Fix cli bug about getting arguments["validator"].

jsonschema/cli.py

@@ -191,8 +191,6 @@ def _namedAnyWithDefault(name):
 
 def parse_args(args):
     arguments = vars(parser.parse_args(args=args or ["--help"]))
-    if arguments["validator"] is None:
-        arguments["validator"] = validator_for(arguments["schema"])
     if arguments["output"] != "plain" and arguments["error_format"]:
         raise parser.error(
             "--error-format can only be used with --output plain"
@@ -229,6 +227,9 @@ def run(arguments, stdout=sys.stdout, stderr=sys.stderr, stdin=sys.stdin):
     except _CannotLoadFile:
         return 1
 
+    if arguments["validator"] is None:
+        arguments["validator"] = validator_for(schema)
+
     try:
         arguments["validator"].check_schema(schema)
     except SchemaError as error:

jsonschema/tests/test_cli.py

@@ -11,7 +11,7 @@
 from jsonschema import Draft4Validator, __version__, cli
 from jsonschema.exceptions import SchemaError, ValidationError
 from jsonschema.tests._helpers import captured_output
-from jsonschema.validators import _LATEST_VERSION, validate
+from jsonschema.validators import _LATEST_VERSION, validate, validator_for
 
 
 def fake_validator(*errors):
@@ -691,6 +691,47 @@ def test_real_validator(self):
             stderr="",
         )
 
+    def test_draft07_check_const(self):
+        schema = """
+                {
+                    "$schema": "http://json-schema.org/draft-07/schema#",
+                    "properties": {
+                        "value": {
+                            "type": "string",
+                            "const": "check"
+                        }
+                    }
+                }
+                """
+        instance = """{"value": "2"}"""
+        self.assertOutputs(
+            files=dict(some_schema=schema, some_instance=instance),
+            argv=["-i", "some_instance", "some_schema"],
+            exit_code=1,
+            stdout="",
+            stderr="2: 'check' was expected\n",
+        )
+
+    def test_draft04_not_check_const(self):
+        schema = """
+                {
+                    "$schema": "http://json-schema.org/draft-04/schema#",
+                    "properties": {
+                        "value": {
+                            "type": "string",
+                            "const": "check"
+                        }
+                    }
+                }
+                """
+        instance = """{"value": "2"}"""
+        self.assertOutputs(
+            files=dict(some_schema=schema, some_instance=instance),
+            argv=["-i", "some_instance", "some_schema"],
+            stdout="",
+            stderr="",
+        )
+
 
 class TestParser(TestCase):
 
@@ -724,6 +765,7 @@ def test_latest_validator_is_the_default(self):
                 "mem://some/schema",
             ]
         )
+        arguments["validator"] = validator_for(arguments["schema"])
         self.assertIs(arguments["validator"], _LATEST_VERSION)
 
     def test_unknown_output(self):