@Colin Brough - this was recently discussed on a thread internal to InterSystems, and I credit @Eduard Lebedyuk 
for the following options, which were suggested within the context of Enabled/Disabled Business Hosts on different environments using the same Production (some don't apply to your question about logging and testing, but I include them all for completeness):

1. Track a separate production class for each environment.
2. Use SDS to effectively disable Business Hosts (for example, by setting the Port property to an empty string).
3. Create a custom adapter/business host that has SDS configurable setting "RealEnable", which would be checked in OnInit or OnProcess input.
4. Use Interoperability Schedules, with Business Host always off/on.

I think (1) and (3) would be most likely to work for you here.

Also, it's not going to help you in the immediate term, but be aware that TestingEnabled (along with some other fields) is supported for SDS starting in InterSystems IRIS 2023.3 (I am very excited about that!!)

Sounds like you are using client-side source control in a shared development environment ... this is just a formula for frustration.  Either use private dev instances with client-side source control, or use server-side source control with a shared dev instance.  This was the theme of a presentation we did at G.S. a couple of times.  See https://community.intersystems.com/post/new-video-shared-development-21s...
NOTE - This was given a 2nd time where we used VSCode and not Atelier but I can't find that posting for some reason.   However the principles are identical whether you're using Atelier or VSCode ... they use the same APIs to manage source with the server.  

The issue is that you need the logic to run synchronously in process so that it can actually write out the JavaScript as part of the response to the web client. If you job off the logic it will run in a separate process and there is no way to return the JavaScript to the caller because this is done asynchronously and the response has already been sent by the time your job will finish in all likelihood. If you need something to run asynchronously then use the #call() command in your CSP page.

@Pietro Montorfano - VSCode use with CCR is definitely supported.  You just need to make sure that your workspace is properly defined with isfs, etc to get you access to the files on the server.  Since CCR uses server-side source control hooks, you can actually have people using Studio and VSCode concurrently against your BASE Environment.

We've tried to make it as easy as possible by allowing you to export the VSCode workspace definition directly from CCR (credit: @Timothy Leavitt ).  Go to your Environment Details page and use the "Export (VSCode)" button on the top of your Environment list:

Please try it and let us know if it works for you.  P.S. would you mind adding the #ccr tag to your question so others can easily find it?

@Abhishek Raj - start with reviewing the documentation for new features, and Upgrade Compatibility checklists:

This will be the most comprehensive collection of suggestions, things to know, and 'gotcha's' to be aware of.  

Beyond reading the docs and seeing what is applicable to your environment, do a practice upgrade of your application and TEST, TEST, TEST :)  

Lastly, make sure you review the supported platform list for 2018.1 and 2015.2:

2018.1: https://docs.intersystems.com/latest/csp/docbook/DocBook.UI.Page.cls?KEY...

2015.2: https://cedocs.intersystems.com/ens20152/csp/docbook/DocBook.UI.Page.cls...

Hope that helps!

@Alexey Maslov  - check out https://openexchange.intersystems.com/package/isc-codetidy .... this package includes automatic expansion of ObjectScript commands.  Even if you don't want to use the whole package, you can find the sample code to do expansion.

@Evan Gabhart  - can you please advise as to the specific class where the expansion code can be found?

@Ephraim Malane - without having the actual CCR IDs, most likely the case is that your CCR deployed through TEST added a file, and CCR will automatically detect if the CCR that added a file is not yet in the target environment and therefore will prevent other CCRs from 'leap-frogging' past it.  This is because if you leap past a CCR which originally adds a file, if you later need to back out the CCR it will result in a 'delete' of the file from all environments (because you're undoing an 'add').  

Probably the best bet for you is to reach out to Support so they can help you manually move the 'add' into the CCR that you want to move forward.  You will probably also need help cleaning up the CCR that you cancelled, as I am guessing that the backout failed due to edits already being promoted to TEST on top of the 'add' that you are trying to back out from there.

As we looked into things further on our side, it appears as though the UNIX 'hostname'.  We were able to resolve the issue in UNIX by doing the following to change the hostname to 'mynewhost':

log in as root
hostname mynewhost
echo mynewhost > /etc/hostname

The 2nd line will change the hostname in the current processes, and the 3rd will make sure that the change will persist during a reboot.  

Hope this is helpful to someone else.

@Colin Brough - all great questions!  I'll provide some thoughts and I am sure others will chime in as well.  One question that I have which may impact the answers is what your current source control approach is?  Are you using serverside source control hooks with Studio or some other approach?

  • Take Atelier off the list and drop it from consideration... it is deprecated new work shouldn't be started with it
  • VSCode is the path forward for InterSystems technologies; it used the Atelier REST APIs and therefore you can use it on Caché 2018.x (originally added in 2016.2 IIRC)
  • You can typically use VSCode alongside Studio, depending on your answer to the above question about your source control approach.  If you are using no source control, or if you are using serverside source control, then Studio and VSCode can both be used against the instance in mixed mode (my team has been doing this for years)
  • I can't speak to what you lose with VSCode but I believe that at this point the answer is either 'very little' or 'nothing' for all intents and purposes
  • I can't speak to Studio Templates (hopefully someone else can weigh in)

This video may also be helpful to you: https://community.intersystems.com/post/video-visual-studio-code-objects... 

Hope this is a good starting point.