Make FileInfo available to both read/write of files

fix_includes.py

@@ -530,7 +530,7 @@ class FileInfo(object):
     return FileInfo.DEFAULT_LINESEP
 
 
-def _ReadFile(filename):
+def _ReadFile(filename, fileinfo):
   """Read from filename and return a list of file lines."""
   try:
     return open(filename).read().splitlines()
@@ -539,12 +539,9 @@ def _ReadFile(filename):
   return None
 
 
-def _WriteFile(filename, file_lines):
+def _WriteFile(filename, fileinfo, file_lines):
   """Write the given file-lines to the file."""
   try:
-    # Detect encoding details
-    fileinfo = FileInfo.parse(filename)
-
     # Open file in binary mode to preserve line endings
     with open(filename, 'wb') as f:
       f.write(fileinfo.linesep.join(file_lines))
@@ -2006,7 +2003,9 @@ def FixManyFiles(iwyu_records, flags):
   files_fixed = 0
   for iwyu_record in iwyu_records:
     try:
-      file_contents = _ReadFile(iwyu_record.filename)
+      fileinfo = FileInfo.parse(iwyu_record.filename)
+
+      file_contents = _ReadFile(iwyu_record.filename, fileinfo)
       if not file_contents:
         continue
 
@@ -2019,7 +2018,7 @@ def FixManyFiles(iwyu_records, flags):
       if flags.dry_run:
         PrintFileDiff(old_lines, fixed_lines)
       else:
-        _WriteFile(iwyu_record.filename, fixed_lines)
+        _WriteFile(iwyu_record.filename, fileinfo, fixed_lines)
 
       files_fixed += 1
     except FixIncludesError as why:

fix_includes_test.py

@@ -46,12 +46,15 @@ class FakeFlags(object):
 class FixIncludesBase(unittest.TestCase):
   """Does setup that every test will want."""
 
-  def _ReadFile(self, filename):
+  def _ReadFile(self, filename, fileinfo):
     assert filename in self.before_map, filename
     return self.before_map[filename]
 
-  def _WriteFile(self, filename, file_lines):
-      self.actual_after_contents.extend(file_lines)
+  def _ParseFileInfo(self, filename):
+      return fix_includes.FileInfo('\n')
+
+  def _WriteFile(self, filename, fileinfo, contents):
+      return self.actual_after_contents.extend(contents)
 
   def setUp(self):
     self.flags = FakeFlags()
@@ -63,7 +66,11 @@ class FixIncludesBase(unittest.TestCase):
 
     # INPUT: fix_includes._ReadFile takes a filename
     # and returns the contents of filename (as a list).
+    # FileInfo controls encoding details of the file,
+    # wire it to return something that agrees with the
+    # tests.
     fix_includes._ReadFile = self._ReadFile
+    fix_includes.FileInfo.parse = self._ParseFileInfo
 
     # OUTPUT: Instead of writing to file, save full output.
     self.actual_after_contents = []