Clarifying env and var in Go-Task with Practical Examples

[bayeslearner]

I've been exploring Go-Task and came across some intriguing aspects regarding var and env. Their usage and impact on task outputs seem nuanced, and I'd appreciate some community insights. Here's a sample YAML file for context:

version: '3'

vars:
  CONFIG: '{{.CONFIG | default "Debug"}}'

tasks:
  foo:
    env:
      CONFIG: '{{.CONFIG}}'
    deps:
    - task: bar
    cmds:
    - echo $CONFIG Configuration for task foo
    - task: bar
    silent: true

  bar:
    env:
      CONFIG: '{{.CONFIG}}'
    cmds:
    - echo $CONFIG Configuration for task bar
    silent: true

The output:

CONFIG=Release task -t testfile.yml  foo 
Release Configuration for task bar
Release Configuration for task foo
Release Configuration for task bar

Alongside understanding the output for this configuration, I have a few more queries:

1. Are env and var treated the same in Go-Task, and what are their fundamental differences?
   It seems they are not identical and exist in different namespaces, similar to other programming languages.

2. How does scoping work with Go-Task vars?
   Are they dynamically reevaluated like local variables in other languages?

3. Are there different ways to pass env, and do they override global env?
   Do local env variables inherit global env values but override them in case of a conflict? So the local env doesn't have to define ALL env if you know it exists as a global env?

4. How do we distinguish between vars and env in the provided script?
   What confuses me is that in the global var section, {{.CONFIG}} seems to be using an env for setting a regular var. Is this due to the precedence rule where it tries to find a var to use, but as a last resort, it will fetch an environment variable of the same name if it exists?

5. Are local env variables reevaluated every time a task runs?
   When the task bar is invoked, is the env variable re-evaluated?

Could someone kindly provide insights or explanations on these points? There are still many open issues involving env/var interactions such as #1276 #203