Merge pull request #148 from SteveL-MSFT/expermental-feature-user-experience

Draft of experimental feature user experience RFC

Author: SteveL-MSFT

1-Draft/RFC0000-Experimental-Feature-User-Experience.md

@@ -0,0 +1,102 @@
+---
+RFC: RFC0000
+Author: Steve Lee
+Status: Draft
+SupercededBy: N/A
+Version: 1.0
+Area: Microsoft.PowerShell.Core
+Comments Due: 12/1/2018
+Plan to implement: Yes
+---
+
+# Experimental Feature User Experience
+
+[Experimental Feature Flags](https://github.com/PowerShell/PowerShell-RFC/blob/master/5-Final/RFC0029-Support-Experimental-Features.md)
+enable developers to expose experimental features to users to gather feedback before finalizing design.
+That feature was focused on the developer and did not make it easy for users to discover and enable experimental features.
+This RFC addresses the user experience.
+
+## Motivation
+
+    As a PowerShell user,
+    I can discover and enable experimental features,
+    so that I can try new capabilities safely and provide feedback.
+
+## Specification
+
+### Get-ExperimentalFeature *Breaking Change*
+
+Currently, `Get-ExperimentalFeature` requires the `-ListAvailable` switch to enumerate available experimental features.
+This was modeled after `Get-Module -ListAvailable`.
+Without the switch, `Get-ExperimentalFeature` only shows the enabled experimental features, which by default is none.
+Most users will try this cmdlet without the switch and assume there are no experimental features to try.
+
+Since there are likely not many experimental features available at any point in time and less enabled,
+it would make sense to remove the `-ListAvailable` switch and simply display all experimental features.
+The current output already has a column indicating if the experimental feature is enabled allowing for easy filtering.
+
+### System and User scope powershell.config.json
+
+Enabling experimental features automatically requires creating or updating a `powershell.config.json` file in `$PSHOME`
+which is read at startup which affects all users or from `$HOME\Documents\PowerShell\powershell.config.json` on Windows
+and from `$HOME/.config/powershell/powershell.config.json` on Linux and macOS per user.
+
+Experimental features are currently not being read from the user config and this RFC will enable reading
+of the user config in addition to the system config.
+In the case where the user config exists, it will take precedence over the system config for experimental features
+in that the system config is not read for experimental features.
+System config is not policy so this should be acceptable and expected.
+
+### Enable and Disable cmdlets
+
+```none
+Enable-ExperimentalFeature [[-Name] <string[]>] [-Scope { CurrentUser | AllUsers }] [<CommonParameters>]
+
+Disable-ExperimentalFeature [[-Name] <string[]>] [-Scope { CurrentUser | AllUsers }] [<CommonParameters>]
+```
+
+These cmdlets allow users to selectively enable and disable experimental features.
+
+The `-Name` parameter shall accept `ValueFromPipelineByPropertyName` and is the name of the experimental feature.
+
+The `-Scope` parameter is optional and defaults to `CurrentUser` and will create or update the
+`powershell.config.json` in `$HOME\Documents\PowerShell\powershell.config.json` on Windows
+and from `$HOME/.config/powershell/powershell.config.json` on Linux and macOS.
+If `-Scope` is `AllUsers`, it will create or update `$PSHOME\powershell.config.json`.
+
+Experimental features are read and enabled at PowerShell startup, so a warning message will be provided informing the user:
+> Experimental feature changes will only be applied after restarting PowerShell.
+
+Upon success, there is no output other than the warning message.
+
+## Alternate Proposals and Considerations
+
+### Enabled property
+
+Currently, an experimental feature has an `Enabled` property that is `true` or `false`.
+In addition to the warning message that a restart is required after changing experimental feature status,
+the `Enabled` property could be changed to an enum instead of a boolean: True, False, Pending.
+However, since experimental features is expected to be used by more advanced users,
+this seems unnecessary.
+
+Alternatively, we can add a `RestartRequired` property to indicate an enabled feature is pending.
+
+### Features that were previously Experimental
+
+In the case where an Experimental Feature no longer experimental (whether accepted or rejected),
+the config file may still have that feature listed.
+We can add a `State` property that has enum values: Available, NotAvailable.
+This `State` can also convey the `RestartRequired` state.
+If this becomes a problem in the future, we can have cmdlets to help clean-up non-valid settings in the
+configuration (which will be more than just experimental features).
+Since this is additive, this is currently outside the scope of this RFC.
+
+### PowerShell instance specific configuration
+
+The system (AllUsers) configuration is in `$PSHOME` and specific to that instance of PowerShell.
+The user config is global to all instances of PowerShell which can create problems.
+For experimental features, this is not a big issue as experimental features listed to
+be enabled in the config file that don't exist are silently ignored.
+However, other configuration that one may want to apply to a preview release and not a
+stable release cannot be applied except for AllUsers currently.
+This should be addressed in a separate configuration RFC.