From ee9c2874a9a5cb886060635c9b1aeec16bbc9e55 Mon Sep 17 00:00:00 2001
From: Anthony Sottile <asottile@umich.edu>
Date: Sat, 12 Sep 2020 11:56:37 -0700
Subject: [PATCH] fix skipping of physical checks when file does not end in
 newline

---
 .pre-commit-config.yaml        |  2 ++
 src/flake8/checker.py          | 17 +++++++++++++----
 tests/integration/test_main.py | 31 +++++++++++++++++++++++++++++++
 3 files changed, 46 insertions(+), 4 deletions(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index b03ff3c..e1b34f3 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -2,6 +2,8 @@ repos:
 -   repo: https://github.com/pre-commit/pre-commit-hooks
     rev: v2.3.0
     hooks:
+    -   id: debug-statements
+        exclude: ^tests/fixtures/example-code/invalid-syntax.py$
     -   id: end-of-file-fixer
     -   id: trailing-whitespace
         exclude: ^tests/fixtures/diffs/
diff --git a/src/flake8/checker.py b/src/flake8/checker.py
index ea8b5d3..be1c7f7 100644
--- a/src/flake8/checker.py
+++ b/src/flake8/checker.py
@@ -564,9 +564,10 @@ class FileChecker(object):
         parens = 0
         statistics = self.statistics
         file_processor = self.processor
+        prev_physical = ""
         for token in file_processor.generate_tokens():
             statistics["tokens"] += 1
-            self.check_physical_eol(token)
+            self.check_physical_eol(token, prev_physical)
             token_type, text = token[0:2]
             processor.log_token(LOG, token)
             if token_type == tokenize.OP:
@@ -574,6 +575,7 @@ class FileChecker(object):
             elif parens == 0:
                 if processor.token_is_newline(token):
                     self.handle_newline(token_type)
+            prev_physical = token[4]
 
         if file_processor.tokens:
             # If any tokens are left over, process them
@@ -609,11 +611,18 @@ class FileChecker(object):
         else:
             self.run_logical_checks()
 
-    def check_physical_eol(self, token):
+    def check_physical_eol(self, token, prev_physical):
+        # type: (processor._Token, str) -> None
         """Run physical checks if and only if it is at the end of the line."""
+        # a newline token ends a single physical line.
         if processor.is_eol_token(token):
-            # Obviously, a newline token ends a single physical line.
-            self.run_physical_checks(token[4])
+            # if the file does not end with a newline, the NEWLINE
+            # token is inserted by the parser, but it does not contain
+            # the previous physical line in `token[4]`
+            if token[4] == "":
+                self.run_physical_checks(prev_physical)
+            else:
+                self.run_physical_checks(token[4])
         elif processor.is_multiline_string(token):
             # Less obviously, a string that contains newlines is a
             # multiline string, either triple-quoted or with internal
diff --git a/tests/integration/test_main.py b/tests/integration/test_main.py
index ce8ad13..69cb12b 100644
--- a/tests/integration/test_main.py
+++ b/tests/integration/test_main.py
@@ -212,6 +212,37 @@ x = """
     assert out == err == ''
 
 
+def test_physical_line_file_not_ending_in_newline(tmpdir, capsys):
+    """See https://github.com/PyCQA/pycodestyle/issues/960."""
+    t_py_src = 'def f():\n\tpass'
+
+    with tmpdir.as_cwd():
+        tmpdir.join('t.py').write(t_py_src)
+        _call_main(['t.py'], retv=1)
+
+    out, err = capsys.readouterr()
+    assert out == '''\
+t.py:2:1: W191 indentation contains tabs
+t.py:2:6: W292 no newline at end of file
+'''
+
+
+@pytest.mark.xfail(strict=True)  # currently awaiting fix in pycodestyle
+def test_physical_line_file_not_ending_in_newline_trailing_ws(tmpdir, capsys):
+    """See https://github.com/PyCQA/pycodestyle/issues/960."""
+    t_py_src = 'x = 1   '
+
+    with tmpdir.as_cwd():
+        tmpdir.join('t.py').write(t_py_src)
+        _call_main(['t.py'], retv=1)
+
+    out, err = capsys.readouterr()
+    assert out == '''\
+t.py:1:6: W291 trailing whitespace
+t.py:1:10: W292 no newline at end of file
+'''
+
+
 def test_obtaining_args_from_sys_argv_when_not_explicity_provided(capsys):
     """Test that arguments are obtained from 'sys.argv'."""
     with mock.patch('sys.argv', ['flake8', '--help']):