all: Add dynamic type, attribute, and function support

.changes/unreleased/FEATURES-20240311-175905.yaml

@@ -0,0 +1,6 @@
+kind: FEATURES
+body: 'types/basetypes: Added `DynamicType` and `DynamicValue` implementations for
+  dynamic value handling'
+time: 2024-03-11T17:59:05.67474-04:00
+custom:
+  Issue: "147"

.changes/unreleased/FEATURES-20240311-180136.yaml

@@ -0,0 +1,7 @@
+kind: FEATURES
+body: 'types/basetypes: Added interfaces `basetypes.DynamicTypable`, `basetypes.DynamicValuable`,
+  and `basetypes.DynamicValuableWithSemanticEquals` for dynamic custom type and value
+  implementations'
+time: 2024-03-11T18:01:36.888566-04:00
+custom:
+  Issue: "147"

.changes/unreleased/FEATURES-20240311-180351.yaml

@@ -0,0 +1,6 @@
+kind: FEATURES
+body: 'resource/schema: Added `DynamicAttribute` implementation for dynamic value
+  handling'
+time: 2024-03-11T18:03:51.559347-04:00
+custom:
+  Issue: "147"

.changes/unreleased/FEATURES-20240311-180418.yaml

@@ -0,0 +1,6 @@
+kind: FEATURES
+body: 'datasource/schema: Added `DynamicAttribute` implementation for dynamic value
+  handling'
+time: 2024-03-11T18:04:18.042171-04:00
+custom:
+  Issue: "147"

.changes/unreleased/FEATURES-20240311-180430.yaml

@@ -0,0 +1,6 @@
+kind: FEATURES
+body: 'provider/schema: Added `DynamicAttribute` implementation for dynamic value
+  handling'
+time: 2024-03-11T18:04:30.200616-04:00
+custom:
+  Issue: "147"

.changes/unreleased/FEATURES-20240311-180515.yaml

@@ -0,0 +1,5 @@
+kind: FEATURES
+body: 'function: Added `DynamicParameter` and `DynamicReturn` for dynamic value handling`'
+time: 2024-03-11T18:05:15.196275-04:00
+custom:
+  Issue: "147"

.changes/unreleased/FEATURES-20240311-180859.yaml

@@ -0,0 +1,6 @@
+kind: FEATURES
+body: 'resource/schema/dynamicdefault: New package with `StaticValue` implementation
+  for dynamic schema-based default values'
+time: 2024-03-11T18:08:59.479664-04:00
+custom:
+  Issue: "147"

.changes/unreleased/FEATURES-20240311-181044.yaml

@@ -0,0 +1,6 @@
+kind: FEATURES
+body: 'resource/schema/dynamicplanmodifier: New package with built-in implementations
+  for dynamic value plan modification.'
+time: 2024-03-11T18:10:44.015502-04:00
+custom:
+  Issue: "147"

.changes/unreleased/FEATURES-20240311-181151.yaml

@@ -0,0 +1,6 @@
+kind: FEATURES
+body: 'resource/schema/defaults: New `Dynamic` interface for dynamic schema-based
+  default implementations'
+time: 2024-03-11T18:11:51.403326-04:00
+custom:
+  Issue: "147"

.changes/unreleased/FEATURES-20240311-181242.yaml

@@ -0,0 +1,6 @@
+kind: FEATURES
+body: 'resource/schema/planmodifier: New `Dynamic` interface for dynamic value plan
+  modification implementations'
+time: 2024-03-11T18:12:42.945376-04:00
+custom:
+  Issue: "147"

