Refactor to not leak global state

Author: Talha Malik

jsonschema/cli.py

@@ -22,8 +22,8 @@ def _json_file(path):
         return json.load(file)
 
 
-def _read_from_stdin():
-    return json.loads(sys.stdin.read())
+def _read_from_stdin(stdin):
+    return json.loads(stdin.read())
 
 
 parser = argparse.ArgumentParser(
@@ -80,14 +80,14 @@ def main(args=sys.argv[1:]):
     sys.exit(run(arguments=parse_args(args=args)))
 
 
-def run(arguments, stdout=sys.stdout, stderr=sys.stderr):
+def run(arguments, stdout=sys.stdout, stderr=sys.stderr, stdin=sys.stdin):
     error_format = arguments["error_format"]
     validator = arguments["validator"](schema=arguments["schema"])
 
     validator.check_schema(arguments["schema"])
 
     errored = False
-    for instance in arguments["instances"] or (_read_from_stdin(),):
+    for instance in arguments["instances"] or (_read_from_stdin(stdin),):
         for error in validator.iter_errors(instance):
             stderr.write(error_format.format(error=error))
             errored = True

jsonschema/tests/test_cli.py

@@ -3,11 +3,6 @@
 import subprocess
 import sys
 
-try:
-    from StringIO import StringIO
-except ImportError:
-    from io import StringIO
-
 from jsonschema import Draft4Validator, ValidationError, cli, __version__
 from jsonschema.compat import NativeIO
 from jsonschema.exceptions import SchemaError
@@ -156,8 +151,7 @@ def test_version(self):
         self.assertEqual(version, __version__)
 
     def test_piping(self):
-        sys.stdin = StringIO("{}")
-        stdout, stderr = NativeIO(), NativeIO()
+        stdout, stderr, stdin = NativeIO(), NativeIO(), NativeIO("{}")
         exit_code = cli.run(
             {
                 "validator": fake_validator(),
@@ -167,6 +161,7 @@ def test_piping(self):
             },
             stdout=stdout,
             stderr=stderr,
+            stdin=stdin,
         )
         self.assertFalse(stdout.getvalue())
         self.assertFalse(stderr.getvalue())