Allow the user to generate a valid iri based on a uuid

atom.go

@@ -1,10 +1,12 @@
 package atom
 
 import (
+	"fmt"
 	"mime"
 	"regexp"
 	"strings"
 
+	"github.com/google/uuid"
 	"golang.org/x/text/language"
 )
 
@@ -61,8 +63,17 @@ func isXMLMediaType(mediaType string) bool {
 // isValidMediaType checks whether a string is a valid media type. It returns a
 // bool.
 func isValidMediaType(mediaType string) bool {
-	_, _, err := mime.ParseMediaType(mediaType)
-	return err == nil
+	mediaType, _, err := mime.ParseMediaType(mediaType)
+	if err != nil {
+		return false
+	}
+
+	typeParts := strings.Split(mediaType, "/")
+	if len(typeParts) != 2 || typeParts[0] == "" || typeParts[1] == "" {
+		return false
+	}
+
+	return true
 }
 
 // isValidLanguageTag checks whether a LanguageTag is valid. It returns a bool.
@@ -70,3 +81,8 @@ func isValidLanguageTag(tag LanguageTag) bool {
 	_, err := language.Parse(string(tag))
 	return err == nil
 }
+
+// NewURN generates an new valid IRI based on a UUID. It returns an IRI.
+func NewURN() IRI {
+	return IRI(fmt.Sprint("urn:uuid:", uuid.New()))
+}

entry.go

@@ -34,14 +34,16 @@ type Entry struct {
 // the atom:entry contains an atom:source element that contains an atom:author
 // element or, in an Atom Feed Document, the atom:feed element contains an
 // atom:author element itself.
-func (e *Entry) checkAuthors() error {
+func (e *Entry) checkAuthors(authorInFeed bool) error {
 	if e.Authors == nil {
+		if !authorInFeed {
 			if e.Source == nil {
 				return errors.New("no authors set in entry")
 			}
 			if e.Source.Authors == nil {
 				return errors.New("no authors set in entry")
 			}
+		}
 	} else {
 		for i, a := range e.Authors {
 			if err := a.Check(); err != nil {
@@ -138,7 +140,7 @@ func (e *Entry) Check() error {
 		}
 	}
 
-	if err := e.checkAuthors(); err != nil {
+	if err := e.checkAuthors(true); err != nil {
 		return fmt.Errorf("entry %v: %v", e.ID.URI, err)
 	}
 
@@ -211,7 +213,7 @@ func (e *Entry) Check() error {
 		// is not an XML media type [RFC3023], does not begin with "text/", and
 		// does not end with "/xml" or "+xml".
 		mediaType := e.Content.getType()
-		if !isXMLMediaType(mediaType) && !strings.HasPrefix(mediaType, "text/") {
+		if isValidMediaType(mediaType) && !isXMLMediaType(mediaType) && !strings.HasPrefix(mediaType, "text/") {
 			return fmt.Errorf("no summary element of entry %v but media type not xml", e.ID.URI)
 		}
 	}

feed.go

@@ -128,7 +128,7 @@ func (f *Feed) Check() error {
 	// least one atom:author element.
 	if f.Authors == nil {
 		for _, e := range f.Entries {
-			if err := e.checkAuthors(); err != nil {
+			if err := e.checkAuthors(false); err != nil {
 				return fmt.Errorf("no authors set in feed %v: %v", f.ID.URI, err)
 			}
 		}

id.go

@@ -3,8 +3,6 @@ package atom
 import (
 	"errors"
 	"fmt"
-
-	"github.com/google/uuid"
 )
 
 type ID struct {
@@ -13,8 +11,8 @@ type ID struct {
 }
 
 // NewID creates a new ID. It returns a *ID.
-func NewID() *ID {
-	return &ID{URI: IRI(fmt.Sprint("urn:uuid:", uuid.New()))}
+func NewID(id string) *ID {
+	return &ID{URI: IRI(id)}
 }
 
 // Check checks the ID for incompatibilities with RFC4287. It returns an error.

link.go

@@ -38,17 +38,23 @@ func (l *Link) Check() error {
 		}
 	}
 
-	if strings.Contains(l.Rel, ":") || !isValidIRI(IRI(l.Rel)) {
+	if l.Rel != "" {
+		if strings.Contains(l.Rel, ":") && !isValidIRI(IRI(l.Rel)) {
 			return fmt.Errorf("rel attribute %v of link %v not correctly formatted", l.Rel, l.Href)
 		}
+	}
 
+	if l.Type != "" {
 		if !isValidMediaType(string(l.Type)) {
 			return fmt.Errorf("type attribute %v of link %v invalid media type", l.Type, l.Href)
 		}
+	}
 
+	if l.HrefLang != "" {
 		if !isValidLanguageTag(l.HrefLang) {
 			return fmt.Errorf("hreflang attribute %v of link %v invalid language tag", l.Type, l.HrefLang)
 		}
+	}
 
 	if l.Content == nil {
 		return fmt.Errorf("no content element of link %v", l.Href)