Merge branch 'main' into releasenotes

CHANGES.md

@@ -17,6 +17,9 @@ and the first release covered by our new stability policy.
 - For stubs, one blank line between class attributes and methods is now kept if there's
   at least one pre-existing blank line (#2736)
 - Black now normalizes string prefix order (#2297)
+- Remove spaces around power operators if both operands are simple (#2726)
+- Work around bug that causes unstable formatting in some cases in the presence of the
+  magic trailing comma (#2807)
 
 ### Parser
 
@@ -47,6 +50,9 @@ and the first release covered by our new stability policy.
   Jupyter Notebooks (#2744)
 - Allow setting custom cache directory on all platforms with environment variable
   `BLACK_CACHE_DIR` (#2739).
+- Enable Python 3.10+ by default, without any extra need to specify
+  `--target-version=py310`. (#2758)
+- Make passing `SRC` or `--code` mandatory and mutually exclusive (#2804)
 
 ### Output
 

README.md

@@ -64,16 +64,13 @@ Further information can be found in our docs:
 
 - [Usage and Configuration](https://black.readthedocs.io/en/stable/usage_and_configuration/index.html)
 
-### NOTE: This is a beta product
-
 _Black_ is already [successfully used](https://github.com/psf/black#used-by) by many
-projects, small and big. Black has a comprehensive test suite, with efficient parallel
-tests, and our own auto formatting and parallel Continuous Integration runner. However,
-_Black_ is still beta. Things will probably be wonky for a while. This is made explicit
-by the "Beta" trove classifier, as well as by the "b" in the version number. What this
-means for you is that **until the formatter becomes stable, you should expect some
-formatting to change in the future**. That being said, no drastic stylistic changes are
-planned, mostly responses to bug reports.
+projects, small and big. _Black_ has a comprehensive test suite, with efficient parallel
+tests, and our own auto formatting and parallel Continuous Integration runner. Now that
+we have become stable, you should not expect large formatting to changes in the future.
+Stylistic changes will mostly be responses to bug reports and support for new Python
+syntax. For more information please refer to the
+[The Black Code Style](docs/the_black_code_style/index.rst).
 
 Also, as a safety measure which slows down processing, _Black_ will check that the
 reformatted code still produces a valid AST that is effectively equivalent to the

docs/faq.md

@@ -17,20 +17,17 @@ though.
 
 ## Is Black safe to use?
 
-Yes, for the most part. _Black_ is strictly about formatting, nothing else. But because
-_Black_ is still in [beta](index.rst), some edges are still a bit rough. To combat
-issues, the equivalence of code after formatting is
+Yes. _Black_ is strictly about formatting, nothing else. Black strives to ensure that
+after formatting the AST is
 [checked](the_black_code_style/current_style.md#ast-before-and-after-formatting) with
 limited special cases where the code is allowed to differ. If issues are found, an error
 is raised and the file is left untouched. Magical comments that influence linters and
 other tools, such as `# noqa`, may be moved by _Black_. See below for more details.
 
 ## How stable is Black's style?
 
-Quite stable. _Black_ aims to enforce one style and one style only, with some room for
-pragmatism. However, _Black_ is still in beta so style changes are both planned and
-still proposed on the issue tracker. See
-[The Black Code Style](the_black_code_style/index.rst) for more details.
+Stable. _Black_ aims to enforce one style and one style only, with some room for
+pragmatism. See [The Black Code Style](the_black_code_style/index.rst) for more details.
 
 Starting in 2022, the formatting output will be stable for the releases made in the same
 year (other than unintentional bugs). It is possible to opt-in to the latest formatting

docs/index.rst

@@ -18,16 +18,14 @@ can focus on the content instead.
 
 Try it out now using the `Black Playground <https://black.vercel.app>`_.
 
-.. admonition:: Note - this is a beta product
+.. admonition:: Note - Black is now stable!
 
