QOL Improvements for Classes

[agowa]

Summary of the new feature / enhancement

I'd like to suggest a few small quality of live improvements to PowerShell Classes.

1. Allow chaining Constructors (instead of having to an additional hidden internal function)

class T {
  T() {$this.T("something")}
  T($something) {Do-Something}
}

2. Fix default value handling for methods and functions in classes (this syntax is currently valid, but the default values are just ignored, requiring to create extra function definition to specify the default values in a way that actually works):

class T {
  something($mandatory, $optional="", $optional2=$false) {}
}
[T]::new().something("mandatoryvalue") | Should -Work # ParentContainsErrorRecordException: Cannot find an overload for "something" and the argument count: "1".

3. Add support for parameter validation to avoid boilerplate validation code for simple things like ValidateSet or NotNullOrEmpty
4. Add support for typed properties that aren't FixedSize. This could be archived by adding a (virtual) generic for ArrayList to use it like [System.Collections.Arraylist[String]] instead of [String[]] to get a "Non IsFixedSize" version of it. The main annoyance currently is that .Add() doesn't work when the list IsFixedSize.
5. Add an Enum Type (or better a annotation or attribute) that serializes and deserializes as the value instead of it's index key to replace [ValidateSet('string1', 'string2','string3')][string]$variable with a proper type without requiring a bunch of custom serialization and deserialization code. So that ConvertTo-Json and ConvertFrom-Json continue to work, but that proper types can be used for the attribute instead of having to check for the string value within the script.
6. Document that having a constructor with a single parameter but without type class T{ T() {}; T($name) {}} breaks type casting if not implemented explicitely within that constructor. Currently the documentation only mentions the parameterless one, but not the one with a single parameter without a specified type (is this intentional or a bug?)

class T{
  [string]$a
  [string]$b = "some default"
  [string]$name

  T() {}
  T($name) {
    $this.name = $name
  }
}
[T]@{
  a="Test"
  b="Values"
  name="SomeName"
} # Should return an object of Type T with a, b, and name initialized to the specified values, but instead it'll pass the HashTable to the T($name) constructor, which is currently not documented in the constructor section of about_Classes

8. Not technically classes related, but as classes drop everything that is not explicitly returned, having a modifier for normal functions (outside of classes) to act the same would be great to get rid of $null = and | Out-Null in almost every line of such a function... [DefaultOut(Out-Null)] function Do-Something() { Do-Something -WithOutput; return "Only thing that is returned"}

Proposed technical implementation details (optional)

No response

[ThomasNieto]

Related #6418

[mklement0]

Also:

• Fix Various PowerShell Class Issues #6652