Configuration option to trigger a rebuild if a variable changes

[lukbukkit]

Hello,
I'm using Task version 3.0.0 on Windows and I'm very happy about this build tool.

While using this program, I noticed one feature would be very helpful: Trigger a rebuild based on the change of a variable.
In my case, it's the PURGE variable which if activated, generates a smaller file.

If I run at first task build assets and then task build assets PURGE=true, no rebuild is triggered. But in this case it would be very useful, because the output file would change. Of course you can use the --force option to always trigger a rebuild.

I tried to implement my own workaround. But this does only work on Unix shells (/bin/bash, Git Bash ...) and not if you're using the PowerShell.

Here you can take a look at my Taskfile.yml

version: '3'

tasks:
  assets:
    desc: Creates the assets using yarn
    dir: resources
    cmds:
      - yarn
      - yarn run build
      - echo "{{if .PURGE}}true{{else}}false{{end}}" > last_build_mode # my workaround
    sources:
      - styles.css
    generates:
      - output.css
    status:
      - cat last_build_mode
      - test "{{if .PURGE}}true{{else}}false{{end}}" = $(cat last_build_mode) # my workaround
    env:
      NODE_ENV:
        sh: echo {{if .PURGE}} production {{else}} development {{end}}

My suggestion would be to add a new field like var-deps, where you can specify variables which trigger a rebuild.

version: '3'

tasks:
  assets:
    desc: Creates the assets using yarn
    dir: resources
    cmds:
      - yarn
      - yarn run build
    sources:
      - styles.css
    generates:
      - output.css
    var-deps: 
      - PURGE

Thanks a lot for this useful software. :)

[andreynering]

Hi @lukbukkit, thanks for opening this issue!

This sounds like a very valid use case / feature request.

[andreynering]

I'd like to note that, specifically for sources when using the checksum mode, there's actually a way of achieving that currently:

version: '3'

tasks:
  my-task:
    # ...
    label: 'my-task-{{.VARIABLE}}'

The label: prop is used to identify the task, so concatenating a variable there will make it have a different key when that changes.

This will not work for timestamp mode or plain status:, though. So this feature request still makes sense.

[sylv-io]

There is an alternative workaround by using a helper script for status:
system-transparency/system-transparency@38fd6cb

tl;dr: it creates a config file under .task/config/<target> based on a variable name pattern. Any change does trigger a rebuild.

However the script .task_config.sh is written specifically for the project, but you could adapt it to generate a sub-config based on your own variable name pattern.

IMHO this could be a great new task feature 👍 If there is interest, i would give it a try.