Parenthesize conditional expressions (#2278)

Co-authored-by: Jordan Ephron <JEphron@users.noreply.github.com>
Co-authored-by: Richard Si <63936253+ichard26@users.noreply.github.com>
Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>

diff --git a/CHANGES.md b/CHANGES.md
index 587ca8a2a0dd532805a9005c2aed28fec4f5ff2b..2da0fb4720c1bc12cc2a01c75f117f700a47aa9d 100644 (file)
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -16,6 +16,7 @@
 
 <!-- Changes that affect Black's preview style -->
 
+- Add parentheses around `if`-`else` expressions (#2278)
 - Improve the performance on large expressions that contain many strings (#3467)
 - Fix a crash in preview style with assert + parenthesized string (#3415)
 - Fix crashes in preview style with walrus operators used in function return annotations

diff --git a/src/black/__init__.py b/src/black/__init__.py
index f00749aaed81146dbadc7778cf49bad23af6e3c5..9f44722bfaee89373932ad062dedf52ac145eacc 100644 (file)
--- a/src/black/__init__.py
+++ b/src/black/__init__.py
@@ -478,16 +478,20 @@ def main(  # noqa: C901
             )
 
             normalized = [
-                (source, source)
-                if source == "-"
-                else (normalize_path_maybe_ignore(Path(source), root), source)
+                (
+                    (source, source)
+                    if source == "-"
+                    else (normalize_path_maybe_ignore(Path(source), root), source)
+                )
                 for source in src
             ]
             srcs_string = ", ".join(
                 [
-                    f'"{_norm}"'
-                    if _norm
-                    else f'\033[31m"{source} (skipping - invalid)"\033[34m'
+                    (
+                        f'"{_norm}"'
+                        if _norm
+                        else f'\033[31m"{source} (skipping - invalid)"\033[34m'
+                    )
                     for _norm, source in normalized
                 ]
             )

diff --git a/src/black/linegen.py b/src/black/linegen.py
index 2e75bc945066d148f1cc03f673107cc0918e6f22..4da75b28235c96b2d96204d532d7cd6552a0e9d4 100644 (file)
--- a/src/black/linegen.py
+++ b/src/black/linegen.py
@@ -140,6 +140,22 @@ class LineGenerator(Visitor[Line]):
                 self.current_line.append(node)
         yield from super().visit_default(node)
 
+    def visit_test(self, node: Node) -> Iterator[Line]:
+        """Visit an `x if y else z` test"""
+
+        if Preview.parenthesize_conditional_expressions in self.mode:
+            already_parenthesized = (
+                node.prev_sibling and node.prev_sibling.type == token.LPAR
+            )
+
+            if not already_parenthesized:
+                lpar = Leaf(token.LPAR, "")
+                rpar = Leaf(token.RPAR, "")
+                node.insert_child(0, lpar)
+                node.append_child(rpar)
+
+        yield from self.visit_default(node)
+
     def visit_INDENT(self, node: Leaf) -> Iterator[Line]:
         """Increase indentation level, maybe yield a line."""
         # In blib2to3 INDENT never holds comments.

diff --git a/src/black/mode.py b/src/black/mode.py
index a104d1b9862da1e194f4ba096e9872e5726dea68..775805ae9600a30c0001ce1f67dff27a4b2ff122 100644 (file)
--- a/src/black/mode.py
+++ b/src/black/mode.py
@@ -161,6 +161,7 @@ class Preview(Enum):
     # NOTE: string_processing requires wrap_long_dict_values_in_parens
     # for https://github.com/psf/black/issues/3117 to be fixed.
     string_processing = auto()
+    parenthesize_conditional_expressions = auto()
     skip_magic_trailing_comma_in_subscript = auto()
     wrap_long_dict_values_in_parens = auto()
 

diff --git a/tests/data/conditional_expression.py b/tests/data/conditional_expression.py
new file mode 100644 (file)
index 0000000..620a12d
--- /dev/null
+++ b/tests/data/conditional_expression.py
@@ -0,0 +1,160 @@
+long_kwargs_single_line = my_function(
+    foo="test, this is a sample value",
+    bar=some_long_value_name_foo_bar_baz if some_boolean_variable else some_fallback_value_foo_bar_baz,
+    baz="hello, this is a another value",
+)
+
+multiline_kwargs_indented = my_function(
+    foo="test, this is a sample value",
+    bar=some_long_value_name_foo_bar_baz
+    if some_boolean_variable
+    else some_fallback_value_foo_bar_baz,
+    baz="hello, this is a another value",
+)
+
+imploding_kwargs = my_function(
+    foo="test, this is a sample value",
+    bar=a
+    if foo
+    else b,
+    baz="hello, this is a another value",
+)
+
+imploding_line = (
+    1
+    if 1 + 1 == 2
+    else 0
+)
+
+exploding_line = "hello this is a slightly long string" if some_long_value_name_foo_bar_baz else "this one is a little shorter"
+
+positional_argument_test(some_long_value_name_foo_bar_baz if some_boolean_variable else some_fallback_value_foo_bar_baz)
+
+def weird_default_argument(x=some_long_value_name_foo_bar_baz
+        if SOME_CONSTANT
+        else some_fallback_value_foo_bar_baz):
+    pass
+
+nested = "hello this is a slightly long string" if (some_long_value_name_foo_bar_baz if
+                                                    nesting_test_expressions else some_fallback_value_foo_bar_baz) \
+    else "this one is a little shorter"
+
+generator_expression = (
+    some_long_value_name_foo_bar_baz if some_boolean_variable else some_fallback_value_foo_bar_baz for some_boolean_variable in some_iterable
+)
+
+
+def limit_offset_sql(self, low_mark, high_mark):
+    """Return LIMIT/OFFSET SQL clause."""
+    limit, offset = self._get_limit_offset_params(low_mark, high_mark)
+    return " ".join(
+        sql
+        for sql in (
+            "LIMIT %d" % limit if limit else None,
+            ("OFFSET %d" % offset) if offset else None,
+        )
+        if sql
+    )
+
+
+def something():
+    clone._iterable_class = (
+        NamedValuesListIterable
+        if named
+        else FlatValuesListIterable
+        if flat
+        else ValuesListIterable
+    )
+
+# output
+
+long_kwargs_single_line = my_function(
+    foo="test, this is a sample value",
+    bar=(
+        some_long_value_name_foo_bar_baz
+        if some_boolean_variable
+        else some_fallback_value_foo_bar_baz
+    ),
+    baz="hello, this is a another value",
+)
+
+multiline_kwargs_indented = my_function(
+    foo="test, this is a sample value",
+    bar=(
+        some_long_value_name_foo_bar_baz
+        if some_boolean_variable
+        else some_fallback_value_foo_bar_baz
+    ),
+    baz="hello, this is a another value",
+)
+
+imploding_kwargs = my_function(
+    foo="test, this is a sample value",
+    bar=a if foo else b,
+    baz="hello, this is a another value",
+)
+
+imploding_line = 1 if 1 + 1 == 2 else 0
+
+exploding_line = (
+    "hello this is a slightly long string"
+    if some_long_value_name_foo_bar_baz
+    else "this one is a little shorter"
+)
+
+positional_argument_test(
+    some_long_value_name_foo_bar_baz
+    if some_boolean_variable
+    else some_fallback_value_foo_bar_baz
+)
+
+
+def weird_default_argument(
+    x=(
+        some_long_value_name_foo_bar_baz
+        if SOME_CONSTANT
+        else some_fallback_value_foo_bar_baz
+    ),
+):
+    pass
+
+
+nested = (
+    "hello this is a slightly long string"
+    if (
+        some_long_value_name_foo_bar_baz
+        if nesting_test_expressions
+        else some_fallback_value_foo_bar_baz
+    )
+    else "this one is a little shorter"
+)
+
+generator_expression = (
+    (
+        some_long_value_name_foo_bar_baz
+        if some_boolean_variable
+        else some_fallback_value_foo_bar_baz
+    )
+    for some_boolean_variable in some_iterable
+)
+
+
+def limit_offset_sql(self, low_mark, high_mark):
+    """Return LIMIT/OFFSET SQL clause."""
+    limit, offset = self._get_limit_offset_params(low_mark, high_mark)
+    return " ".join(
+        sql
+        for sql in (
+            "LIMIT %d" % limit if limit else None,
+            ("OFFSET %d" % offset) if offset else None,
+        )
+        if sql
+    )
+
+
+def something():
+    clone._iterable_class = (
+        NamedValuesListIterable
+        if named
+        else FlatValuesListIterable if flat else ValuesListIterable
+    )