Merge pull request #218 from helenst/git-hook

Added git hook and documentation

4 files changed, 103 insertions, 1 deletions

diff --git a/ACKNOWLEDGEMENTS.md b/ACKNOWLEDGEMENTS.md
index 51a96dc6..bda4b724 100644
--- a/ACKNOWLEDGEMENTS.md
+++ b/ACKNOWLEDGEMENTS.md
@@ -38,6 +38,7 @@ Code Contributors
 - Elliott Sales de Andrade (@qulogic)
 - Kasper Jacobsen (@dinoshauer)
 - Sebastian Pipping (@hartwork)
+- Helen Sherwood-Taylor (@helenst)
 
 --------------------------------------------
 
diff --git a/README.md b/README.md
index 7a5f4ef7..e32d334e 100644
--- a/README.md
+++ b/README.md
@@ -391,6 +391,25 @@ https://gist.github.com/acdha/8717683
 
 Which can help to ensure a certain level of code quality throughout a project.
 
+
+Git hook
+========
+
+isort provides a hook function that can be integrated into your Git pre-commit script to check
+Python code before committing.
+
+To cause the commit to fail if there are isort errors (strict mode), include the following in
+`.git/hooks/pre-commit`:
+
+    from isort.hooks import git_hook
+
+    if __name__ == '__main__':
+        sys.exit(git_hook(strict=True))
+
+If you just want to display warnings, but allow the commit to happen anyway, call git_hook without
+the `strict` parameter.
+
+
 Why isort?
 ======================
 
diff --git a/isort/hooks.py b/isort/hooks.py
new file mode 100644
index 00000000..15b6d408
--- /dev/null
+++ b/isort/hooks.py
@@ -0,0 +1,82 @@
+"""isort.py.
+
+Defines a git hook to allow pre-commit warnings and errors about import order.
+
+usage:
+    exit_code = git_hook(strict=True)
+
+Copyright (C) 2015  Helen Sherwood-Taylor
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated
+documentation files (the "Software"), to deal in the Software without restriction, including without limitation
+the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and
+to permit persons to whom the Software is furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all copies or
+substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
+TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF
+CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+OTHER DEALINGS IN THE SOFTWARE.
+
+"""
+import subprocess
+
+from isort import SortImports
+
+
+def get_output(command):
+    """
+    Run a command and return raw output
+
+    :param str command: the command to run
+    :returns: the stdout output of the command
+    """
+    return subprocess.check_output(command.split())
+
+
+def get_lines(command):
+    """
+    Run a command and return lines of output
+
+    :param str command: the command to run
+    :returns: list of whitespace-stripped lines output by command
+    """
+    stdout = get_output(command)
+    return [line.strip().decode('utf-8') for line in stdout.splitlines()]
+
+
+def git_hook(strict=False):
+    """
+    Git pre-commit hook to check staged files for isort errors
+
+    :param bool strict - if True, return number of errors on exit,
+        causing the hook to fail. If False, return zero so it will
+        just act as a warning.
+
+    :return number of errors if in strict mode, 0 otherwise.
+    """
+
+    # Get list of files modified and staged
+    diff_cmd = "git diff-index --cached --name-only --diff-filter=ACMRTUXB HEAD"
+    files_modified = get_lines(diff_cmd)
+
+    errors = 0
+    for filename in files_modified:
+        if filename.endswith('.py'):
+            # Get the staged contents of the file
+            staged_cmd = "git show :%s" % filename
+            staged_contents = get_output(staged_cmd)
+
+            sort = SortImports(
+                file_path=filename,
+                file_contents=staged_contents.decode(),
+                check=True
+            )
+
+            if sort.incorrectly_sorted:
+                errors += 1
+
+    return errors if strict else 0
diff --git a/isort/isort.py b/isort/isort.py
index 6b6518eb..d7a3a71b 100644
--- a/isort/isort.py
+++ b/isort/isort.py
@@ -83,7 +83,7 @@ class SortImports(object):
 
         file_name = file_path
         self.file_path = file_path or ""
-        if file_path:
+        if file_path and not file_contents:
             file_path = os.path.abspath(file_path)
             if self._should_skip(file_path):
                 if self.config['verbose']: