tokenizer: skip lines that are just slash and whitespace (#4343)

tusharsadhwani · web-flow · commit b677a643c532 · 2024-06-01T13:01:36.000-07:00
diff --git a/AUTHORS.md b/AUTHORS.md
@@ -181,6 +181,7 @@ Multiple contributions by:
 - [Tony Narlock](mailto:tony@git-pull.com)
 - [Tsuyoshi Hombashi](mailto:tsuyoshi.hombashi@gmail.com)
 - [Tushar Chandra](mailto:tusharchandra2018@u.northwestern.edu)
+- [Tushar Sadhwani](mailto:tushar.sadhwani000@gmail.com)
 - [Tzu-ping Chung](mailto:uranusjr@gmail.com)
 - [Utsav Shah](mailto:ukshah2@illinois.edu)
 - utsav-dbx
diff --git a/CHANGES.md b/CHANGES.md
@@ -34,6 +34,8 @@
 - Fix regression where Black failed to parse a multiline f-string containing another
   multiline string (#4339)
 
+- Fix bug with Black incorrectly parsing empty lines with a backslash (#4343)
+
 ### Performance
 
 <!-- Changes that improve Black's performance. -->
diff --git a/src/blib2to3/pgen2/tokenize.py b/src/blib2to3/pgen2/tokenize.py
@@ -608,6 +608,12 @@ def generate_tokens(
         except StopIteration:
             line = ""
         lnum += 1
+
+        # skip lines that are just indent characters ending with a slash
+        # to avoid storing that line's indent information.
+        if not contstr and line.rstrip("\n").strip(" \t\f") == "\\":
+            continue
+
         pos, max = 0, len(line)
 
         if contstr:  # continued string
diff --git a/tests/data/cases/backslash_before_indent.py b/tests/data/cases/backslash_before_indent.py
@@ -0,0 +1,24 @@
+# flags: --minimum-version=3.10
+class Plotter:
+\
+    pass
+
+class AnotherCase:
+  \
+    """Some
+    \
+    Docstring
+    """
+
+# output
+
+class Plotter:
+
+    pass
+
+
+class AnotherCase:
+    """Some
+    \
+    Docstring
+    """
diff --git a/tests/data/cases/comment_after_escaped_newline.py b/tests/data/cases/comment_after_escaped_newline.py
@@ -14,5 +14,7 @@ def bob():  # pylint: disable=W9016
     pass
 
 
-def bobtwo():  # some comment here
+def bobtwo():
+
+    # some comment here
     pass
diff --git a/tests/data/cases/form_feeds.py b/tests/data/cases/form_feeds.py
@@ -156,6 +156,7 @@ def something(self):
 
 #
 
+
 #
 pass
 

Original file line number	Diff line number	Diff line change
`@@ -156,6 +156,7 @@ def something(self):`
`156`	`156`
`157`	`157`	`#`
`158`	`158`
	`159`	`+`
`159`	`160`	`#`
`160`	`161`	`pass`
`161`	`162`