[BZ#1677677] Fatal Error in Mapping Wizard: When mapping more than one source cluster, cannot switch between clusters on storage step

[mturley]

Associated RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=1677677

I observed this bug while testing #1030, but it also appears to be present on master.

1. Open the Create Infrastructure Mapping wizard.
2. On the "Map Compute" step, add mappings for at least two different source clusters.
3. Proceed to the "Map Storage" step, and try to select a cluster in the dropdown.
4. An error appears, the cluster is not selected, and you cannot proceed.

The line that is causing the error is here: https://github.com/ManageIQ/manageiq-v2v/blob/master/app/javascript/react/screens/App/Mappings/screens/MappingWizard/components/MappingWizardDatastoresStep/MappingWizardDatastoresStep.js#L109
Apparently, there is an issue with the reference to this.setState being set as a default parameter value in the function definition, which is causing React to get confused about this internally.

The fix is pretty simple (use this.setState directly in the method body instead of assigning it and calling it by reference), but (a) I don't really understand why it doesn't work as written, and (b) I don't know why we're only seeing this now, I'm pretty sure it was working fine when that code was introduced in #796.

@himdel, @mzazrivec , @Hyperkid123 .. would you guys mind helping me figure out what's going on here and identify which ManageIQ releases are affected? I imagine we should also make sure QE is testing this wizard with more than one source cluster.. I'm surprised we didn't catch it sooner. I'll post a PR shortly to fix the bug, but I'm not sure how to proceed with damage control here.

[mturley]

Maybe this started happening at some earlier React version upgrade? I'm having trouble getting my local dev environment working on older versions at the moment.