feat: add fmt capabilities

server/handler/documentFormatting.go

@@ -0,0 +1,45 @@
+package handler
+
+import (
+	"bytes"
+	"os"
+
+	"cuelang.org/go/cue/format"
+	"github.com/tliron/glsp"
+	protocol "github.com/tliron/glsp/protocol_3_16"
+	"go.lsp.dev/uri"
+)
+
+func (h *Handler) documentFormatting(_ *glsp.Context, params *protocol.DocumentFormattingParams) ([]protocol.TextEdit, error) {
+	h.log.Debugf("Format: %s", params.TextDocument.URI)
+	h.log.Debugf("params: %#v", params)
+
+	_uri, err := uri.Parse(params.TextDocument.URI)
+	source, err := os.ReadFile(_uri.Filename())
+	if err != nil {
+		return nil, h.wrapError(err)
+	}
+
+	h.log.Debugf("Find source of %s", _uri.Filename)
+	_fmt, err := format.Source(source, format.UseSpaces(2), format.TabIndent(false)) // TODO: gather from params.Options?
+	if err != nil {
+		return nil, h.wrapError(err)
+	}
+
+	h.log.Debugf("Source formatted: %s", _uri.Filename)
+	start := protocol.Position{Line: 0, Character: 0}
+
+	nl := []byte("\n")
+	ll := bytes.Count(source, nl)
+	end := protocol.Position{Line: uint32(ll), Character: 0}
+
+	edit := protocol.TextEdit{
+		Range: protocol.Range{
+			Start: start,
+			End:   end,
+		},
+		NewText: string(_fmt),
+	}
+
+	return []protocol.TextEdit{edit}, nil
+}

server/handler/handler.go

@@ -42,6 +42,7 @@ func New(opts ...Options) *Handler {
 		TextDocumentHover:      h.documentHover,
 		TextDocumentDidChange:  h.documentDidChange,
 		TextDocumentDidClose:   h.documentDidClose,
+		TextDocumentFormatting: h.documentFormatting,
 	}
 
 	return h

server/handler/initialize.go

@@ -99,5 +99,8 @@ func (h *Handler) capabilities() protocol.ServerCapabilities {
 	capabilities.DefinitionProvider = true
 	capabilities.HoverProvider = true
 
+	// Formatting
+	capabilities.DocumentFormattingProvider = true
+
 	return capabilities
 }