fix(json): serialize non-dict data as JSON in binary mode

CHANGELOG.md

@@ -6,6 +6,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+
+- Fixed binary content mode producing invalid JSON for list, boolean and other
+  non-dict JSON data (e.g. `['a']` instead of `["a"]`).
+
 ## [2.2.0]
 
 ### Changed

src/cloudevents/core/formats/json.py

@@ -172,18 +172,17 @@ def write_data(
         if isinstance(data, str):
             return data.encode("utf-8")
 
-        # If data is a dict and content type is JSON, serialize as JSON
-        if isinstance(data, dict):
-            content_type = datacontenttype or self.DEFAULT_CONTENT_TYPE
-            if re.match(JSONFormat.JSON_CONTENT_TYPE_PATTERN, content_type):
-                return dumps(data, cls=_JSONEncoderWithDatetime).encode("utf-8")
-
-            # for other contenttypes we still try to generate a json-decodable string
-            # if not possible, a string representing
-            try:
-                return dumps(data, cls=_JSONEncoderWithDatetime).encode("utf-8")
-            except TypeError:
-                pass
+        # Any other value (dict, list, number, bool) is serialized as JSON
+        content_type = datacontenttype or self.DEFAULT_CONTENT_TYPE
+        if re.match(JSONFormat.JSON_CONTENT_TYPE_PATTERN, content_type):
+            return dumps(data, cls=_JSONEncoderWithDatetime).encode("utf-8")
+
+        # for other contenttypes we still try to generate a json-decodable string
+        # if not possible, a string representing
+        try:
+            return dumps(data, cls=_JSONEncoderWithDatetime).encode("utf-8")
+        except TypeError:
+            pass
 
         # according to the spec, we return an encoded string per default
         # careful: the result is not json-decodable as the dict keys are single-quoted

tests/test_core/test_format/test_json.py

@@ -14,6 +14,7 @@
 
 from datetime import datetime, timezone
 from json import loads
+from typing import Any
 
 import pytest
 
@@ -339,6 +340,18 @@ def test_write_data_dict(content_type: str) -> None:
     assert loads(result) == data
 
 
+@pytest.mark.parametrize(
+    "content_type", [None, "application/json", "application/octet-stream"]
+)
+@pytest.mark.parametrize("data", [["a", {"b": None}], True, 1.5])
+def test_write_data_non_dict_json_value(content_type: str, data: Any) -> None:
+    formatter = JSONFormat()
+    result = formatter.write_data(data, datacontenttype=content_type)
+
+    assert isinstance(result, bytes)
+    assert loads(result) == data
+
+
 @pytest.mark.parametrize("content_type", [None, "application/json"])
 def test_read_data_json_body(content_type: str) -> None:
     formatter = JSONFormat()