Enhance --verbose

CHANGES.md

@@ -22,6 +22,8 @@
   `values: Tuple[int, ...] = 1, 2, 3`) now implies 3.8+ (#2708)
 - For stubs, one blank line between class attributes and methods is now kept if there's
   at least one pre-existing blank line (#2736)
+- Verbose mode also now describes how a project root was discovered and which paths will
+  be formatted. (#2526)
 
 ### Packaging
 

src/black/__init__.py

@@ -31,6 +31,7 @@
 )
 
 import click
+from click.core import ParameterSource
 from dataclasses import replace
 from mypy_extensions import mypyc_attr
 
@@ -411,8 +412,37 @@ def main(
     config: Optional[str],
 ) -> None:
     """The uncompromising code formatter."""
-    if config and verbose:
-        out(f"Using configuration from {config}.", bold=False, fg="blue")
+    ctx.ensure_object(dict)
+    root, method = find_project_root(src) if code is None else (None, None)
+    ctx.obj["root"] = root
+
+    if verbose:
+        if root:
+            out(
+                f"Identified `{root}` as project root containing a {method}.",
+                fg="blue",
+            )
+
+            normalized = [
+                (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'
+                    for _norm, source in normalized
+                ]
+            )
+            out(f"Sources to be formatted: {srcs_string}", fg="blue")
+
+        if config:
+            config_source = ctx.get_parameter_source("config")
+            if config_source in (ParameterSource.DEFAULT, ParameterSource.DEFAULT_MAP):
+                out("Using configuration from project root.", fg="blue")
+            else:
+                out(f"Using configuration in '{config}'.", fg="blue")
 
     error_msg = "Oh no! 💥 💔 💥"
     if required_version and required_version != __version__:
@@ -516,14 +546,12 @@ def get_sources(
     stdin_filename: Optional[str],
 ) -> Set[Path]:
     """Compute the set of files to be formatted."""
-
-    root = find_project_root(src)
     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)
-        gitignore = get_gitignore(root)
+        gitignore = get_gitignore(ctx.obj["root"])
     else:
         gitignore = None
 
@@ -536,7 +564,7 @@ def get_sources(
             is_stdin = False
 
         if is_stdin or p.is_file():
-            normalized_path = normalize_path_maybe_ignore(p, root, report)
+            normalized_path = normalize_path_maybe_ignore(p, ctx.obj["root"], report)
             if normalized_path is None:
                 continue
 
@@ -563,7 +591,7 @@ def get_sources(
             sources.update(
                 gen_python_files(
                     p.iterdir(),
-                    root,
+                    ctx.obj["root"],
                     include,
                     exclude,
                     extend_exclude,

src/black/files.py

@@ -31,14 +31,18 @@
 
 
 @lru_cache()
-def find_project_root(srcs: Sequence[str]) -> Path:
+def find_project_root(srcs: Sequence[str]) -> Tuple[Path, str]:
     """Return a directory containing .git, .hg, or pyproject.toml.
 
     That directory will be a common parent of all files and directories
     passed in `srcs`.
 
     If no directory in the tree contains a marker that would specify it's the
     project root, the root of the file system is returned.
+
+    Returns a two-tuple with the first element as the project root path and
+    the second element as a string describing the method by which the
+    project root was discovered.
     """
     if not srcs:
         srcs = [str(Path.cwd().resolve())]
@@ -58,20 +62,20 @@ def find_project_root(srcs: Sequence[str]) -> Path:
 
     for directory in (common_base, *common_base.parents):
         if (directory / ".git").exists():
-            return directory
+            return directory, ".git directory"
 
         if (directory / ".hg").is_dir():
-            return directory
+            return directory, ".hg directory"
 
         if (directory / "pyproject.toml").is_file():
-            return directory
+            return directory, "pyproject.toml"
 
-    return directory
+    return directory, "file system root"
 
 
 def find_pyproject_toml(path_search_start: Tuple[str, ...]) -> Optional[str]:
     """Find the absolute filepath to a pyproject.toml if it exists"""
-    path_project_root = find_project_root(path_search_start)
+    path_project_root, _ = find_project_root(path_search_start)
     path_pyproject_toml = path_project_root / "pyproject.toml"
     if path_pyproject_toml.is_file():
         return str(path_pyproject_toml)
@@ -133,7 +137,9 @@ def get_gitignore(root: Path) -> PathSpec:
 
 
 def normalize_path_maybe_ignore(
-    path: Path, root: Path, report: Report
+    path: Path,
+    root: Path,
+    report: Optional[Report] = None,
 ) -> Optional[str]:
     """Normalize `path`. May return `None` if `path` was ignored.
 