.changes/unreleased/FEATURES-20240311-181424.yaml

@@ -0,0 +1,5 @@
+kind: FEATURES
+body: 'schema/validator: New `Dynamic` interface for dynamic value schema validation'
+time: 2024-03-11T18:14:24.809064-04:00
+custom:
+  Issue: "147"

attr/value.go

@@ -17,6 +17,12 @@ const (
 	// NullValueString should be returned by Value.String() implementations
 	// when Value.IsNull() returns true.
 	NullValueString = "<null>"
+
+	// UnsetValueString should be returned by Value.String() implementations
+	// when Value does not contain sufficient information to display to users.
+	//
+	// This is primarily used for invalid Dynamic Value implementations.
+	UnsetValueString = "<unset>"
 )
 
 // Value defines an interface for describing data associated with an attribute.

datasource/schema/dynamic_attribute.go

@@ -0,0 +1,188 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: MPL-2.0
+
+package schema
+
+import (
+	"github.com/hashicorp/terraform-plugin-framework/attr"
+	"github.com/hashicorp/terraform-plugin-framework/internal/fwschema"
+	"github.com/hashicorp/terraform-plugin-framework/internal/fwschema/fwxschema"
+	"github.com/hashicorp/terraform-plugin-framework/schema/validator"
+	"github.com/hashicorp/terraform-plugin-framework/types"
+	"github.com/hashicorp/terraform-plugin-framework/types/basetypes"
+	"github.com/hashicorp/terraform-plugin-go/tftypes"
+)
+
+// Ensure the implementation satisifies the desired interfaces.
+var (
+	_ Attribute                                = DynamicAttribute{}
+	_ fwxschema.AttributeWithDynamicValidators = DynamicAttribute{}
+)
+
+// DynamicAttribute represents a schema attribute that is a dynamic, rather
+// than a single static type. Static types are always preferable over dynamic
+// types in Terraform as practitioners will receive less helpful configuration
+// assistance from validation error diagnostics and editor integrations. When
+// retrieving the value for this attribute, use types.Dynamic as the value type
+// unless the CustomType field is set.
+//
+// The concrete value type for a dynamic is determined at runtime in this order:
+//  1. By Terraform, if defined in the configuration (if Required or Optional).
+//  2. By the provider (if Computed).
+//
+// Once the concrete value type has been determined, it must remain consistent between
+// plan and apply or Terraform will return an error.
+type DynamicAttribute struct {
+	// CustomType enables the use of a custom attribute type in place of the
+	// default basetypes.DynamicType. When retrieving data, the basetypes.DynamicValuable
+	// associated with this custom type must be used in place of types.Dynamic.
+	CustomType basetypes.DynamicTypable
+
+	// Required indicates whether the practitioner must enter a value for
+	// this attribute or not. Required and Optional cannot both be true,
+	// and Required and Computed cannot both be true.
+	Required bool
+
+	// Optional indicates whether the practitioner can choose to enter a value
+	// for this attribute or not. Optional and Required cannot both be true.
+	Optional bool
+
+	// Computed indicates whether the provider may return its own value for
+	// this Attribute or not. Required and Computed cannot both be true. If
+	// Required and Optional are both false, Computed must be true, and the
+	// attribute will be considered "read only" for the practitioner, with
+	// only the provider able to set its value.
+	Computed bool
+
+	// Sensitive indicates whether the value of this attribute should be
+	// considered sensitive data. Setting it to true will obscure the value
+	// in CLI output. Sensitive does not impact how values are stored, and
+	// practitioners are encouraged to store their state as if the entire
+	// file is sensitive.
+	Sensitive bool
+
+	// Description is used in various tooling, like the language server, to
+	// give practitioners more information about what this attribute is,
+	// what it's for, and how it should be used. It should be written as
+	// plain text, with no special formatting.
+	Description string
+
+	// MarkdownDescription is used in various tooling, like the
+	// documentation generator, to give practitioners more information
+	// about what this attribute is, what it's for, and how it should be
+	// used. It should be formatted using Markdown.
