wrap filters/conditionals in a try-except block

allows accessing undefined fields without exception or locals().get(…)
but hides mistakes/typos/etc by evaluating to False without feedback

performance loss compared to the previous version without try-except
is negligible (~20ns for me)

docs/configuration.rst

@@ -6085,6 +6085,18 @@ Description
     this cache.
 
 
+filters-environment
+-------------------
+Type
+    ``bool``
+Default
+    ``true``
+Description
+    Evaluate filter expressions raising an exception as ``false``
+    instead of aborting the current extractor run
+    by wrapping them in a `try`/`except` block.
+
+
 format-separator
 ----------------
 Type

gallery_dl/__init__.py

@@ -105,6 +105,11 @@ def main():
 
             output.ANSI = True
 
+        # filter environment
+        filterenv = config.get((), "filters-environment", True)
+        if not filterenv:
+            util.compile_expression = util.compile_expression_raw
+
         # format string separator
         separator = config.get((), "format-separator")
         if separator:

gallery_dl/util.py

@@ -616,11 +616,28 @@ else:
     Popen = subprocess.Popen
 
 
-def compile_expression(expr, name="<expr>", globals=None):
+def compile_expression_raw(expr, name="<expr>", globals=None):
     code_object = compile(expr, name, "eval")
     return functools.partial(eval, code_object, globals or GLOBALS)
 
 
+def compile_expression_tryexcept(expr, name="<expr>", globals=None):
+    code_object = compile(expr, name, "eval")
+
+    def _eval(locals=None, globals=(globals or GLOBALS), co=code_object):
+        try:
+            return eval(co, globals, locals)
+        except exception.GalleryDLException:
+            raise
+        except Exception:
+            return False
+
+    return _eval
+
+
+compile_expression = compile_expression_tryexcept
+
+
 def import_file(path):
     """Import a Python module from a filesystem path"""
     path, name = os.path.split(path)

test/test_util.py

@@ -134,19 +134,18 @@ class TestPredicate(unittest.TestCase):
         with self.assertRaises(SyntaxError):
             util.FilterPredicate("(")
 
-        with self.assertRaises(exception.FilterError):
-            util.FilterPredicate("a > 1")(url, {"a": None})
-
-        with self.assertRaises(exception.FilterError):
-            util.FilterPredicate("b > 1")(url, {"a": 2})
+        self.assertFalse(
+            util.FilterPredicate("a > 1")(url, {"a": None}))
+        self.assertFalse(
+            util.FilterPredicate("b > 1")(url, {"a": 2}))
 
         pred = util.FilterPredicate(["a < 3", "b < 4", "c < 5"])
         self.assertTrue(pred(url, {"a": 2, "b": 3, "c": 4}))
         self.assertFalse(pred(url, {"a": 3, "b": 3, "c": 4}))
         self.assertFalse(pred(url, {"a": 2, "b": 4, "c": 4}))
         self.assertFalse(pred(url, {"a": 2, "b": 3, "c": 5}))
-        with self.assertRaises(exception.FilterError):
-            pred(url, {"a": 2})
+
+        self.assertFalse(pred(url, {"a": 2}))
 
     def test_build_predicate(self):
         pred = util.build_predicate([])
@@ -445,6 +444,7 @@ class TestOther(unittest.TestCase):
         self.assertEqual(expr({"a": 1, "b": 2, "c": 3}), 7)
         self.assertEqual(expr({"a": 9, "b": 9, "c": 9}), 90)
 
+        expr = util.compile_expression_raw("a + b * c")
         with self.assertRaises(NameError):
             expr()
         with self.assertRaises(NameError):