Improve LSP diagnostic info (#3436)

private/buf/buflsp/file.go

@@ -614,7 +614,7 @@ func (f *file) RunLints(ctx context.Context) bool {
 			},
 			Code:     annotation.Type(),
 			Severity: protocol.DiagnosticSeverityError,
-			Source:   "buf lint",
+			Source:   serverName,
 			Message:  annotation.Message(),
 		})
 	}

private/buf/buflsp/report.go

@@ -17,8 +17,6 @@
 package buflsp
 
 import (
-	"fmt"
-
 	"github.com/bufbuild/protocompile/linker"
 	"github.com/bufbuild/protocompile/parser"
 	"github.com/bufbuild/protocompile/reporter"
@@ -79,7 +77,8 @@ func newDiagnostic(err reporter.ErrorWithPos, isWarning bool) protocol.Diagnosti
 		// essentially a bug that will result in worse diagnostics until fixed.
 		Range:    protocol.Range{Start: pos, End: pos},
 		Severity: protocol.DiagnosticSeverityError,
-		Message:  fmt.Sprintf("%s:%d:%d: %s", err.GetPosition().Filename, err.GetPosition().Line, err.GetPosition().Col, err.Unwrap().Error()),
+		Message:  err.Unwrap().Error(),
+		Source:   serverName,
 	}
 
 	if isWarning {

private/buf/buflsp/server.go

@@ -28,6 +28,10 @@ import (
 	"go.lsp.dev/protocol"
 )
 
+const (
+	serverName = "buf-lsp"
+)
+
 const (
 	semanticTypeType = iota
 	semanticTypeStruct
@@ -82,7 +86,7 @@ func (s *server) Initialize(
 		return nil, err
 	}
 
-	info := &protocol.ServerInfo{Name: "buf-lsp"}
+	info := &protocol.ServerInfo{Name: serverName}
 	if buildInfo, ok := debug.ReadBuildInfo(); ok {
 		info.Version = buildInfo.Main.Version
 	}