problem_report: write CompressedValue in chunks as well

In problem reports binary data is compressed in chunks of 1 MB. Each
compressed chunk is base64 encoded and written as one line in the
problem report file. This is the rule for all binary data formats except
for `CompressedValue`.

The problem report files are text files. Text editors like gedit might
choke on text files that have huge lines. So the problem report should
wrap the lines at a reasonable length.

So write `CompressedValue` in chunks as well.

problem_report.py

@@ -307,7 +307,8 @@ def write(self, file: typing.IO[bytes]) -> None:
         # legacy zlib format
         file.write(zlib.decompress(self.compressed_value))
 
-    def _iter_compressed_value(self, chunk_size: int) -> Iterator[bytes]:
+    def iter_compressed(self, chunk_size: int = CHUNK_SIZE) -> Iterator[bytes]:
+        """Iterate over the compressed content in chunks."""
         assert self.compressed_value
         for i in range(0, self.get_compressed_size(), chunk_size):
             yield self.compressed_value[i : i + chunk_size]
@@ -320,9 +321,7 @@ def __len__(self) -> int:
 
         # legacy zlib format and zstandard
         length = 0
-        for block in self.decode_compressed_stream(
-            self._iter_compressed_value(CHUNK_SIZE)
-        ):
+        for block in self.decode_compressed_stream(self.iter_compressed()):
             length += len(block)
         return length
 
@@ -670,13 +669,9 @@ def _generate_compressed_chunks(self, key: str) -> Generator[bytes]:
         # TODO: split into smaller subgenerators
         # pylint: disable=too-many-branches
         value = self.data[key]
-        if isinstance(value, CompressedFile):
+        if isinstance(value, (CompressedFile, CompressedValue)):
             yield from value.iter_compressed()
             return
-        if isinstance(value, CompressedValue):
-            assert value.compressed_value is not None
-            yield value.compressed_value
-            return
         gzip_header = (
             GZIP_HEADER_START
             + b"\010\000\000\000\000\002\377"

tests/unit/test_problem_report.py

@@ -14,7 +14,7 @@
 import time
 import unittest
 import unittest.mock
-from unittest.mock import MagicMock
+from unittest.mock import MagicMock, patch
 
 try:
     import zstandard
@@ -411,6 +411,30 @@ def test_write_empty_fileobj(self) -> None:
         out = io.BytesIO()
         self.assertRaises(OSError, pr.write, out)
 
+    @patch("problem_report.CompressedValue.iter_compressed.__defaults__", (48,))
+    def test_write_compressed_value(self) -> None:
+        """Write a report with a multi-line compressed value."""
+        report = problem_report.ProblemReport(date="now!")
+        report["BinValue"] = problem_report.CompressedValue(
+            compressed_value=b"\x1f\x8b\x08\x00\x00\x00\x00\x00\x02\xff\x0b\xc9HUH\xcc"
+            b"+.O-R(\xc9W\xc8\xc9LK\xd5Q(\x01\x8a\x95\xe6e\x96\xa5\x16\x15\x03y\x89y)"
+            b"\n\xa9@veIFf^:\x00\xa6\xbfr\x950\x00\x00\x00"
+        )
+        out = io.BytesIO()
+        report.write(out)
+        self.assertEqual(
+            out.getvalue().decode(),
+            textwrap.dedent(
+                """\
+                ProblemType: Crash
+                Date: now!
+                BinValue: base64
+                 H4sIAAAAAAAC/wvJSFVIzCsuTy1SKMlXyMlMS9VRKAGKleZllqUWFQN5iXkpCqlA
+                 dmVJRmZeOgCmv3KVMAAAAA==
+                """
+            ),
+        )
+
     def test_read_file(self) -> None:
         """Read a report with binary data."""
         bin_report = textwrap.dedent(