Improve multiline_string_handling with ternaries and dictionaries

CHANGES.md

@@ -22,6 +22,7 @@
 
 - Fix a bug where one-liner functions/conditionals marked with `# fmt: skip`
   would still be formatted (#4552)
+- Improve `multiline_string_handling` with ternaries and dictionaries (#4657)
 
 ### Configuration
 

src/black/lines.py

@@ -872,6 +872,12 @@ def is_line_short_enough(  # noqa: C901
             max_level_to_update = min(max_level_to_update, leaf.bracket_depth)
 
         if is_multiline_string(leaf):
+            if leaf.parent and (
+                leaf.parent.type == syms.test
+                or (leaf.parent.parent and leaf.parent.parent.type == syms.dictsetmaker)
+            ):
+                # Keep ternary and dictionary values parenthesized
+                return False
             if len(multiline_string_contexts) > 0:
                 # >1 multiline string cannot fit on a single line - force split
                 return False

tests/data/cases/preview_multiline_strings.py

@@ -182,7 +182,75 @@ def dastardly_default_value(
 expected: {expected_result}
 actual: {some_var}"""
 
+
+def foo():
+    a = {
+        xxxx_xxxxxxx.xxxxxx_xxxxxxxxxxxx_xxxxxx_xx_xxx_xxxxxx: {
+            "xxxxx": """Sxxxxx xxxxxxxxxxxx xxx xxxxx (xxxxxx xxx xxxxxxx)""",
+            "xxxxxxxx": (
+                """Sxxxxxxx xxxxxxxx, xxxxxxx xx xxxxxxxxx
+                xxxxxxxxxxxxx xxxxxxx xxxxxxxxx xxx-xxxxxxxxxx xxxxxx xx xxx-xxxxxx"""
+            ),
+            "xxxxxxxx": """Sxxxxxxx xxxxxxxx, xxxxxxx xx xxxxxxxxx
+                xxxxxxxxxxxxx xxxxxxx xxxxxxxxx xxx-xxxxxxxxxx xxxxxx xx xxx-xxxxxx"""
+        },
+    }
+
+
+xxxx_xxxxxxx.xxxxxx_xxxxxxxxxxxx_xxxxxx_xx_xxx_xxxxxx = {
+    "xxxxx": """Sxxxxx xxxxxxxxxxxx xxx xxxxx (xxxxxx xxx xxxxxxx)""",
+    "xxxxxxxx": (
+        """Sxxxxxxx xxxxxxxx, xxxxxxx xx xxxxxxxxx
+    xxxxxxxxxxxxx xxxxxxx xxxxxxxxx xxx-xxxxxxxxxx xxxxxx xx xxx-xxxxxx"""
+    ),
+    "xxxxx_xxxxxxxxxx_xxxxxxxxx_xx": (
+        """
+a
+a
+a
+a
+a"""
+    ),
+    "xx_xxxxx_xxxxxxxxxx_xxxxxxxxx_xx": """
+a
+a
+a
+a
+a""",
+}
+
+a = """
+""" if """
+""" == """
+""" else """
+"""
+
+a = """
+""" if b else """
+"""
+
+a = """
+""" if """
+""" == """
+""" else b
+
+a = b if """
+""" == """
+""" else """
+"""
+
+a = """
+""" if b else c
+
+a = c if b else """
+"""
+
+a = b if """
+""" == """
+""" else c
+
 # output
+
 """cow
 say""",
 call(
@@ -399,3 +467,106 @@ def dastardly_default_value(
 assert some_var == expected_result, f"""
 expected: {expected_result}
 actual: {some_var}"""
+
+
+def foo():
+    a = {
+        xxxx_xxxxxxx.xxxxxx_xxxxxxxxxxxx_xxxxxx_xx_xxx_xxxxxx: {
+            "xxxxx": """Sxxxxx xxxxxxxxxxxx xxx xxxxx (xxxxxx xxx xxxxxxx)""",
+            "xxxxxxxx": (
+                """Sxxxxxxx xxxxxxxx, xxxxxxx xx xxxxxxxxx
+                xxxxxxxxxxxxx xxxxxxx xxxxxxxxx xxx-xxxxxxxxxx xxxxxx xx xxx-xxxxxx"""
+            ),
+            "xxxxxxxx": (
+                """Sxxxxxxx xxxxxxxx, xxxxxxx xx xxxxxxxxx
+                xxxxxxxxxxxxx xxxxxxx xxxxxxxxx xxx-xxxxxxxxxx xxxxxx xx xxx-xxxxxx"""
+            ),
+        },
+    }
+
+
+xxxx_xxxxxxx.xxxxxx_xxxxxxxxxxxx_xxxxxx_xx_xxx_xxxxxx = {
+    "xxxxx": """Sxxxxx xxxxxxxxxxxx xxx xxxxx (xxxxxx xxx xxxxxxx)""",
+    "xxxxxxxx": (
+        """Sxxxxxxx xxxxxxxx, xxxxxxx xx xxxxxxxxx
+    xxxxxxxxxxxxx xxxxxxx xxxxxxxxx xxx-xxxxxxxxxx xxxxxx xx xxx-xxxxxx"""
+    ),
+    "xxxxx_xxxxxxxxxx_xxxxxxxxx_xx": (
+        """
+a
+a
+a
+a
+a"""
+    ),
+    "xx_xxxxx_xxxxxxxxxx_xxxxxxxxx_xx": (
+        """
+a
+a
+a
+a
+a"""
+    ),
+}
+
+a = (
+    """
+"""
+    if """
+"""
+    == """
+"""
+    else """
+"""
+)
+
+a = (
+    """
+"""
+    if b
+    else """
+"""
+)
+
+a = (
+    """
+"""
+    if """
+"""
+    == """
+"""
+    else b
+)
+
+a = (
+    b
+    if """
+"""
+    == """
+"""
+    else """
+"""
+)
+
+a = (
+    """
+"""
+    if b
+    else c
+)
+
+a = (
+    c
+    if b
+    else """
+"""
+)
+
+a = (
+    b
+    if """
+"""
+    == """
+"""
+    else c
+)