packer: automatically validate when creating a core

command/meta.go

@@ -49,11 +49,6 @@ func (m *Meta) Core(tpl *template.Template) (*packer.Core, error) {
 		return nil, fmt.Errorf("Error initializing core: %s", err)
 	}
 
-	// Validate it
-	if err := core.Validate(); err != nil {
-		return nil, err
-	}
-
 	return core, nil
 }
 

packer/core.go

@@ -72,6 +72,9 @@ func NewCore(c *CoreConfig) (*Core, error) {
 		variables:  c.Variables,
 		builds:     builds,
 	}
+	if err := result.validate(); err != nil {
+		return nil, err
+	}
 	if err := result.init(); err != nil {
 		return nil, err
 	}
@@ -205,11 +208,11 @@ func (c *Core) Build(n string) (Build, error) {
 	}, nil
 }
 
-// Validate does a full validation of the template.
+// validate does a full validation of the template.
 //
-// This will automatically call template.Validate() in addition to doing
+// This will automatically call template.validate() in addition to doing
 // richer semantic checks around variables and so on.
-func (c *Core) Validate() error {
+func (c *Core) validate() error {
 	// First validate the template in general, we can't do anything else
 	// unless the template itself is valid.
 	if err := c.template.Validate(); err != nil {

packer/core_test.go

@@ -376,15 +376,11 @@ func TestCoreValidate(t *testing.T) {
 			t.Fatalf("err: %s\n\n%s", tc.File, err)
 		}
 
-		core, err := NewCore(&CoreConfig{
+		_, err = NewCore(&CoreConfig{
 			Template:  tpl,
 			Variables: tc.Vars,
 		})
-		if err != nil {
-			t.Fatalf("err: %s\n\n%s", tc.File, err)
-		}
-
-		if err := core.Validate(); (err != nil) != tc.Err {
+		if (err != nil) != tc.Err {
 			t.Fatalf("err: %s\n\n%s", tc.File, err)
 		}
 	}

packer/test-fixtures/build-prov-skip.json

@@ -1,6 +1,9 @@
 {
     "builders": [{
         "type": "test"
+    }, {
+        "name": "foo",
+        "type": "test"
     }],
 
     "provisioners": [{