Function TestMigratedErrorPassingThroughAsUnknown

errbase/migrations_test.go:226–265

Scenario 4: migrated error passing through node that does not know about the error type whatsoever. - v2 renames foo -> bar - v2.a, v2.b and v0 are connected: v2.a -> v0 -> v2.b (v0 does not know about error foo at all) - v2.a sends an error to v2.b via v0:

(t *testing.T)

//   (v0 does not know about error foo at all)
// - v2.a sends an error to v2.b via v0:
func TestMigratedErrorPassingThroughAsUnknown(t *testing.T) {
	defer errbase.TestingWithEmptyMigrationRegistry()()

	// == Scenario on v2.a ==
	origErr := barErr{}
	// Register the fact that foo was migrated to bar.
	errbase.RegisterTypeMigration(myPkgPath, "errbase_test.fooErr", origErr)
	// Send the error to v1.
	enc := errbase.EncodeError(context.Background(), origErr)
	// Clean up the decoder, so that type becomes unknown for further tests.
	errbase.RegisterLeafDecoder(errbase.GetTypeKey(origErr), nil)
	// Erase the migration we have set up above, so that the test
	// underneath does not know about it.
	defer errbase.TestingWithEmptyMigrationRegistry()()

	// == Scenario on v1 ==
	// Receive the error from v2.b. Will decode as opaqueLeaf{}.
	dec := errbase.DecodeError(context.Background(), enc)
	// Send the error to v2.b.
	enc2 := errbase.EncodeError(context.Background(), dec)

	// == Scenario on v2.b ==
	// Register the fact that foo was migrated to bar.
	errbase.RegisterTypeMigration(myPkgPath, "errbase_test.fooErr", barErr{})
	errbase.RegisterLeafDecoder(errbase.GetTypeKey(barErr{}),
		func(_ context.Context, _ string, _ []string, _ proto.Message) error { return barErr{} })
	// Receive the error from v1.
	dec2 := errbase.DecodeError(context.Background(), enc2)
	// Clean up the decoder, so that type becomes unknown for further tests.
	errbase.RegisterLeafDecoder(errbase.GetTypeKey(barErr{}), nil)
	// Erase the migration we have set up above, so that the test
	// underneath does not know about it.
	defer errbase.TestingWithEmptyMigrationRegistry()()

	// Main test: check that v2.b recognized the foo error
	// that was passed from v2.a.
	if _, ok := dec2.(barErr); !ok {
		t.Errorf("migration failed; expected type barErr, got %T", dec2)
	}
}

// Scenario 5: comparison between migrated and non-migrated errors
// on 3rd party node that doesn't know about the type.