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go-sdk/mcp
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Filename Latest commit message Latest commit date
Recoordinate 0eb1600eef
 mcp: avoid panicking when a resource handler returns nil (#1176) 
### What

`readResource` dereferenced the handler's result before the `if res ==
nil`
check that was meant to guard it. A `ResourceHandler` returning `(nil,
nil)`
therefore panicked instead of returning an error:

- modern clients: `handleMultiRoundTripResult` calls `res.setResultType`
on the
  nil result, and
- older clients: `res.setDefaultCacheableValues()` runs on the nil
result.

Either way the `if res == nil` guard a few lines below was dead code.

### Why it matters

Request handlers run in their own goroutine and nothing recovers, so the
panic
does not just fail the one request. It terminates the whole server
process and
every concurrent session.

The sibling handlers already avoid this: `callTool` and `getPrompt` both
guard
their result with `if err == nil && res != nil` before touching it, so a
`(nil, nil)` return flows up and becomes a normal error response.

### Change

Move the nil check in `readResource` ahead of
`handleMultiRoundTripResult` and
`setDefaultCacheableValues`, so a nil result returns the existing
descriptive
error (`read handler returned nil information`) instead of panicking.
Added a
regression test that drives a resource handler returning `(nil, nil)`
through
the server and asserts a clean error.
2026-08-17 10:44:53 +02:00
..
testdata mcp: update return meta in DiscoverResult (SEP-2575) (#1097) 2026-07-16 16:10:12 +02:00
cache.go mcp: do not enforce TTL on cached tool (#1053) 2026-07-07 13:43:10 +02:00
capabilities_test.go mcp: add 2026-07-28 to the supported protocol versions (#1020) 2026-06-24 12:02:56 +02:00
client.go mcp: avoid Client.Connect leaks (#1158) 2026-08-10 08:52:50 +00:00
client_example_test.go mcp: block server initiated requests (SEP-2322) (#1057) 2026-07-08 15:17:41 +02:00
client_list_test.go mcp: allow any value for schemas (#517) 2025-09-26 11:55:54 -04:00
client_test.go mcp: export ClientSessionOptions.ProtocolVersion (#1127) 2026-08-03 15:29:52 +02:00
cmd.go mcp: speed up TestCommandTransportDuration 2025-09-12 12:00:29 -04:00
cmd_export_test.go mcp: speed up TestCommandTransportDuration 2025-09-12 12:00:29 -04:00
cmd_test.go all: modernize code (#868) 2026-03-31 10:58:02 +02:00
conformance_test.go mcp: add 2026-07-28 to the supported protocol versions (#1020) 2026-06-24 12:02:56 +02:00
content.go mcp: Deprecate roots, sampling and logging (SEP-2577) (#1017) 2026-06-23 11:11:08 +02:00
content_nil_test.go mcp: update return meta in DiscoverResult (SEP-2575) (#1097) 2026-07-16 16:10:12 +02:00
content_test.go mcp: switch icon theme to named string type (#733) 2025-12-19 16:44:10 -05:00
elicitation_test.go mcp: export ClientSessionOptions.ProtocolVersion (#1127) 2026-08-03 15:29:52 +02:00
error_test.go mcp: avoid panicking when a resource handler returns nil (#1176) 2026-08-17 10:44:53 +02:00
event.go mcp: avoid double-copy of payload in writeEvent (#1106) 2026-07-24 10:07:06 +02:00
event_test.go mcp: handle empty chunks in MemoryEventStore (#862) 2026-03-27 16:58:03 +01:00
features.go mcp: minor cleanup of some TODOs (#332) 2025-08-20 12:55:19 -04:00
features_test.go mcp: change tool handler design (#325) 2025-08-20 19:36:34 -04:00
logging.go mcp: Deprecate roots, sampling and logging (SEP-2577) (#1017) 2026-06-23 11:11:08 +02:00
mcp.go mcp: fix inaccurate package doc (#534) 2025-09-26 14:16:10 -04:00
mcp_example_test.go mcp: add 2026-07-28 to the supported protocol versions (#1020) 2026-06-24 12:02:56 +02:00
mcp_test.go mcp: export ClientSessionOptions.ProtocolVersion (#1127) 2026-08-03 15:29:52 +02:00
