fix(gengapic): use recursive resource name heuristic

internal/gengapic/gengapic.go

@@ -886,12 +886,12 @@ func (g *generator) resourceNameField(m *descriptorpb.MethodDescriptorProto) str
 		return ""
 	}
 
-	var candidates []string
-	for _, f := range msg.GetField() {
-		if proto.HasExtension(f.GetOptions(), annotations.E_ResourceReference) {
-			candidates = append(candidates, f.GetName())
-		}
-	}
+	// Recursively find fields with the annotation, up to 2 levels deep.
+	// This covers top-level "name" or "parent" fields, and also nested
+	// fields like "secret.name" (AIP-134).
+	candidates := g.findFieldsMatching(msg, "", 2, func(f *descriptorpb.FieldDescriptorProto) bool {
+		return proto.HasExtension(f.GetOptions(), annotations.E_ResourceReference)
+	})
 
 	if len(candidates) == 0 {
 		return ""
@@ -920,3 +920,36 @@ func (g *generator) resourceNameField(m *descriptorpb.MethodDescriptorProto) str
 
 	return candidates[0]
 }
+
+// findFieldsMatching recursively scans the given message and its nested sub-messages
+// (up to the specified depth) for fields that satisfy the provided filter predicate.
+// It returns a slice of dot-notation strings representing the full paths to these
+// fields from the root message (e.g., "secret.name"), which are used to generate
+// idiomatic Go accessors.
+func (g *generator) findFieldsMatching(msg *descriptorpb.DescriptorProto, prefix string, depth int, filter func(*descriptorpb.FieldDescriptorProto) bool) []string {
+	if depth <= 0 {
+		return nil
+	}
+
+	var candidates []string
+	for _, f := range msg.GetField() {
+		name := f.GetName()
+		if prefix != "" {
+			name = prefix + "." + name
+		}
+
+		if filter(f) {
+			candidates = append(candidates, name)
+		}
+
+		// Recurse into nested messages.
+		if f.GetType() == descriptorpb.FieldDescriptorProto_TYPE_MESSAGE {
+			nestedType := g.descInfo.Type[f.GetTypeName()]
+			if nestedMsg, ok := nestedType.(*descriptorpb.DescriptorProto); ok {
+				candidates = append(candidates, g.findFieldsMatching(nestedMsg, name, depth-1, filter)...)
+			}
+		}
+	}
+
+	return candidates
+}

internal/gengapic/resource_name_test.go

@@ -0,0 +1,137 @@
+// Copyright 2026 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package gengapic
+
+import (
+	"testing"
+
+	"github.com/googleapis/gapic-generator-go/internal/pbinfo"
+	"google.golang.org/genproto/googleapis/api/annotations"
+	"google.golang.org/protobuf/proto"
+	"google.golang.org/protobuf/types/descriptorpb"
+)
+
+func TestResourceNameField(t *testing.T) {
+	optsResRef := &descriptorpb.FieldOptions{}
+	proto.SetExtension(optsResRef, annotations.E_ResourceReference, &annotations.ResourceReference{
+		Type: "foo.googleapis.com/Bar",
+	})
+
+	extraMsg := &descriptorpb.DescriptorProto{
+		Name: proto.String("ExtraMessage"),
+		Field: []*descriptorpb.FieldDescriptorProto{
+			{
+				Name:    proto.String("name"),
+				Type:    typep(descriptorpb.FieldDescriptorProto_TYPE_STRING),
+				Options: optsResRef,
+			},
+		},
+	}
+
+	inputType := &descriptorpb.DescriptorProto{
+		Name: proto.String("InputType"),
+		Field: []*descriptorpb.FieldDescriptorProto{
+			{
+				Name: proto.String("top_level"),
+				Type: typep(descriptorpb.FieldDescriptorProto_TYPE_STRING),
+			},
+			{
+				Name:     proto.String("nested"),
+				Type:     typep(descriptorpb.FieldDescriptorProto_TYPE_MESSAGE),
+				TypeName: proto.String(".my.pkg.ExtraMessage"),
+			},
+		},
+	}
+
+	inputTypeWithTopLevel := &descriptorpb.DescriptorProto{
+		Name: proto.String("InputTypeWithTopLevel"),
+		Field: []*descriptorpb.FieldDescriptorProto{
+			{
+				Name:    proto.String("name"),
+				Type:    typep(descriptorpb.FieldDescriptorProto_TYPE_STRING),
+				Options: optsResRef,
+			},
+			{
+				Name:     proto.String("nested"),
+				Type:     typep(descriptorpb.FieldDescriptorProto_TYPE_MESSAGE),
+				TypeName: proto.String(".my.pkg.ExtraMessage"),
+			},
+		},
+	}
+
+	for _, tst := range []struct {
+		name       string
+		inputType  *descriptorpb.DescriptorProto
+		httpRule   *annotations.HttpRule
+		wantField  string
+		extraTypes map[string]pbinfo.ProtoType
+	}{
+		{
+			name:      "nested_resource_field",
+			inputType: inputType,
+			wantField: "nested.name",
+			extraTypes: map[string]pbinfo.ProtoType{
+				".my.pkg.ExtraMessage": extraMsg,
+			},
+		},
+		{
+			name:      "top_level_resource_field",
+			inputType: inputTypeWithTopLevel,
+			wantField: "name",
+			extraTypes: map[string]pbinfo.ProtoType{
+				".my.pkg.ExtraMessage": extraMsg,
+			},
+		},
+		{
+			name:      "tie_breaking_with_http_path",
+			inputType: inputTypeWithTopLevel,
+			httpRule: &annotations.HttpRule{
+				Pattern: &annotations.HttpRule_Get{
+					Get: "/v1/{nested.name=*}",
+				},
+			},
+			wantField: "nested.name",
+			extraTypes: map[string]pbinfo.ProtoType{
+				".my.pkg.ExtraMessage": extraMsg,
+			},
+		},
+	} {
+		t.Run(tst.name, func(t *testing.T) {
+			m := &descriptorpb.MethodDescriptorProto{
+				Name:      proto.String("MyMethod"),
+				InputType: proto.String(".my.pkg." + tst.inputType.GetName()),
+				Options:   &descriptorpb.MethodOptions{},
+			}
+			if tst.httpRule != nil {
+				proto.SetExtension(m.Options, annotations.E_Http, tst.httpRule)
+			}
+
+			g := &generator{
+				descInfo: pbinfo.Info{
+					Type: map[string]pbinfo.ProtoType{
+						".my.pkg." + tst.inputType.GetName(): tst.inputType,
+					},
+				},
+			}
+			for k, v := range tst.extraTypes {
+				g.descInfo.Type[k] = v
+			}
+
+			if got := g.resourceNameField(m); got != tst.wantField {
+				t.Errorf("resourceNameField(%s) = %q, want %q", tst.name, got, tst.wantField)
+			}
+		})
+	}
+}