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internal/mcp: implement logging

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Provide a ServerSession method that directly implements the spec
method.

Also provide a custom slog.Handler that writes a notification on each
log call. It uses a slog.JSONHandler to format the message as JSON, then
adds the additional fields of LoggingMessageParams.

I decided that the direct method should handle levels, since that is
in the spec, but that rate-limiting is an extra feature, so is only
provided in the slog handler.

Change-Id: I1190ca124e992e61fb633ac52ee3492c8e6d99c9
Reviewed-on: https://go-review.googlesource.com/c/tools/+/674498
Auto-Submit: Jonathan Amsterdam <jba@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Sam Thanawalla <samthanawalla@google.com>
Reviewed-by: Robert Findley <rfindley@google.com>
This commit is contained in:
Jonathan Amsterdam 2025-05-12 08:35:02 -04:00 • committed by Gopher Robot
commit edda031578
1 changed files with 416 additions and 42 deletions
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29
mcp/generate.go
View file

@ -19,6 +19,7 @@ import (
"go/format"
"io"
"log"
"maps"
"net/http"
"os"
"reflect"
@ -110,7 +111,18 @@ var declarations = config{
Name: "-",
Fields: config{"Params": {Name: "ListToolsParams"}},
},
"ListToolsResult": {},
"ListToolsResult": {},
"loggingCapabilities": {Substitute: "struct{}"},
"LoggingLevel": {},
"LoggingMessageNotification": {
Name: "-",
Fields: config{
"Params": {
Name: "LoggingMessageParams",
Fields: config{"Data": {Substitute: "any"}},
},
},
},
"ModelHint": {},
"ModelPreferences": {},
"PingRequest": {
@ -153,8 +165,13 @@ var declarations = config{
"Prompts": {Name: "promptCapabilities"},
"Resources": {Name: "resourceCapabilities"},
"Tools": {Name: "toolCapabilities"},
"Logging": {Name: "loggingCapabilities"},
},
},
"SetLevelRequest": {
Name: "-",
Fields: config{"Params": {Name: "SetLevelParams"}},
},
"Tool": {
Fields: config{"InputSchema": {Substitute: "*jsonschema.Schema"}},
},
@ -220,7 +237,7 @@ import (
}
// Write out method names.
fmt.Fprintln(buf, `const (`)
for name, s := range schema.Definitions {
for _, name := range slices.Sorted(maps.Keys(schema.Definitions)) {
prefix := "method"
method, found := strings.CutSuffix(name, "Request")
if !found {
@ -228,7 +245,7 @@ import (
method, found = strings.CutSuffix(name, "Notification")
}
if found {
if ms, ok := s.Properties["method"]; ok {
if ms, ok := schema.Definitions[name].Properties["method"]; ok {
if c := ms.Const; c != nil {
fmt.Fprintf(buf, "%s%s = %q\n", prefix, method, *c)
}
@ -395,9 +412,9 @@ func writeType(w io.Writer, config *typeConfig, def *jsonschema.Schema, named ma
fieldTypeSchema = rs
}
needPointer := isStruct(fieldTypeSchema)
// Special case: there are no sampling capabilities defined, but
// we want it to be a struct for future expansion.
if !needPointer && name == "sampling" {
// Special case: there are no sampling or logging capabilities defined,
// but we want them to be structs for future expansion.
if !needPointer && (name == "sampling" || name == "logging") {
needPointer = true
}
if config != nil && config.Fields[export] != nil {