I've been thinking a lot about this general idea the past couple weeks, and had even considered writing a plugin last weekend before I got sick

I think a more generic "require" syntax would be ideal for example:

require 'junit' /* plugin artifactId */
require 'parallel-text-executor'

Which could be expanded upon with the keyword arguments in groovy to support additional requirement statements in the future, e.g.

/* Naturally all of these could be squished into one require statement */
require plugin: 'junit'
require core: '1.642.4'
require tool: ['Maven' : '3.3.3']

I'm curious what hrmpw and abayer think of this syntax.

The simplest approach would simply be a step which fails if some of the requested plugins are missing or too old:

Mostly agreed, i suggest that the pipeline should abort because of missing dependencies with console outputs stating this Jenkins instance is lacking the required dependencies to execute this pipeline. I generally interpret failures to mean the Pipeline is broken (user error) rather than something requiring a user/administrator cooperation to rectify. I don't have much better reasoning than that, but an abort would catch my gaze a lot sooner than a failure, unfortunately

As far as version restricting goes, in my mind I was thinking on punting on that for now until some more users using any require syntax.

Based on your example above I don't know if you intended that you could specify a version for plugins like you did for Tools

require 'junit'  /* simply checks for any version */

or

require ['junit' : '1.11']  /* checks for that version */

or

require ['junit' : '>1.11'] /* 1.11 or above */

This might be too much like gemspec notation it would be clear what is needed.

hrmpw with tools, there is no "version range" in the Tool installers right now, so in my head it was a fairly direct mapping selecting a version from a dropdown in a Freestyle job configuration page. If we were to support "just use Maven, any maven" i think that would be venturing too far from what Jenkins currently does.

The reason for avoiding the version ranges right now, in my opinion, is that I'm not confident the right thing that would meet users' needs would be specifying a singular version (could be too restrictive), specify a base version (could be too relaxed) and don't want to introduce the full maven version range syntax into this

-1 on a generic require step. See JENKINS-28718 for the case of tools.

jglick I don't see how my proposal and JENKINS-28718 are mutually exclusive, unless you're referring to automatically installing tools (which I think is a fun feature but I would immediately disable it in any production environment).

I view a generic require step as a useful way to allow a script to safely declare runtime dependencies and nothing more. Every scripting environment, even JavaScript these days, has a similar syntax.

I'm +1 overall - tools will need a fair amount of work to support a real version concept, but I'm actually beginning to kick around ideas for that anyway.

Also, this would be handy, particularly with regards to tools, with Plumber - I was planning to put in some try/catch logic once tool management actually becomes a thing (which itself still depends on a consistent way to do version discovery), but if we can just use "require" that'd be smoother.

Again -1 on a general require. Particular things that might be needed are better handled with dedicated steps or system.