Fix python compatibility test when a new generated code imports an old version(2.6.1 or older) generated code.

1 files changed, 10 insertions, 1 deletions

diff --git a/src/google/protobuf/compiler/python/python_generator.cc b/src/google/protobuf/compiler/python/python_generator.cc
index f5769128..f83f155a 100644
--- a/src/google/protobuf/compiler/python/python_generator.cc
+++ b/src/google/protobuf/compiler/python/python_generator.cc
@@ -1380,8 +1380,17 @@ void Generator::FixOptionsForMessage(const Descriptor& descriptor) const {
 void Generator::CopyPublicDependenciesAliases(
     const string& copy_from, const FileDescriptor* file) const {
   for (int i = 0; i < file->public_dependency_count(); ++i) {
+    string module_name = ModuleName(file->public_dependency(i)->name());
     string module_alias = ModuleAlias(file->public_dependency(i)->name());
-    printer_->Print("$alias$ = $copy_from$.$alias$\n", "alias", module_alias,
+    // There's no module alias in the dependent file if it was generated by
+    // an old protoc (less than 3.0.0-alpha-1). Use module name in this
+    // situation.
+    printer_->Print("try:\n"
+                    "  $alias$ = $copy_from$.$alias$\n"
+                    "except AttributeError:\n"
+                    "  $alias$ = $copy_from$.$module$\n",
+                    "alias", module_alias,
+                    "module", module_name,
                     "copy_from", copy_from);
     CopyPublicDependenciesAliases(copy_from, file->public_dependency(i));
   }