protoc-gen-terraform

protoc plugin to generate Terraform Framework schema definitions and getter/setter methods from gogo/protobuf .proto files.

Installation

Install the generator binary.

go install github.com/gravitational/protoc-gen-terraform

Usage

Given that you have gogo/protobuf and gravitational/teleport/api in your $GOSRC dir:

mkdir -p ./tfschema
protoc \
    -I$(go env GOPATH)/src/github.com/gravitational/teleport/api/types \
    -I$(go env GOPATH)/src/github.com/gogo/protobuf \
    -I$(go env GOPATH)/src \
    --plugin=./build/protoc-gen-terraform \
    --terraform_out=types=RoleSpecV4,pkg=types:tfschema \
    types.proto

This command will generate types_terraform.go in tfschema folder.

See Makefile for details.

Options

Options can be set using either CLI args or YAML. The path to the config file can be specified with config argument. Be advised that some options can only be set via the config file

Setting target and default package name

By default, generated code is assumed to reside in the same package as your go generated code.

Use target_package_name option to change the target package name:

target_package_name=tfschema

Please also specify the full name of the go package where your generated code is located:

default_package_name="github.com/gravitational/teleport/api/types"

If package import paths are not being correctly found automatically, use the import_path_overrides field in the yaml config to override the import path for specific package names.

import_path_overrides:
    "types": "github.com/gravitational/teleport/api/types"

Specifying types to export

List message names you want to export in types option:

types=UserV2+RoleV3

Excluding fields

Let's consider we have the following proto definition:

message Metadata {
    string ID = 1;
}

message User {
    Metadata Metadata = 1;
}

message AuthPreference {
    Metadata Metadata = 1;
}

Specify exclude_fields option:

exclude_fields=Metadata.ID+AuthPreference.Metadata.Name

In this case, Metadata.ID would be omitted for both User and AuthPreference, and Metadata.Name would be omitted for AuthPreference only. User.Metadata.Name won't be affected.

Terraform Schema flags

You can specify Required: true (required_fields), Computed: true (computed_fields) and Sensitive: true (sensitive_fields) flags for your Terraform schema:

required_fields=Metadata.Name

You also can set list of Validators and PlanModifiers using configuration file:

validators:
    "Metadata.Expires":
        - rfc3339TimeValidator

plan_modifiers:
    "Role.Options":
        - "github.com/hashicorp/terraform-plugin-framework/tfsdk.RequiresReplace()"

UseStateForUnknown by default

The following setting:

use_state_for_unknown_by_default: true

will add tfsdk.UseStateForUnknown() PlanModifier to all computed fields.

Injecting fields into schema

There are cases when you need to add fields not existing in the object to schema. For example, artificial id field is required for Terraform acceptance tests to work. You can achieve it using injected_fields option:

injected_fields:
  Test: # Path to inject
    -
      name: id
      type: github.com/hashicorp/terraform-plugin-framework/types.StringType
      computed: true

Schema field naming

Schema field names are extracted from json tag by default. If a json tag is missing, a snake case of a field name is used.

If you need to rename field in schema, use name_overrides option:

name_overrides:
    "Role.Spec.AWSRoleARNs": aws_arns

Custom fields

If your proto generated objects use type alias for duration fields, you can set custom_duration to the name of a custom duration type.

time_type, duration_type and schema_types options are used to override Terraform types.

time_type:
    type: "TimeType"                    # attr.Type
    value_type: "TimeValue"             # attr.Value
    cast_to_type: "time.Time"           # TimeValue.Value type
    cast_from_type: "time.Time"         # Go object field type
    type_constructor: UseRFC3339Time()  # Function to put into schema definition Type, will generate TimeType{} if missing

Custom duration value

If your schema uses the following definition for the duration fields:

int64 MaxSessionTTL = 2 [ (gogoproto.casttype) = "Duration" ];

you can set the duration_custom_type to make such fields act as duration custom type:

duration_custom_type=Duration

Generated methods

Copy*ToTerraform and Copy*FromTerraform methods are generated for every .proto message. They convert Terraform state object to go proto type and vice versa using normal go assignment operations (no reflect).

CopyFrom

Copies Terraform data to an object.

The signatures for Test resource would be the following:

// CopyTestFromTerraform copies Terraform object fields to obj
// tf must have all the object attrs present (including null and unknown). 
// Hence, tf must be the result of req.Plan.Get or similar Terraform method.
// Otherwise, error would be returned.
func CopyTestFromTerraform(tf types.Object, obj *Test) diag.Diagnostics

They can be used as following:

// Create template resource create method
func (r resource) Create(ctx context.Context, req tfsdk.CreateResourceRequest, resp *tfsdk.CreateResourceResponse) {
    var plan types.Object
    diags := req.Plan.Get(ctx, &plan)
    resp.Diagnostics.Append(diags...)
    if resp.Diagnostics.HasError() {
        return
    }

    obj := types.Object{}
    diags := tfschema.CopyObjFromTerraform(plan, &obj)	
    resp.Diagnostics.Append(diags...)	
    if resp.Diagnostics.HasError() {
        return
    }
}

The following rules apply:

Source Terraform object must contain values for all target object fields.
Unknown values are treated as nulls. Target object value would be set to either nil or zero value.

So, the source Terraform object might be Plan, State or Object.

CopyTo

Copies object to Terraform object.

func CopyTestToTerraform(obj Test, tf *types.Object, updateOnly bool) error

Target Terraform object must have AttrTypes for all fields of Object.

The following rules apply:

All target attributes are marked as known.
In case an attribute is present in AttrTypes, but is missing in AttrValues, it is created.

Note on gogoproto.customtype

If a field has gogoproto.customtype flag, schema and converters for this field can not be generated automatically. You need to define Gen<type>Schema, Copy<type>FromTerraform, Copy<type>ToTerraform methods.

suffixes option can be used to control method names:

suffixes:
    "github.com/gravitational/teleport/api/types/wrappers.Traits": "Traits"

In the example above, GenTraitsSchema method will be called. Without this option, method name would be GenGithubComGravitationalTeleportApiTypesWrappersTraits.

Note on empty messages

Protobuf allows to define messages with no fields. Terraform treats such objects as errors. If a message has no fields, generator defines an artificial active field in the schema. It will always be null.

Testing

Run:

make test

Build and test using Docker

cd build.assets
make build test

On Mac M1 use:

cd build.assets
make build test PROTOC_PLATFORM=linux-aarch_64

Printing version

protoc-gen-terraform version

will print version number and quit.

Releasing the new version

Current version number resides in the VERSION file. To update the file contents from current git tag, run:

git tag v1.1.1
go generate