core.getInput does not tell the caller if the returned value is defined in the yaml or not

[lukka]

Describe the enhancement
core.getInput() should allow the caller to understand whether the value is explicitly set in the yaml file, or whether it is not.
Right now you get an empty string, either when it is not defined, either when the user defined it as an empty string.

Code Snippet

this would allow this code:

const inputValue = core.getInput(inputName) ?? defaultValue;

Right now you have to use this instead:

const inputValue = core.getInput(inputName) || defaultValue;

which is not the same.

Use case
e.g. An action's input is a string which is a list of flags, if the default is "-v" and the user wants to have no flags at all (e.g. flags: ""), having this explicitly stated as input (e.g. flags: "") would be always (uncorrectly) replaced by the default (when using ||). To overcome this the user is forced to define a in the yaml the input as blank space instead (e.g. flags: " ")

[joshmgross]

Action inputs support defining a default value in the action.yml file: https://help.github.com/en/actions/automating-your-workflow-with-github-actions/metadata-syntax-for-github-actions#inputsinput_iddefault

core.getInput will handle using that value instead.

Is there a use case where defining the default in code after getInput is preferred?

[lukka]

Yes, if the default value is established at runtime (i.e. it cannot be specified in the action.yml).

[TheMrMilchmann]

To add to this, I'm currently running into an issue where an input parameter requires (basically) a relative path whose default is platform-dependent and thus, configured at runtime. In this case, since the empty string is a valid value, the behavior for explicit input (use the empty string) and no input (calculate platform-dependent default) should be different.

In the meantime, I ended up working around it by introducing another input parameter which serves as a boolean toggle for the abovementioned. (However, I don't think this is desirable.)

[mxcl]

I want to know if the user specified a YAML null, (ie. null or ~) where 'null' (the string) could be another possible input. I guess this is not possible.