Fix multiline strings unnecessarily wrapped in optional parentheses

Fixes #215

diff --git a/README.md b/README.md
index 8b7b2bd820331ee79c2ed5deaf87c88cbc253a30..3eb8ee4f131bb3bd234b457071895318932bf44c 100644 (file)
--- a/README.md
+++ b/README.md
@@ -653,6 +653,9 @@ More details can be found in [CONTRIBUTING](CONTRIBUTING.md).
 * fixed non-deterministic formatting when multiple pairs of removable parentheses
   were used (#183)
 
+* fixed multiline strings being unnecessarily wrapped in optional
+  parentheses in long assignments (#215)
+
 * fixed not splitting long from-imports with only a single name
 
 * fixed Python 3.6+ file discovery by also looking at function calls with

diff --git a/black.py b/black.py
index 4b5f19edced61f1ebbcf7bf06f12d172c377d68d..298597bcb30f8aad947056fc8583327a75814d5e 100644 (file)
--- a/black.py
+++ b/black.py
@@ -1315,7 +1315,7 @@ class LineGenerator(Visitor[Line]):
         The relevant Python language `keywords` for a given statement will be
         NAME leaves within it. This methods puts those on a separate line.
 
-        `parens` holds a set of string leaf values immeditely after which
+        `parens` holds a set of string leaf values immediately after which
         invisible parens should be put.
         """
         normalize_invisible_parens(node, parens_after=parens)
@@ -2361,7 +2361,7 @@ def normalize_invisible_parens(node: Node, parens_after: Set[str]) -> None:
                 rpar = Leaf(token.RPAR, ")")
                 index = child.remove() or 0
                 node.insert_child(index, Node(syms.atom, [lpar, child, rpar]))
-            else:
+            elif not (isinstance(child, Leaf) and is_multiline_string(child)):
                 # wrap child in invisible parentheses
                 lpar = Leaf(token.LPAR, "")
                 rpar = Leaf(token.RPAR, "")
@@ -2472,6 +2472,12 @@ def is_vararg(leaf: Leaf, within: Set[NodeType]) -> bool:
     return p.type in within
 
 
+def is_multiline_string(leaf: Leaf) -> bool:
+    """Return True if `leaf` is a multiline string that actually spans many lines."""
+    value = leaf.value.lstrip("furbFURB")
+    return value[:3] in {'"""', "'''"} and "\n" in value
+
+
 def is_stub_suite(node: Node) -> bool:
     """Return True if `node` is a suite with a stub body."""
     if (

diff --git a/tests/comments3.py b/tests/comments3.py
index c1f0e7598aa84751a4a63c41aff99dfcb2f0e2ea..e95bd21ca9edaf6af7049c06ff967b54883c92ae 100644 (file)
--- a/tests/comments3.py
+++ b/tests/comments3.py
@@ -1,4 +1,7 @@
 def func():
+    x = """
+    a really long string
+    """
     lcomp3 = [
         # This one is actually too long to fit in a single line.
         element.split("\n", 1)[0]