protoc-gen-gorm

Purpose

A protobuf (https://developers.google.com/protocol-buffers/) compiler plugin designed to simplify the API calls needed to perform simple object persistence tasks. This is currently accomplished by creating a secondary .pb.gorm.go file which contains sister objects to those generated in the standard .pb.go file satisfying these criteria:

• Go field decorators/tags can be defined by option in the .proto file for GORM/SQL
• There are options for dropping fields from the PB object, or adding additional fields (not generally recommended, as it reduces clarity of .proto file)
• Converters between PB version and ORM version of the objects are included
• Hook interfaces allow for custom application logic

Prerequisites

1. Protobuf Compiler

The protobuf compiler (protoc) is required.

Official instructions

Abbreviated version

2. Golang Protobuf Code Generator

Get the golang protobuf code generator:

go get -u github.com/golang/protobuf/protoc-gen-go

3. Vendored Dependencies

Retrieve and install the vendored dependencies for this project with dep:

dep ensure

Installation

To use this tool, install it from code with make install, go install directly, or go get github.com/infobloxopen/protoc-gen-gorm.

Usage

Once installed, the --gorm_out=. or --gorm_out=${GOPATH}src option can be specified in a protoc command to generate the .pb.gorm.go files.

Any message types with the option (gorm.opts).ormable = true will have the following autogenerated:

• A struct with ORM compatible types and the "ORM" suffix
• GORM tags built from the field options [(gorm.field).tag = {..., tag: value, ...}].
• A {PbType}.ToORM and {TypeORM}.ToPB function
• Additional, unexposed fields added from the option (gorm.opts) = {include: []}, either of a built-in type e.g. {type: "int32", name: "secret_key"}, or an imported type, e.g. {type: "StringArray", name: "array", package:"github.com/lib/pq"}.
• Barebones C/U/R/D/L handlers that accept the protobuf versions (as from an API call), a context (used with the multiaccount option and for collection operators https://github.com/infobloxopen/atlas-app-toolkit#collection-operators), and a gorm.DB then perform the basic operation on the DB with the object
• Interface hooks for before and after each conversion that can be implemented to add custom handling.

Any services with the option (gorm.server).autogen = true will have basic grpc server generated:

• For service methods with names starting with Create|Read|Update|Delete generated implementation will call basic CRUD handlers.
• For other methods return &MethodResponse{}, nil stub is generated.

For CRUD methods to be generated correctly you need to follow specific conventions:

• Request messages for Create and Update methods should have an Ormable Type in a field named payload, for Read and Delete methods an id field is required. Nothing is required in the List request.
• Response messages for Create, Read, and Update require an Ormable Type in a field named result and for List a repeated Ormable Type named results.
• Delete methods require the (gorm.method).object_type option to indicate which Ormable Type it should delete, and has no response type requirements.

To customize the generated server, embed it into a new type and override any desired functions.

If conventions are not met stubs are generated for CRUD methods. As seen in the feature_demo/demo_service example.

To leverage DB specific features, specify the DB engine during generation using the --gorm_out="engine={postgres,...}:{path}". Currently only Postgres has special type support, any other choice will behave as default.

The generated code can also integrate with the grpc server gorm transaction middleware provided in the atlas-app-toolkit using the service level option option (gorm.server).txn_middleware = true.

Examples

Example .proto files and generated .pb.gorm.go files are included in the 'example' directory. The user file contains model examples from GORM documentation, the feature_demo/demo_types demonstrates the type handling and multi_account functions, and the feature_demo/demo_service shows the service autogeneration.

Running make example will recompile all these test proto files, if you want to test the effects of changing the options and fields.

