Validate Configuration

Resources support validating an entire practitioner configuration in either declarative or imperative logic. Feedback, such as required syntax or acceptable combinations of values, is returned via diagnostics.

This page describes implementation details for validating entire resource configurations, typically referencing multiple attributes. Further documentation is available for other configuration validation concepts:

Single attribute validation is a schema-based mechanism for implementing attribute-specific validation logic.
Type validation is a schema-based mechanism for implementing reusable validation logic for any attribute using the type.

Configuration validation in Terraform occurs without provider configuration ("offline"), so therefore the resource Configure method will not have been called. To implement validation with a configured API client, use plan modification instead, which occurs during Terraform's planning phase.

ConfigValidators Method

The resource.ResourceWithConfigValidators interface follows a similar pattern to attribute validation and allows for a more declarative approach. This enables consistent validation logic across multiple resources. Each validator intended for this interface must implement the resource.ConfigValidator interface.

During execution of the terraform validate, terraform plan and terraform apply commands, Terraform calls the provider ValidateResourceConfig RPC, in which the framework calls the ConfigValidators method on resources that implement the resource.ResourceWithConfigValidators interface.

The terraform-plugin-framework-validators Go module has a collection of common use case resource configuration validators in the resourcevalidator package. These use path expressions for matching attributes.

This example will raise an error if a practitioner attempts to configure both attribute_one and attribute_two:

// Other methods to implement the resource.Resource interface are omitted for brevity
type ThingResource struct {}

func (r ThingResource) ConfigValidators(ctx context.Context) []resource.ConfigValidator {
    return []resource.ConfigValidator{
        resourcevalidator.Conflicting(
            path.MatchRoot("attribute_one"),
            path.MatchRoot("attribute_two"),
        ),
    }
}

ValidateConfig Method

The resource.ResourceWithValidateConfig interface is more imperative in design and is useful for validating unique functionality across multiple attributes that typically applies to a single resource.

During execution of the terraform validate, terraform plan and terraform apply commands, Terraform calls the provider ValidateResourceConfig RPC, in which the framework calls the ValidateConfig method on providers that implement the resource.ResourceWithValidateConfig interface.

This example will raise a warning if a practitioner attempts to configure attribute_one, but not attribute_two:

// Other methods to implement the resource.Resource interface are omitted for brevity
type ThingResource struct {}

type ThingResourceModel struct {
    AttributeOne types.String `tfsdk:"attribute_one"`
    AttributeTwo types.String `tfsdk:"attribute_two"`
}

func (r ThingResource) ValidateConfig(ctx context.Context, req resource.ValidateConfigRequest, resp *resource.ValidateConfigResponse) {
    var data ThingResourceModel

    resp.Diagnostics.Append(req.Config.Get(ctx, &data)...)

    if resp.Diagnostics.HasError() {
        return
    }

    // If attribute_one is not configured, return without warning.
    if data.AttributeOne.IsNull() || data.AttributeOne.IsUnknown() {
        return
    }

    // If attribute_two is not null, return without warning.
    if !data.AttributeTwo.IsNull() {
        return
    }

    resp.Diagnostics.AddAttributeWarning(
        path.Root("attribute_two"),
        "Missing Attribute Configuration",
        "Expected attribute_two to be configured with attribute_one. "+
            "The resource may return unexpected results.",
    )
}