Add collapse-nested-brackets option

CHANGELOG.md

@@ -2,7 +2,10 @@
 
 ## [Unreleased]
 
+## [0.1.3] - 2023-05-06
+
 - Added
+  - A new configurable option: `--collapse-nested-brackets`
   - A helper script and corresponding tox testenv to check version and changelog
 
 ## [0.1.2] - 2023-05-04

README.md

@@ -208,6 +208,82 @@ var3 = "not wrapped, if the line gets too long"
 | `pyproject.toml` usage | `wrap-line-with-long-string = true` under `[tool.cercis]` |
 | `pre-commit` usage     | `args: [--wrap-line-with-long-string=False]`              |
 
+### 3.4. Collapse nested brackets
+
+_Cercis_ by default collapses nested brackets to make the code more compact.
+
+<table>
+  <tr>
+    <td>
+
+```python
+# Cercis's default style
+
+# If line length limit is 30
+value = np.array([
+    [1, 2, 3, 4, 5],
+    [6, 7, 8, 9, 0],
+])
+
+
+
+# If line length limit is 10
+value = function({
+    1,
+    2,
+    3,
+    4,
+    5,
+})
+
+
+```
+
+  </td>
+
+  <td>
+
+```python
+# Black's style (not configurable)
+
+# If line length limit is 30
+value = np.array(
+    [
+        [1, 2, 3, 4, 5],
+        [6, 7, 8, 9, 0],
+    ]
+)
+
+# If line length limit is 10
+value = function(
+    {
+        1,
+        2,
+        3,
+        4,
+        5,
+    }
+)
+```
+
+  </td>
+
+  </tr>
+</table>
+
+| Option                 |                                                         |
+| ---------------------- | ------------------------------------------------------- |
+| Name                   | `--collapse-nested-brackets`                            |
+| Abbreviation           | `-cnb`                                                  |
+| Default                | `True`                                                  |
+| Black's style          | `False`                                                 |
+| Command line usage     | `cercis -cnb=True myScript.py`                          |
+| `pyproject.toml` usage | `collapse-nested-brackets = true` under `[tool.cercis]` |
+| `pre-commit` usage     | `args: [--collapse-nested-brackets=False]`              |
+
+The code implementation of this option comes from
+[Pyink](https://github.com/google/pyink), another forked project from Black.
+
 ## 4. How to configure _Cercis_
 
 ### 4.1. Dynamically in the command line

pyproject.toml

@@ -9,6 +9,7 @@
 line-length = 88
 function-definition-extra-indent = true
 single-quote = false
+collapse-nested-brackets = false  # use Black style to reduce chances of future merge conflicts
 target-version = ['py37', 'py38']
 include = '\.pyi?$'
 extend-exclude = '''
@@ -33,7 +34,7 @@ build-backend = "hatchling.build"
 
 [project]
 name = "cercis"
-version = "0.1.2"
+version = "0.1.3"
 description = "A more configurable Python code formatter"
 license = { text = "MIT" }
 requires-python = ">=3.7"

src/cercis/__init__.py

@@ -39,6 +39,7 @@
 from cercis.cache import Cache, get_cache_info, read_cache, write_cache
 from cercis.comments import normalize_fmt_off
 from cercis.const import (
+    DEFAULT_COLLAPSE_NESTED_BRACKETS,
     DEFAULT_EXCLUDES,
     DEFAULT_FUNCTION_DEFINITION_EXTRA_INDENT,
     DEFAULT_INCLUDES,
@@ -246,6 +247,17 @@ def validate_regex(
         " wrap that line with the string put in parentheses."
     ),
 )
+@click.option(
+    "-cnb",
+    "--collapse-nested-brackets",
+    type=bool,
+    show_default=True,
+    default=DEFAULT_COLLAPSE_NESTED_BRACKETS,
+    help=(
+        "If True, collapse nested brackets on one line, instead of exploding"
+        " into multiple levels in multiple lines"
+    ),
+)
 @click.option(
     "-t",
     "--target-version",
@@ -466,6 +478,7 @@ def main(  # noqa: C901
         function_definition_extra_indent: bool,
         single_quote: bool,
         wrap_line_with_long_string: bool,
+        collapse_nested_brackets: bool,
         target_version: List[TargetVersion],
         check: bool,
         diff: bool,
@@ -591,6 +604,7 @@ def main(  # noqa: C901
         function_definition_extra_indent=function_definition_extra_indent,
         single_quote=single_quote,
         wrap_line_with_long_string=wrap_line_with_long_string,
+        collapse_nested_brackets=collapse_nested_brackets,
     )
 
     if code is not None:

src/cercis/const.py

@@ -5,3 +5,4 @@
 DEFAULT_FUNCTION_DEFINITION_EXTRA_INDENT = True
 DEFAULT_SINGLE_QUOTE = False
 DEFAULT_WRAP_LINE_WITH_LONG_STRING = False
+DEFAULT_COLLAPSE_NESTED_BRACKETS = True

src/cercis/linegen.py

@@ -75,6 +75,7 @@
     hug_power_op,
 )
 from cercis.utils_line_wrapping import check_eligibility_to_opt_out_of_line_wrapping
+from cercis.utils_linegen import perform_collapse_nested_brackets
 
