pardes - writes the whole text through one open of the body, so a page over 8 MiB arrives whole, not as its last chunk

Each 8 MiB chunk went in by its own Client.write, which opens a body
with OTRUNC, so every chunk replaced the one before and a long page
kept only its tail, with exit 0. The text now goes in through one open,
truncated once and written at rising offsets; a long write is timed by
its progress, each 9P write answered within 30 s rather than the whole
transfer within 2. fs.py pages 11 MiB of numbered lines and compares
the body byte for byte, and pages past the 256 MiB cap and checks the
first 256 MiB and the cut note.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

1 files changed, 23 insertions, 0 deletions

diff --git a/test/fs.py b/test/fs.py
index b2f52c3e..789021bd 100644
--- a/test/fs.py
+++ b/test/fs.py
@@ -1467,6 +1467,29 @@ def test(binary, quic=False):
             assert serials() - before == {made_now}, (serials(), before)
             assert client.read(f'/pane/{made_now}/body') == b'again\nprogress 100%\n'
             client.remove(f'/pane/{made_now}')
+            # More than one 8 MiB write's worth arrives whole, byte for byte,
+            # in the one +Pager (each write once replaced the last).
+            big = b''.join(b'line %08d of the paged text\n' % i for i in range(400000))  # ~11 MiB
+            assert len(big) > 8 * 1024 * 1024
+            fed = subprocess.run([binary, '-'], cwd=root, env=env, input=big,
+                                 stdout=subprocess.PIPE, stderr=subprocess.PIPE, timeout=120)
+            assert fed.returncode == 0, fed.stderr
+            big_pane, = serials() - before
+            assert client.read(f'/pane/{big_pane}/body') == big, 'the paged body is not the text'
+            # Past the 256 MiB cap: the first 256 MiB, then the cut note.
+            cap = 256 * 1024 * 1024
+            huge = subprocess.Popen(['sh', '-c', f'yes 0123456789abcdef | head -c {cap + 4096}'], stdout=subprocess.PIPE)
+            fed = subprocess.run([binary, '-'], cwd=root, env=env, stdin=huge.stdout,
+                                 stdout=subprocess.PIPE, stderr=subprocess.PIPE, timeout=600)
+            huge.wait()
+            assert fed.returncode == 0, fed.stderr
+            assert serials() - before == {big_pane}
+            got = client.read(f'/pane/{big_pane}/body')
+            note = b'\n[pardes: the rest of stdin is cut: a pane holds at most a file\'s limit]\n'
+            assert got.endswith(note) and len(got) == cap + len(note), (len(got), got[-120:])
+            assert got[:cap] == (b'0123456789abcdef\n' * (cap // 17 + 1))[:cap]
+            del got, big
+            client.remove(f'/pane/{big_pane}')
             # From a directory whose name could not be a ctl line: the
             # session's directory's +Pager, the text whole, no stray +New.
             odd = root / 'two\nlines'