Variables getting cached in different iteration

[ShivKJ]

Description

• i am running "for-loop" in Taskfile
• in each iteration, i am running another task which is calculating epoch in its vars
• but in each iteration i am getting same value of epoch even though sleep is added to produce new epoch value.

Question: Does Task "cache" the variable values?

Expectation: My expectation is that if another task (say B) is called in a task, then every time task B is invoked, it should be calculating variables in vars. This is specially useful when looping is involved.

Version

3.44.1

Operating system

MacOS

Experiments Enabled

No response

Example Taskfile

version: 3

silent: true

tasks:
  test:
    vars:
      X: [A, B, C]

    cmds:
      - for:
          var: X
          as: x

        task: test-one

        vars:
          x: '{{.x}}'

  test-one:
    internal: true

    vars:
      epoch_time_now:
        sh: date +%s%N

    cmds:
      - echo "epoch_time_now={{.epoch_time_now}} with x={{.x}}" # this value does not change across different iteration
      - sleep 1 # adding sleep to ensure that next iteration sees different epoch value but still getting the same value of epoch_time_now

[trulede]

@ShivKJ Unfortunately these dynamic variables are cached.

task/compiler.go

Line 159 in 242523c

if result, ok := c.dynamicCache[*v.Sh]; ok {

You may ask @andreynering if this behaviour is really necessary with the modern Task implementation. The codebase and operation would be simpler without this (and other similar strategies). When people want to "cache" dynamic variables and get a performance gain, they can simply define a global variable to take that value, and then reference that variable as required.

There may be a work around. I can't find anything in the new doc. But you can imagine what you need to do.

[ShivKJ]

..."cache" dynamic variables and get a performance gain, they can simply define a global variable to take that value...

Yup.

...But you can imagine what you need to do....

@trulede Could you elaborate it ? I tried with epoch_time_now: $(date +%s%N) but thenepoch_time_now will generate new time everytime it is used. I also tried to pass epoch_time_now from parent task but it is getting cached there too .

@andreynering Is there a way to avoid caching. While running the for loop, one would require some variable to change in every iteration, i.e., to be calculated dynamically and caching will defeat the purpose.

To be on a safer side, we can also add a option cache to enable (as a default option)/disable this feature, something like this,

    vars:
      epoch_time_now:
        sh: date +%s%N
        cache: false

[trulede]

Better just don't cache ... if you clearly want X and instead get Y, then its just a bug. Nice idea, but it you want X and get Y, not good.

Anyway, @ShivKJ, you want to do something like:

sh: echo "{{.x}}" > /dev/null; date +%s%N

which will not avoid the cache, but should avoid the "cache effect" you observe.

[ShivKJ]

Thanks @trulede, this resolves the issue for me.