Update JSON formatter to encode bytes as Base64 strings.

.changes/next-release/bugfix-Formatter-25003.json

@@ -0,0 +1,5 @@
+{
+  "type": "bugfix",
+  "category": "Formatter",
+  "description": "Update JSON formatter to encode raw bytes as UTF-8."
+}

awscli/utils.py

@@ -10,6 +10,7 @@
 # distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF
 # ANY KIND, either express or implied. See the License for the specific
 # language governing permissions and limitations under the License.
+import base64
 import contextlib
 import csv
 import datetime
@@ -185,11 +186,14 @@ def operation_uses_document_types(operation_model):
 
 
 def json_encoder(obj):
-    """JSON encoder that formats datetimes as ISO8601 format."""
+    """JSON encoder that formats datetimes as ISO8601 format
+    and encodes bytes to UTF-8 Base64 string."""
     if isinstance(obj, datetime.datetime):
         return obj.isoformat()
+    elif isinstance(obj, bytes):
+        return base64.b64encode(obj).decode("utf-8")
     else:
-        return obj
+        raise TypeError('Encountered unrecognized type in JSON encoder.')
 
 
 @contextlib.contextmanager

tests/unit/output/test_json_output.py

@@ -11,6 +11,10 @@
 # distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF
 # ANY KIND, either express or implied. See the License for the specific
 # language governing permissions and limitations under the License.
+import base64
+import contextlib
+import io
+import sys
 from botocore.compat import json
 import platform
 from awscli.formatter import JSONFormatter
@@ -127,3 +131,26 @@ def test_fully_buffered_handles_io_error(self):
         # we still should have called the flush() on the
         # stream.
         fake_closed_stream.flush.assert_called_with()
+
+
+class TestBinaryData(unittest.TestCase):
+    def test_binary_data_gets_base64_encoded(self):
+        args = mock.Mock(query=None)
+        raw_bytes = b'foo'
+        response = {'BinaryValue': raw_bytes}
+        stdout_b = io.BytesIO()
+        stdout = io.TextIOWrapper(stdout_b, newline='\n')
+        formatter = JSONFormatter(args)
+
+        with contextlib.redirect_stdout(stdout):
+            formatter('command-name', response, sys.stdout)
+            stdout.flush()
+
+        assert (
+            stdout_b.getvalue()
+            == (
+                '{\n'
+                f'    "BinaryValue": "{base64.b64encode(raw_bytes).decode("utf-8")}"\n'
+                '}\n'
+            ).encode()
+        )