fwserver: validate each ListResult

Author: bbasata

internal/fwserver/server_listresource.go

@@ -5,7 +5,6 @@ package fwserver
 
 import (
 	"context"
-	"iter"
 
 	"github.com/hashicorp/terraform-plugin-framework/diag"
 	"github.com/hashicorp/terraform-plugin-framework/internal/logging"
@@ -33,17 +32,17 @@ type ListRequest struct {
 
 // ListResultsStream represents a streaming response to a ListRequest.  An
 // instance of this struct is supplied as an argument to the provider's List
-// function. The provider should set a Results iterator function that yields
+// function. The provider should set a Results iterator function that pushes
 // zero or more results of type ListResult.
 //
 // For convenience, a provider implementation may choose to convert a slice of
 // results into an iterator using [slices.Values].
 //
 // [slices.Values]: https://pkg.go.dev/slices#Values
 type ListResourceStream struct {
-	// Results is a function that emits ListResult values via its yield
+	// Results is a function that emits ListResult values via its push
 	// function argument.
-	Results iter.Seq[ListResult]
+	Results ListResults
 }
 
 // ListResult represents a listed managed resource instance.
@@ -69,6 +68,11 @@ type ListResult struct {
 	Diagnostics diag.Diagnostics
 }
 
+// ListResults is a function type that accepts a function to push ListResult
+// values. This type can be used anywhere that an iterator of type
+// iter.Seq[ListResult] can be used.
+type ListResults func(push func(ListResult) bool)
+
 // ListResource implements the framework server ListResource RPC.
 func (s *Server) ListResource(ctx context.Context, fwReq *ListRequest, fwStream *ListResourceStream) {
 	listResource := fwReq.ListResource
@@ -85,19 +89,40 @@ func (s *Server) ListResource(ctx context.Context, fwReq *ListRequest, fwStream
 	logging.FrameworkTrace(ctx, "Called provider defined ListResource")
 
 	if stream.Results == nil {
-		// If the provider returned a nil results stream, we treat it as an empty stream.
-		stream.Results = func(func(list.ListResult) bool) {}
+		// If the provider returned a nil results stream, we return an empty stream.
+		stream.Results = list.NoListResults
 	}
 
-	fwStream.Results = listResourceEventStreamAdapter(stream.Results)
+	fwStream.Results = processListResults(req, stream.Results)
+}
+
+func processListResults(req list.ListRequest, stream list.ListResults) ListResults {
+	return func(push func(ListResult) bool) {
+		for result := range stream {
+			if !push(processListResult(req, result)) {
+				return
+			}
+		}
+	}
 }
 
-func listResourceEventStreamAdapter(stream iter.Seq[list.ListResult]) iter.Seq[ListResult] {
-	// TODO: is this any more efficient than a for-range?
-	return func(yieldFw func(ListResult) bool) {
-		yield := func(event list.ListResult) bool {
-			return yieldFw(ListResult(event))
+// processListResult validates the content of a list.ListResult and returns a
+// ListResult
+func processListResult(req list.ListRequest, result list.ListResult) ListResult {
+	if result.Identity == nil {
+		return ListResult{
+			Diagnostics: diag.Diagnostics{
+				diag.NewErrorDiagnostic("Incomplete List Result", "ListResult.Identity is nil."),
+			},
 		}
-		stream(yield)
 	}
+
+	if req.IncludeResource && result.Resource == nil {
+		result.Diagnostics.AddWarning(
+			"Incomplete List Result",
+			"ListRequest.IncludeResource is true and ListResult.Resource is nil.",
+		)
+	}
+
+	return ListResult(result)
 }

list/list_resource.go

@@ -5,7 +5,6 @@ package list
 
 import (
 	"context"
-	"iter"
 
 	"github.com/hashicorp/terraform-plugin-framework/diag"
 	"github.com/hashicorp/terraform-plugin-framework/resource"
@@ -102,18 +101,25 @@ type ListRequest struct {
 // ListResultsStream represents a streaming response to a ListRequest.  An
 // instance of this struct is supplied as an argument to the provider's
 // ListResource function. The provider should set a Results iterator function
-// that yields zero or more results of type ListResult.
+// that pushes zero or more results of type ListResult.
 //
 // For convenience, a provider implementation may choose to convert a slice of
 // results into an iterator using [slices.Values].
 //
 // [slices.Values]: https://pkg.go.dev/slices#Values
 type ListResultsStream struct {
-	// Results is a function that emits ListResult values via its yield
+	// Results is a function that emits ListResult values via its push
 	// function argument.
-	Results iter.Seq[ListResult]
+	Results ListResults
 }
 
+// ListResults is a function type that accepts a function to push ListResult
+// values. This type can be used anywhere that an iterator of type
+// iter.Seq[ListResult] can be used.
+type ListResults func(push func(ListResult) bool)
+
+var NoListResults = func(func(ListResult) bool) {}
+
 // ListResult represents a listed managed resource instance.
 type ListResult struct {
 	// Identity is the identity of the managed resource instance.