fix pattern lookup match escaping on F expressions

[timgraham]

Escape $regexMatch special characters instead of LIKE special chars.

This is complemented by a patch to the Django fork which fails unless each of these replacements are made:

diff --git a/tests/expressions/tests.py b/tests/expressions/tests.py
index 36624649e5..60c88e42e2 100644
--- a/tests/expressions/tests.py
+++ b/tests/expressions/tests.py
@@ -1229,6 +1229,17 @@ class ExpressionsTests(TestCase):
                 Employee(firstname="Jean-Claude", lastname="Claude%"),
                 Employee(firstname="Johnny", lastname="Joh\\n"),
                 Employee(firstname="Johnny", lastname="_ohn"),
+                Employee(firstname="Johnny", lastname="^Joh"),
+                Employee(firstname="Johnny", lastname="Johnny$"),
+                Employee(firstname="Johnny", lastname="Joh."),
+                Employee(firstname="Johnny", lastname="[J]ohnny"),
+                Employee(firstname="Johnny", lastname="(J)ohnny"),
+                Employee(firstname="Johnny", lastname="J*ohnny"),
+                Employee(firstname="Johnny", lastname="J+ohnny"),
+                Employee(firstname="Johnny", lastname="J?ohnny"),
+                Employee(firstname="Johnny", lastname="J{1}ohnny"),
+                Employee(firstname="Johnny", lastname="J|ohnny"),
+                Employee(firstname="Johnny", lastname="J-ohnny"),
             ]
         )
         claude = Employee.objects.create(firstname="Jean-Claude", lastname="Claude")

[WaVEV]

Is it ready to review?

[Jibola]

So this will trigger 13 $replaceAll calls when doing lookups?

[WaVEV]

is there a way to do that replacements in python? and pass the final string. if it is, so we can use re.escape .

[timgraham]

When the value to be matched is a string, re.escape() handles it. This code is only for the case when regexMatch's regex is a column.