feat(dart): Support a revised exception hierarchy (#3429)

Pairs with googleapis/google-cloud-dart#101

Also removes `typedDataImport` (cleanup).

Author: brianquinlan

internal/sidekick/dart/annotate.go

@@ -381,6 +381,7 @@ func (annotate *annotateModel) annotateModel(options map[string]string) error {
 	// Add the import for ServiceClient and related functionality.
 	if len(model.Services) > 0 {
 		annotate.imports[serviceClientImport] = true
+		annotate.imports[serviceExceptionImport] = true
 	}
 
 	// `protobuf.dart` defines `JsonEncodable`, which is needed by any API that defines an `enum` or `message`.

internal/sidekick/dart/dart.go

@@ -28,11 +28,11 @@ import (
 )
 
 const (
-	typedDataImport     = "dart:typed_data"
-	httpImport          = "package:http/http.dart as http"
-	serviceClientImport = "package:google_cloud_rpc/service_client.dart"
-	encodingImport      = "package:google_cloud_protobuf/src/encoding.dart"
-	protobufImport      = "package:google_cloud_protobuf/protobuf.dart"
+	httpImport             = "package:http/http.dart as http"
+	serviceClientImport    = "package:google_cloud_rpc/service_client.dart"
+	serviceExceptionImport = "package:google_cloud_rpc/exceptions.dart"
+	encodingImport         = "package:google_cloud_protobuf/src/encoding.dart"
+	protobufImport         = "package:google_cloud_protobuf/protobuf.dart"
 )
 
 var needsCtorValidation = map[string]string{

internal/sidekick/dart/templates/lib/method.mustache

@@ -19,8 +19,8 @@ limitations under the License.
 {{/Codec.DocLines}}
 ///
 /// Throws a [http.ClientException] if there were problems communicating with
-/// the API service. Throws a [StatusException] if the API failed with a
-/// [Status] message. Throws a [ServiceException] for any other failure.
+/// the API service. Throws a [ServiceException] if the API method failed for
+/// any reason.
 {{#Codec.ServerSideStreaming}}
 Stream<{{Codec.ResponseType}}> {{Codec.Name}}({{Codec.RequestType}} request) {
   final url = Uri.https(_host, '{{PathInfo.Codec.PathFmt}}'