add initial lsp support

internal/lsp/protocol/tsdocument-changes.go

@@ -0,0 +1,81 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package protocol
+
+import (
+	"encoding/json"
+	"fmt"
+)
+
+// DocumentChange is a union of various file edit operations.
+//
+// Exactly one field of this struct is non-nil; see [DocumentChange.Valid].
+//
+// See https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#resourceChanges
+type DocumentChange struct {
+	TextDocumentEdit *TextDocumentEdit
+	CreateFile       *CreateFile
+	RenameFile       *RenameFile
+	DeleteFile       *DeleteFile
+}
+
+// Valid reports whether the DocumentChange sum-type value is valid,
+// that is, exactly one of create, delete, edit, or rename.
+func (ch DocumentChange) Valid() bool {
+	n := 0
+	if ch.TextDocumentEdit != nil {
+		n++
+	}
+	if ch.CreateFile != nil {
+		n++
+	}
+	if ch.RenameFile != nil {
+		n++
+	}
+	if ch.DeleteFile != nil {
+		n++
+	}
+	return n == 1
+}
+
+func (d *DocumentChange) UnmarshalJSON(data []byte) error {
+	var m map[string]any
+	if err := json.Unmarshal(data, &m); err != nil {
+		return err
+	}
+
+	if _, ok := m["textDocument"]; ok {
+		d.TextDocumentEdit = new(TextDocumentEdit)
+		return json.Unmarshal(data, d.TextDocumentEdit)
+	}
+
+	// The {Create,Rename,Delete}File types all share a 'kind' field.
+	kind := m["kind"]
+	switch kind {
+	case "create":
+		d.CreateFile = new(CreateFile)
+		return json.Unmarshal(data, d.CreateFile)
+	case "rename":
+		d.RenameFile = new(RenameFile)
+		return json.Unmarshal(data, d.RenameFile)
+	case "delete":
+		d.DeleteFile = new(DeleteFile)
+		return json.Unmarshal(data, d.DeleteFile)
+	}
+	return fmt.Errorf("DocumentChanges: unexpected kind: %q", kind)
+}
+
+func (d *DocumentChange) MarshalJSON() ([]byte, error) {
+	if d.TextDocumentEdit != nil {
+		return json.Marshal(d.TextDocumentEdit)
+	} else if d.CreateFile != nil {
+		return json.Marshal(d.CreateFile)
+	} else if d.RenameFile != nil {
+		return json.Marshal(d.RenameFile)
+	} else if d.DeleteFile != nil {
+		return json.Marshal(d.DeleteFile)
+	}
+	return nil, fmt.Errorf("empty DocumentChanges union value")
+}