Add check to enforce literal syntax for Python builtin types
This check requires authors to initialize empty or zero builtin types
using the literal syntax (e.g., `{}` instead of `dict()`).
Authors may ignore this requirement for certain builtins using the
`--ignore` option.
Authors may also forbid calling `dict()` with keyword arguments
(`dict(a=1, b=2)`) using the `--no-allow-dict-kwargs` flag.
diff --git a/pre_commit_hooks/check_builtin_literals.py b/pre_commit_hooks/check_builtin_literals.py
new file mode 100644
index 0000000..1213288
--- /dev/null
+++ b/pre_commit_hooks/check_builtin_literals.py
@@ -0,0 +1,90 @@
+from __future__ import unicode_literals
+
+import argparse
+import ast
+import collections
+import sys
+
+
+BUILTIN_TYPES = {
+ 'complex': '0j',
+ 'dict': '{}',
+ 'float': '0.0',
+ 'int': '0',
+ 'list': '[]',
+ 'str': "''",
+ 'tuple': '()',
+}
+
+
+BuiltinTypeCall = collections.namedtuple('BuiltinTypeCall', ['name', 'line', 'column'])
+
+
+class BuiltinTypeVisitor(ast.NodeVisitor):
+ def __init__(self, ignore=None, allow_dict_kwargs=True):
+ self.builtin_type_calls = []
+ self.ignore = set(ignore) if ignore else set()
+ self.allow_dict_kwargs = allow_dict_kwargs
+
+ def _check_dict_call(self, node):
+ return self.allow_dict_kwargs and (getattr(node, 'kwargs', None) or getattr(node, 'keywords', None))
+
+ def visit_Call(self, node):
+ if node.func.id not in set(BUILTIN_TYPES).difference(self.ignore):
+ return
+ if node.func.id == 'dict' and self._check_dict_call(node):
+ return
+ elif node.args:
+ return
+ self.builtin_type_calls.append(
+ BuiltinTypeCall(node.func.id, node.lineno, node.col_offset),
+ )
+
+
+def check_file_for_builtin_type_constructors(filename, ignore=None, allow_dict_kwargs=True):
+ tree = ast.parse(open(filename, 'rb').read(), filename=filename)
+ visitor = BuiltinTypeVisitor(ignore=ignore, allow_dict_kwargs=allow_dict_kwargs)
+ visitor.visit(tree)
+ return visitor.builtin_type_calls
+
+
+def parse_args(argv):
+ def parse_ignore(value):
+ return set(value.split(','))
+
+ parser = argparse.ArgumentParser()
+ parser.add_argument('filenames', nargs='*')
+ parser.add_argument('--ignore', type=parse_ignore, default=set())
+
+ allow_dict_kwargs = parser.add_mutually_exclusive_group(required=False)
+ allow_dict_kwargs.add_argument('--allow-dict-kwargs', action='store_true')
+ allow_dict_kwargs.add_argument('--no-allow-dict-kwargs', dest='allow_dict_kwargs', action='store_false')
+ allow_dict_kwargs.set_defaults(allow_dict_kwargs=True)
+
+ return parser.parse_args(argv)
+
+
+def main(argv=None):
+ args = parse_args(argv)
+ rc = 0
+ for filename in args.filenames:
+ calls = check_file_for_builtin_type_constructors(
+ filename,
+ ignore=args.ignore,
+ allow_dict_kwargs=args.allow_dict_kwargs,
+ )
+ if calls:
+ rc = rc or 1
+ for call in calls:
+ print(
+ '{filename}:{call.line}:{call.column} - Replace {call.name}() with {replacement}'.format(
+ filename=filename,
+ call=call,
+ replacement=BUILTIN_TYPES[call.name],
+ ),
+ )
+ return rc
+
+
+if __name__ == '__main__':
+ sys.exit(main())
