Fix INTERNAL ERROR caused by removing parens from pointless string (#1888)

Fixes #1846.

src/black/__init__.py

@@ -3271,7 +3271,8 @@ class StringParenStripper(StringTransformer):
 
     Requirements:
         The line contains a string which is surrounded by parentheses and:
-            - The target string is NOT the only argument to a function call).
+            - The target string is NOT the only argument to a function call.
+            - The target string is NOT a "pointless" string.
             - If the target string contains a PERCENT, the brackets are not
               preceeded or followed by an operator with higher precedence than
               PERCENT.
@@ -3295,6 +3296,14 @@ def do_match(self, line: Line) -> TMatchResult:
             if leaf.type != token.STRING:
                 continue
 
+            # If this is a "pointless" string...
+            if (
+                leaf.parent
+                and leaf.parent.parent
+                and leaf.parent.parent.type == syms.simple_stmt
+            ):
+                continue
+
             # Should be preceded by a non-empty LPAR...
             if (
                 not is_valid_index(idx - 1)

tests/data/long_strings__regression.py

@@ -375,6 +375,27 @@ def xxxxxxx_xxxxxx(xxxx):
 print(f"Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam. {[f'{i}' for i in range(10)]}")
 x = f"This is a long string which contains an f-expr that should not split {{{[i for i in range(5)]}}}."
 
+# The parens should NOT be removed in this case.
+(
+    "my very long string that should get formatted if I'm careful to make sure it goes"
+    " over 88 characters which it has now"
+)
+
+# The parens should NOT be removed in this case.
+(
+    "my very long string that should get formatted if I'm careful to make sure it goes over 88 characters which"
+    " it has now"
+)
+
+# The parens should NOT be removed in this case.
+(
+    "my very long string"
+    " that should get formatted"
+    " if I'm careful to make sure"
+    " it goes over 88 characters which"
+    " it has now"
+)
+
 # output
 
 
@@ -844,3 +865,24 @@ def xxxxxxx_xxxxxx(xxxx):
     "This is a long string which contains an f-expr that should not split"
     f" {{{[i for i in range(5)]}}}."
 )
+
+# The parens should NOT be removed in this case.
+(
+    "my very long string that should get formatted if I'm careful to make sure it goes"
+    " over 88 characters which it has now"
+)
+
+# The parens should NOT be removed in this case.
+(
+    "my very long string that should get formatted if I'm careful to make sure it goes"
+    " over 88 characters which it has now"
+)
+
+# The parens should NOT be removed in this case.
+(
+    "my very long string"
+    " that should get formatted"
+    " if I'm careful to make sure"
+    " it goes over 88 characters which"
+    " it has now"
+)