fix(update/etag): assign etag field on resource if request dont have

Before tests were only generated if the update request object included
a etag field.

AIP specifies that update method can piggyback on the etag field on
the resource instead of adding it to the request object.

https://google.aip.dev/154#etags-on-request-methods

README.md

@@ -200,8 +200,8 @@ Sample skips:
 | update time          | Field update_time should be updated when the resource is updated.                                           | Generated only if all are true: <ul><li>has Create method</li><li>Create method does not return long-running operation</li><li>has Update method</li><li>Update method does not return long-running operation</li><li>has field 'update_time'</li></ul> |
 | persisted            | The updated resource should be persisted and reachable with Get.                                            | Generated only if all are true: <ul><li>has Update method</li><li>Update method does not return long-running operation</li><li>has Get method</li></ul>                                                                                                 |
 | preserve create_time | The field create_time should be preserved when a '\*'-update mask is used.                                  | Generated only if all are true: <ul><li>has Update method</li><li>Update method does not return long-running operation</li><li>has field 'create_time'</li><li>resource has any required fields</li></ul>                                               |
-| etag mismatch        | Method should fail with Aborted if the supplied etag doesnt match the current etag value.                   | Generated only if all are true: <ul><li>has Update method</li><li>request has etag field</li><li>has field 'etag'</li></ul>                                                                                                                             |
-| etag updated         | Field etag should have a new value when the resource is successfully updated.                               | Generated only if all are true: <ul><li>has Update method</li><li>request has etag field</li><li>has field 'etag'</li></ul>                                                                                                                             |
+| etag mismatch        | Method should fail with Aborted if the supplied etag doesnt match the current etag value.                   | Generated only if all are true: <ul><li>has Update method</li><li>has field 'etag'</li></ul>                                                                                                                                                            |
+| etag updated         | Field etag should have a new value when the resource is successfully updated.                               | Generated only if all are true: <ul><li>has Update method</li><li>has field 'etag'</li></ul>                                                                                                                                                            |
 | not found            | Method should fail with NotFound if the resource does not exist.                                            | Generated only if all are true: <ul><li>has Update method</li></ul>                                                                                                                                                                                     |
 | invalid update mask  | The method should fail with InvalidArgument if the update_mask is invalid.                                  | Generated only if all are true: <ul><li>has Update method</li><li>Update method has update_mask</li></ul>                                                                                                                                               |
 | required fields      | Method should fail with InvalidArgument if any required field is missing when called with '\*' update_mask. | Generated only if all are true: <ul><li>has Update method</li><li>resource has any required fields</li></ul>                                                                                                                                            |

internal/aiptest/update/etag.go

@@ -18,7 +18,6 @@ var etagMismatch = suite.Test{
 	},
 	OnlyIf: suite.OnlyIfs(
 		onlyif.HasMethod(aipreflect.MethodTypeUpdate),
-		onlyif.HasRequestEtag(aipreflect.MethodTypeUpdate),
 		onlyif.HasField("etag"),
 	),
 	Generate: func(f *protogen.GeneratedFile, scope suite.Scope) error {
@@ -32,8 +31,10 @@ var etagMismatch = suite.Test{
 		util.MethodUpdate{
 			Resource: scope.Resource,
 			Method:   updateMethod,
-			Msg:      "created",
+			Parent:   "parent",
+			Name:     "created.Name",
 			Etag:     util.EtagLiteral("99999"),
+			EtagTest: true,
 		}.Generate(f, "_", "err", ":=")
 		f.P(ident.AssertEqual, "(t, ", ident.Codes(codes.Aborted), ",", ident.StatusCode, "(err), err)")
 		return nil
@@ -48,7 +49,6 @@ var etagUpdated = suite.Test{
 	},
 	OnlyIf: suite.OnlyIfs(
 		onlyif.HasMethod(aipreflect.MethodTypeUpdate),
-		onlyif.HasRequestEtag(aipreflect.MethodTypeUpdate),
 		onlyif.HasField("etag"),
 	),
 	Generate: func(f *protogen.GeneratedFile, scope suite.Scope) error {
@@ -65,9 +65,16 @@ var etagUpdated = suite.Test{
 			Parent:   "parent",
 			Name:     "created.Name",
 			Etag:     "created.Etag",
+			EtagTest: true,
 		}.Generate(f, "updated", "err", ":=")
 		f.P(ident.AssertNilError, "(t, err)")
-		f.P(ident.AssertCheck, "(t, updated.Etag != created.Etag)")
+
+		if !util.ReturnsLRO(updateMethod.Desc) {
+			// only assert etag is different if the resource is returned.
+			f.P(ident.AssertCheck, "(t, updated.Etag != created.Etag)")
+		} else {
+			f.P("_ = updated") // prevent unused error.
+		}
 		return nil
 	},
 }

internal/util/method.go

@@ -95,6 +95,7 @@ type MethodUpdate struct {
 	Msg        string
 	UpdateMask []string
 	Etag       string
+	EtagTest   bool
 }
 
 func (m MethodUpdate) Generate(f *protogen.GeneratedFile, response, err, assign string) {
@@ -111,6 +112,14 @@ func (m MethodUpdate) Generate(f *protogen.GeneratedFile, response, err, assign
 		}
 		f.P("msg.Name = ", m.Name)
 	}
+	if m.EtagTest && !HasEtagField(m.Method.Input.Desc) && HasEtagField(m.Method.Output.Desc) {
+		// Request object does not have an etag field, but the resource has.
+		if m.Etag != "" {
+			f.P("msg.Etag = ", m.Etag)
+		} else {
+			f.P(`msg.Etag = created.Etag // assign etag from the created resource`)
+		}
+	}
 	f.P(response, ", ", err, " ", assign, " fx.Service().", m.Method.GoName, "(fx.Context(), &", m.Method.Input.GoIdent, "{") //nolint:lll
 	if m.Msg != "" {
 		f.P(upper, ":", m.Msg, ",")