From c2327c83b28aa9ae6e7ea7078f17033c23e34d9c Mon Sep 17 00:00:00 2001
From: =?utf8?q?=C5=81ukasz=20Langa?= <lukasz@langa.pl>
Date: Tue, 19 Jun 2018 23:46:58 -0700
Subject: [PATCH] More tests for `# fmt: off`

Two more known limitations that I don't feel like solving now.  Probably very
low priority.
---
 black.py               |  3 +++
 tests/data/fmtonoff.py | 44 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 47 insertions(+)

diff --git a/black.py b/black.py
index 0f966ae..f1b1c30 100644
--- a/black.py
+++ b/black.py
@@ -2577,6 +2577,9 @@ def convert_one_fmt_off_pair(node: Node) -> bool:
                         continue
 
                 ignored_nodes = list(generate_ignored_nodes(leaf))
+                if not ignored_nodes:
+                    continue
+
                 first = ignored_nodes[0]  # Can be a container node with the `leaf`.
                 parent = first.parent
                 prefix = first.prefix
diff --git a/tests/data/fmtonoff.py b/tests/data/fmtonoff.py
index 373e5c7..74b52ec 100644
--- a/tests/data/fmtonoff.py
+++ b/tests/data/fmtonoff.py
@@ -53,6 +53,27 @@ def example(session):
         .order_by(models.Customer.id.asc())\
         .all()
     # fmt: on
+def off_and_on_without_data():
+    """All comments here are technically on the same prefix.
+
+    The comments between will be formatted. This is a known limitation.
+    """
+    # fmt: off
+
+
+        #hey, that won't work
+
+
+    # fmt: on
+    pass
+def on_and_off_broken():
+    """Another known limitation."""
+    # fmt: on
+    # fmt: off
+    this=should.not_be.formatted()
+    but=it  is  formatted
+    because . the . handling . inside . generate_ignored_nodes()
+    doesnt . consider . ordering . within . one . prefix
 def long_lines():
     if True:
         typedargslist.extend(
@@ -201,6 +222,29 @@ def example(session):
     # fmt: on
 
 
+def off_and_on_without_data():
+    """All comments here are technically on the same prefix.
+
+    The comments between will be formatted. This is a known limitation.
+    """
+    # fmt: off
+
+    # hey, that won't work
+
+    # fmt: on
+    pass
+
+
+def on_and_off_broken():
+    """Another known limitation."""
+    # fmt: on
+    # fmt: off
+    this = should.not_be.formatted()
+    but = it is formatted
+    because.the.handling.inside.generate_ignored_nodes()
+    doesnt.consider.ordering.within.one.prefix
+
+
 def long_lines():
     if True:
         typedargslist.extend(
-- 
2.39.5