MP4: Remove item when empty string is set (#929)

This will make the behavior for MP4 tags compliant to the API
documentation and consistent with other tag formats.

2 files changed, 22 insertions, 5 deletions

diff --git a/taglib/mp4/mp4tag.cpp b/taglib/mp4/mp4tag.cpp
index bc95ad10..de41c58d 100644
--- a/taglib/mp4/mp4tag.cpp
+++ b/taglib/mp4/mp4tag.cpp
@@ -775,31 +775,41 @@ MP4::Tag::track() const
 void
 MP4::Tag::setTitle(const String &value)
 {
-  d->items["\251nam"] = StringList(value);
+  setTextItem("\251nam", value);
 }
 
 void
 MP4::Tag::setArtist(const String &value)
 {
-  d->items["\251ART"] = StringList(value);
+  setTextItem("\251ART", value);
 }
 
 void
 MP4::Tag::setAlbum(const String &value)
 {
-  d->items["\251alb"] = StringList(value);
+  setTextItem("\251alb", value);
 }
 
 void
 MP4::Tag::setComment(const String &value)
 {
-  d->items["\251cmt"] = StringList(value);
+  setTextItem("\251cmt", value);
 }
 
 void
 MP4::Tag::setGenre(const String &value)
 {
-  d->items["\251gen"] = StringList(value);
+  setTextItem("\251gen", value);
+}
+
+void
+MP4::Tag::setTextItem(const String &key, const String &value)
+{
+  if (!value.isEmpty()) {
+    d->items[key] = StringList(value);
+  } else {
+    d->items.erase(key);
+  }
 }
 
 void
diff --git a/taglib/mp4/mp4tag.h b/taglib/mp4/mp4tag.h
index e5b70af3..ccee8e06 100644
--- a/taglib/mp4/mp4tag.h
+++ b/taglib/mp4/mp4tag.h
@@ -106,6 +106,13 @@ namespace TagLib {
         void removeUnsupportedProperties(const StringList& properties);
         PropertyMap setProperties(const PropertyMap &properties);
 
+    protected:
+        /*!
+         * Sets the value of \a key to \a value, overwriting any previous value.
+         * If \a value is empty, the item is removed.
+         */
+        void setTextItem(const String &key, const String &value);
+
     private:
         AtomDataList parseData2(const Atom *atom, int expectedFlags = -1,
                                 bool freeForm = false);