Migrating computed blocks

This page explains how to migrate computed-only blocks from SDKv2 to the framework. Refer to Blocks if you are looking for information about migrating blocks that are practitioner configurable.

Background

Some providers, resources, and data sources include repeatable nested blocks in their attributes. Some blocks contain fields with Computed: true, which means that the provider code can define the value or that it could come from the output of terraform apply (e.g., the ID of an EC2 instance).

Migrating computed blocks in protocol version 5

If your provider uses protocol version 5, migrate computed blocks by using a list attribute whose elements are objects.

In SDKv2, blocks are defined by an attribute whose type is either TypeList or TypeSet, and whose Elem field is set to a schema.Resource that contains a map of the block's attribute names to corresponding schemaSchema structs.

In the framework, when working with protocol version 5, implement computed blocks by using a ListAttribute which has an ElementType of types.ObjectType.

map[string]*schema.Schema{
    "example": {
        Type:     schema.TypeList,
        Computed: true,
        Elem: &schema.Resource{
            Schema: map[string]*schema.Schema{
                "nested_example": {
                        Type:        schema.TypeString,
                        Computed:    true,
                        /* ... */

The following example shows how the block is defined with the framework after the migration.

map[string]schema.Attribute{
"example": schema.ListAttribute{
    Computed: true,
    ElementType: types.ObjectType{
        AttrTypes: map[string]attr.Type{
            "nested_example":  types.StringType,
            /* ... */

Migrating computed blocks in protocol version 6

If your provider uses protocol version 6, migrate computed blocks by using nested attributes.

In SDKv2, blocks are defined by an attribute whose type is either TypeList or TypeSet, and whose Elem field is set to a schema.Resource that contains a map of the block's attribute names to corresponding schemaSchema structs.

In the framework, when working with protocol version 6, we recommend that you define computed blocks using nested attributes. This example shows usage of ListNestedAttribute as this provides configuration references with list index syntax as is the case when using schema.TypeList in SDKv2. SingleNestedAttribute is a good choice for single underlying objects which results in a breaking change but also allows dropping [0] in configuration references. Remember to only introduce breaking changes to your provider in major version updates.

map[string]schema.Attribute{
"example": schema.ListNestedAttribute{
    Computed: true,
    NestedObject: schema.NestedAttributeObject{
        Attributes: map[string]schema.Attribute{
            "nested_example": schema.StringAttribute{
                Computed: true,
                /* ... */

Migration Notes

• When using protocol version 5 specify ElementType as types.ObjectType when migrating blocks that are computed from SDKv2 to the framework.
• When using protocol version 6, use nested attributes when migrating blocks that are computed from SDKv2 to the framework.

Examples

Migrate a computed block

Schema: map[string]*schema.Schema{
"example_nested_block": {
        Type:     schema.TypeList,
        Computed: true,
        Elem: &schema.Resource{
            Schema: map[string]*schema.Schema{
                "example_block_attribute": {
                    Type:        schema.TypeString,
                    Computed:    true,
                    /* ... */
                },

map[string]schema.Attribute{
    "example_nested_block": schema.ListAttribute{
        ElementType: types.ObjectType{
            AttrTypes: map[string]attr.Type{
                "example_block_attribute":  types.StringType,
            },
        },
        Computed:            true,
        /* ... */