attr/xattr: Consider Deprecating tftypes.Value Handling In Preference of attr.Value Handling

[bflad]

Module version

v1.0.0

Use-cases

Provider developers should not need to drop down to the github.com/hashicorp/terraform-plugin-go/tftypes type system when creating custom types via attr.Value with validation. In particular:

attr/xattr.TypeWithValidate

• Validate(context.Context, tftypes.Value, path.Path) diag.Diagnostics

Attempted Solutions

Proposal

Similar to the framework type system specific types/basetypes package interfaces, such as StringTypable/StringValuable, introduce validation interfaces that are based on the framework types. Potentially a new types/validation package. The types/basetypes package cannot be used as diag.Diagnostics has a dependency on basetypes.SetValue.

The existing attr/xattr.TypeWithValidate interface and its Validate method would be deprecated, instead encouraging the usage of the new interfaces. The attr/xattr package cannot be removed until the next major version due to compatibility promises.

Proposed types/validation package:

package validation

type Bool interface {
  basetypes.BoolValuable

  ValidateBool(context.Context, BoolRequest, *BoolResponse)
}

type Float64 interface {
  basetypes.Float64Valuable

  ValidateFloat64(context.Context, Float64Request, *Float64Response)
}

type Int64 interface {
  basetypes.Int64Valuable

  ValidateInt64(context.Context, Int64Request, *Int64Response)
}

type List interface {
  basetypes.ListValuable

  ValidateList(context.Context, ListRequest, *ListResponse)
}

type Map interface {
  basetypes.MapValuable

  ValidateMap(context.Context, MapRequest, *MapResponse)
}

type Number interface {
  basetypes.NumberValuable

  ValidateNumber(context.Context, NumberRequest, *NumberResponse)
}

type Object interface {
  basetypes.ObjectValuable

  ValidateObject(context.Context, ObjectRequest, *ObjectResponse)
}

type Set interface {
  basetypes.SetValuable

  ValidateSet(context.Context, SetRequest, *SetResponse)
}

type String interface {
  basetypes.StringValuable

  ValidateString(context.Context, StringRequest, *StringResponse)
}

Note this proposal switches implementation to a request/response pattern similar to other framework handling so that future changes to the requests/responses can be done without updates to the interfaces themselves. Those types can be fairly straightforward for now to match the existing handling:

type BoolRequest struct {
  Path  path.Path
  Value basetypes.BoolValue
}

type BoolResponse struct {
  Diagnostics diag.Diagnostics
}

Inside the framework where the attr/xattr.TypeWithValidate interface is referenced will need to be switched to a type switch, e.g.

switch xxx.(type) {
case xattr.TypeWithValidate:
// existing tftypes handling
case validation.Bool:
// use basetypes.BoolValuable interface get basetypes.BoolValue
// call ValidateBool() and handle diagnostics
// ... other type cases ...
}

References

• Reexamine where we convert from Terraform values into attr.Values. #172
• attr: Remove Requirement for tftypes Handling from Exported Type/Value Interfaces #588

[bflad]

This issue is a little more poignant now that we are trying to introduce functions, where function argument data has an argument position instead of a path. Might be a good time to fix this.

[bflad]

@bendbennett should we create a v2.0.0 issue to remove the deprecated bits?

[bendbennett]

v2.0.0 issue to remove the deprecated xattr.TypeWithValidate - #978

[bflad]

Awesome!!

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