Fill in TODOs.

This required updating some of the request/response types. It also
required modifying how things implement
ApplyTerraform5AttributePathStep, so we could get at the
schema.Attribute instead of just the attr.Type. All tests still pass.

data_source.go

@@ -21,8 +21,8 @@ type DataSourceType interface {
 // DataSource implements a data source instance.
 type DataSource interface {
 	// Read is called when the provider must read data source values in
-	// order to update state. Planned state values should be read from the
-	// ReadResourceRequest and new state values set on the
-	// ReadResourceResponse.
-	Read(context.Context, *ReadResourceRequest, *ReadResourceResponse)
+	// order to update state. Config values should be read from the
+	// ReadDataSourceRequest and new state values set on the
+	// ReadDataSourceResponse.
+	Read(context.Context, ReadDataSourceRequest, *ReadDataSourceResponse)
 }

request.go

@@ -73,3 +73,16 @@ type DeleteResourceRequest struct {
 	// from knowing the value at request time.
 	Config Config
 }
+
+// ReadDataSourceRequest represents a request for the provider to read a data
+// source, i.e., update values in state according to the real state of the
+// data source. An instance of this request struct is supplied as an argument
+// to the data source's Read function.
+type ReadDataSourceRequest struct {
+	// Config is the configuration the user supplied for the data source.
+	//
+	// This configuration may contain unknown values if a user uses
+	// interpolation or other functionality that would prevent Terraform
+	// from knowing the value at request time.
+	Config Config
+}

resource.go

@@ -25,21 +25,21 @@ type Resource interface {
 	// and planned state values should be read from the
 	// CreateResourceRequest and new state values set on the
 	// CreateResourceResponse.
-	Create(context.Context, *CreateResourceRequest, *CreateResourceResponse)
+	Create(context.Context, CreateResourceRequest, *CreateResourceResponse)
 
 	// Read is called when the provider must read resource values in order
 	// to update state. Planned state values should be read from the
 	// ReadResourceRequest and new state values set on the
 	// ReadResourceResponse.
-	Read(context.Context, *ReadResourceRequest, *ReadResourceResponse)
+	Read(context.Context, ReadResourceRequest, *ReadResourceResponse)
 
 	// Update is called to update the state of the resource. Config, planned
 	// state, and prior state values should be read from the
 	// UpdateResourceRequest and new state values set on the
 	// UpdateResourceResponse.
-	Update(context.Context, *UpdateResourceRequest, *UpdateResourceResponse)
+	Update(context.Context, UpdateResourceRequest, *UpdateResourceResponse)
 
 	// Delete is called when the provider must delete the resource. Config
 	// values may be read from the DeleteResourceRequest.
-	Delete(context.Context, *DeleteResourceRequest, *DeleteResourceResponse)
+	Delete(context.Context, DeleteResourceRequest, *DeleteResourceResponse)
 }

response.go

@@ -237,6 +237,11 @@ func (r *UpdateResourceResponse) AddAttributeError(attributePath *tftypes.Attrib
 // an argument to the resource's Delete function, in which the provider
 // should set values on the DeleteResourceResponse as appropriate.
 type DeleteResourceResponse struct {
+	// State is the state of the resource following the Delete operation.
+	// This field is pre-populated from UpdateResourceRequest.Plan and
+	// should be set during the resource's Update operation.
+	State State
+
 	// Diagnostics report errors or warnings related to deleting the
 	// resource. An empty slice indicates a successful operation with no
 	// warnings or errors generated.
@@ -284,3 +289,18 @@ func (r *DeleteResourceResponse) AddAttributeError(attributePath *tftypes.Attrib
 		Severity:  tfprotov6.DiagnosticSeverityError,
 	})
 }
+
+// ReadDataSourceResponse represents a response to a ReadDataSourceRequest. An
+// instance of this response struct is supplied as an argument to the data
+// source's Read function, in which the provider should set values on the
+// ReadDataSourceResponse as appropriate.
+type ReadDataSourceResponse struct {
+	// State is the state of the data source following the Read operation.
+	// This field should be set during the resource's Read operation.
+	State State
+
+	// Diagnostics report errors or warnings related to reading the data
+	// source. An empty slice indicates a successful operation with no
+	// warnings or errors generated.
+	Diagnostics []*tfprotov6.Diagnostic
+}

schema/attribute.go

@@ -1,7 +1,10 @@
 package schema
 
 import (
+	"errors"
+
 	"github.com/hashicorp/terraform-plugin-framework/attr"
+	"github.com/hashicorp/terraform-plugin-go/tftypes"
 )
 
