resources: Improve composition of Validate API in resources

This now appropriately calls the Base method.

docs/resource-guide.md

@@ -106,6 +106,17 @@ specifications, it should generate an error. If you notice that this method is
 quite large, it might be an indication that you should reconsider the parameter
 list and interface to this resource. This method is called _before_ `Init`.
 
+#### Example
+```golang
+// Validate reports any problems with the struct definition.
+func (obj *FooRes) Validate() error {
+	if obj.Answer != 42 { // validate whatever you want
+		return fmt.Errorf("expected an answer of 42")
+	}
+	return obj.BaseRes.Validate() // remember to call the base method!
+}
+```
+
 ### Init
 ```golang
 Init() error

resources/exec.go

@@ -85,7 +85,7 @@ func (obj *ExecRes) Validate() error {
 		return fmt.Errorf("Don't poll when we have a watch command.")
 	}
 
-	return nil
+	return obj.BaseRes.Validate()
 }
 
 // Init runs some startup code for this resource.

resources/file.go

@@ -107,7 +107,7 @@ func (obj *FileRes) Validate() error {
 	//	return fmt.Errorf("Can't specify an empty source when creating a Dir.")
 	//}
 
-	return nil
+	return obj.BaseRes.Validate()
 }
 
 // Init runs some startup code for this resource.

resources/hostname.go

@@ -92,7 +92,7 @@ func (obj *HostnameRes) Validate() error {
 	if obj.PrettyHostname == "" && obj.StaticHostname == "" && obj.TransientHostname == "" {
 		return ErrResourceInsufficientParameters
 	}
-	return nil
+	return obj.BaseRes.Validate()
 }
 
 // Init runs some startup code for this resource.

resources/msg.go

@@ -89,7 +89,7 @@ func (obj *MsgRes) Validate() error {
 			return fmt.Errorf("Fields cannot begin with _.")
 		}
 	}
-	return nil
+	return obj.BaseRes.Validate()
 }
 
 // Init runs some startup code for this resource.

resources/noop.go

@@ -53,7 +53,7 @@ func (obj *NoopRes) Default() Res {
 
 // Validate if the params passed in are valid data.
 func (obj *NoopRes) Validate() error {
-	return nil
+	return obj.BaseRes.Validate()
 }
 
 // Init runs some startup code for this resource.

resources/nspawn.go

@@ -85,7 +85,11 @@ func (obj *NspawnRes) Validate() error {
 	if _, exists := validStates[obj.State]; !exists {
 		return fmt.Errorf("Invalid State: %s", obj.State)
 	}
-	return obj.svc.Validate()
+
+	if err := obj.svc.Validate(); err != nil { // composite resource
+		return errwrap.Wrapf(err, "validate failed for embedded svc")
+	}
+	return obj.BaseRes.Validate()
 }
 
 // Init runs some startup code for this resource.

resources/password.go

@@ -76,7 +76,7 @@ func (obj *PasswordRes) Default() Res {
 
 // Validate if the params passed in are valid data.
 func (obj *PasswordRes) Validate() error {
-	return nil
+	return obj.BaseRes.Validate()
 }
 
 // Init generates a new password for this resource if one was not provided. It

resources/pkg.go

@@ -73,7 +73,7 @@ func (obj *PkgRes) Validate() error {
 		return fmt.Errorf("State cannot be empty!")
 	}
 
-	return nil
+	return obj.BaseRes.Validate()
 }
 
 // Init runs some startup code for this resource.

resources/resources.go

@@ -242,6 +242,11 @@ func (obj *BaseUID) Reversed() bool {
 	return *obj.reversed
 }
 
+// Validate reports any problems with the struct definition.
+func (obj *BaseRes) Validate() error {
+	return nil
+}
+
 // Init initializes structures like channels if created without New constructor.
 func (obj *BaseRes) Init() error {
 	if obj.kind == "" {

resources/svc.go

@@ -69,7 +69,7 @@ func (obj *SvcRes) Validate() error {
 	if obj.Startup != "enabled" && obj.Startup != "disabled" && obj.Startup != "" {
 		return fmt.Errorf("Startup must be either `enabled` or `disabled` or undefined.")
 	}
-	return nil
+	return obj.BaseRes.Validate()
 }
 
 // Init runs some startup code for this resource.

resources/timer.go

@@ -62,7 +62,7 @@ func (obj *TimerRes) Default() Res {
 
 // Validate the params that are passed to TimerRes.
 func (obj *TimerRes) Validate() error {
-	return nil
+	return obj.BaseRes.Validate()
 }
 
 // Init runs some startup code for this resource.

resources/virt.go

@@ -122,7 +122,7 @@ func (obj *VirtRes) Init() error {
 
 // Validate if the params passed in are valid data.
 func (obj *VirtRes) Validate() error {
-	return nil
+	return obj.BaseRes.Validate()
 }
 
 func (obj *VirtRes) connect() (conn *libvirt.Connect, err error) {