From b94bb2229ba57f7afb6b026a3fd7f0abca661b1e Mon Sep 17 00:00:00 2001
From: Eryx-Z <Eryx-Z@users.noreply.github.com>
Date: Sat, 17 Oct 2026 07:57:17 +0800
Subject: [PATCH 1/3] Cache directory collection when multiple file args share
 a parent

Session.collect disabled the collection cache for a file's parent
Directory whenever the remaining match part was a single file path.
That made N explicit file arguments from the same directory re-walk
the directory N times (quadratic in directory size).

Keep using the cache for Directory nodes unless --keep-duplicates is
set; file-level non-dedup is already handled in genitems.

Fixes #15187.
---
 src/_pytest/main.py        | 12 +++++++++++-
 testing/test_collection.py | 24 ++++++++++++++++++++++++
 2 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/src/_pytest/main.py b/src/_pytest/main.py
index d43a68b4679..ab754a96449 100644
--- a/src/_pytest/main.py
+++ b/src/_pytest/main.py
@@ -992,11 +992,21 @@ def collect(self) -> Iterator[nodes.Item | nodes.Collector]:
                 else:
                     # For backward compat, files given directly multiple
                     # times on the command line should not be deduplicated.
-                    handle_dupes = not (
+                    # That intent applies to File nodes (handled in genitems);
+                    # Directory/Package parents must still use the collection
+                    # cache, otherwise N file args from the same directory
+                    # re-walk the directory N times (#15187). Keep the cache
+                    # off under --keep-duplicates so a file named twice still
+                    # gets two Module nodes.
+                    file_arg_leaf = (
                         len(matchparts) == 1
                         and isinstance(matchparts[0], Path)
                         and matchparts[0].is_file()
                     )
+                    handle_dupes = (
+                        isinstance(matchnode, nodes.Directory)
+                        and not self.config.option.keepduplicates
+                    ) or not file_arg_leaf
                     rep, duplicate = self._collect_one_node(matchnode, handle_dupes)
                     if not duplicate and not rep.passed:
                         # Report collection failures here to avoid failing to
diff --git a/testing/test_collection.py b/testing/test_collection.py
index f7cdc60a1c3..9834e1e58a8 100644
--- a/testing/test_collection.py
+++ b/testing/test_collection.py
@@ -2807,3 +2807,27 @@ def test1(x):
             "Duplicates:     a",
         ]
     )
+
+
+def test_directory_collection_cached_for_multiple_file_args(pytester: Pytester) -> None:
+    """File args from one directory must not re-collect that directory each time.
+
+    See https://github.com/pytest-dev/pytest/issues/15187
+    """
+    calls: dict[str, int] = {}
+
+    class Plugin:
+        def pytest_collect_file(self, file_path: Path) -> None:
+            calls[file_path.name] = calls.get(file_path.name, 0) + 1
+
+    for i in range(5):
+        pytester.makepyfile(**{f"test_{i:04d}": "def test_x():\n    pass\n"})
+
+    files = [pytester.path / f"test_{i:04d}.py" for i in range(5)]
+    result = pytester.runpytest(
+        "--collect-only", "-q", "-p", "no:cacheprovider", *map(str, files), plugins=[Plugin()]
+    )
+    assert result.ret == 0
+    # Each file offered once (plus possibly non-test files; assert the repeated ones)
+    for i in range(5):
+        assert calls.get(f"test_{i:04d}.py", 0) == 1, calls

From eb2baaa0634d434181cab98f6433348a5eac5060 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Fri, 16 Oct 2026 23:59:08 +0000
Subject: [PATCH 2/3] [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci
---
 testing/test_collection.py | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/testing/test_collection.py b/testing/test_collection.py
index 9834e1e58a8..881c560ff59 100644
--- a/testing/test_collection.py
+++ b/testing/test_collection.py
@@ -2825,7 +2825,12 @@ def pytest_collect_file(self, file_path: Path) -> None:
 
     files = [pytester.path / f"test_{i:04d}.py" for i in range(5)]
     result = pytester.runpytest(
-        "--collect-only", "-q", "-p", "no:cacheprovider", *map(str, files), plugins=[Plugin()]
+        "--collect-only",
+        "-q",
+        "-p",
+        "no:cacheprovider",
+        *map(str, files),
+        plugins=[Plugin()],
     )
     assert result.ret == 0
     # Each file offered once (plus possibly non-test files; assert the repeated ones)

From 67e984f7135e7996bda0496790ac93893620af4b Mon Sep 17 00:00:00 2001
From: Eryx-Z <41898282+Eryx-Z@users.noreply.github.com>
Date: Sat, 17 Oct 2026 09:44:37 +0800
Subject: [PATCH 3/3] Add changelog entry for directory collection cache

---
 changelog/15187.bugfix.rst | 3 +++
 1 file changed, 3 insertions(+)
 create mode 100644 changelog/15187.bugfix.rst

diff --git a/changelog/15187.bugfix.rst b/changelog/15187.bugfix.rst
new file mode 100644
index 00000000000..27f285e2804
--- /dev/null
+++ b/changelog/15187.bugfix.rst
@@ -0,0 +1,3 @@
+Directory collection is now cached when multiple file path arguments share a
+parent directory (unless ``--keep-duplicates`` is set), avoiding repeated
+directory scans during collection.