tokens = shlex.split(logic)
+        logic_tokens = self._shlex_split(logic)
         token_iter = iter(logic_tokens)
         while True:
             end_parens = 0