 // Attribute defines the constraints and behaviors of a single field in a
@@ -62,3 +65,13 @@ type Attribute struct {
 	// instructing them on what upgrade steps to take.
 	DeprecationMessage string
 }
+
+func (a Attribute) ApplyTerraform5AttributePathStep(step tftypes.AttributePathStep) (interface{}, error) {
+	if a.Type != nil {
+		return a.Type.ApplyTerraform5AttributePathStep(step)
+	}
+	if a.Attributes != nil {
+		return a.Attributes.ApplyTerraform5AttributePathStep(step)
+	}
+	return nil, errors.New("Attribute has no type or nested attributes")
+}

schema/nested_attributes.go

@@ -1,8 +1,11 @@
 package schema
 
 import (
+	"fmt"
+
 	"github.com/hashicorp/terraform-plugin-framework/attr"
 	"github.com/hashicorp/terraform-plugin-framework/types"
+	"github.com/hashicorp/terraform-plugin-go/tftypes"
 )
 
 type NestingMode uint8
@@ -38,6 +41,7 @@ const (
 // attributes must be associated with a unique key. Unlike SetNestedAttributes,
 // the key must be explicitly set by the user.
 type NestedAttributes interface {
+	tftypes.AttributePathStepper
 	AttributeType() attr.Type
 	GetNestingMode() NestingMode
 	GetAttributes() map[string]Attribute
@@ -54,6 +58,34 @@ func (n nestedAttributes) GetAttributes() map[string]Attribute {
 
 func (n nestedAttributes) unimplementable() {}
 
+func (n nestedAttributes) ApplyTerraform5AttributePathStep(step tftypes.AttributePathStep) (interface{}, error) {
+	a, ok := step.(tftypes.AttributeName)
+	if !ok {
+		return nil, fmt.Errorf("can't apply %T to Attributes", step)
+	}
+	res, ok := n[string(a)]
+	if !ok {
+		return nil, fmt.Errorf("no attribute %q on Attributes", a)
+	}
+	return res, nil
+}
+
+// AttributeType returns an attr.Type corresponding to the nested attributes.
+func (n nestedAttributes) AttributeType() attr.Type {
+	attrTypes := map[string]attr.Type{}
+	for name, attr := range n.GetAttributes() {
+		if attr.Type != nil {
+			attrTypes[name] = attr.Type
+		}
+		if attr.Attributes != nil {
+			attrTypes[name] = attr.Attributes.AttributeType()
+		}
+	}
+	return types.ObjectType{
+		AttrTypes: attrTypes,
+	}
+}
+
 // SingleNestedAttributes nests `attributes` under another attribute, only
 // allowing one instance of that group of attributes to appear in the
 // configuration.
@@ -79,22 +111,6 @@ func (s singleNestedAttributes) GetMaxItems() int64 {
 	return 0
 }
 
-// AttributeType returns an attr.Type corresponding to the nested attributes.
-func (s singleNestedAttributes) AttributeType() attr.Type {
-	attrTypes := map[string]attr.Type{}
-	for name, attr := range s.GetAttributes() {
-		if attr.Type != nil {
-			attrTypes[name] = attr.Type
-		}
-		if attr.Attributes != nil {
-			attrTypes[name] = attr.Attributes.AttributeType()
-		}
-	}
-	return types.ObjectType{
-		AttrTypes: attrTypes,
-	}
-}
-
 // ListNestedAttributes nests `attributes` under another attribute, allowing
 // multiple instances of that group of attributes to appear in the
 // configuration. Minimum and maximum numbers of times the group can appear in
@@ -134,20 +150,17 @@ func (l listNestedAttributes) GetMaxItems() int64 {
 
