codec.go

// Copyright 2024 The Go Language Server Authors
// SPDX-License-Identifier: BSD-3-Clause

package protocol

import "go.lsp.dev/jsonrpc2"

// lspCodec is the [jsonrpc2.Codec] that marshals LSP message payloads (request
// params and response results) with the generated union-aware [Marshal] and
// [Unmarshal], so sealed-interface union values round-trip correctly over the
// wire. Already-encoded [jsonrpc2.RawMessage] values pass through verbatim,
// matching the jsonrpc2 JSONCodec contract.
//
// It is installed on every connection by [NewServer] and [NewClient] via
// [jsonrpc2.WithCodec].
type lspCodec struct{}

// compile-time check that lspCodec satisfies the Codec contract.
var _ jsonrpc2.Codec = lspCodec{}

// Marshal implements [jsonrpc2.Codec].
func (lspCodec) Marshal(v any) ([]byte, error) {
	switch m := v.(type) {
	case jsonrpc2.RawMessage:
		if m == nil {
			return []byte("null"), nil
		}
		return m, nil
	case *jsonrpc2.RawMessage:
		if m == nil || *m == nil {
			return []byte("null"), nil
		}
		return *m, nil
	}
	return Marshal(v)
}

// Unmarshal implements [jsonrpc2.Codec].
//
// Raw messages are copied verbatim, matching the [jsonrpc2.JSONCodec]
// ownership contract. Typed protocol payloads delegate to Unmarshal, whose
// generated byte decoders own one copy of the input and may alias unescaped
// strings and raw JSON value fields into that per-message copy.
func (lspCodec) Unmarshal(data []byte, v any) error {
	if p, ok := v.(*jsonrpc2.RawMessage); ok {
		b := make(jsonrpc2.RawMessage, len(data))
		copy(b, data)
		*p = b
		return nil
	}
	return Unmarshal(data, v)
}