Support formatting using gofmt and gofumpt

internal/lsp/format.go

@@ -0,0 +1,46 @@
+package lsp
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"log/slog"
+	"math"
+
+	"github.com/harry-hov/gnopls/internal/tools"
+
+	"go.lsp.dev/jsonrpc2"
+	"go.lsp.dev/protocol"
+)
+
+func (s *server) Formatting(ctx context.Context, reply jsonrpc2.Replier, req jsonrpc2.Request) error {
+	var params protocol.DocumentFormattingParams
+	if err := json.Unmarshal(req.Params(), &params); err != nil {
+		return sendParseError(ctx, reply, err)
+	}
+
+	uri := params.TextDocument.URI
+	file, ok := s.snapshot.Get(uri.Filename())
+	if !ok {
+		return reply(ctx, nil, errors.New("snapshot not found"))
+	}
+
+	formatted, err := tools.Format(string(file.Src), s.formatOpt)
+	if err != nil {
+		return reply(ctx, nil, err)
+	}
+
+	slog.Info("format " + string(params.TextDocument.URI.Filename()))
+	return reply(ctx, []protocol.TextEdit{
+		{
+			Range: protocol.Range{
+				Start: protocol.Position{Line: 0, Character: 0},
+				End: protocol.Position{
+					Line:      math.MaxInt32,
+					Character: math.MaxInt32,
+				},
+			},
+			NewText: string(formatted),
+		},
+	}, nil)
+}

internal/lsp/server.go

@@ -60,6 +60,8 @@ func (s *server) ServerHandler(ctx context.Context, reply jsonrpc2.Replier, req
 		return s.DidOpen(ctx, reply, req)
 	case "textDocument/didSave":
 		return s.DidSave(ctx, reply, req)
+	case "textDocument/formatting":
+		return s.Formatting(ctx, reply, req)
 	default:
 		return jsonrpc2.MethodNotFoundHandler(ctx, reply, req)
 	}

internal/tools/format.go

@@ -1,9 +1,34 @@
 package tools
 
+import (
+	"errors"
+	"go/format"
+
+	gofumpt "mvdan.cc/gofumpt/format"
+)
+
 type FormattingOption int
 
 const (
 	Gofmt FormattingOption = iota
 	Gofumpt
 )
 
+func Format(data string, opt FormattingOption) ([]byte, error) {
+	switch opt {
+	case Gofmt:
+		return RunGofmt(data)
+	case Gofumpt:
+		return RunGofumpt(data)
+	default:
+		return nil, errors.New("gnopls: invalid formatting option")
+	}
+}
+
+func RunGofmt(data string) ([]byte, error) {
+	return format.Source([]byte(data))
+}
+
+func RunGofumpt(data string) ([]byte, error) {
+	return gofumpt.Source([]byte(data), gofumpt.Options{})
+}