Read log output by chunks if a line is too long

Fixes #1096.

Modified-by: Povilas Kanapickas <povilas@radix.lt>
Signed-off-by: Yusuke Matsubara <whym@whym.org>

tests/unit/test_compose_run_log_format.py

@@ -0,0 +1,58 @@
+# SPDX-License-Identifier: GPL-2.0
+# pylint: disable=protected-access
+
+import io
+import unittest
+
+from podman_compose import Podman
+
+
+class DummyReader:
+    def __init__(self, data=[]):
+        self.data = data
+
+    async def readuntil(self, x):
+        return self.data.pop(0)
+
+    def at_eof(self):
+        return len(self.data) == 0
+
+
+class TestComposeRunLogFormat(unittest.IsolatedAsyncioTestCase):
+    def setUp(self):
+        self.p = get_minimal_podman()
+        self.buffer = io.StringIO()
+
+    async def test_single_line_single_chunk(self):
+        reader = DummyReader([b'hello, world\n'])
+        await self.p._format_stream(reader, self.buffer, 'LL:')
+        self.assertEqual(self.buffer.getvalue(), 'LL: hello, world\n')
+
+    async def test_empty_line(self):
+        reader = DummyReader([b'\n'])
+        await self.p._format_stream(reader, self.buffer, 'LL:')
+        self.assertEqual(self.buffer.getvalue(), 'LL: \n')
+
+    async def test_line_split(self):
+        reader = DummyReader([b'hello,', b' world\n'])
+        await self.p._format_stream(reader, self.buffer, 'LL:')
+        self.assertEqual(self.buffer.getvalue(), 'LL: hello, world\n')
+
+    async def test_two_lines_in_one_chunk(self):
+        reader = DummyReader([b'hello\nbye\n'])
+        await self.p._format_stream(reader, self.buffer, 'LL:')
+        self.assertEqual(self.buffer.getvalue(), 'LL: hello\nLL: bye\n')
+
+    async def test_double_blank(self):
+        reader = DummyReader([b'hello\n\n\nbye\n'])
+        await self.p._format_stream(reader, self.buffer, 'LL:')
+        self.assertEqual(self.buffer.getvalue(), 'LL: hello\nLL: \nLL: \nLL: bye\n')
+
+    async def test_no_new_line_at_end(self):
+        reader = DummyReader([b'hello\nbye'])
+        await self.p._format_stream(reader, self.buffer, 'LL:')
+        self.assertEqual(self.buffer.getvalue(), 'LL: hello\nLL: bye\n')
+
+
+def get_minimal_podman():
+    return Podman(None)