RegisterWithDotnetSuggest does not work if `dotnet-suggest` is installed later

[dorssel]

RegisterWithDotnetSuggest() uses a sentinel file and effectively only (tries to) register once. A good thing in itself, but if the user installs dotnet-suggest after the System.CommandLine application, then the registration fails (of course) and is never attempted again.

This requires the user to either run dotnet-suggest register explicitly, or remove the (obscure, undocumented) sentinel file.

This is not an uncommon scenario:

• software states "supports command completion"
• user installs software and finds out command completion does not work
• user seeks help and finds out dotnet-suggest + shim need to be installed
• user install dotnet-suggest + shim as instructed
• command completion still does not work, as the software never attempts to register again

The IntelliSense for the developer (me in this case) isn't very helpful either, as RegisterWithDotnetSuggest() says: "ensures that ...", while nothing is really ensured.

[BobSilent]

To add some scenarios here, as I just analyzed some strange behaviour:

If the user moved the executable, after it was registered, the completition is no longer possible e.g. download a zip file with a command, first extract it to some temp location, execute it, test it, later on move it to another location.

also i observed, that after registering for dotnet-suggest, i needed to open a new powershell in order to get the completition.

To be complete (for my own lookup later)

%USERPROFILE%\.dotnet-suggest-registration.txt

executable full path which is registered.

%TEMP%\system-commandline-sentinel-files

sentinel files location, once a file is located here, no new registration is possible.

For Cleanup:

delete .dotnet-suggest-registration.txt 
clear directory content system-commandline-sentinel-files

1. open a new shell
2. call exe with e.g. -?
3. open new shell => tab completition works

[KyleKolander]

Damn! Thank you @BobSilent !!! I was just banging my head against a wall wondering WTF?!? I followed your steps and my app now has completion support. This is a pretty bad bug... hopefully it gets prioritized.

[KalleOlaviNiemitalo]

A similar scenario: I build a command-line application and run it from the bin/Debug directory. It registers itself with dotnet suggest, and tab completion works in PowerShell. Then I build the Release configuration of the same version and run it from the bin/Release directory. It does not register itself because the assembly name matches the sentinel file that was created for the debug binary. Tab completion does not work.