Enable tab completion for variables that are of enum type

Summary of the new feature/enhancement

When setting preference variables like $ErrorActionPreference, it would be great to help users discover allowed values by:

$ErrorActionPreference = <tab>

instead of trying to set it to something invalid and seeing the allowed values in the error message.

[SteveL-MSFT]

I think string is definitely more user friendly.

[mklement0]

Good question, @SeeminglyScience.

I’m thinking that even $ErrorActionPreference = <tab> (no opening quote) should complete to a string (e.g, $ErrorActionPreference = 'Stop'), for two reasons:

• Using types and static properties is an advanced technique, and strings are more concise and provide better symmetry with use in arguments (e.g., -ErrorAction Stop), where use of the static property expression would be impractical (e.g., -ErrorAction ([System.Management.Automation.ActionPreference]::Stop))

• With flag enumerations, a string value is easier to modify later (again with tab-completion support), especially when new flags are added (e.g., 'Compiled' -> 'Compiled, IgnoreCase' vs. [System.Text.RegularExpressions.RegexOptions]::Compiled -> [System.Text.RegularExpressions.RegexOptions]::Compiled -bor [System.Text.RegularExpressions.RegexOptions]::IgnoreCase)