Clean up provisioned modules on error; refactor Run(); add Validate()

Modules that return an error during provisioning should still be cleaned
up so that they don't leak any resources they may have allocated before
the error occurred. Cleanup should be able to run even if Provision does
not complete fully.

1 files changed, 9 insertions, 0 deletions

diff --git a/context.go b/context.go
index 2fd84d5..c29aa1d 100644
--- a/context.go
+++ b/context.go
@@ -131,6 +131,14 @@ func (ctx Context) LoadModule(name string, rawMsg json.RawMessage) (interface{},
 	if prov, ok := val.(Provisioner); ok {
 		err := prov.Provision(ctx)
 		if err != nil {
+			// incomplete provisioning could have left state
+			// dangling, so make sure it gets cleaned up
+			if cleanerUpper, ok := val.(CleanerUpper); ok {
+				err2 := cleanerUpper.Cleanup()
+				if err2 != nil {
+					err = fmt.Errorf("%v; additionally, cleanup: %v", err, err2)
+				}
+			}
 			return nil, fmt.Errorf("provision %s: %v", mod.Name, err)
 		}
 	}
@@ -138,6 +146,7 @@ func (ctx Context) LoadModule(name string, rawMsg json.RawMessage) (interface{},
 	if validator, ok := val.(Validator); ok {
 		err := validator.Validate()
 		if err != nil {
+			// since the module was already provisioned, make sure we clean up
 			if cleanerUpper, ok := val.(CleanerUpper); ok {
 				err2 := cleanerUpper.Cleanup()
 				if err2 != nil {