+	MarkdownDescription string
+
+	// DeprecationMessage defines warning diagnostic details to display when
+	// practitioner configurations use this Attribute. The warning diagnostic
+	// summary is automatically set to "Attribute Deprecated" along with
+	// configuration source file and line information.
+	//
+	// Set this field to a practitioner actionable message such as:
+	//
+	//  - "Configure other_attribute instead. This attribute will be removed
+	//    in the next major version of the provider."
+	//  - "Remove this attribute's configuration as it no longer is used and
+	//    the attribute will be removed in the next major version of the
+	//    provider."
+	//
+	// In Terraform 1.2.7 and later, this warning diagnostic is displayed any
+	// time a practitioner attempts to configure a value for this attribute and
+	// certain scenarios where this attribute is referenced.
+	//
+	// In Terraform 1.2.6 and earlier, this warning diagnostic is only
+	// displayed when the Attribute is Required or Optional, and if the
+	// practitioner configuration sets the value to a known or unknown value
+	// (which may eventually be null). It has no effect when the Attribute is
+	// Computed-only (read-only; not Required or Optional).
+	//
+	// Across any Terraform version, there are no warnings raised for
+	// practitioner configuration values set directly to null, as there is no
+	// way for the framework to differentiate between an unset and null
+	// configuration due to how Terraform sends configuration information
+	// across the protocol.
+	//
+	// Additional information about deprecation enhancements for read-only
+	// attributes can be found in:
+	//
+	//  - https://github.com/hashicorp/terraform/issues/7569
+	//
+	DeprecationMessage string
+
+	// Validators define value validation functionality for the attribute. All
+	// elements of the slice of AttributeValidator are run, regardless of any
+	// previous error diagnostics.
+	//
+	// Many common use case validators can be found in the
+	// github.com/hashicorp/terraform-plugin-framework-validators Go module.
+	//
+	// If the Type field points to a custom type that implements the
+	// xattr.TypeWithValidate interface, the validators defined in this field
+	// are run in addition to the validation defined by the type.
+	Validators []validator.Dynamic
+}
+
+// ApplyTerraform5AttributePathStep always returns an error as it is not
+// possible to step further into a DynamicAttribute.
+func (a DynamicAttribute) ApplyTerraform5AttributePathStep(step tftypes.AttributePathStep) (interface{}, error) {
+	return a.GetType().ApplyTerraform5AttributePathStep(step)
+}
+
+// Equal returns true if the given Attribute is a DynamicAttribute
+// and all fields are equal.
+func (a DynamicAttribute) Equal(o fwschema.Attribute) bool {
+	if _, ok := o.(DynamicAttribute); !ok {
+		return false
+	}
+
+	return fwschema.AttributesEqual(a, o)
+}
+
+// GetDeprecationMessage returns the DeprecationMessage field value.
+func (a DynamicAttribute) GetDeprecationMessage() string {
+	return a.DeprecationMessage
+}
+
+// GetDescription returns the Description field value.
+func (a DynamicAttribute) GetDescription() string {
+	return a.Description
+}
+
+// GetMarkdownDescription returns the MarkdownDescription field value.
+func (a DynamicAttribute) GetMarkdownDescription() string {
+	return a.MarkdownDescription
+}
+
+// GetType returns types.DynamicType or the CustomType field value if defined.
+func (a DynamicAttribute) GetType() attr.Type {
+	if a.CustomType != nil {
+		return a.CustomType
+	}
+
+	return types.DynamicType
+}
+
+// IsComputed returns the Computed field value.
+func (a DynamicAttribute) IsComputed() bool {
+	return a.Computed
+}
+
+// IsOptional returns the Optional field value.
+func (a DynamicAttribute) IsOptional() bool {
+	return a.Optional
+}
+
+// IsRequired returns the Required field value.
+func (a DynamicAttribute) IsRequired() bool {
+	return a.Required
+}
+
+// IsSensitive returns the Sensitive field value.
+func (a DynamicAttribute) IsSensitive() bool {
+	return a.Sensitive
+}
+
+// DynamicValidators returns the Validators field value.
+func (a DynamicAttribute) DynamicValidators() []validator.Dynamic {
+	return a.Validators
+}