r/tfe_workspace: Fix panic when trigger_prefixes = [""]

[nfagerlund]

Description

A customer reported this panic via support. Sebastian clued me in that this is an extremely cursed known behavior in sdkv2, where it munges a list of strings containing one empty string into a list containing a single nil, so you must do a type assert on the inner elements.

Note that the Update function already did exactly this (around line 655 or so)! So there was no panic if you changed trigger_prefixes to the fatal value after the resource already existed.

Remember to:

• Update the Change Log
• Update the Documentation

Testing plan

Config:

provider "tfe" {
  hostname = <YOURS>
}

resource "tfe_workspace" "ex-splodo" {
  auto_apply                    = true
  file_triggers_enabled         = true
  name                          = "jan24-trigger-prefixes-panic-repro"
  organization                  = <YOURS>
  queue_all_runs                = true
  structured_run_output_enabled = true
  terraform_version             = "1.5.1"
  trigger_prefixes              = [""] # <-- RIGHT HERE, THIS IS THE GUY
}

Try to create the resource with a tf apply; should panic as soon as you say "yes" after the plan.

External links

• Prior art PR that @sebasslash dug up

Output from acceptance tests

I'm internal, just check CI.