Remove whitespaces of whitespace-only files (#3348)

[etc/vim.git] / src / black / __init__.py

diff --git a/src/black/__init__.py b/src/black/__init__.py
index d9fba41ebd34136560e09ae296e1a4a425dec8f5..7d7ddbe093017e80915b450a2f87a8b785c332b8 100644 (file)
--- a/src/black/__init__.py
+++ b/src/black/__init__.py
@@ -30,6 +30,7 @@ from typing import (
 import click
 from click.core import ParameterSource
 from mypy_extensions import mypyc_attr
+from pathspec import PathSpec
 from pathspec.patterns.gitwildmatch import GitWildMatchPatternError
 
 from _black_version import version as __version__
@@ -497,8 +498,10 @@ def main(  # noqa: C901
             user_level_config = str(find_user_pyproject_toml())
             if config == user_level_config:
                 out(
-                    "Using configuration from user-level config at "
-                    f"'{user_level_config}'.",
+                    (
+                        "Using configuration from user-level config at "
+                        f"'{user_level_config}'."
+                    ),
                     fg="blue",
                 )
             elif config_source in (
@@ -625,6 +628,11 @@ def get_sources(
     sources: Set[Path] = set()
     root = ctx.obj["root"]
 
+    using_default_exclude = exclude is None
+    exclude = re_compile_maybe_verbose(DEFAULT_EXCLUDES) if exclude is None else exclude
+    gitignore: Optional[PathSpec] = None
+    root_gitignore = get_gitignore(root)
+
     for s in src:
         if s == "-" and stdin_filename:
             p = Path(stdin_filename)
@@ -658,16 +666,11 @@ def get_sources(
 
             sources.add(p)
         elif p.is_dir():
-            if exclude is None:
-                exclude = re_compile_maybe_verbose(DEFAULT_EXCLUDES)
-                gitignore = get_gitignore(root)
-                p_gitignore = get_gitignore(p)
-                # No need to use p's gitignore if it is identical to root's gitignore
-                # (i.e. root and p point to the same directory).
-                if gitignore != p_gitignore:
-                    gitignore += p_gitignore
-            else:
-                gitignore = None
+            if using_default_exclude:
+                gitignore = {
+                    root: root_gitignore,
+                    root / p: get_gitignore(p),
+                }
             sources.update(
                 gen_python_files(
                     p.iterdir(),
@@ -914,7 +917,7 @@ def format_file_contents(src_contents: str, *, fast: bool, mode: Mode) -> FileCo
     valid by calling :func:`assert_equivalent` and :func:`assert_stable` on it.
     `mode` is passed to :func:`format_str`.
     """
-    if not src_contents.strip():
+    if not mode.preview and not src_contents.strip():
         raise NothingChanged
 
     if mode.is_ipynb:
@@ -1011,6 +1014,9 @@ def format_ipynb_string(src_contents: str, *, fast: bool, mode: Mode) -> FileCon
     Operate cell-by-cell, only on code cells, only for Python notebooks.
     If the ``.ipynb`` originally had a trailing newline, it'll be preserved.
     """
+    if mode.preview and not src_contents:
+        raise NothingChanged
+
     trailing_newline = src_contents[-1] == "\n"
     modified = False
     nb = json.loads(src_contents)
@@ -1103,6 +1109,13 @@ def _format_str_once(src_contents: str, *, mode: Mode) -> str:
     dst_contents = []
     for block in dst_blocks:
         dst_contents.extend(block.all_lines())
+    if mode.preview and not dst_contents:
+        # Use decode_bytes to retrieve the correct source newline (CRLF or LF),
+        # and check if normalized_content has more than one line
+        normalized_content, _, newline = decode_bytes(src_contents.encode("utf-8"))
+        if "\n" in normalized_content:
+            return newline
+        return ""
     return "".join(dst_contents)