mrtr.go mcp: bump protocol version from 2026-06-30 to 2026-07-28 (#1015) 2026-06-22 09:53:04 +02:00
mrtr_test.go mcp: export ClientSessionOptions.ProtocolVersion (#1127) 2026-08-03 15:29:52 +02:00
prompt.go mcp: align PromptHandler args with other handlers (#348) 2025-08-22 10:44:05 -04:00
protocol.go mcp: update return meta in DiscoverResult (SEP-2575) (#1097) 2026-07-16 16:10:12 +02:00
protocol_test.go mcp: include resultType on new-protocol responses (#1060) 2026-07-13 11:51:19 +00:00
requests.go mcp: Implement subscriptions/listen rpc (SEP-2575) (#1007) 2026-06-22 18:57:36 +02:00
resource.go mcp: align resource not found error code with sep-2164 (#931) 2026-05-05 16:20:02 +02:00
resource_test.go mcp/Resource: Refactor URI Template Matching with uritemplate Library (#100) 2025-07-08 15:52:54 -04:00
sampling_test.go mcp: export ClientSessionOptions.ProtocolVersion (#1127) 2026-08-03 15:29:52 +02:00
schema_cache.go perf: add schema caching to avoid repeated reflection (#685) 2026-01-20 20:16:46 -05:00
schema_cache_test.go all: modernize code (#868) 2026-03-31 10:58:02 +02:00
server.go mcp: avoid panicking when a resource handler returns nil (#1176) 2026-08-17 10:44:53 +02:00
server_example_test.go mcp: add 2026-07-28 to the supported protocol versions (#1020) 2026-06-24 12:02:56 +02:00
server_test.go mcp: export ClientSessionOptions.ProtocolVersion (#1127) 2026-08-03 15:29:52 +02:00
session.go mcp: support stateless streamable sessions (#277) 2025-08-11 16:43:46 -04:00
shared.go mcp: update return meta in DiscoverResult (SEP-2575) (#1097) 2026-07-16 16:10:12 +02:00
shared_test.go mcp: update return meta in DiscoverResult (SEP-2575) (#1097) 2026-07-16 16:10:12 +02:00
sse.go mcp: limit SSE discover supportedVersions to SSE-defined revisions (#1121) 2026-08-05 15:36:22 +02:00
sse_example_test.go SSE: Add support for SSE handler options (#508) 2025-09-19 13:01:57 -04:00
sse_test.go mcp: limit SSE discover supportedVersions to SSE-defined revisions (#1121) 2026-08-05 15:36:22 +02:00
streamable.go mcp: fix typo in protocol version comment (#1156) 2026-08-10 09:10:06 +02:00
streamable_bench_test.go all: modernize code (#868) 2026-03-31 10:58:02 +02:00
streamable_client.go mcp: do not call DELETE for sessionless & doc adjustments (#960) 2026-05-15 21:47:34 +02:00
streamable_client_test.go mcp: fix error propagation to prevent session closing (#1118) 2026-08-04 11:02:36 +02:00
streamable_example_test.go mcp: add 2026-07-28 to the supported protocol versions (#1020) 2026-06-24 12:02:56 +02:00
streamable_headers.go mcp: fix ListTools panic and null normalization on malformed tools (#1120) 2026-07-30 10:06:14 +02:00
streamable_headers_test.go mcp: fix ListTools panic and null normalization on malformed tools (#1120) 2026-07-30 10:06:14 +02:00
streamable_server.go mcp: simplify stream state management in streamable transport 2025-12-10 13:28:25 -05:00
streamable_test.go mcp: allow asynchronous cancel notification (#1151) 2026-08-07 10:43:17 +02:00
tool.go mcp: tool.InputSchema and tool.OutputSchema validation (SEP-2106) (#1009) 2026-06-16 13:55:47 +02:00
tool_example_test.go mcp: allow any value for schemas (#517) 2025-09-26 11:55:54 -04:00
tool_test.go mcp: tool.InputSchema and tool.OutputSchema validation (SEP-2106) (#1009) 2026-06-16 13:55:47 +02:00
transport.go mcp: allow asynchronous cancel notification (#1151) 2026-08-07 10:43:17 +02:00
transport_example_test.go mcp: update return meta in DiscoverResult (SEP-2575) (#1097) 2026-07-16 16:10:12 +02:00
transport_test.go fix(jsonrpc2): decode requests when method key is present (#1000) 2026-06-16 09:57:18 +02:00
util.go all: use case-sensitive JSON unmarshaling (#807) 2026-02-18 16:38:36 +01:00