Fix nargs=REMAINDER and empty value issues (#285, #296)

configargparse.py

@@ -956,6 +956,10 @@ def parse_known_args(
         for action in actions_with_env_var_values:
             key = action.env_var
             value = env_vars[key]
+            # Skip empty string env vars for args with nargs to match YAML behavior
+            # where empty values are treated as None/not present (see issue #296)
+            if value == "" and action.nargs:
+                continue
             # Make list-string into list.
             if action.nargs or isinstance(action, argparse._AppendAction):
                 nargs = True
@@ -968,10 +972,24 @@ def parse_known_args(
                         value = [elem.strip() for elem in value[1:-1].split(",")]
             env_var_args += self.convert_item_to_command_line_arg(action, key, value)
 
-        if nargs:
-            args = args + env_var_args
+        # Insert env var args before the first optional arg (starts with -)
+        # to preserve -- separator and positional args that come after it.
+        insertion_index = 0
+        for i, arg in enumerate(args):
+            if arg.startswith(tuple(self.prefix_chars)):
+                insertion_index = i
+                break
         else:
-            args = env_var_args + args
+            # No optional args found. Check if any positional arg uses REMAINDER.
+            # If so, prepend config args to avoid them being consumed by REMAINDER.
+            # Otherwise, append to end (original behavior) to avoid issues with
+            # nargs="+" consuming positional args.
+            has_remainder = any(
+                a.is_positional_arg and a.nargs == argparse.REMAINDER
+                for a in self._actions
+            )
+            insertion_index = 0 if has_remainder else len(args)
+        args = args[:insertion_index] + env_var_args + args[insertion_index:]
 
         if env_var_args:
             self._source_to_settings[_ENV_VAR_SOURCE_KEY] = OrderedDict(
@@ -1039,6 +1057,11 @@ def parse_known_args(
                         )
                     )
 
+                # Skip empty string values for args with nargs to match YAML behavior
+                # where empty values are treated as None/not present (see issue #296)
+                if value == "" and action and action.nargs:
+                    continue
+
                 if not discard_this_key:
                     config_args += self.convert_item_to_command_line_arg(
                         action, key, value
@@ -1054,10 +1077,24 @@ def parse_known_args(
                     ):
                         nargs = True
 
-            if nargs:
-                args = args + config_args
+            # Insert config args before the first optional arg (starts with -)
+            # to preserve -- separator and positional args that come after it.
+            insertion_index = 0
+            for i, arg in enumerate(args):
+                if arg.startswith(tuple(self.prefix_chars)):
+                    insertion_index = i
+                    break
             else:
-                args = config_args + args
+                # No optional args found. Check if any positional arg uses REMAINDER.
+                # If so, prepend config args to avoid them being consumed by REMAINDER.
+                # Otherwise, append to end (original behavior) to avoid issues with
+                # nargs="+" consuming positional args.
+                has_remainder = any(
+                    a.is_positional_arg and a.nargs == argparse.REMAINDER
+                    for a in self._actions
+                )
+                insertion_index = 0 if has_remainder else len(args)
+            args = args[:insertion_index] + config_args + args[insertion_index:]
 
         # save default settings for use by print_values()
         default_settings = OrderedDict()

tests/test_configargparse.py

@@ -1344,6 +1344,83 @@ def error_func(path):
             args="-g file.txt",
         )
 
+    def testRemainderWithConfigFile(self):
+        """Test that nargs=REMAINDER works correctly with config files.
+        Regression test for issue #285."""
+        # Create a config file
+        config_file = tempfile.NamedTemporaryFile(mode="w", delete=False, suffix=".cfg")
+        config_file.write("config_file_option=value_from_config\n")
+        config_file.flush()
+        config_file.close()
+
+        try:
+            self.initParser()
+            self.parser.add_argument(
+                "--config", is_config_file=True, default=config_file.name
+            )
+            self.parser.add_argument("--config_file_option", nargs="*", default=None)
+            self.parser.add_argument(
+                "remainder_option", nargs=argparse.REMAINDER, default=None
+            )
+
+            # Test that REMAINDER doesn't swallow config file args
+            ns = self.parse(args=["test"])
+            self.assertEqual(ns.remainder_option, ["test"])
+            self.assertEqual(ns.config_file_option, ["value_from_config"])
+
+            # Test with multiple remainder args
+            ns = self.parse(args=["test", "arg1", "arg2"])
+            self.assertEqual(ns.remainder_option, ["test", "arg1", "arg2"])
+            self.assertEqual(ns.config_file_option, ["value_from_config"])
+
+        finally:
+            os.unlink(config_file.name)
+
+    def testEmptyValuesIgnored(self):
+        """Test that empty string values from config files and env vars are ignored.
+        Regression test for issue #296."""
+        # Test 1: Empty value in config file
+        config_file = tempfile.NamedTemporaryFile(
+            mode="w", delete=False, suffix=".conf"
+        )
+        config_file.write("test-opt=\n")  # Empty value
+        config_file.flush()
+        config_file.close()
+
+        try:
+            self.initParser()
+            self.parser.add_argument(
+                "--config", is_config_file=True, default=config_file.name
+            )
+            self.parser.add_argument(
+                "--test-opt", nargs=2, default=["default1", "default2"]
+            )
+
+            # Empty config value should be ignored, default should be used
+            ns = self.parse(args=[])
+            self.assertEqual(ns.test_opt, ["default1", "default2"])
+
+        finally:
+            os.unlink(config_file.name)
+
+        # Test 2: Empty environment variable
+        self.initParser()
+        self.parser.add_argument(
+            "--test-opt", nargs=2, env_var="TEST_OPT", default=["default1", "default2"]
+        )
+
+        old_env = os.environ.get("TEST_OPT")
+        try:
+            os.environ["TEST_OPT"] = ""  # Empty env var
+            # Empty env var should be ignored, default should be used
+            ns = self.parse(args=[])
+            self.assertEqual(ns.test_opt, ["default1", "default2"])
+        finally:
+            if old_env is not None:
+                os.environ["TEST_OPT"] = old_env
+            elif "TEST_OPT" in os.environ:
+                del os.environ["TEST_OPT"]
+
 
 class TestConfigFileParsers(TestCase):
     """Test ConfigFileParser subclasses in isolation"""