fix(cql2-text): unescape the quotes of strings

pygeofilter/parsers/cql2_text/grammar.lark

@@ -135,7 +135,8 @@ bbox: "BBOX"i "(" full_number "," full_number "," full_number "," full_number ")
 BOOLEAN.2: ( "TRUE"i | "FALSE"i)
 
 DOUBLE_QUOTED: "\"" /.*?/ "\""
-SINGLE_QUOTED: "'" /.*?/ "'"
+// CQL2 escapes a quote as '' or \'
+SINGLE_QUOTED: /'(?:[^'\\]|\\.|'')*'/
 
 DATE: /[0-9]{4}-?[0-1][0-9]-?[0-3][0-9]/
 DATETIME: /[0-9]{4}-?[0-1][0-9]-?[0-3][0-9][T ][0-2][0-9]:?[0-5][0-9]:?[0-5][0-9](\.[0-9]+)?(Z|[+-][0-9]{2}:[0-9]{2})?/

pygeofilter/parsers/cql2_text/parser.py

@@ -27,6 +27,7 @@
 
 import logging
 import os.path
+import re
 
 from lark import Lark, logger, v_args
 
@@ -185,7 +186,13 @@ def DOUBLE_QUOTED(self, token):
         return token[1:-1]
 
     def SINGLE_QUOTED(self, token):
-        return token[1:-1]
+        # '' and \' stand for a quote, the other backslashes are kept for LIKE
+        return re.sub(
+            r"''|\\(.)",
+            lambda m: "'" if m[0] == "''" or m[1] == "'" else m[0],
+            token[1:-1],
+            flags=re.S,
+        )
 
     def geometry(self, value):
         return values.Geometry(value)

tests/parsers/cql2_text/test_parser.py

@@ -175,6 +175,36 @@ def test_string_not_like():
     )
 
 
+def test_string_doubled_quote():
+    result = parse("attr = 'it''s'")
+    assert result == ast.Equal(ast.Attribute("attr"), "it's")
+
+
+def test_string_backslash_quote():
+    result = parse(r"attr = 'it\'s'")
+    assert result == ast.Equal(ast.Attribute("attr"), "it's")
+
+
+def test_string_only_quotes():
+    assert parse("attr = ''") == ast.Equal(ast.Attribute("attr"), "")
+    assert parse("attr = ''''") == ast.Equal(ast.Attribute("attr"), "'")
+
+
+def test_strings_end_at_their_quote():
+    result = parse("attr = 'a' OR attr = 'b'")
+    assert result == ast.Or(
+        ast.Equal(ast.Attribute("attr"), "a"),
+        ast.Equal(ast.Attribute("attr"), "b"),
+    )
+
+
+def test_string_like_keeps_backslashes():
+    result = parse(r"attr LIKE '100\%'")
+    assert result.pattern == r"100\%"
+    result = parse(r"attr LIKE 'a\\''%'")
+    assert result.pattern == r"a\\'%"
+
+
 def test_attribute_in_list():
     result = parse("attr IN (1, 2, 3, 4)")
     assert result == ast.In(