-   *Black* is already `successfully used <https://github.com/psf/black#used-by>`_ by
+   *Black* is `successfully used <https://github.com/psf/black#used-by>`_ by
    many projects, small and big. *Black* has a comprehensive test suite, with efficient
-   parallel tests, our own auto  formatting and parallel Continuous Integration runner.
-   However, *Black* is still beta. Things will probably be wonky for a while. This is
-   made explicit by the "Beta" trove classifier, as well as by the "b" in the version
-   number. What this means for you is that **until the formatter becomes stable, you
-   should expect some formatting to change in the future**. That being said, no drastic
-   stylistic changes are planned, mostly responses to bug reports.
+   parallel tests, our own auto formatting and parallel Continuous Integration runner.
+   Now that we have become stable, you should not expect large formatting to changes in
+   the future. Stylistic changes will mostly be responses to bug reports and support for new Python
+   syntax.
 
    Also, as a safety measure which slows down processing, *Black* will check that the
    reformatted code still produces a valid AST that is effectively equivalent to the

docs/the_black_code_style/current_style.md

@@ -284,6 +284,26 @@ multiple lines. This is so that _Black_ is compliant with the recent changes in
 [PEP 8](https://www.python.org/dev/peps/pep-0008/#should-a-line-break-before-or-after-a-binary-operator)
 style guide, which emphasizes that this approach improves readability.
 
+Almost all operators will be surrounded by single spaces, the only exceptions are unary
+operators (`+`, `-`, and `~`), and power operators when both operands are simple. For
+powers, an operand is considered simple if it's only a NAME, numeric CONSTANT, or
+attribute access (chained attribute access is allowed), with or without a preceding
+unary operator.
+
+```python
+# For example, these won't be surrounded by whitespace
+a = x**y
+b = config.base**5.2
+c = config.base**runtime.config.exponent
+d = 2**5
+e = 2**~5
+
+# ... but these will be surrounded by whitespace
+f = 2 ** get_exponent()
+g = get_x() ** get_y()
+h = config['base'] ** 2
+```
+
 ### Slices
 
 PEP 8

docs/usage_and_configuration/the_basics.md

@@ -4,11 +4,11 @@ Foundational knowledge on using and configuring Black.
 
 _Black_ is a well-behaved Unix-style command-line tool:
 
-- it does nothing if no sources are passed to it;
+- it does nothing if it finds no sources to format;
 - it will read from standard input and write to standard output if `-` is used as the
   filename;
 - it only outputs messages to users on standard error;
-- exits with code 0 unless an internal error occurred (or `--check` was used).
+- exits with code 0 unless an internal error occurred or a CLI option prompted it.
 
 ## Usage
 

fuzz.py

@@ -32,7 +32,9 @@
         black.FileMode,
         line_length=st.just(88) | st.integers(0, 200),
         string_normalization=st.booleans(),
+        preview=st.booleans(),
         is_pyi=st.booleans(),
+        magic_trailing_comma=st.booleans(),
     ),
 )
 def test_idempotent_any_syntatically_valid_python(

src/black/__init__.py

@@ -431,6 +431,17 @@ def main(
 ) -> None:
     """The uncompromising code formatter."""
     ctx.ensure_object(dict)
+
+    if src and code is not None:
+        out(
+            main.get_usage(ctx)
+            + "\n\n'SRC' and 'code' cannot be passed simultaneously."
+        )
+        ctx.exit(1)
+    if not src and code is None:
+        out(main.get_usage(ctx) + "\n\nOne of 'SRC' or 'code' is required.")
+        ctx.exit(1)
+
     root, method = find_project_root(src) if code is None else (None, None)
     ctx.obj["root"] = root
 
