From 7300ed2687701bbcb02eac9baa7f5c2197cf1397 Mon Sep 17 00:00:00 2001
From: Jacob Walls <jacobtylerwalls@gmail.com>
Date: Fri, 23 Feb 2024 18:08:33 -0500
Subject: [PATCH] Discover `.pyi` files (#9241)

---
 .pyenchant_pylint_custom_dict.txt   |  1 +
 doc/whatsnew/fragments/9097.feature |  5 +++++
 pylint/lint/pylinter.py             |  8 ++++----
 tests/lint/unittest_lint.py         | 22 ++++++++++++++++++++++
 tests/regrtest_data/pyi/foo.pyi     |  1 +
 5 files changed, 33 insertions(+), 4 deletions(-)
 create mode 100644 doc/whatsnew/fragments/9097.feature
 create mode 100644 tests/regrtest_data/pyi/foo.pyi

diff --git a/.pyenchant_pylint_custom_dict.txt b/.pyenchant_pylint_custom_dict.txt
index 712ab70cca..fd4fed00c3 100644
--- a/.pyenchant_pylint_custom_dict.txt
+++ b/.pyenchant_pylint_custom_dict.txt
@@ -261,6 +261,7 @@ proc
 py
 pyenchant
 pyfile
+pyi
 pylint
 pylintdict
 pylintrc
diff --git a/doc/whatsnew/fragments/9097.feature b/doc/whatsnew/fragments/9097.feature
new file mode 100644
index 0000000000..51874b3604
--- /dev/null
+++ b/doc/whatsnew/fragments/9097.feature
@@ -0,0 +1,5 @@
+Discover ``.pyi`` files when linting.
+
+These can be ignored with the ``ignore-patterns`` setting.
+
+Closes #9097
diff --git a/pylint/lint/pylinter.py b/pylint/lint/pylinter.py
index 541d05f8ef..30250154e6 100644
--- a/pylint/lint/pylinter.py
+++ b/pylint/lint/pylinter.py
@@ -584,8 +584,8 @@ def prepare_checkers(self) -> list[BaseChecker]:
     def should_analyze_file(modname: str, path: str, is_argument: bool = False) -> bool:
         """Returns whether a module should be checked.
 
-        This implementation returns True for all python source file, indicating
-        that all files should be linted.
+        This implementation returns True for all python source files (.py and .pyi),
+        indicating that all files should be linted.
 
         Subclasses may override this method to indicate that modules satisfying
         certain conditions should not be linted.
@@ -599,7 +599,7 @@ def should_analyze_file(modname: str, path: str, is_argument: bool = False) -> b
         """
         if is_argument:
             return True
-        return path.endswith(".py")
+        return path.endswith((".py", ".pyi"))
 
     # pylint: enable=unused-argument
 
@@ -646,7 +646,7 @@ def _discover_files(self, files_or_modules: Sequence[str]) -> Iterator[str]:
                         yield from (
                             os.path.join(root, file)
                             for file in files
-                            if file.endswith(".py")
+                            if file.endswith((".py", ".pyi"))
                         )
             else:
                 yield something
diff --git a/tests/lint/unittest_lint.py b/tests/lint/unittest_lint.py
index 7e4b4dfcca..00e410b469 100644
--- a/tests/lint/unittest_lint.py
+++ b/tests/lint/unittest_lint.py
@@ -1047,6 +1047,28 @@ def test_by_module_statement_value(initialized_linter: PyLinter) -> None:
         assert module_stats["statement"] == linter2.stats.statement
 
 
+def test_finds_pyi_file() -> None:
+    run = Run(
+        [join(REGRTEST_DATA_DIR, "pyi")],
+        exit=False,
+    )
+    assert run.linter.current_file is not None
+    assert run.linter.current_file.endswith("foo.pyi")
+
+
+def test_recursive_finds_pyi_file() -> None:
+    run = Run(
+        [
+            "--recursive",
+            "y",
+            join(REGRTEST_DATA_DIR, "pyi"),
+        ],
+        exit=False,
+    )
+    assert run.linter.current_file is not None
+    assert run.linter.current_file.endswith("foo.pyi")
+
+
 @pytest.mark.parametrize(
     "ignore_parameter,ignore_parameter_value",
     [
diff --git a/tests/regrtest_data/pyi/foo.pyi b/tests/regrtest_data/pyi/foo.pyi
new file mode 100644
index 0000000000..c4e5bcc800
--- /dev/null
+++ b/tests/regrtest_data/pyi/foo.pyi
@@ -0,0 +1 @@
+foo = 1