protoedit

A Go library for programmatically editing Protocol Buffer (.proto) files while preserving formatting and comments.

API

Method	Appends to
Append.ToService(name, content)	Service body (RPCs, options)
Append.ToMessage(name, content)	Message body (fields, nested types)
Append.ToEnum(name, content)	Enum body (values)
Append.ToFile(content)	End of file (top-level declarations)

All methods reparse the AST after modification, enabling chained operations.

Comment preservation – All original comments and formatting are retained

Installation

go get github.com/whhygee/protoedit

Usage

editor, err := protoedit.New(protoContent)
if err != nil {
    return err
}

// Add a new RPC to a service
editor.Append.ToService("UserService", rpcDefinition)

// Add a field to a message
editor.Append.ToMessage("CreateUserRequest", fieldDefinition)

// Add a value to an enum
editor.Append.ToEnum("Status", enumValueDefinition)

// Add new top-level definitions
editor.Append.ToFile(messageDefinitions)

result := editor.String()

How It Works

protoedit uses bufbuild/protocompile to parse proto files and extract position information. Edits are performed by inserting content at the correct byte offsets, then re-parsing to update positions for subsequent modifications.

Chained operations work correctly:

editor.Append.ToFile(newMessage)
editor.Append.ToMessage("NewMessage", field)  // AST is fresh