From 61ca66558ea90b646a2c67b37e2c0dabf41bb5f1 Mon Sep 17 00:00:00 2001
From: NIK-TIGER-BILL <nik.tiger.bill@github.com>
Date: Thu, 28 May 2026 00:04:42 +0000
Subject: [PATCH 1/2] fix(capture): guard snap() against closed tmpfile
 (#14528)

When collection short-circuits (e.g. no tests found in a dot-prefix path),
the capture teardown can call snap() on a capture whose tmpfile has already
been closed by done().  This produces:

    ValueError: I/O operation on closed file.

Add an early closed-file guard to all snap() implementations so they
gracefully return their EMPTY_BUFFER instead of raising.

Fixes #14528

Signed-off-by: NIK-TIGER-BILL <nik.tiger.bill@github.com>
---
 src/_pytest/capture.py  |  6 ++++++
 testing/test_capture.py | 28 ++++++++++++++++++++++++++++
 2 files changed, 34 insertions(+)

diff --git a/src/_pytest/capture.py b/src/_pytest/capture.py
index 6d98676be5f..48b2f153de7 100644
--- a/src/_pytest/capture.py
+++ b/src/_pytest/capture.py
@@ -449,6 +449,8 @@ class SysCapture(SysCaptureBase[str]):
 
     def snap(self) -> str:
         self._assert_state("snap", ("started", "suspended"))
+        if getattr(self.tmpfile, "closed", False):
+            return self.EMPTY_BUFFER
         assert isinstance(self.tmpfile, CaptureIO)
         res = self.tmpfile.getvalue()
         self.tmpfile.seek(0)
@@ -566,6 +568,8 @@ class FDCaptureBinary(FDCaptureBase[bytes]):
 
     def snap(self) -> bytes:
         self._assert_state("snap", ("started", "suspended"))
+        if getattr(self.tmpfile, "closed", False):
+            return self.EMPTY_BUFFER
         self.tmpfile.seek(0)
         res = self.tmpfile.buffer.read()
         self.tmpfile.seek(0)
@@ -588,6 +592,8 @@ class FDCapture(FDCaptureBase[str]):
 
     def snap(self) -> str:
         self._assert_state("snap", ("started", "suspended"))
+        if getattr(self.tmpfile, "closed", False):
+            return self.EMPTY_BUFFER
         self.tmpfile.seek(0)
         res = self.tmpfile.read()
         self.tmpfile.seek(0)
diff --git a/testing/test_capture.py b/testing/test_capture.py
index 7aaba99fe43..34f62115e46 100644
--- a/testing/test_capture.py
+++ b/testing/test_capture.py
@@ -1750,3 +1750,31 @@ def pytest_terminal_summary(config):
     match = re.search(r"^value: '(.*)'\r?$", rest, re.MULTILINE)
     assert match is not None
     assert match.group(1) == "hi"
+
+
+
+def test_snap_on_closed_tmpfile() -> None:
+    """Regression test for #14528: snap() should not crash when tmpfile is closed."""
+    # FDCapture
+    cap = capture.FDCapture(1)
+    cap.start()
+    cap.done()
+    assert cap.snap() == ''
+
+    # FDCaptureBinary
+    capb = capture.FDCaptureBinary(1)
+    capb.start()
+    capb.done()
+    assert capb.snap() == b''
+
+    # SysCapture
+    caps = capture.SysCapture(1)
+    caps.start()
+    caps.done()
+    assert caps.snap() == ''
+
+    # SysCaptureBinary
+    capsb = capture.SysCaptureBinary(1)
+    capsb.start()
+    capsb.done()
+    assert capsb.snap() == b''

From 41db7a3f5e93a227954ca9ef7eb261a1fa2ead1d Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Thu, 28 May 2026 00:07:10 +0000
Subject: [PATCH 2/2] [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci
---
 testing/test_capture.py | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/testing/test_capture.py b/testing/test_capture.py
index 34f62115e46..dc1edafd5d5 100644
--- a/testing/test_capture.py
+++ b/testing/test_capture.py
@@ -1752,29 +1752,28 @@ def pytest_terminal_summary(config):
     assert match.group(1) == "hi"
 
 
-
 def test_snap_on_closed_tmpfile() -> None:
     """Regression test for #14528: snap() should not crash when tmpfile is closed."""
     # FDCapture
     cap = capture.FDCapture(1)
     cap.start()
     cap.done()
-    assert cap.snap() == ''
+    assert cap.snap() == ""
 
     # FDCaptureBinary
     capb = capture.FDCaptureBinary(1)
     capb.start()
     capb.done()
-    assert capb.snap() == b''
+    assert capb.snap() == b""
 
     # SysCapture
     caps = capture.SysCapture(1)
     caps.start()
     caps.done()
-    assert caps.snap() == ''
+    assert caps.snap() == ""
 
     # SysCaptureBinary
     capsb = capture.SysCaptureBinary(1)
     capsb.start()
     capsb.done()
-    assert capsb.snap() == b''
+    assert capsb.snap() == b""