Add check-docstring-first hook.
diff --git a/pre_commit_hooks/check_docstring_first.py b/pre_commit_hooks/check_docstring_first.py
new file mode 100644
index 0000000..da5425d
--- /dev/null
+++ b/pre_commit_hooks/check_docstring_first.py
@@ -0,0 +1,63 @@
+from __future__ import absolute_import
+from __future__ import unicode_literals
+
+import argparse
+import io
+import tokenize
+
+
+NON_CODE_TOKENS = frozenset((
+ tokenize.COMMENT, tokenize.ENDMARKER, tokenize.NEWLINE, tokenize.NL,
+))
+
+
+def check_docstring_first(src, filename='<unknown>'):
+ """Returns nonzero if the source has what looks like a docstring that is
+ not at the beginning of the source.
+
+ A string will be considered a docstring if it is a STRING token with a
+ col offset of 0.
+ """
+ found_docstring_line = None
+ found_code_line = None
+
+ tok_gen = tokenize.generate_tokens(io.StringIO(src).readline)
+ for tok_type, _, (sline, scol), _, _ in tok_gen:
+ # Looks like a docstring!
+ if tok_type == tokenize.STRING and scol == 0:
+ if found_docstring_line is not None:
+ print(
+ '{0}:{1} Multiple module docstrings '
+ '(first docstring on line {2}).'.format(
+ filename, sline, found_docstring_line,
+ )
+ )
+ return 1
+ elif found_code_line is not None:
+ print(
+ '{0}:{1} Module docstring appears after code '
+ '(code seen on line {2}).'.format(
+ filename, sline, found_code_line,
+ )
+ )
+ return 1
+ else:
+ found_docstring_line = sline
+ elif tok_type not in NON_CODE_TOKENS and found_code_line is None:
+ found_code_line = sline
+
+ return 0
+
+
+def main(argv=None):
+ parser = argparse.ArgumentParser()
+ parser.add_argument('filenames', nargs='*')
+ args = parser.parse_args(argv)
+
+ retv = 0
+
+ for filename in args.filenames:
+ contents = io.open(filename).read()
+ retv |= check_docstring_first(contents, filename=filename)
+
+ return retv