@@ -569,7 +580,6 @@ def get_sources(
 ) -> Set[Path]:
     """Compute the set of files to be formatted."""
     sources: Set[Path] = set()
-    path_empty(src, "No Path provided. Nothing to do 😴", quiet, verbose, ctx)
 
     if exclude is None:
         exclude = re_compile_maybe_verbose(DEFAULT_EXCLUDES)
@@ -958,17 +968,7 @@ def check_stability_and_equivalence(
     content differently.
     """
     assert_equivalent(src_contents, dst_contents)
-
-    # Forced second pass to work around optional trailing commas (becoming
-    # forced trailing commas on pass 2) interacting differently with optional
-    # parentheses.  Admittedly ugly.
-    dst_contents_pass2 = format_str(dst_contents, mode=mode)
-    if dst_contents != dst_contents_pass2:
-        dst_contents = dst_contents_pass2
-        assert_equivalent(src_contents, dst_contents, pass_num=2)
-        assert_stable(src_contents, dst_contents, mode=mode)
-    # Note: no need to explicitly call `assert_stable` if `dst_contents` was
-    # the same as `dst_contents_pass2`.
+    assert_stable(src_contents, dst_contents, mode=mode)
 
 
 def format_file_contents(src_contents: str, *, fast: bool, mode: Mode) -> FileContent:
@@ -1098,7 +1098,7 @@ def format_ipynb_string(src_contents: str, *, fast: bool, mode: Mode) -> FileCon
         raise NothingChanged
 
 
-def format_str(src_contents: str, *, mode: Mode) -> FileContent:
+def format_str(src_contents: str, *, mode: Mode) -> str:
     """Reformat a string and return new contents.
 
     `mode` determines formatting options, such as how many characters per line are
@@ -1128,6 +1128,16 @@ def f(
         hey
 
     """
+    dst_contents = _format_str_once(src_contents, mode=mode)
+    # Forced second pass to work around optional trailing commas (becoming
+    # forced trailing commas on pass 2) interacting differently with optional
+    # parentheses.  Admittedly ugly.
+    if src_contents != dst_contents:
+        return _format_str_once(dst_contents, mode=mode)
+    return dst_contents
+
+
+def _format_str_once(src_contents: str, *, mode: Mode) -> str:
     src_node = lib2to3_parse(src_contents.lstrip(), mode.target_versions)
     dst_contents = []
     future_imports = get_future_imports(src_node)
@@ -1357,7 +1367,10 @@ def assert_equivalent(src: str, dst: str, *, pass_num: int = 1) -> None:
 
 def assert_stable(src: str, dst: str, mode: Mode) -> None:
     """Raise AssertionError if `dst` reformats differently the second time."""
-    newdst = format_str(dst, mode=mode)
+    # We shouldn't call format_str() here, because that formats the string
+    # twice and may hide a bug where we bounce back and forth between two
+    # versions.
+    newdst = _format_str_once(dst, mode=mode)
     if dst != newdst:
         log = dump_to_file(
             str(mode),

src/black/linegen.py

@@ -21,8 +21,8 @@
 from black.numerics import normalize_numeric_literal
 from black.strings import get_string_prefix, fix_docstring
 from black.strings import normalize_string_prefix, normalize_string_quotes
-from black.trans import Transformer, CannotTransform, StringMerger
-from black.trans import StringSplitter, StringParenWrapper, StringParenStripper
+from black.trans import Transformer, CannotTransform, StringMerger, StringSplitter
+from black.trans import StringParenWrapper, StringParenStripper, hug_power_op
 from black.mode import Mode, Feature, Preview
 
 from blib2to3.pytree import Node, Leaf
@@ -404,6 +404,9 @@ def _rhs(
                 transformers = [delimiter_split, standalone_comment_split, rhs]
             else:
                 transformers = [rhs]
+    # It's always safe to attempt hugging of power operations and pretty much every line
+    # could match.
+    transformers.append(hug_power_op)
 
     for transform in transformers:
         # We are accumulating lines in `result` because we might want to abort

src/black/trans.py

@@ -24,9 +24,9 @@
 import sys
 
 if sys.version_info < (3, 8):
-    from typing_extensions import Final
+    from typing_extensions import Literal, Final
 else:
-    from typing import Final
+    from typing import Literal, Final
 
 from mypy_extensions import trait
 
@@ -71,6 +71,88 @@ def TErr(err_msg: str) -> Err[CannotTransform]:
     return Err(cant_transform)
 
