extract file contents read into separate method

1 files changed, 46 insertions, 40 deletions

diff --git a/isort/isort.py b/isort/isort.py
index 3776bb01..370c6b72 100644
--- a/isort/isort.py
+++ b/isort/isort.py
@@ -26,6 +26,7 @@ OTHER DEALINGS IN THE SOFTWARE.
 """
 import copy
 import itertools
+import locale
 import os
 import re
 import sys
@@ -84,7 +85,6 @@ class _SortImports(object):
         self.file_encoding = 'utf-8'
         file_name = file_path
         self.file_path = file_path or ""
-
         if file_path:
             file_path = os.path.abspath(file_path)
             if check_skip:
@@ -98,34 +98,26 @@ class _SortImports(object):
                     self.skipped = True
                     if self.config['verbose']:
                         print("WARNING: {0} was skipped as it's listed in 'skip' setting"
-                            " or matches a glob in 'skip_glob' setting".format(file_path))
+                              " or matches a glob in 'skip_glob' setting".format(file_path))
                     file_contents = None
+
             if not self.skipped and not file_contents:
-                file_encoding = coding_check(file_path)
-                with open(file_path, encoding=file_encoding, newline='') as file_to_import_sort:
-                    try:
-                        file_contents = file_to_import_sort.read()
-                        self.file_path = file_path
-                        self.file_encoding = file_encoding
-                        encoding_success = True
-                    except UnicodeDecodeError:
-                        encoding_success = False
-
-                if not encoding_success:
-                    with open(file_path, newline='') as file_to_import_sort:
-                        try:
-                            file_contents = file_to_import_sort.read()
-                            self.file_path = file_path
-                            self.file_encoding = file_to_import_sort.encoding
-                        except UnicodeDecodeError:
-                            encoding_success = False
-                            file_contents = None
-                            self.skipped = True
-                            if self.config['verbose']:
-                                print("WARNING: {} was skipped as it couldn't be opened with the given "
-                                      "{} encoding or {} fallback encoding".format(file_path,
-                                                                                   self.file_encoding,
-                                                                                   file_to_import_sort.encoding))
+                preferred_encoding = determine_file_encoding(file_path)
+                # default encoding for open(mode='r') on the system
+                fallback_encoding = locale.getpreferredencoding(False)
+
+                file_contents, used_encoding = self.read_file_contents(file_path,
+                                                                       encoding=preferred_encoding,
+                                                                       fallback_encoding=fallback_encoding)
+                if used_encoding is None:
+                    self.skipped = True
+                    if self.config['verbose']:
+                        print("WARNING: {} was skipped as it couldn't be opened with the given "
+                              "{} encoding or {} fallback encoding".format(file_path,
+                                                                           self.file_encoding,
+                                                                           fallback_encoding))
+                else:
+                    self.file_encoding = used_encoding
 
         if file_contents is None or ("isort:" + "skip_file") in file_contents:
             self.skipped = True
@@ -134,10 +126,7 @@ class _SortImports(object):
                 sys.stdout.write(file_contents)
             return
 
-        if self.config['line_ending']:
-            self.line_separator = self.config['line_ending']
-        else:
-            self.line_separator = utils.infer_line_separator(file_contents)
+        self.line_separator = self.determine_line_separator(file_contents)
 
         self.in_lines = file_contents.split(self.line_separator)
         self.original_num_of_lines = len(self.in_lines)
@@ -172,19 +161,20 @@ class _SortImports(object):
         self.output = self.line_separator.join(self.out_lines)
         if self.config['atomic']:
             try:
-                compile(self._strip_top_comments(self.out_lines, self.line_separator), self.file_path, 'exec', 0, 1)
+                out_lines_without_top_comment = self._strip_top_comments(self.out_lines, self.line_separator)
+                compile(out_lines_without_top_comment, self.file_path, 'exec', 0, 1)
             except SyntaxError:
                 self.output = file_contents
                 self.incorrectly_sorted = True
                 try:
-                    compile(self._strip_top_comments(self.in_lines, self.line_separator), self.file_path, 'exec', 0, 1)
+                    in_lines_without_top_comment = self._strip_top_comments(self.in_lines, self.line_separator)
+                    compile(in_lines_without_top_comment, self.file_path, 'exec', 0, 1)
                     print("ERROR: {0} isort would have introduced syntax errors, please report to the project!".
                           format(self.file_path))
                 except SyntaxError:
                     print("ERROR: {0} File contains syntax errors.".format(self.file_path))
 
                 return
-
         if check:
             check_output = self.output
             check_against = file_contents
@@ -199,7 +189,6 @@ class _SortImports(object):
 
             print("ERROR: {0} Imports are incorrectly sorted.".format(self.file_path))
             self.incorrectly_sorted = True
-
         if show_diff or self.config['show_diff']:
             self._show_diff(file_contents)
         elif write_to_stdout:
@@ -223,6 +212,27 @@ class _SortImports(object):
                     print("Fixing {0}".format(self.file_path))
                 output_file.write(self.output)
 
+    def determine_line_separator(self, file_contents: str) -> str:
+        if self.config['line_ending']:
+            return self.config['line_ending']
+        else:
+            return utils.infer_line_separator(file_contents)
+
+    def read_file_contents(self, file_path: str, encoding: str, fallback_encoding: str) -> Tuple[Optional[str], Optional[str]]:
+        with open(file_path, encoding=encoding, newline='') as file_to_import_sort:
+            try:
+                file_contents = file_to_import_sort.read()
+                return file_contents, encoding
+            except UnicodeDecodeError:
+                pass
+
+        with open(file_path, encoding=fallback_encoding, newline='') as file_to_import_sort:
+            try:
+                file_contents = file_to_import_sort.read()
+                return file_contents, fallback_encoding
+            except UnicodeDecodeError:
+                return None, None
+
     @property
     def correctly_sorted(self) -> bool:
         return not self.incorrectly_sorted
@@ -1088,11 +1098,7 @@ class _SortImports(object):
                         self.imports[placed_module][import_type][module] = None
 
 
-def coding_check(
-    fname: str,
-    default: str = 'utf-8'
-) -> str:
-
+def determine_file_encoding(fname: str, default: str = 'utf-8') -> str:
     # see https://www.python.org/dev/peps/pep-0263/
     pattern = re.compile(br'coding[:=]\s*([-\w.]+)')