 // AttributeType returns an attr.Type corresponding to the nested attributes.
 func (l listNestedAttributes) AttributeType() attr.Type {
-	attrTypes := map[string]attr.Type{}
-	for name, attr := range l.GetAttributes() {
-		if attr.Type != nil {
-			attrTypes[name] = attr.Type
-		}
-		if attr.Attributes != nil {
-			attrTypes[name] = attr.Attributes.AttributeType()
-		}
-	}
 	return types.ListType{
-		ElemType: types.ObjectType{
-			AttrTypes: attrTypes,
-		},
+		ElemType: l.nestedAttributes.AttributeType(),
+	}
+}
+
+func (l listNestedAttributes) ApplyTerraform5AttributePathStep(step tftypes.AttributePathStep) (interface{}, error) {
+	_, ok := step.(tftypes.ElementKeyInt)
+	if !ok {
+		return nil, fmt.Errorf("can't apply %T to ListNestedAttributes", step)
 	}
+	return l.nestedAttributes, nil
 }
 
 // SetNestedAttributes nests `attributes` under another attribute, allowing
@@ -194,6 +207,14 @@ func (s setNestedAttributes) AttributeType() attr.Type {
 	return nil
 }
 
+func (s setNestedAttributes) ApplyTerraform5AttributePathStep(step tftypes.AttributePathStep) (interface{}, error) {
+	_, ok := step.(tftypes.ElementKeyValue)
+	if !ok {
+		return nil, fmt.Errorf("can't use %T on sets", step)
+	}
+	return s.nestedAttributes, nil
+}
+
 // MapNestedAttributes nests `attributes` under another attribute, allowing
 // multiple instances of that group of attributes to appear in the
 // configuration. Each group will need to be associated with a unique string by
@@ -237,3 +258,11 @@ func (m mapNestedAttributes) AttributeType() attr.Type {
 	// TODO fill in implementation when types.MapType is available
 	return nil
 }
+
+func (m mapNestedAttributes) ApplyTerraform5AttributePathStep(step tftypes.AttributePathStep) (interface{}, error) {
+	_, ok := step.(tftypes.ElementKeyString)
+	if !ok {
+		return nil, fmt.Errorf("can't use %T on maps", step)
+	}
+	return m.nestedAttributes, nil
+}

schema/schema.go

@@ -36,12 +36,7 @@ type Schema struct {
 func (s Schema) ApplyTerraform5AttributePathStep(step tftypes.AttributePathStep) (interface{}, error) {
 	if v, ok := step.(tftypes.AttributeName); ok {
 		if attr, ok := s.Attributes[string(v)]; ok {
-			if attr.Type != nil {
-				return attr.Type, nil
-			}
-			if attr.Attributes != nil {
-				return attr.Attributes.AttributeType(), nil
-			}
+			return attr, nil
 		}
 		return nil, fmt.Errorf("could not find attribute %q in schema", v)
 	}
@@ -69,12 +64,20 @@ func (s Schema) AttributeTypeAtPath(path *tftypes.AttributePath) (attr.Type, err
 		return nil, fmt.Errorf("%v still remains in the path: %w", remaining, err)
 	}
 
-	attrType, ok := rawType.(attr.Type)
+	typ, ok := rawType.(attr.Type)
+	if ok {
+		return typ, nil
+	}
+
+	a, ok := rawType.(Attribute)
 	if !ok {
-		return nil, fmt.Errorf("got non-attr.Type result %v with type %T", rawType, rawType)
+		return nil, fmt.Errorf("got unexpected type %T", rawType)
+	}
+	if a.Type != nil {
+		return a.Type, nil
 	}
 
-	return attrType, nil
+	return a.Attributes.AttributeType(), nil
 }
 func (s Schema) TerraformType(ctx context.Context) tftypes.Type {
 	attrTypes := map[string]tftypes.Type{}
@@ -83,8 +86,21 @@ func (s Schema) TerraformType(ctx context.Context) tftypes.Type {
 			attrTypes[name] = attr.Type.TerraformType(ctx)
 		}
 		if attr.Attributes != nil {
-			// TODO: handle nested attributes
+			attrTypes[name] = attr.Attributes.AttributeType().TerraformType(ctx)
 		}
 	}
 	return tftypes.Object{AttributeTypes: attrTypes}
 }
+
+func (s Schema) AttributeAtPath(path *tftypes.AttributePath) (Attribute, error) {
+	res, remaining, err := tftypes.WalkAttributePath(s, path)
+	if err != nil {
+		return Attribute{}, fmt.Errorf("%v still remains in the path: %w", remaining, err)
+	}
+
+	a, ok := res.(Attribute)
+	if !ok {
+		return Attribute{}, fmt.Errorf("got unexpected type %T", res)
+	}
+	return a, nil
+}