Apply Registry Entries Last During Update Flow

[Trenly]

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• This pull request is related to an issue.
  • Resolves Registry keys updated before portable installation was successful #5190

This PR makes it so that the registry entries for a portable application are only applied if the DesiredState was applied successfully

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Microsoft Reviewers: Open in CodeFlow

[florelis]

/azp run

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[JohnMcPMS]

The code was this way intentionally, although I would agree that it probably didn't properly consider the update case.

On fresh install, the goal was to write to the registry first to create a handle for user action in the event of catastrophic failure. To say that plainly, if we crashed in the middle of the installation, the ARP registry entry would provide some means to uninstall the package.

On upgrade, I agree that this is flawed. Overwriting the state before completing the state change is an issue.

To achieve both of these goals, I think the answer is splitting the ARP registry writes into two portions:

1. Ensure that a base registry key and values exist to enable at least uninstall. On upgrades I would expect that this is a no-op.
2. Write the completed state (such as version, maybe only version?) into the existing key. In all cases this should create a situation where an upgrade remains available after an upgrade failure.

[Trenly]

Makes sense; I'll look to see if theres an easy way to do that