fix(output): match JSON media types case-insensitively

docs/README.md

@@ -653,6 +653,8 @@ If your command includes some data [request items](#request-items), they are ser
 You can use `--json, -j` to explicitly set `Accept` to `application/json` regardless of whether you are sending data (it’s a shortcut for setting the header via the usual header notation: `http url Accept:'application/json, */*;q=0.5'`).
 Additionally, HTTPie will try to detect JSON responses even when the `Content-Type` is incorrectly `text/plain` or unknown.
 
+JSON media types are matched case-insensitively, so `Application/JSON` is formatted the same way as `application/json`.
+
 ### Non-string JSON fields
 
 Non-string JSON fields use the `:=` separator, which allows you to embed arbitrary JSON data into the resulting JSON object.
@@ -2598,4 +2600,3 @@ BSD-3-Clause: [LICENSE](https://github.com/httpie/cli/blob/master/LICENSE).
 ### Authors
 
 [Jakub Roztocil](https://roztocil.co) ([@jakubroztocil](https://twitter.com/jakubroztocil)) created HTTPie and [these fine people](https://github.com/httpie/cli/blob/master/AUTHORS.md) have contributed.
-

httpie/output/formatters/json.py

@@ -10,6 +10,7 @@ def __init__(self, **kwargs):
         self.enabled = self.format_options['json']['format']
 
     def format_body(self, body: str, mime: str) -> str:
+        mime = mime.lower()
         maybe_json = [
             'json',
             'javascript',

tests/test_json.py

@@ -112,6 +112,23 @@ def test_duplicate_keys_support_from_response():
     assert JSON_WITH_DUPES_FORMATTED_UNSORTED in r
 
 
+@pytest.mark.parametrize('content_type', [
+    'APPLICATION/JSON',
+    'Application/Problem+JSON; charset=utf-8',
+])
+@responses.activate
+def test_json_formatter_accepts_case_insensitive_media_types(content_type):
+    responses.add(
+        responses.GET,
+        DUMMY_URL,
+        body='{"message":"ok"}',
+        content_type=content_type,
+    )
+    response = http('--pretty=format', '--body', DUMMY_URL)
+
+    assert '{\n    "message": "ok"\n}' in response
+
+
 def test_duplicate_keys_support_from_input_file():
     """JSON file with duplicate keys should be handled correctly."""
     args = (