 # types
 LeafID = int
@@ -747,19 +748,41 @@ def _first_right_hand_split(
     tail_leaves.reverse()
     body_leaves.reverse()
     head_leaves.reverse()
+
+    collapse_nested_brackets_return_values = perform_collapse_nested_brackets(
+        line=line,
+        opening_bracket=opening_bracket,
+        closing_bracket=closing_bracket,
+        head_leaves=head_leaves,
+        body_leaves=body_leaves,
+        tail_leaves=tail_leaves,
+        mode=mode,
+        bracket_split_build_line_func=bracket_split_build_line,
+        bracket_split_component=_BracketSplitComponent,
+    )
+
+    head_leaves = collapse_nested_brackets_return_values.head_leaves
+    body_leaves = collapse_nested_brackets_return_values.body_leaves
+    tail_leaves = collapse_nested_brackets_return_values.tail_leaves
+    body = collapse_nested_brackets_return_values.body
+
     head = bracket_split_build_line(
         head_leaves,
         line,
         opening_bracket,
         component=_BracketSplitComponent.head,
         mode=mode,
     )
-    body = bracket_split_build_line(
-        body_leaves,
-        line,
-        opening_bracket,
-        component=_BracketSplitComponent.body,
-        mode=mode,
+    body = (
+        body
+        if body is not None
+        else bracket_split_build_line(
+            body_leaves,
+            line,
+            opening_bracket,
+            component=_BracketSplitComponent.body,
+            mode=mode,
+        )
     )
     tail = bracket_split_build_line(
         tail_leaves,

src/cercis/mode.py

@@ -18,6 +18,7 @@
     from typing import Final
 
 from cercis.const import (
+    DEFAULT_COLLAPSE_NESTED_BRACKETS,
     DEFAULT_FUNCTION_DEFINITION_EXTRA_INDENT,
     DEFAULT_LINE_LENGTH,
     DEFAULT_SINGLE_QUOTE,
@@ -192,6 +193,7 @@ class Mode:
     function_definition_extra_indent: bool = DEFAULT_FUNCTION_DEFINITION_EXTRA_INDENT
     single_quote: bool = DEFAULT_SINGLE_QUOTE
     wrap_line_with_long_string: bool = DEFAULT_WRAP_LINE_WITH_LONG_STRING
+    collapse_nested_brackets: bool = DEFAULT_COLLAPSE_NESTED_BRACKETS
 
     def __post_init__(self) -> None:
         if self.experimental_string_processing:

src/cercis/utils_linegen.py

@@ -0,0 +1,85 @@
+from dataclasses import dataclass
+from typing import TYPE_CHECKING, Callable, List, Optional, Type
+
+from blib2to3.pgen2 import token
+from blib2to3.pytree import Leaf
+from cercis.lines import Line
+from cercis.nodes import CLOSING_BRACKETS, OPENING_BRACKETS
+
+if TYPE_CHECKING:
+    from cercis.linegen import _BracketSplitComponent
+    from cercis.mode import Mode
+
+
+@dataclass
+class CollapseNestedBracketsReturnValues:
+    head_leaves: List[Leaf]
+    body_leaves: List[Leaf]
+    tail_leaves: List[Leaf]
+    body: Optional[Line]
+
+
+def perform_collapse_nested_brackets(
+        *,
+        line: Line,
+        opening_bracket: Leaf,
+        closing_bracket: Leaf,
+        head_leaves: List[Leaf],
+        body_leaves: List[Leaf],
+        tail_leaves: List[Leaf],
+        mode: "Mode",
+        bracket_split_build_line_func: Callable[..., Line],
+        bracket_split_component: "Type[_BracketSplitComponent]",
+) -> CollapseNestedBracketsReturnValues:
+    """
+    The code of this function comes from a wonderful implementation
+    from another Black fork: https://github.com/google/pyink/blob/f93771c02e9a26ce9508c59d69c9337c95797eac/src/pyink/linegen.py#L778-L815  # noqa: B950
+
+    Pyink inherits the license of Black, which is already included in this
+    repo (the file OLD_LICENSE).
+    """
+    opening_brackets: List[Leaf] = [opening_bracket]
+    body: Optional[Line] = None
+    if mode.collapse_nested_brackets and not (
+        # Only look inside when it doesn't start with invisible parens.
+        opening_bracket.type == token.LPAR
+        and not opening_bracket.value
+        and closing_bracket.type == token.RPAR
+        and not closing_bracket.value
+    ):
+        # Find an inner body...
+        inner_body_leaves = list(body_leaves)
+        inner_opening_brackets: List[Leaf] = []
+        inner_closing_brackets: List[Leaf] = []
+        while (
+            len(inner_body_leaves) >= 2
+            and inner_body_leaves[0].type in OPENING_BRACKETS
+            and inner_body_leaves[-1].type in CLOSING_BRACKETS
+            and inner_body_leaves[-1].opening_bracket is inner_body_leaves[0]
+        ):
+            inner_opening_brackets.append(inner_body_leaves.pop(0))
+            inner_closing_brackets.insert(0, inner_body_leaves.pop())
+        if len(inner_body_leaves) < len(body_leaves):
+            inner_body = bracket_split_build_line_func(
+                inner_body_leaves,
+                line,
+                opening_brackets[0],
+                component=bracket_split_component.body,
+                mode=mode,
+            )
+            if inner_body.should_split_rhs or (
+                inner_body_leaves and inner_body_leaves[-1].type == token.COMMA
+            ):
+                # Only when the inner body itself will be split or ends with a comma,
+                # should we prefer not break immediately nested brackets.
+                body_leaves = inner_body_leaves
+                head_leaves.extend(inner_opening_brackets)
+                tail_leaves = inner_closing_brackets + tail_leaves
+                body = inner_body  # No need to re-calculate body.
+
+    return CollapseNestedBracketsReturnValues(
+        head_leaves=head_leaves,
+        body_leaves=body_leaves,
+        tail_leaves=tail_leaves,
+        body=body,
+    )