[util] add "defaultdict" filters-environment

allows accessing undefined values without raising an exception,
but preserves other errors like TypeError, AttributeError, etc

docs/configuration.rst

@@ -6855,13 +6855,22 @@ Description
 filters-environment
 -------------------
 Type
-    ``bool``
+    * ``bool``
+    * ``string``
 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.
+    Evaluate filter expressions in a special environment
+    preventing them from raising fatal exceptions.
+
+    ``true`` or ``"tryexcept"``:
+        Wrap expressions in a `try`/`except` block;
+        Evaluate expressions raising an exception as ``false``
+    ``false`` or ``"raw"``:
+        Do not wrap expressions in a special environment
+    ``"defaultdict"``:
+        Prevent exceptions when accessing undefined variables
+        by using a `defaultdict <https://docs.python.org/3/library/collections.html#collections.defaultdict>`__
 
 
 format-separator

gallery_dl/__init__.py

@@ -107,8 +107,15 @@ def main():
 
         # filter environment
         filterenv = config.get((), "filters-environment", True)
-        if not filterenv:
+        if filterenv is True:
+            pass
+        elif not filterenv:
             util.compile_expression = util.compile_expression_raw
+        elif isinstance(filterenv, str):
+            if filterenv == "raw":
+                util.compile_expression = util.compile_expression_raw
+            elif filterenv.startswith("default"):
+                util.compile_expression = util.compile_expression_defaultdict
 
         # format string separator
         separator = config.get((), "format-separator")

gallery_dl/util.py

@@ -21,6 +21,7 @@ import datetime
 import functools
 import itertools
 import subprocess
+import collections
 import urllib.parse
 from http.cookiejar import Cookie
 from email.utils import mktime_tz, parsedate_tz
@@ -702,6 +703,20 @@ def compile_expression_raw(expr, name="<expr>", globals=None):
     return functools.partial(eval, code_object, globals or GLOBALS)
 
 
+def compile_expression_defaultdict(expr, name="<expr>", globals=None):
+    global GLOBALS_DEFAULT
+    GLOBALS_DEFAULT = collections.defaultdict(lambda: NONE, GLOBALS)
+
+    global compile_expression_defaultdict
+    compile_expression_defaultdict = compile_expression_defaultdict_impl
+    return compile_expression_defaultdict_impl(expr, name, globals)
+
+
+def compile_expression_defaultdict_impl(expr, name="<expr>", globals=None):
+    code_object = compile(expr, name, "eval")
+    return functools.partial(eval, code_object, globals or GLOBALS_DEFAULT)
+
+
 def compile_expression_tryexcept(expr, name="<expr>", globals=None):
     code_object = compile(expr, name, "eval")
 
@@ -711,7 +726,7 @@ def compile_expression_tryexcept(expr, name="<expr>", globals=None):
         except exception.GalleryDLException:
             raise
         except Exception:
-            return False
+            return NONE
 
     return _eval
 

test/test_util.py

@@ -300,6 +300,87 @@ class TestCookiesTxt(unittest.TestCase):
         )
 
