Feature request: Configurable subtask forcing

[sevberg]

Intro

I'm interested in using Taskfile with the gentle force experiment activated, however I would like to have a bit more control over which tasks get "forced", and which don't. I can imagine doing this with something like a force: [flag] argument similar to run, which I will explain below. Of course, other solutions would be welcome as well :)

Status Quo

To showcase my current challenge, I'll use this example Taskfile, which I hope is clear enough without description (If not, I can edit this..)

version: '3'

vars:
  COUNTRIES: DEU USA CHN

tasks:
  prepare_country:
    requires:
      vars: [iso3]
    label: 'prepare_country iso3={{.iso3}}'
    cmds:
      - 'echo "PREPARING: {{.iso3}}"'
      - touch data/prepared_{{.iso3}}.csv
    sources:
      - data/input_{{.iso3}}.csv
    generates:
      - data/prepared_{{.iso3}}.csv

  analyze_country:
    deps:
      - task: prepare_country
        vars:
          iso3: '{{.iso3}}'
    requires:
      vars: [iso3]
    label: 'analyze_country iso3={{.iso3}}'
    cmds:
      - 'echo "ANALYZING: {{.iso3}}"'
      - touch data/analyzed_{{.iso3}}.csv
    sources:
      - data/prepared_{{.iso3}}.csv
    generates:
      - data/analyzed_{{.iso3}}.csv
  
  analyze_all:
    cmds:
      - for: { var: COUNTRIES }
        task: analyze_country
        vars:
          iso3: '{{.ITEM}}'

Where the files data/input_[country].csv were manually created on my filesystem.

When I invoke the analyze_all task with the command...

TASK_X_GENTLE_FORCE=1 task analyze_all --force

...then all tasks and sub tasks are executed. If I run that same command again, then all tasks are skipped (besides of course the analyze_all task which isn't actually doing meaningful work). As far as I can tell, this is as-expected with the current implementation of Gentle Forcing.

That said, what I would like to have happen is that executing TASK_X_GENTLE_FORCE=1 task analyze_all --force would somehow know that I want to force the "primary children" of the analyze_all task, i.e. the analyze_country tasks, but not their dependencies (i.e. the prepare_country tasks).

Proposal

In general I really like the Gentle Force behaviour, and I don't suggest changing it. However in this edge case I would be happy with something like a force: when_forced argument which I could add to the subtask invocations in my analyze_all task. This could look like:

version: '3'

vars:
  COUNTRIES: DEU USA CHN

tasks:
  prepare_country:
    requires:
      vars: [iso3]
    label: 'prepare_country iso3={{.iso3}}'
    cmds:
      - 'echo "PREPARING: {{.iso3}}"'
      - touch data/prepared_{{.iso3}}.csv
    sources:
      - data/input_{{.iso3}}.csv
    generates:
      - data/prepared_{{.iso3}}.csv

  analyze_country:
    deps:
      - task: prepare_country
        vars:
          iso3: '{{.iso3}}'
    requires:
      vars: [iso3]
    label: 'analyze_country iso3={{.iso3}}'
    cmds:
      - 'echo "ANALYZING: {{.iso3}}"'
      - touch data/analyzed_{{.iso3}}.csv
    sources:
      - data/prepared_{{.iso3}}.csv
    generates:
      - data/analyzed_{{.iso3}}.csv
  
  analyze_all:
    cmds:
      - for: { var: COUNTRIES }
        task: analyze_country 
        force: when_forced  # <------------------ HERE
        vars:
          iso3: '{{.ITEM}}'

In this case force: when_forced could mean "force this sub task if the current task is forced".

Other possible values could include:

• force: always, so that subtask is always executed
• force: never, which could be the default and would maintain the current behaviour of Gentle Force