Migrating attribute default values

This page explains how to migrate attribute defaults in SDKv2 to the framework.

Background

Default values set a value for an attribute when the Terraform configuration does not provide one. Use the Default field on an attribute's schema to set default values in SDKv2 and the framework. Refer to Default in the framework documentation for details.

Default values support is only available in the framework for resource attributes. Handle default values for data source attributes within the data source Read method and default values for provider attributes within the provider Configure method.

Migrate an attribute with a default value

In SDKv2, you define default values for a primitive attribute type by the Default field on the attribute's schema. These primitive attriutes include the TypeBool, TypeFloat, TypeInt, TypeString types. Alternatively, the you can use the DefaultFunc function to compute a default value for an attribute.

In the framework, you set default values with the Default field on your attribute's definition.

The following code shows a basic implementation of a default value for a primitive attribute type in SDKv2.

func resourceExample() *schema.Resource {
    return &schema.Resource{
         /* ... */
        Schema: map[string]*schema.Schema{
            "attribute_example": {
                Default:     2048,
                /* ... */
            },
        /* ... */

The following shows the same section of provider code after the migration.

import (
  "context"

  "github.com/hashicorp/terraform-plugin-framework/resource"
  "github.com/hashicorp/terraform-plugin-framework/resource/schema"
  "github.com/hashicorp/terraform-plugin-framework/resource/schema/booldefault"
)

func (r *resourceExample) Schema(ctx context.Context, req resource.SchemaRequest, resp *resource.SchemaResponse) {
    resp.Schema = schema.Schema{
        /* ... */
        Attributes: map[string]schema.Attribute{
            "attribute_example": schema.BoolAttribute{
                Default: booldefault.StaticBool(true),
                /* ... */

Migration Notes

Remember the following differences between SDKv2 and the framework when completing the migration.

• In SDKv2, default values are set with the Default or DefaultFunc fields on an attribute's schema.Schema struct. In the framework, you must assign set the Default field on an attribute to set a default value.

Examples

The following examples demostrate how to migrate default values to the framework.

Resource attribute default values

Migrate a resource default value to the framework.

The following example shows the implementation of the Default field for the example_attribute attribute on the exampleResource resource with SDKv2.

func exampleResource() *schema.Resource {
    return &schema.Resource{
        Schema: map[string]*schema.Schema{
            "example_attribute": {
                Default:     2048,
                /* ... */
            },
            /* ... */

The following shows the same section of code after the migration.

This code implements the PlanModifiers field for the example_attribute attribute with the framework.

func (r *exampleResource) Schema(ctx context.Context, req resource.SchemaRequest, resp *resource.SchemaResponse) {
    resp.Schema = schema.Schema{
        Attributes: map[string]schema.Attribute{
            "example_attribute": schema.Int64Attribute{
                Default: int64default.StaticInt64(2048)
                /* ... */
            },
            /* ... */
        },
    }, nil
}