clang-format: Add capability to format the diff on save in vim.

With this patch, one can configure a BufWrite hook that will make the
clang-format integration compute a diff of the current buffer with the file
that's on disk and format all changed lines. This should create a
zero-overhead auto-format solution that doesn't require the file to
already be clang-format clean to avoid spurious diffs.

Review: https://reviews.llvm.org/D32429

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@305665 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 13 insertions, 2 deletions

diff --git a/tools/clang-format/clang-format.py b/tools/clang-format/clang-format.py
index ae8a6ebf74..2412566346 100644
--- a/tools/clang-format/clang-format.py
+++ b/tools/clang-format/clang-format.py
@@ -63,8 +63,19 @@ def main():
   # Determine range to format.
   if vim.eval('exists("l:lines")') == '1':
     lines = vim.eval('l:lines')
+  elif vim.eval('exists("l:formatdiff")') == '1':
+    with open(vim.current.buffer.name, 'r') as f:
+      ondisk = f.read().splitlines();
+    sequence = difflib.SequenceMatcher(None, ondisk, vim.current.buffer)
+    lines = []
+    for op in reversed(sequence.get_opcodes()):
+      if op[0] not in ['equal', 'delete']:
+        lines += ['-lines', '%s:%s' % (op[3] + 1, op[4])]
+    if lines == []:
+      return
   else:
-    lines = '%s:%s' % (vim.current.range.start + 1, vim.current.range.end + 1)
+    lines = ['-lines', '%s:%s' % (vim.current.range.start + 1,
+                                  vim.current.range.end + 1)]
 
   # Determine the cursor position.
   cursor = int(vim.eval('line2byte(line("."))+col(".")')) - 2
@@ -82,7 +93,7 @@ def main():
   # Call formatter.
   command = [binary, '-style', style, '-cursor', str(cursor)]
   if lines != 'all':
-    command.extend(['-lines', lines])
+    command += lines
   if fallback_style:
     command.extend(['-fallback-style', fallback_style])
   if vim.current.buffer.name: