Handle more huggable immediately nested parens/brackets. (#4012)

Fixes #4011

CHANGES.md

@@ -14,6 +14,9 @@
 
 <!-- Changes that affect Black's preview style -->
 
+- Additional cases of immediately nested tuples, lists, and dictionaries are now
+  indented less (#4012)
+
 ### Configuration
 
 <!-- Changes to how Black can be configured -->

docs/conf.py

@@ -149,15 +149,13 @@ def make_pypi_svg(version: str) -> None:
 # Grouping the document tree into LaTeX files. List of tuples
 # (source start file, target name, title,
 #  author, documentclass [howto, manual, or own class]).
-latex_documents = [
-    (
+latex_documents = [(
     master_doc,
     "black.tex",
     "Documentation for Black",
     "Łukasz Langa and contributors to Black",
     "manual",
-    )
-]
+)]
 
 
 # -- Options for manual page output ------------------------------------------
@@ -172,8 +170,7 @@ def make_pypi_svg(version: str) -> None:
 # Grouping the document tree into Texinfo files. List of tuples
 # (source start file, target name, title, author,
 #  dir menu entry, description, category)
-texinfo_documents = [
-    (
+texinfo_documents = [(
     master_doc,
     "Black",
     "Documentation for Black",
@@ -181,8 +178,7 @@ def make_pypi_svg(version: str) -> None:
     "Black",
     "The uncompromising Python code formatter",
     "Miscellaneous",
-    )
-]
+)]
 
 
 # -- Options for Epub output -------------------------------------------------

docs/the_black_code_style/future_style.md

@@ -116,8 +116,7 @@ my_dict = {
 ### Improved multiline dictionary and list indentation for sole function parameter
 
 For better readability and less verticality, _Black_ now pairs parentheses ("(", ")")
-with braces ("{", "}") and square brackets ("[", "]") on the same line for single
-parameter function calls. For example:
+with braces ("{", "}") and square brackets ("[", "]") on the same line. For example:
 
 ```python
 foo(
@@ -127,6 +126,14 @@ foo(
         3,
     ]
 )
+
+nested_array = [
+    [
+        1,
+        2,
+        3,
+    ]
+]
 ```
 
 will be changed to:
@@ -137,6 +144,12 @@ foo([
     2,
     3,
 ])
+
+nested_array = [[
+    1,
+    2,
+    3,
+]]
 ```
 
 This also applies to list and dictionary unpacking:

src/black/cache.py

@@ -124,9 +124,9 @@ def filtered_cached(self, sources: Iterable[Path]) -> Tuple[Set[Path], Set[Path]
 
     def write(self, sources: Iterable[Path]) -> None:
         """Update the cache file data and write a new cache file."""
-        self.file_data.update(**{
-            str(src.resolve()): Cache.get_file_data(src) for src in sources
-        })
+        self.file_data.update(
+            **{str(src.resolve()): Cache.get_file_data(src) for src in sources}
+        )
         try:
             CACHE_DIR.mkdir(parents=True, exist_ok=True)
             with tempfile.NamedTemporaryFile(

src/black/handle_ipynb_magics.py

@@ -17,16 +17,13 @@
 from black.output import out
 from black.report import NothingChanged
 
-TRANSFORMED_MAGICS = frozenset(
-    (
+TRANSFORMED_MAGICS = frozenset((
     "get_ipython().run_cell_magic",
     "get_ipython().system",
     "get_ipython().getoutput",
     "get_ipython().run_line_magic",
-    )
-)
-TOKENS_TO_IGNORE = frozenset(
-    (
+))
+TOKENS_TO_IGNORE = frozenset((
     "ENDMARKER",
     "NL",
     "NEWLINE",
@@ -34,10 +31,8 @@
     "DEDENT",
     "UNIMPORTANT_WS",
     "ESCAPED_NL",
-    )
-)
-PYTHON_CELL_MAGICS = frozenset(
-    (
+))
+PYTHON_CELL_MAGICS = frozenset((
     "capture",
     "prun",
     "pypy",
@@ -45,8 +40,7 @@
     "python3",
     "time",
     "timeit",
-    )
-)
+))
 TOKEN_HEX = secrets.token_hex
 
 

src/black/linegen.py

@@ -817,22 +817,63 @@ def _first_right_hand_split(
     body_leaves.reverse()
     head_leaves.reverse()
 
-    if Preview.hug_parens_with_braces_and_square_brackets in line.mode:
-        is_unpacking = 1 if body_leaves[0].type in [token.STAR, token.DOUBLESTAR] else 0
+    body: Optional[Line] = None
     if (
-            tail_leaves[0].type == token.RPAR
+        Preview.hug_parens_with_braces_and_square_brackets in line.mode
         and tail_leaves[0].value
         and tail_leaves[0].opening_bracket is head_leaves[-1]
-            and body_leaves[-1].type in [token.RBRACE, token.RSQB]
-            and body_leaves[-1].opening_bracket is body_leaves[is_unpacking]
     ):
-            head_leaves = head_leaves + body_leaves[: 1 + is_unpacking]
-            tail_leaves = body_leaves[-1:] + tail_leaves
-            body_leaves = body_leaves[1 + is_unpacking : -1]
+        inner_body_leaves = list(body_leaves)
+        hugged_opening_leaves: List[Leaf] = []
+        hugged_closing_leaves: List[Leaf] = []
+        is_unpacking = body_leaves[0].type in [token.STAR, token.DOUBLESTAR]
+        unpacking_offset: int = 1 if is_unpacking else 0
+        while (
+            len(inner_body_leaves) >= 2 + unpacking_offset
+            and inner_body_leaves[-1].type in CLOSING_BRACKETS
+            and inner_body_leaves[-1].opening_bracket
+            is inner_body_leaves[unpacking_offset]
+        ):
+            if unpacking_offset:
+                hugged_opening_leaves.append(inner_body_leaves.pop(0))
+                unpacking_offset = 0
+            hugged_opening_leaves.append(inner_body_leaves.pop(0))
+            hugged_closing_leaves.insert(0, inner_body_leaves.pop())
+
+        if hugged_opening_leaves and inner_body_leaves:
+            inner_body = bracket_split_build_line(
+                inner_body_leaves,
+                line,
+                hugged_opening_leaves[-1],
+                component=_BracketSplitComponent.body,
+            )
+            if (
+                line.mode.magic_trailing_comma
+                and inner_body_leaves[-1].type == token.COMMA
+            ):
+                should_hug = True
+            else:
+                line_length = line.mode.line_length - sum(
+                    len(str(leaf))
+                    for leaf in hugged_opening_leaves + hugged_closing_leaves
+                )
+                if is_line_short_enough(
+                    inner_body, mode=replace(line.mode, line_length=line_length)
+                ):
+                    # Do not hug if it fits on a single line.
+                    should_hug = False
+                else:
+                    should_hug = True
+            if should_hug:
+                body_leaves = inner_body_leaves
+                head_leaves.extend(hugged_opening_leaves)
+                tail_leaves = hugged_closing_leaves + tail_leaves
+                body = inner_body  # No need to re-calculate the body again later.
 
     head = bracket_split_build_line(
         head_leaves, line, opening_bracket, component=_BracketSplitComponent.head
     )
+    if body is None:
         body = bracket_split_build_line(
             body_leaves, line, opening_bracket, component=_BracketSplitComponent.body
         )

tests/data/cases/preview_hug_parens_with_braces_and_square_brackets.py

@@ -128,6 +128,19 @@ def foo_square_brackets(request):
 func({"short line"})
 func({"long line", "long long line", "long long long line", "long long long long line", "long long long long long line"})
 func({{"long line", "long long line", "long long long line", "long long long long line", "long long long long long line"}})
+func(("long line", "long long line", "long long long line", "long long long long line", "long long long long long line"))
+func((("long line", "long long line", "long long long line", "long long long long line", "long long long long long line")))
+func([["long line", "long long line", "long long long line", "long long long long line", "long long long long long line"]])
+
+# Do not hug if the argument fits on a single line.
+func({"fit line", "fit line", "fit line", "fit line", "fit line", "fit line", "fit line"})
+func(("fit line", "fit line", "fit line", "fit line", "fit line", "fit line", "fit line"))
+func(["fit line", "fit line", "fit line", "fit line", "fit line", "fit line", "fit line"])
+func(**{"fit line", "fit line", "fit line", "fit line", "fit line", "fit line", "fit---"})
+func(*("fit line", "fit line", "fit line", "fit line", "fit line", "fit line", "fit----"))
+array = [{"fit line", "fit line", "fit line", "fit line", "fit line", "fit line", "fit line"}]
+array = [("fit line", "fit line", "fit line", "fit line", "fit line", "fit line", "fit line")]
+array = [["fit line", "fit line", "fit line", "fit line", "fit line", "fit line", "fit line"]]
 
 foooooooooooooooooooo(
     [{c: n + 1 for c in range(256)} for n in range(100)] + [{}], {size}
@@ -137,6 +150,13 @@ def foo_square_brackets(request):
     [1, 2, 3, 4, 5, 6, 7, 8, 9, 10], {x}, "a string", [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
 )
 
+nested_mapping = {"key": [{"a very long key 1": "with a very long value", "a very long key 2": "with a very long value"}]}
+nested_array = [[["long line", "long long line", "long long long line", "long long long long line", "long long long long long line"]]]
+explicit_exploding = [[["short", "line",],],]
+single_item_do_not_explode = Context({
+    "version": get_docs_version(),
+})
+
 foo(*["long long long long long line", "long long long long long line", "long long long long long line"])
 
 foo(*[str(i) for i in range(100000000000000000000000000000000000000000000000000000000000)])
@@ -152,6 +172,9 @@ def foo_square_brackets(request):
 
 foo(**{x: y for x, y in enumerate(["long long long long line","long long long long line"])})
 
+# Edge case when deciding whether to hug the brackets without inner content.
+very_very_very_long_variable = very_very_very_long_module.VeryVeryVeryVeryLongClassName([[]])
+
 for foo in ["a", "b"]:
     output.extend([
         individual
@@ -276,9 +299,9 @@ def foo_square_brackets(request):
 )
 
 func([x for x in "short line"])
-func([
-    x for x in "long line long line long line long line long line long line long line"
-])
+func(
+    [x for x in "long line long line long line long line long line long line long line"]
+)
 func([
     x
     for x in [
@@ -295,15 +318,60 @@ def foo_square_brackets(request):
     "long long long long line",
     "long long long long long line",
 })
-func({
-    {
+func({{
     "long line",
     "long long line",
     "long long long line",
     "long long long long line",
     "long long long long long line",
-    }
-})
+}})
+func((
+    "long line",
+    "long long line",
+    "long long long line",
+    "long long long long line",
+    "long long long long long line",
+))
+func(((
+    "long line",
+    "long long line",
+    "long long long line",
+    "long long long long line",
+    "long long long long long line",
+)))
+func([[
+    "long line",
+    "long long line",
+    "long long long line",
+    "long long long long line",
+    "long long long long long line",
+]])
+
+# Do not hug if the argument fits on a single line.
+func(
+    {"fit line", "fit line", "fit line", "fit line", "fit line", "fit line", "fit line"}
+)
+func(
+    ("fit line", "fit line", "fit line", "fit line", "fit line", "fit line", "fit line")
+)
+func(
+    ["fit line", "fit line", "fit line", "fit line", "fit line", "fit line", "fit line"]
+)
+func(
+    **{"fit line", "fit line", "fit line", "fit line", "fit line", "fit line", "fit---"}
+)
+func(
+    *("fit line", "fit line", "fit line", "fit line", "fit line", "fit line", "fit----")
+)
+array = [
+    {"fit line", "fit line", "fit line", "fit line", "fit line", "fit line", "fit line"}
+]
+array = [
+    ("fit line", "fit line", "fit line", "fit line", "fit line", "fit line", "fit line")
+]
+array = [
+    ["fit line", "fit line", "fit line", "fit line", "fit line", "fit line", "fit line"]
+]
 
 foooooooooooooooooooo(
     [{c: n + 1 for c in range(256)} for n in range(100)] + [{}], {size}
@@ -313,6 +381,31 @@ def foo_square_brackets(request):
     [1, 2, 3, 4, 5, 6, 7, 8, 9, 10], {x}, "a string", [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
 )
 
+nested_mapping = {
+    "key": [{
+        "a very long key 1": "with a very long value",
+        "a very long key 2": "with a very long value",
+    }]
+}
+nested_array = [[[
+    "long line",
+    "long long line",
+    "long long long line",
+    "long long long long line",
+    "long long long long long line",
+]]]
+explicit_exploding = [
+    [
+        [
+            "short",
+            "line",
+        ],
+    ],
+]
+single_item_do_not_explode = Context({
+    "version": get_docs_version(),
+})
+
 foo(*[
     "long long long long long line",
     "long long long long long line",
@@ -334,6 +427,11 @@ def foo_square_brackets(request):
     x: y for x, y in enumerate(["long long long long line", "long long long long line"])
 })
 
+# Edge case when deciding whether to hug the brackets without inner content.
+very_very_very_long_variable = very_very_very_long_module.VeryVeryVeryVeryLongClassName(
+    [[]]
+)
+
 for foo in ["a", "b"]:
     output.extend([
         individual

tests/data/cases/preview_long_strings__regression.py

@@ -611,14 +611,13 @@ def foo():
 
 class A:
     def foo():
-        XXXXXXXXXXXX.append(
-            (
-                "xxx_xxxxxxxxxx(xxxxx={}, xxxx={}, xxxxx, xxxx_xxxx_xxxxxxxxxx={})"
-                .format(xxxxx, xxxx, xxxx_xxxx_xxxxxxxxxx),
+        XXXXXXXXXXXX.append((
+            "xxx_xxxxxxxxxx(xxxxx={}, xxxx={}, xxxxx, xxxx_xxxx_xxxxxxxxxx={})".format(
+                xxxxx, xxxx, xxxx_xxxx_xxxxxxxxxx
+            ),
             my_var,
             my_other_var,
-            )
-        )
+        ))
 
 
 class A: