fix(server): treat text/* mime types case-insensitively for FileResource#2918
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ly-wang19 wants to merge 2 commits into
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fix(server): treat text/* mime types case-insensitively for FileResource#2918ly-wang19 wants to merge 2 commits into
ly-wang19 wants to merge 2 commits into
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Media types are case-insensitive (RFC 9110, section 8.3.1), and StreamableHTTPServerTransport._check_accept_headers already lowercases the Accept media types before comparing. _check_content_type did not, so a spec-valid request with a mixed/upper-case Content-Type (e.g. "Application/JSON") was rejected with 415 Unsupported Media Type. Lowercase the parsed Content-Type media type before comparing to CONTENT_TYPE_JSON, consistent with _check_accept_headers. Adds a unit test for case-insensitive matching (the _check_content_type path was previously no-cover).
FileResource.set_binary_from_mime_type decides whether to read a file as text
or bytes via `mime_type.startswith("text/")`, but media types are
case-insensitive (RFC 9110, section 8.3.1). A FileResource declared with an
upper/mixed-case text type (e.g. "Text/Markdown") was misclassified as binary
and read with read_bytes instead of read_text.
Normalize with .lower() before the prefix check, consistent with the other
media-type checks in the SDK (transport_security, client streamable_http).
Adds a regression test.
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Summary
FileResource.set_binary_from_mime_typedecides whether to read a file as text or bytes from itsmime_typeviamime_type.startswith("text/"). Media types are case-insensitive (RFC 9110, §8.3.1), so aFileResourcedeclared with an upper/mixed-case text type — e.g.mime_type="Text/Markdown"— is misclassified as binary and read withread_bytesinstead ofread_text, returning abytesblob to clients instead of text.Fix
Lower-case the mime type before the prefix check, consistent with the SDK's other media-type checks (
transport_security, clientstreamable_http).Test
Added
test_uppercase_text_mime_type_is_treated_as_text: aFileResource(mime_type="Text/Markdown")keepsis_binaryFalse.Verified red→green: the new test fails on
main(treated as binary) and passes with the fix.uv run pytest tests/server/mcpserver/resources/test_file_resources.py→ 8 passed;ruff check/ruff format --checkclean.