 
+class TestCompileExpression(unittest.TestCase):
+
+    def test_compile_expression(self):
+        expr = util.compile_expression("1 + 2 * 3")
+        self.assertEqual(expr(), 7)
+        self.assertEqual(expr({"a": 1, "b": 2, "c": 3}), 7)
+        self.assertEqual(expr({"a": 9, "b": 9, "c": 9}), 7)
+
+        expr = util.compile_expression("a + b * c")
+        self.assertEqual(expr({"a": 1, "b": 2, "c": 3}), 7)
+        self.assertEqual(expr({"a": 9, "b": 9, "c": 9}), 90)
+
+        with self.assertRaises(SyntaxError):
+            util.compile_expression("")
+        with self.assertRaises(SyntaxError):
+            util.compile_expression("x++")
+
+        expr = util.compile_expression("1 and abort()")
+        with self.assertRaises(exception.StopExtraction):
+            expr()
+
+    def test_compile_expression_raw(self):
+        expr = util.compile_expression_raw("a + b * c")
+        with self.assertRaises(NameError):
+            expr()
+        with self.assertRaises(NameError):
+            expr({"a": 2})
+
+        expr = util.compile_expression_defaultdict("int.param")
+        with self.assertRaises(AttributeError):
+            expr({"a": 2})
+
+    def test_compile_expression_tryexcept(self):
+        expr = util.compile_expression_tryexcept("a + b * c")
+        self.assertIs(expr(), util.NONE)
+        self.assertIs(expr({"a": 2}), util.NONE)
+
+        expr = util.compile_expression_tryexcept("int.param")
+        self.assertIs(expr({"a": 2}), util.NONE)
+
+    def test_compile_expression_defaultdict(self):
+        expr = util.compile_expression_defaultdict("a + b * c")
+        self.assertIs(expr(), util.NONE)
+        self.assertIs(expr({"a": 2}), util.NONE)
+
+        expr = util.compile_expression_defaultdict("int.param")
+        with self.assertRaises(AttributeError):
+            expr({"a": 2})
+
+    def test_custom_globals(self):
+        value = {"v": "foobar"}
+        result = "8843d7f92416211de9ebb963ff4ce28125932878"
+
+        expr = util.compile_expression("hash_sha1(v)")
+        self.assertEqual(expr(value), result)
+
+        expr = util.compile_expression("hs(v)", globals={"hs": util.sha1})
+        self.assertEqual(expr(value), result)
+
+        with tempfile.TemporaryDirectory() as path:
+            file = path + "/module_sha1.py"
+            with open(file, "w") as fp:
+                fp.write("""
+import hashlib
+def hash(value):
+    return hashlib.sha1(value.encode()).hexdigest()
+""")
+            module = util.import_file(file)
+
+        expr = util.compile_expression("hash(v)", globals=module.__dict__)
+        self.assertEqual(expr(value), result)
+
+        GLOBALS_ORIG = util.GLOBALS
+        try:
+            util.GLOBALS = module.__dict__
+            expr = util.compile_expression("hash(v)")
+        finally:
+            util.GLOBALS = GLOBALS_ORIG
+        self.assertEqual(expr(value), result)
+
+
 class TestOther(unittest.TestCase):
 
     def test_bencode(self):
@@ -434,31 +515,6 @@ class TestOther(unittest.TestCase):
         self.assertEqual(util.sha1(None),
                          "da39a3ee5e6b4b0d3255bfef95601890afd80709")
 
-    def test_compile_expression(self):
-        expr = util.compile_expression("1 + 2 * 3")
-        self.assertEqual(expr(), 7)
-        self.assertEqual(expr({"a": 1, "b": 2, "c": 3}), 7)
-        self.assertEqual(expr({"a": 9, "b": 9, "c": 9}), 7)
-
-        expr = util.compile_expression("a + b * c")
-        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):
-            expr({"a": 2})
-
-        with self.assertRaises(SyntaxError):
-            util.compile_expression("")
-        with self.assertRaises(SyntaxError):
-            util.compile_expression("x++")
-
-        expr = util.compile_expression("1 and abort()")
-        with self.assertRaises(exception.StopExtraction):
-            expr()
-
     def test_import_file(self):
         module = util.import_file("datetime")
         self.assertIs(module, datetime)
@@ -478,37 +534,6 @@ value = 123
         self.assertEqual(module.value, 123)
         self.assertIs(module.datetime, datetime)
 
-    def test_custom_globals(self):
-        value = {"v": "foobar"}
-        result = "8843d7f92416211de9ebb963ff4ce28125932878"
-
-        expr = util.compile_expression("hash_sha1(v)")
-        self.assertEqual(expr(value), result)
-
-        expr = util.compile_expression("hs(v)", globals={"hs": util.sha1})
-        self.assertEqual(expr(value), result)
-
-        with tempfile.TemporaryDirectory() as path:
-            file = path + "/module_sha1.py"
-            with open(file, "w") as fp:
-                fp.write("""
-import hashlib
-def hash(value):
-    return hashlib.sha1(value.encode()).hexdigest()
-""")
-            module = util.import_file(file)
-
-        expr = util.compile_expression("hash(v)", globals=module.__dict__)
-        self.assertEqual(expr(value), result)
-
-        GLOBALS_ORIG = util.GLOBALS
-        try:
-            util.GLOBALS = module.__dict__
-            expr = util.compile_expression("hash(v)")
-        finally:
-            util.GLOBALS = GLOBALS_ORIG
-        self.assertEqual(expr(value), result)
-
     def test_build_duration_func(self, f=util.build_duration_func):
 
         def test_single(df, v):