1 files changed, 109 insertions, 0 deletions
diff --git a/.gitlab/linters/linter.py b/.gitlab/linters/linter.py
new file mode 100644
index 0000000000..ec4f3581a8
--- /dev/null
+++ b/.gitlab/linters/linter.py
@@ -0,0 +1,109 @@
+"""
+Utilities for linters
+"""
+
+import os
+import sys
+import re
+import textwrap
+import subprocess
+from typing import List, Optional
+from collections import namedtuple
+
+def lint_failure(file, line_no, line_content, message):
+    """ Print a lint failure message. """
+    wrapper = textwrap.TextWrapper(initial_indent='  ',
+                                   subsequent_indent='    ')
+    body = wrapper.fill(message)
+    msg = '''
+    {file}:
+
+             |
+      {line_no:5d}  |  {line_content}
+             |
+
+    {body}
+    '''.format(file=file, line_no=line_no,
+               line_content=line_content,
+               body=body)
+
+    print(textwrap.dedent(msg))
+
+def get_changed_files(base_commit, head_commit,
+                      subdir: str = '.'):
+    """ Get the files changed by the given range of commits. """
+    cmd = ['git', 'diff', '--name-only',
+           base_commit, head_commit, '--', subdir]
+    files = subprocess.check_output(cmd)
+    return files.decode('UTF-8').split('\n')
+
+Warning = namedtuple('Warning', 'path,line_no,line_content,message')
+
+class Linter(object):
+    """
+    A :class:`Linter` must implement :func:`lint`, which looks at the
+    given path and calls :func:`add_warning` for any lint issues found.
+    """
+    def __init__(self):
+        self.warnings = [] # type: List[Warning]
+
+    def add_warning(self, w: Warning):
+        self.warnings.append(w)
+
+    def lint(self, path):
+        pass
+
+class LineLinter(Linter):
+    """
+    A :class:`LineLinter` must implement :func:`lint_line`, which looks at
+    the given line from a file and calls :func:`add_warning` for any lint
+    issues found.
+    """
+    def lint(self, path):
+        if os.path.isfile(path):
+            with open(path, 'r') as f:
+                for line_no, line in enumerate(f):
+                    self.lint_line(path, line_no+1, line)
+
+    def lint_line(self, path, line_no, line):
+        pass
+
+class RegexpLinter(LineLinter):
+    """
+    A :class:`RegexpLinter` produces the given warning message for
+    all lines matching the given regular expression.
+    """
+    def __init__(self, regex, message):
+        LineLinter.__init__(self)
+        self.re = re.compile(regex)
+        self.message = message
+
+    def lint_line(self, path, line_no, line):
+        if self.re.search(line):
+            w = Warning(path=path, line_no=line_no, line_content=line[:-1],
+                        message=self.message)
+            self.add_warning(w)
+
+def run_linters(linters: List[Linter],
+                subdir: str = '.') -> None:
+    import argparse
+    parser = argparse.ArgumentParser()
+    parser.add_argument('base', help='Base commit')
+    parser.add_argument('head', help='Head commit')
+    args = parser.parse_args()
+
+    for path in get_changed_files(args.base, args.head, subdir):
+        if path.startswith('.gitlab/linters'):
+            continue
+        for linter in linters:
+            linter.lint(path)
+
+    warnings = [warning
+                for linter in linters
+                for warning in linter.warnings]
+    warnings = sorted(warnings, key=lambda x: (x.path, x.line_no))
+    for w in warnings:
+        lint_failure(w.path, w.line_no, w.line_content, w.message)
+
+    if len(warnings) > 0:
+        sys.exit(1)