Support mixed case Kind

The implementation uses the same validation logic that runs against `Kind` in
apimachinery; i.e. allows any `Kind` value that, when converted to
lowercase, is a valid DNS-1035 label.

Signed-off-by: Hannes Hörl <[email protected]>

pkg/scaffold/resource/resource.go

@@ -79,8 +79,11 @@ func (r *Resource) Validate() error {
 		return fmt.Errorf(
 			"version must match ^v\\d+(alpha\\d+|beta\\d+)?$ (was %s)", r.Version)
 	}
-	if r.Kind != flect.Pascalize(r.Kind) {
-		return fmt.Errorf("kind must be PascalCase (expected %s was %s)", flect.Pascalize(r.Kind), r.Kind)
+
+	validationErrors := isDNS1035Label(strings.ToLower(r.Kind))
+
+	if len(validationErrors) != 0 {
+		return fmt.Errorf("Kind failed validation: %#v", validationErrors)
 	}
 
 	return nil
@@ -96,9 +99,16 @@ const (
 
 	// dns1123SubdomainMaxLength is a subdomain's max length in DNS (RFC 1123)
 	dns1123SubdomainMaxLength int = 253
+
+	dns1035LabelFmt    string = "[a-z]([-a-z0-9]*[a-z0-9])?"
+	dns1035LabelErrMsg string = "a DNS-1035 label must consist of lower case alphanumeric characters or '-', start with an alphabetic character, and end with an alphanumeric character"
+
+	// DNS1035LabelMaxLength is a label's max length in DNS (RFC 1035)
+	dns1035LabelMaxLength int = 63
 )
 
 var dns1123SubdomainRegexp = regexp.MustCompile("^" + dns1123SubdomainFmt + "$")
+var dns1035LabelRegexp = regexp.MustCompile("^" + dns1035LabelFmt + "$")
 
 // IsDNS1123Subdomain tests for a string that conforms to the definition of a
 // subdomain in DNS (RFC 1123).
@@ -113,6 +123,17 @@ func IsDNS1123Subdomain(value string) []string {
 	return errs
 }
 
+func isDNS1035Label(value string) []string {
+	var errs []string
+	if len(value) > dns1035LabelMaxLength {
+		errs = append(errs, maxLenError(dns1035LabelMaxLength))
+	}
+	if !dns1035LabelRegexp.MatchString(value) {
+		errs = append(errs, regexError(dns1035LabelErrMsg, dns1035LabelFmt, "my-name", "abc-123"))
+	}
+	return errs
+}
+
 // MaxLenError returns a string explanation of a "string too long" validation
 // failure.
 func maxLenError(length int) string {

pkg/scaffold/resource/resource_test.go

@@ -71,24 +71,27 @@ var _ = Describe("Resource", func() {
 			Expect(instance.Validate().Error()).To(ContainSubstring("kind cannot be empty"))
 		})
 
-		It("should fail if the Kind is not pascal cased", func() {
-			// Base case
-			instance := &Resource{Group: "crew", Kind: "FirstMate", Version: "v1"}
+		It("should succeed if the Kind is valid, according to core Kubernetes", func() {
+			instance := &Resource{Group: "crew", Kind: "fIRstMate", Version: "v1"}
 			Expect(instance.Validate()).To(Succeed())
+		})
 
-			// Can't detect this case :(
-			instance = &Resource{Group: "crew", Kind: "Firstmate", Version: "v1"}
-			Expect(instance.Validate()).To(Succeed())
+		It("should fail if Kind is too long", func() {
+			var kind string
 
-			instance = &Resource{Group: "crew", Kind: "firstMate", Version: "v1"}
-			Expect(instance.Validate()).NotTo(Succeed())
-			Expect(instance.Validate().Error()).To(ContainSubstring(
-				`kind must be PascalCase (expected FirstMate was firstMate)`))
+			for i := 0; i < 65; i++ {
+				kind += "a"
+			}
 
-			instance = &Resource{Group: "crew", Kind: "firstmate", Version: "v1"}
-			Expect(instance.Validate()).NotTo(Succeed())
-			Expect(instance.Validate().Error()).To(ContainSubstring(
-				`kind must be PascalCase (expected Firstmate was firstmate)`))
+			instance := &Resource{Group: "crew", Kind: kind, Version: "v1"}
+			err := instance.Validate()
+			Expect(err).To(MatchError(ContainSubstring("must be no more than 63 characters")))
+		})
+
+		It("should fail if Kind is invalid, according to core Kubernetes", func() {
+			instance := &Resource{Group: "crew", Kind: "Something withSpaces", Version: "v1"}
+			err := instance.Validate()
+			Expect(err).To(MatchError(ContainSubstring("a DNS-1035 label must consist of lower case alphanumeric characters")))
 		})
 
 		It("should default the Resource by pluralizing the Kind", func() {