 
+def hug_power_op(line: Line, features: Collection[Feature]) -> Iterator[Line]:
+    """A transformer which normalizes spacing around power operators."""
+
+    # Performance optimization to avoid unnecessary Leaf clones and other ops.
+    for leaf in line.leaves:
+        if leaf.type == token.DOUBLESTAR:
+            break
+    else:
+        raise CannotTransform("No doublestar token was found in the line.")
+
+    def is_simple_lookup(index: int, step: Literal[1, -1]) -> bool:
+        # Brackets and parentheses indicate calls, subscripts, etc. ...
+        # basically stuff that doesn't count as "simple". Only a NAME lookup
+        # or dotted lookup (eg. NAME.NAME) is OK.
+        if step == -1:
+            disallowed = {token.RPAR, token.RSQB}
+        else:
+            disallowed = {token.LPAR, token.LSQB}
+
+        while 0 <= index < len(line.leaves):
+            current = line.leaves[index]
+            if current.type in disallowed:
+                return False
+            if current.type not in {token.NAME, token.DOT} or current.value == "for":
+                # If the current token isn't disallowed, we'll assume this is simple as
+                # only the disallowed tokens are semantically attached to this lookup
+                # expression we're checking. Also, stop early if we hit the 'for' bit
+                # of a comprehension.
+                return True
+
+            index += step
+
+        return True
+
+    def is_simple_operand(index: int, kind: Literal["base", "exponent"]) -> bool:
+        # An operand is considered "simple" if's a NAME, a numeric CONSTANT, a simple
+        # lookup (see above), with or without a preceding unary operator.
+        start = line.leaves[index]
+        if start.type in {token.NAME, token.NUMBER}:
+            return is_simple_lookup(index, step=(1 if kind == "exponent" else -1))
+
+        if start.type in {token.PLUS, token.MINUS, token.TILDE}:
+            if line.leaves[index + 1].type in {token.NAME, token.NUMBER}:
+                # step is always one as bases with a preceding unary op will be checked
+                # for simplicity starting from the next token (so it'll hit the check
+                # above).
+                return is_simple_lookup(index + 1, step=1)
+
+        return False
+
+    leaves: List[Leaf] = []
+    should_hug = False
+    for idx, leaf in enumerate(line.leaves):
+        new_leaf = leaf.clone()
+        if should_hug:
+            new_leaf.prefix = ""
+            should_hug = False
+
+        should_hug = (
+            (0 < idx < len(line.leaves) - 1)
+            and leaf.type == token.DOUBLESTAR
+            and is_simple_operand(idx - 1, kind="base")
+            and line.leaves[idx - 1].value != "lambda"
+            and is_simple_operand(idx + 1, kind="exponent")
+        )
+        if should_hug:
+            new_leaf.prefix = ""
+
+        leaves.append(new_leaf)
+
+    yield Line(
+        mode=line.mode,
+        depth=line.depth,
+        leaves=leaves,
+        comments=line.comments,
+        bracket_tracker=line.bracket_tracker,
+        inside_brackets=line.inside_brackets,
+        should_split_rhs=line.should_split_rhs,
+        magic_trailing_comma=line.magic_trailing_comma,
+    )
+
+
 class StringTransformer(ABC):
     """
     An implementation of the Transformer protocol that relies on its

src/black_primer/primer.json

@@ -81,7 +81,7 @@
     },
     "flake8-bugbear": {
       "cli_arguments": ["--experimental-string-processing"],
-      "expect_formatting_changes": false,
+      "expect_formatting_changes": true,
       "git_clone_url": "https://github.com/PyCQA/flake8-bugbear.git",
       "long_checkout": false,
       "py_versions": ["all"]