Supported Types

Within the proto files, the following types are supported:

• standard primitive types uint32, uint64, int32, int64, float, double, bool, string map to the same type at ORM level
• google wrapper types google.protobuf.StringValue, .BoolValue, .UInt32Value, .FloatValue, etc. map to pointers of the internal type at the ORM level, e.g. *string, *bool, *uint32, *float
• [google timestamp type]((https://github.com/golang/protobuf/blob/master/ptypes/timestamp/timestamp.proto) google.protobuf.Timestamp maps to time.Time type at the ORM level
• custom wrapper types gorm.types.UUID and gorm.types.UUIDValue, which wrap strings and convert to a uuid.UUID and *uuid.UUID at the ORM level, from https://github.com/satori/go.uuid. A null or missing gorm.types.UUID will become a ZeroUUID (00000000-0000-0000-0000-000000000000) at the ORM level.
• custom wrapper type gorm.types.JSONValue, which wraps a string in protobuf containing arbitrary JSON and converts to postgres.Jsonb GORM type (https://github.com/jinzhu/gorm/blob/master/dialects/postgres/postgres.go#L59) if Postgres is the selected DB engine, otherwise it is currently dropped.
• custom wrapper type gorm.types.InetValue, which wraps a string and will convert to the types.Inet type at ORM level, which uses the golang net.IPNet type to hold an ip address and mask, IPv4 and IPv6 compatible, with the scan and value functions necessary to write to DBs. Like JSONValue, currently dropped if DB engine is not Postgres
• types can be imported from other .proto files within the same package (protoc invocation) or between packages. All associations can be generated properly within the same package, but cross package only the belongs-to and many-to-many will work.

Associations

The plugin supports the following GORM associations:

• Belongs-To
• Has-One
• Has-Many
• Many-To-Many

Note: polymorphic associations are currently not supported.

Association is defined by adding a field of some ormable message type(either single or repeated).

message Contact {
    option (gorm.opts).ormable = true;
    uint64 id = 1;
    string name = 2;
    repeated Email emails = 3;
    Address home_address = 4;
}

Has-One is a default association for a single message type.

message Contact {
    option (gorm.opts).ormable = true;
    uint64 id = 1;
    string first_name = 2;
    string middle_name = 3;
    string last_name = 4;
    Address address = 5;
}

message Address {
    option (gorm.opts).ormable = true;
    string address = 1;
    string city = 2;
    string state = 3;
    string zip = 4;
    string country = 5;
}

Set (gorm.field).belongs_to option on the field in order to define Belongs-To.

message Contact {
    option (gorm.opts).ormable = true;
    uint64 id = 1;
    string first_name = 2;
    string middle_name = 3;
    string last_name = 4;
    Profile profile = 5 [(gorm.field).belongs_to = {}];
}

message Profile {
    option (gorm.opts).ormable = true;
    uint64 id = 1;
    string name = 2;
    string notes = 3;
}

Has-Many is a default association for a repeated message type.

message Contact {
    option (gorm.opts).ormable = true;
    uint64 id = 1;
    string first_name = 2;
    string middle_name = 3;
    string last_name = 4;
    repeated Email emails = 5;
}

message Email {
    option (gorm.opts).ormable = true;
    string address = 1;
    bool is_primary = 2;
}

Set (gorm.field).many_to_many option on the field in order to define Many-To-Many.

message Contact {
    option (gorm.opts).ormable = true;
    uint64 id = 1;
    string first_name = 2;
    string middle_name = 3;
    string last_name = 4;
    repeated Group groups = 5 [(gorm.field).many_to_many = {}];
}

message Group {
    option (gorm.opts).ormable = true;
    uint64 id = 1;
    string name = 2;
    string notes = 3;
}

For each association type, except Many-To-Many, foreign keys pointing to primary keys(association keys) are automatically created if they don't exist in proto messages, their names correspond to GORM default foreign key names. GORM association tags are also automatically inserted.

Customization

• For each association type you are able to override default foreign key and association key by setting foreignkey and association_foreignkey options.
• For each association type you are able to override default behavior of creating/updating the record. It's references can be created/updated depending on association_autoupdate, association_autocreate and association_save_reference options. Check out official association docs for more information.
• For each association type you are able to set preload option. Check out GORM docs.
• For Has-Many you are able to set position_field so additional field is created if it doesn't exist in proto message to maintain association ordering. Corresponding CRUDL handlers do all the necessary work to maintain the ordering.
• For automatically created foreign key and position field you're able to assign GORM tags by setting foreignkey_tag and position_field_tag options.
• For Many-To-Many you're able to override default join table name and column names by setting jointable, jointable_foreignkey and association_jointable_foreignkey options.

Check out user to see a real example of associations usage.

Limitations

Currently only proto3 is supported.

This project is currently in development, and is expected to undergo "breaking" (and fixing) changes