Q:

Grails upgrade path from 1.3.7 to 3.2.6

I have a Grails application currently running on Grails 1.3.7.  I want to upgrade all the way to 3.2.6.
What would be the optimal path to do this?  Should I just go straight to 3.2.6 and then try to get dependencies and compilation errors straight?  Should I upgrade to 2.0 or 2.5.6 first, then go to 3.2.6?  I feel like smaller steps might be easier, but then it seems like it would be harder to find the proper plugin versions to go along with the Grails version.  I'm looking for the route that will require the least change and generate the least friction.

A:

What would be the optimal path to do this? Should I just go straight
  to 3.2.6 and then try to get dependencies and compilation errors
  straight? Should I upgrade to 2.0 or 2.5.6 first, then go to 3.2.6?

At OCI we have done many many of these upgrades since we released 3.0 over 2 years ago.  I advocate for skipping the 2.5.x step in almost all cases.  Doing the 2.5.x upgrade will require some work that will be undone when you upgrade to 3.2.x and there is no real benefit to paying that additional price.  The 2.5.x upgrade will be easier, but doesn't really buy you anything and you will have to take on the 3.x upgrade after that anyway, so just skip the intermediary step unless you have some specific compelling reason to include it (at this point, almost no apps have a valid justification for including that intermediary 2.5.x step).
I hope that helps.