@@ -143,12 +149,16 @@ def normalize_path_maybe_ignore(
         abspath = path if path.is_absolute() else Path.cwd() / path
         normalized_path = abspath.resolve().relative_to(root).as_posix()
     except OSError as e:
-        report.path_ignored(path, f"cannot be read because {e}")
+        if report:
+            report.path_ignored(path, f"cannot be read because {e}")
         return None
 
     except ValueError:
         if path.is_symlink():
-            report.path_ignored(path, f"is a symbolic link that points outside {root}")
+            if report:
+                report.path_ignored(
+                    path, f"is a symbolic link that points outside {root}"
+                )
             return None
 
         raise

tests/test_black.py

@@ -100,6 +100,8 @@ class FakeContext(click.Context):
 
     def __init__(self) -> None:
         self.default_map: Dict[str, Any] = {}
+        # Dummy root, since most of the tests don't care about it
+        self.obj: Dict[str, Any] = {"root": PROJECT_ROOT}
 
 
 class FakeParameter(click.Parameter):
@@ -1350,10 +1352,17 @@ def test_find_project_root(self) -> None:
             src_python.touch()
 
             self.assertEqual(
-                black.find_project_root((src_dir, test_dir)), root.resolve()
+                black.find_project_root((src_dir, test_dir)),
+                (root.resolve(), "pyproject.toml"),
+            )
+            self.assertEqual(
+                black.find_project_root((src_dir,)),
+                (src_dir.resolve(), "pyproject.toml"),
+            )
+            self.assertEqual(
+                black.find_project_root((src_python,)),
+                (src_dir.resolve(), "pyproject.toml"),
             )
-            self.assertEqual(black.find_project_root((src_dir,)), src_dir.resolve())
-            self.assertEqual(black.find_project_root((src_python,)), src_dir.resolve())
 
     @patch(
         "black.files.find_user_pyproject_toml",
@@ -1756,6 +1765,7 @@ def assert_collected_sources(
     src: Sequence[Union[str, Path]],
     expected: Sequence[Union[str, Path]],
     *,
+    ctx: Optional[FakeContext] = None,
     exclude: Optional[str] = None,
     include: Optional[str] = None,
     extend_exclude: Optional[str] = None,
@@ -1771,7 +1781,7 @@ def assert_collected_sources(
     )
     gs_force_exclude = None if force_exclude is None else compile_pattern(force_exclude)
     collected = black.get_sources(
-        ctx=FakeContext(),
+        ctx=ctx or FakeContext(),
         src=gs_src,
         quiet=False,
         verbose=False,
@@ -1807,9 +1817,11 @@ def test_gitignore_used_as_default(self) -> None:
             base / "b/.definitely_exclude/a.pyi",
         ]
         src = [base / "b/"]
-        assert_collected_sources(src, expected, extend_exclude=r"/exclude/")
+        ctx = FakeContext()
+        ctx.obj["root"] = base
+        assert_collected_sources(src, expected, ctx=ctx, extend_exclude=r"/exclude/")
 
-    @patch("black.find_project_root", lambda *args: THIS_DIR.resolve())
+    @patch("black.find_project_root", lambda *args: (THIS_DIR.resolve(), None))
     def test_exclude_for_issue_1572(self) -> None:
         # Exclude shouldn't touch files that were explicitly given to Black through the
         # CLI. Exclude is supposed to only apply to the recursive discovery of files.
@@ -1992,13 +2004,13 @@ def test_symlink_out_of_root_directory(self) -> None:
         child.is_symlink.assert_called()
         assert child.is_symlink.call_count == 2
 
-    @patch("black.find_project_root", lambda *args: THIS_DIR.resolve())
+    @patch("black.find_project_root", lambda *args: (THIS_DIR.resolve(), None))
     def test_get_sources_with_stdin(self) -> None:
         src = ["-"]
         expected = ["-"]
         assert_collected_sources(src, expected, include="", exclude=r"/exclude/|a\.py")
 
-    @patch("black.find_project_root", lambda *args: THIS_DIR.resolve())
+    @patch("black.find_project_root", lambda *args: (THIS_DIR.resolve(), None))
     def test_get_sources_with_stdin_filename(self) -> None:
         src = ["-"]
         stdin_filename = str(THIS_DIR / "data/collections.py")
@@ -2010,7 +2022,7 @@ def test_get_sources_with_stdin_filename(self) -> None:
             stdin_filename=stdin_filename,
         )
 
-    @patch("black.find_project_root", lambda *args: THIS_DIR.resolve())
+    @patch("black.find_project_root", lambda *args: (THIS_DIR.resolve(), None))
     def test_get_sources_with_stdin_filename_and_exclude(self) -> None:
         # Exclude shouldn't exclude stdin_filename since it is mimicking the
         # file being passed directly. This is the same as
@@ -2026,7 +2038,7 @@ def test_get_sources_with_stdin_filename_and_exclude(self) -> None:
             stdin_filename=stdin_filename,
         )
 
-    @patch("black.find_project_root", lambda *args: THIS_DIR.resolve())
+    @patch("black.find_project_root", lambda *args: (THIS_DIR.resolve(), None))
     def test_get_sources_with_stdin_filename_and_extend_exclude(self) -> None:
         # Extend exclude shouldn't exclude stdin_filename since it is mimicking the
         # file being passed directly. This is the same as
@@ -2042,7 +2054,7 @@ def test_get_sources_with_stdin_filename_and_extend_exclude(self) -> None:
             stdin_filename=stdin_filename,
         )
 
-    @patch("black.find_project_root", lambda *args: THIS_DIR.resolve())
+    @patch("black.find_project_root", lambda *args: (THIS_DIR.resolve(), None))
     def test_get_sources_with_stdin_filename_and_force_exclude(self) -> None:
         # Force exclude should exclude the file when passing it through
         # stdin_filename