mcp: use rand.Text and slog.DiscardHandler over internal implementation (#773)

Address TODOs in code requiring go 1.24 as minimum version

mcp/logging.go: use slog.DiscardHandler, over local implementation
mcp/util.go: use rand.Text, over local implementation

Fixes #772

examples/server/sequentialthinking/main.go

@@ -234,7 +234,7 @@ func deepCopyThoughts(thoughts []*Thought) []*Thought {
 func StartThinking(ctx context.Context, _ *mcp.CallToolRequest, args StartThinkingArgs) (*mcp.CallToolResult, any, error) {
 	sessionID := args.SessionID
 	if sessionID == "" {
-		sessionID = randText()
+		sessionID = rand.Text()
 	}
 
 	estimatedSteps := args.EstimatedSteps
@@ -480,20 +480,6 @@ func ThinkingHistory(ctx context.Context, req *mcp.ReadResourceRequest) (*mcp.Re
 	}, nil
 }
 
-// Copied from crypto/rand.
-// TODO: once 1.24 is assured, just use crypto/rand.
-const base32alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567"
-
-func randText() string {
-	// ⌈log₃₂ 2¹²⁸⌉ = 26 chars
-	src := make([]byte, 26)
-	rand.Read(src)
-	for i := range src {
-		src[i] = base32alphabet[src[i]%32]
-	}
-	return string(src)
-}
-
 func main() {
 	flag.Parse()
 

mcp/event_test.go

@@ -6,6 +6,7 @@ package mcp
 
 import (
 	"context"
+	"crypto/rand"
 	"fmt"
 	"slices"
 	"strings"
@@ -281,7 +282,7 @@ func BenchmarkMemoryEventStore(b *testing.B) {
 			for i := range sessionIDs {
 				sessionIDs[i] = fmt.Sprint(i)
 				for j := range 3 {
-					streamIDs[i][j] = randText()
+					streamIDs[i][j] = rand.Text()
 				}
 			}
 			payload := make([]byte, test.datasize)

mcp/logging.go

@@ -89,21 +89,12 @@ type LoggingHandler struct {
 	handler         slog.Handler
 }
 
-// discardHandler is a slog.Handler that drops all logs.
-// TODO: use slog.DiscardHandler when we require Go 1.24+.
-type discardHandler struct{}
-
-func (discardHandler) Enabled(context.Context, slog.Level) bool  { return false }
-func (discardHandler) Handle(context.Context, slog.Record) error { return nil }
-func (discardHandler) WithAttrs([]slog.Attr) slog.Handler        { return discardHandler{} }
-func (discardHandler) WithGroup(string) slog.Handler             { return discardHandler{} }
-
 // ensureLogger returns l if non-nil, otherwise a discard logger.
 func ensureLogger(l *slog.Logger) *slog.Logger {
 	if l != nil {
 		return l
 	}
-	return slog.New(discardHandler{})
+	return slog.New(slog.DiscardHandler)
 }
 
 // NewLoggingHandler creates a [LoggingHandler] that logs to the given [ServerSession] using a

mcp/server.go

@@ -7,6 +7,7 @@ package mcp
 import (
 	"bytes"
 	"context"
+	"crypto/rand"
 	"encoding/base64"
 	"encoding/gob"
 	"encoding/json"
@@ -175,7 +176,7 @@ func NewServer(impl *Implementation, options *ServerOptions) *Server {
 	}
 
 	if opts.GetSessionID == nil {
-		opts.GetSessionID = randText
+		opts.GetSessionID = rand.Text
 	}
 
 	if opts.Logger == nil { // ensure we have a logger

mcp/sse.go

@@ -7,6 +7,7 @@ package mcp
 import (
 	"bytes"
 	"context"
+	"crypto/rand"
 	"fmt"
 	"io"
 	"net/http"
@@ -216,7 +217,7 @@ func (h *SSEHandler) ServeHTTP(w http.ResponseWriter, req *http.Request) {
 	w.Header().Set("Cache-Control", "no-cache")
 	w.Header().Set("Connection", "keep-alive")
 
-	sessionID = randText()
+	sessionID = rand.Text()
 	endpoint, err := req.URL.Parse("?sessionid=" + sessionID)
 	if err != nil {
 		http.Error(w, "internal error: failed to create endpoint", http.StatusInternalServerError)

mcp/streamable.go

@@ -11,6 +11,7 @@ package mcp
 import (
 	"bytes"
 	"context"
+	crand "crypto/rand"
 	"encoding/json"
 	"errors"
 	"fmt"
@@ -1140,7 +1141,7 @@ func (c *streamableServerConn) servePOST(w http.ResponseWriter, req *http.Reques
 	// Important: don't publish the incoming messages until the stream is
 	// registered, as the server may attempt to respond to imcoming messages as
 	// soon as they're published.
-	stream, err := c.newStream(req.Context(), calls, randText())
+	stream, err := c.newStream(req.Context(), calls, crand.Text())
 	if err != nil {
 		http.Error(w, fmt.Sprintf("storing stream: %v", err), http.StatusInternalServerError)
 		return

mcp/util.go

@@ -5,7 +5,6 @@
 package mcp
 
 import (
-	"crypto/rand"
 	"encoding/json"
 )
 
@@ -15,20 +14,6 @@ func assert(cond bool, msg string) {
 	}
 }
 
-// Copied from crypto/rand.
-// TODO: once 1.24 is assured, just use crypto/rand.
-const base32alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567"
-
-func randText() string {
-	// ⌈log₃₂ 2¹²⁸⌉ = 26 chars
-	src := make([]byte, 26)
-	rand.Read(src)
-	for i := range src {
-		src[i] = base32alphabet[src[i]%32]
-	}
-	return string(src)
-}
-
 // remarshal marshals from to JSON, and then unmarshals into to, which must be
 // a pointer type.
 func remarshal(from, to any) error {