Pass no argument to action command instead of passing empty values

[davidferlay]

Observed

• See action example defined here: https://github.com/launchrctl/launchr/blob/main/example/actions/arguments/action.yaml

➜  launchr git:(main) pl example:arguments
Image "envvars:latest" exists locally

Total number of arguments passed to the script: 2
- Argument 1: ""
- Argument 2: false

• When executing action with options, these options are passed to command as arguments

  command:
    - sh
    - /action/main.sh
    - "{{ .firstoption }}"
    - "{{ .secondoption }}"

• Meaning that their default/empty value is passed to command executed in container even if options are not passed

Expected

• Would be great that no option vlaue is passed to command executed in container when no option is used

➜  launchr git:(main) pl example:arguments
Image "envvars:latest" exists locally

Total number of arguments passed to the script: 0

[lexbritvin]

Considering the latest changes in Arguments and Options, it is now possible to not define "default" for both.

    - name: firstoption
      title: First option
      type: string
    - name: secondoption
      title: Second option
      description: Option to do something
      type: boolean
      default: false

There is no default value for firstoption and it's not required and variable in the template may be string|nil.
There is a default value for secondoption, will be false if not defined. If remove default, possible values may be true|false|nil in templates.

That allows us to make extra validation in actions.

  command:
    - sh
    - /action/main.sh
    - "{{ .firstoption | removeLineIfNil }}"
    - "{{ if not (isNil .secondoption) }}--secondoption={{ .secondoption }}{{ else }}{{ removeLine }}{{ end }}"

New template functions here .Arg | removeLineIfNil - template piping. It will process the template and remove the line if the given value is Nil.
if not (isNil .secondoption) - template condition to only check the value. May be helpful to pass flags as --secondoption={{ .secondoption }}
{{ removeLine }} - removes current line. Useful in condition result like we have in {{ else }}

Please, tell me if you like the naming, and it's clear for you.

[lexbritvin]

@davidferlay please retest after the fix

[davidferlay]

About naming :

• {{ .firstoption | removeLineIfNil }} naming and syntax is easy to understand ✅

• {{ if not (isNil .secondoption) }}--secondoption={{ .secondoption }}{{ else }}{{ removeLine }}{{ end }} is a bit less intuitive to read

  • maybe {{ if not (isNil .secondoption) }} could be replaced by something like {{ if .secondoption isNotNil }}
  • maybe {{ end }} could be renamed {{ endIf }}

Also, during tests I noticed that these conditions do not behave as user would expect when default values are defined in action.yaml:

• if a default option is defined, IfNil and isNil will always be true, regardless of values passed to command
• so maybe Nil should actualy be renamed to NotSet and behave like it
  • {{ .firstoption | removeLineIfNotSet }}
  • {{ if .secondoption isSet }}

[lexbritvin]

We are using standard go templates. The syntax is defined here https://pkg.go.dev/text/template

1. Notation {{ if .secondoption isNotNil }} is impossible in go, because function must go first. We may change the template engine, but I don't see a big need. I see only 1 possible alternative - pongo2, but it seems abandoned
2. Same for {{ endIf }}, it's not a valid go template.
3. |removeLineIfNotSet is impossible to implement, because we pass a value and can't have context (parameter name) inside the filter functions. It's like piping in linux, we don't know how the previous step works. It is applied to all template engines.
4. isSet is more feasible, but only using a parameter name string like {{ if isSet "param_name" }}. Because we pass a value and can't have a parameter name inside a function. We can pass the parameter name as a string to a function to check. More on that in the end of the message.

I think every action has it's own context and can decide how to treat each value and line.
In this particular case we can check explicitly for a default value (false) {{ if .secondoption }}. Same applies for empty string "", int 0, etc.
But a default value can be different, like "my_str", then the condition will be {{ if .secondoption == "my_str" }}.

Summary of what we can have:

1. {{ if isNil .param_name }} {{ removeLine }} {{ end }} - condition operator to check if value is not defined (nil)
2. {{ if isSet .param_name }} {{ removeLine }} {{ end }} is equivalent to {{ if not isNil .param_name }}... - condition operator to check if a value is defined (not nil)
3. {{ if isChanged "param_name" }} ... - to check if a parameter name is explicitly set by user. Use parameter name as a string. I propose isChanged because we use such notation in code if a flag is changed explicitly.
4. {{ removeLineIfNil .param_name }} or {{ .param_name | removeLineIfNil }} - syntax sugar for if isNil then removeLine
5. {{ removeLineIfSet .param_name }} or {{ .param_name | removeLineIfSet }} - syntax sugar for if isSet then removeLine
6. {{ removeLineIfChanged "param_name" }} - syntax sugar for if isChanged then removeLine
7. {{ removeLineIfNotChanged "param_name" }} - syntax sugar for if not isChanged then removeLine