Are Lightning component tags case-sensititve?

Summer 18 is here. Every 4 months salesforce comes with new features, new improvements and changes in platform that help developers, admin to build on salesforce platform. Most of changes are well documented but…

One change that came in summer 18 was lighting tags being case sensitive. With Summer 18 release Salesforce enforced the lightning tags to be case sensitive. So when we started testing on summer 18 pre release org, we found out that our code is not working. Error that was thrown on UI being

This page has an error. You might just need to refresh it. Component class instance initialization error [Definition does not exist on the client for descriptor:markup://lightning:Icon] Failing descriptor: {markup://c:testComponent}

Problem in our code was with <lightning:icon> tag. We have written icon as Icon with I being capital. After some debugging we found out that salesforce has introduced case sensitivity for lighting tags. As most of our code was written in case sensitive tags but in few places case sensitivity was missing.

Another problem with case-sensitive tags were only tags with lightning namespace were made case sensitive. All other tags with ui,aura name space remained case insensitive.

After raising a case with salesforce and raising our concern with salesforce regarding a half baked case sensitivity without any prior notification, they said they will roll back this change before summer 18 release in upcoming patches.

But Salesforce stated that lightning tags are going to be case sensitive going forward. So all the new development should be done by keeping this in mind. Salesforce is going to make all lightning tags case sensitive. There is a link in summer 15 release notes which states that lightning is going to case sensitive(But they didnot meant it then 😉). I think we have another 4 months until salesforce make this change.

Until then keep a eye on aura:If with I capital or lightning:buttonicon with i in icon being small.