From 731ace6f661ab15718513dc11a3de27ceb79da03 Mon Sep 17 00:00:00 2001
From: Hussein Faara <faarahussein@gmail.com>
Date: Thu, 21 Dec 2023 22:40:52 -0800
Subject: [PATCH] Read exclude patterns from .gitignore in absence of
 user-provided patterns (#344)

Use .gitignore to exclude files if --exclude is missing from both
pyproject.toml and the command line. Vulture now requires the
pathspec library to run.
---
 CHANGELOG.md                     |  1 +
 README.md                        |  4 +++
 setup.py                         |  5 ++-
 tests/test_gitignore_patterns.py | 56 ++++++++++++++++++++++++++++++++
 vulture/core.py                  | 17 +++++++++-
 5 files changed, 81 insertions(+), 2 deletions(-)
 create mode 100644 tests/test_gitignore_patterns.py

diff --git a/CHANGELOG.md b/CHANGELOG.md
index d9ec6de8..aa4bc07e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,7 @@
 * Bump flake8, flake8-comprehensions and flake8-bugbear (Sebastian Csar, #341).
 * Switch to tomllib/tomli to support heterogeneous arrays (Sebastian Csar, #340).
 * Provide whitelist parity for `MagicMock` and `Mock` (maxrake).
+* Use .gitignore to exclude files if --exclude is missing from both pyproject.toml and the command line.
 
 # 2.10 (2023-10-06)
 
diff --git a/README.md b/README.md
index 99b2ec81..981d9ef8 100644
--- a/README.md
+++ b/README.md
@@ -83,6 +83,10 @@ If you want to ignore a whole file or directory, use the `--exclude` parameter
 (e.g., `--exclude "*settings.py,*/docs/*.py,*/test_*.py,*/.venv/*.py"`). The
 exclude patterns are matched against absolute paths.
 
+Note that releases after 2.10 will parse the project's .gitignore files for
+exclude patterns if the `--exclude` parameter is unused and if there are no
+exclude patterns in the pyproject.toml file.
+
 #### Flake8 noqa comments
 
 <!-- Hide noqa docs until we decide whether we want to support it.
diff --git a/setup.py b/setup.py
index 48549415..8a049726 100644
--- a/setup.py
+++ b/setup.py
@@ -47,7 +47,10 @@ def find_version(*parts):
         "Programming Language :: Python :: Implementation :: PyPy",
         "Topic :: Software Development :: Quality Assurance",
     ],
-    install_requires=["tomli >= 1.1.0; python_version < '3.11'"],
+    install_requires=[
+        "tomli >= 1.1.0; python_version < '3.11'",
+        "pathspec >= 0.12.1",
+    ],
     entry_points={"console_scripts": ["vulture = vulture.core:main"]},
     python_requires=">=3.8",
     packages=setuptools.find_packages(exclude=["tests"]),
diff --git a/tests/test_gitignore_patterns.py b/tests/test_gitignore_patterns.py
new file mode 100644
index 00000000..0a07adef
--- /dev/null
+++ b/tests/test_gitignore_patterns.py
@@ -0,0 +1,56 @@
+import os
+import pathlib
+import pytest
+import shutil
+
+from . import call_vulture
+from vulture.utils import ExitCode
+
+
+class TempGitignore:
+    def __init__(self, patterns):
+        self.patterns = patterns
+        root = pathlib.Path(".").resolve()
+        self.file = root / ".gitignore"
+        self.tmpfile = root / ".tmp_gitignore"
+
+    def __enter__(self):
+        shutil.move(self.file, self.tmpfile)
+        with open(self.file, "w") as f:
+            f.write("\n".join(self.patterns))
+
+        return self.file
+
+    def __exit__(self, *args):
+        os.remove(self.file)
+        shutil.move(self.tmpfile, self.file)
+
+
+@pytest.fixture(scope="function")
+def gitignore(request):
+    with TempGitignore(request.param) as fpath:
+        yield fpath
+
+
+@pytest.mark.parametrize(
+    "exclude_patterns,gitignore,exit_code",
+    (
+        ([], [], ExitCode.NoDeadCode),
+        ([""], [], ExitCode.NoDeadCode),
+        ([], [""], ExitCode.NoDeadCode),
+        ([""], ["core.py", "utils.py"], ExitCode.NoDeadCode),
+        (["core.py", "utils.py"], [""], ExitCode.DeadCode),
+        ([], ["core.py", "utils.py"], ExitCode.DeadCode),
+    ),
+    indirect=("gitignore",),
+)
+def test_gitignore(exclude_patterns, gitignore, exit_code):
+    def get_csv(paths):
+        return ",".join(os.path.join("vulture", path) for path in paths)
+
+    cli_args = ["vulture/"]
+    if exclude_patterns:
+        cli_args.extend(["--exclude", get_csv(exclude_patterns)])
+
+    assert gitignore.is_file()
+    assert call_vulture(cli_args) == exit_code
diff --git a/vulture/core.py b/vulture/core.py
index b3c845cd..b0f4e64a 100644
--- a/vulture/core.py
+++ b/vulture/core.py
@@ -1,6 +1,7 @@
 import ast
 from fnmatch import fnmatch, fnmatchcase
 from pathlib import Path
+from pathspec import PathSpec
 import pkgutil
 import re
 import string
@@ -114,6 +115,13 @@ def _ignore_variable(filename, varname):
     )
 
 
+def _get_gitignore_pathspec():
+    if (gitignore := Path(".gitignore").resolve()).is_file:
+        with gitignore.open() as fh:
+            return PathSpec.from_lines("gitwildmatch", fh)
+    return PathSpec.from_lines("gitwildmatch", [])
+
+
 class Item:
     """
     Hold the name, type and location of defined code.
@@ -263,9 +271,16 @@ def prepare_pattern(pattern):
             return pattern
 
         exclude = [prepare_pattern(pattern) for pattern in (exclude or [])]
+        gitignore = _get_gitignore_pathspec()
 
         def exclude_path(path):
-            return _match(path, exclude, case=False)
+            # if no exclude patterns are provided through the cli arguments or
+            # a toml file, use .gitignore patterns to inform exclusion
+            return (
+                _match(path, exclude, case=False)
+                if exclude
+                else gitignore.match_file(path)
+            )
 
         paths = [Path(path) for path in paths]