Add defaults.deepcopy function.

[aabouzaid]

What does this PR do?

Expose copy.deepcopy as defaults.deepcopy function.

What issues does this PR fix or reference?

In many case there are multi level of defaults, e.g. global, group, and specific.
And since Python does not copy objects by default but creates bindings, so deep copy is necessary for that cases.

Here is an arbitrary example:

Yaml

vars:
  hosts:
    defaults:
      enabled: True
      aggregate: source
      extra:
        - test
        - stage
    list:
      hos01:
        index: foo
        upstream: bar
      hos02:
        index: foo2
        upstream: bar2

Jinja

{% for host, vars in vars.hosts.list.items() %}
  {% set defaults = salt['defaults.deepcopy'](vars.hosts.defaults) %}
  {% set host_vars = salt['defaults.merge'](defaults, vars) %}
  ....
{% endfor %}

Output

hos01:
  index: foo
  upstream: bar
  enabled: True
  aggregate: source
  extra:
    - test
    - stage

New Behavior

Allow to make deepcopy of objects.

Tests written?

Yes

Commits signed with GPG?

Not yet.

[noelmcloughlin]

Nice idea. This jinja2 example is more efficient?

{% set defaults = salt['defaults.deepcopy'](vars.hosts.defaults) %}
{% for host, vars in vars.hosts.list.items() %}
 {% set host_vars = salt['defaults.merge'](defaults, vars) %}
 ....
{% endfor %}

[noelmcloughlin]

Looks useful for jinja scenarios. thanks!!

[aabouzaid]

@noelmcloughlin

Nope, that's actually the current behavior with normal copy because defaults.merge is merging in place and it doesn't return.

The defaults will be overwritten within 1st iteration.

Here is an example:

vars:
  hosts:
    defaults:
      enabled: True
    list:
      hos01:
        enabled: False
        index: foo
      hos02:
        index: foo2

{% set defaults = salt['defaults.deepcopy'](vars.hosts.defaults) %}
{% for host, vars in vars.hosts.list.items() %}
 {% set host_vars = salt['defaults.merge'](defaults, vars) %}
 ....
{% endfor %}

before loop:
defaults = { enabled: True }

itr01 (host01):
defaults = { enabled: False, index = foo }

itr02 (host02):
defaults = { enabled: False, index = foo2 }

That's why it should make a real copy inside the loop.

[noelmcloughlin]

Thanks for the clear explanation!! @aabouzaid

[rallytime]

Thanks for the tests, too. 👍

[rallytime]

@aabouzaid It looks like your new test isn't passing though. Can you take another look?

https://jenkins.saltstack.com/job/PR/job/salt-pr-linode-ubuntu14-n/17272/testReport/junit/unit.modules.test_defaults/DefaultsTestCase/test_deepcopy/

[aabouzaid]

@rallytime a typo 🙆‍♂️
Fixed :-)