gopls/internal/lsp/protocol: report panics in RPC goroutines

This change adds recover() + bug.Reportf to the generated
dispatch routines for the server and client, so that we learn
through telemetry of unexpected panics in RPC goroutines.

Panics in other goroutines cannot yet be reported, but go1.23's
runtime/debug.SetCrashOutput feature (golang/go#42888) will
make that possible, with some extra work.

Change-Id: I893333d296096632fa47e3238a72b0ac48386375
Reviewed-on: https://go-review.googlesource.com/c/tools/+/548735
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Robert Findley <[email protected]>

gopls/internal/lsp/protocol/generate/main.go

@@ -101,6 +101,7 @@ func writeclient() {
 	"context"
 	"encoding/json"
 
+	"golang.org/x/tools/gopls/internal/util/bug"
 	"golang.org/x/tools/internal/jsonrpc2"
 )
 `)
@@ -109,8 +110,15 @@ func writeclient() {
 		out.WriteString(cdecls[k])
 	}
 	out.WriteString("}\n\n")
-	out.WriteString("func clientDispatch(ctx context.Context, client Client, reply jsonrpc2.Replier, r jsonrpc2.Request) (bool, error) {\n")
-	out.WriteString("\tswitch r.Method() {\n")
+	out.WriteString(`func clientDispatch(ctx context.Context, client Client, reply jsonrpc2.Replier, r jsonrpc2.Request) (bool, error) {
+	defer func() {
+		if x := recover(); x != nil {
+			bug.Reportf("client panic in %s request", r.Method())
+			panic(x)
+		}
+	}()
+	switch r.Method() {
+`)
 	for _, k := range ccases.keys() {
 		out.WriteString(ccases[k])
 	}
@@ -138,6 +146,7 @@ func writeserver() {
 	"context"
 	"encoding/json"
 
+	"golang.org/x/tools/gopls/internal/util/bug"
 	"golang.org/x/tools/internal/jsonrpc2"
 )
 `)
@@ -149,6 +158,12 @@ func writeserver() {
 }
 
 func serverDispatch(ctx context.Context, server Server, reply jsonrpc2.Replier, r jsonrpc2.Request) (bool, error) {
+	defer func() {
+		if x := recover(); x != nil {
+			bug.Reportf("server panic in %s request", r.Method())
+			panic(x)
+		}
+	}()
 	switch r.Method() {
 `)
 	for _, k := range scases.keys() {