packer: Better error handling for template parsing

packer/template.go

@@ -48,11 +48,12 @@ func ParseTemplate(data []byte) (t *Template, err error) {
 	t.Builders = make(map[string]rawBuilderConfig)
 	t.Hooks = rawTpl.Hooks
 
-	for _, v := range rawTpl.Builders {
+	errors := make([]error, 0)
+	for i, v := range rawTpl.Builders {
 		rawType, ok := v["type"]
 		if !ok {
-			// TODO: Missing type error
-			return
+			errors = append(errors, fmt.Errorf("missing 'type' for builder %d", i + 1))
+			continue
 		}
 
 		// Attempt to get the name of the builder. If the "name" key
@@ -67,17 +68,20 @@ func ParseTemplate(data []byte) (t *Template, err error) {
 		name := rawName.(string)
 		typeName := rawType.(string)
 
-		// Check if we already have a builder with this name and record
-		// an error.
-		_, ok = t.Builders[name]
-		if ok {
-			// TODO: We already have a builder with this name
-			return
+		// Check if we already have a builder with this name and error if so
+		if _, ok := t.Builders[name]; ok {
+			errors = append(errors, fmt.Errorf("builder with name '%s' already exists", name))
+			continue
 		}
 
 		t.Builders[name] = rawBuilderConfig{typeName, v}
 	}
 
+	if len(errors) > 0 {
+		err = &MultiError{errors}
+		return
+	}
+
 	return
 }
 

packer/template_test.go

@@ -40,6 +40,20 @@ func TestParseTemplate_Invalid(t *testing.T) {
 	assert.Nil(result, "should have no result")
 }
 
+func TestParseTemplate_BuilderWithoutType(t *testing.T) {
+	assert := asserts.NewTestingAsserts(t, true)
+
+	data := `
+	{
+		"name": "my-image",
+		"builders": [{}]
+	}
+	`
+
+	_, err := ParseTemplate([]byte(data))
+	assert.NotNil(err, "should have error")
+}
+
 func TestParseTemplate_BuilderWithoutName(t *testing.T) {
 	assert := asserts.NewTestingAsserts(t, true)
 
@@ -89,6 +103,29 @@ func TestParseTemplate_BuilderWithName(t *testing.T) {
 	assert.Equal(builder.builderName, "amazon-ebs", "builder should be amazon-ebs")
 }
 
+func TestParseTemplate_BuilderWithConflictingName(t *testing.T) {
+	assert := asserts.NewTestingAsserts(t, true)
+
+	data := `
+	{
+		"name": "my-image",
+		"builders": [
+			{
+				"name": "bob",
+				"type": "amazon-ebs"
+			},
+			{
+				"name": "bob",
+				"type": "foo",
+			}
+		]
+	}
+	`
+
+	_, err := ParseTemplate([]byte(data))
+	assert.NotNil(err, "should have error")
+}
+
 func TestParseTemplate_Hooks(t *testing.T) {
 	assert := asserts.NewTestingAsserts(t, true)