Graceful error handling for offline scenarios in 'aspire new' and 'aspire add' commands

[Copilot]

Problem

When running the aspire new or aspire add commands without an internet connection, the CLI attempts to prompt the user to select from a list of available template versions or packages. Since no templates/packages are available offline, this results in an unhandled exception (System.InvalidOperationException: Cannot show an empty selection prompt).

Changes

This PR adds proper error handling for offline scenarios by:

1. Adding an EmptyChoicesException class to handle cases with no available choices
2. Modifying the InteractionService.PromptForSelectionAsync method to check if the choices collection is empty before attempting to prompt the user
3. Updating command classes to:
   • Check for empty package collections
   • Throw meaningful exceptions with clear error messages
   • Catch and handle these exceptions appropriately

User Experience

When offline or when no templates/packages are found, the user will now receive clear error messages like:

No template versions were found. Please check your internet connection or NuGet source configuration.

No integration packages were found. Please check your internet connection or NuGet source configuration.

Testing

Added tests for:

• Empty collection handling in InteractionService
• Error handling for empty template/package lists in NewCommand and AddCommand

Fixes #9457.

Warning

Firewall rules blocked me from connecting to one or more addresses

I tried to connect to the following addresses, but was blocked by firewall rules:

• dnceng.pkgs.visualstudio.com
  • Triggering command: /home/REDACTED/work/aspire/aspire/.dotnet/dotnet build src/Aspire.Cli/Aspire.Cli.csproj (dns block)
  • Triggering command: /home/REDACTED/work/aspire/aspire/.dotnet/dotnet test tests/Aspire.Cli.Tests/Aspire.Cli.Tests.csproj --filter FullyQualifiedName~InteractionServiceTests|FullyQualifiedName~AddCommand_EmptyPackageList|FullyQualifiedName~NewCommand_EmptyPackageList (dns block)
• pkgs.dev.azure.com
  • Triggering command: /home/REDACTED/work/aspire/aspire/.dotnet/dotnet build src/Aspire.Cli/Aspire.Cli.csproj (dns block)
  • Triggering command: /home/REDACTED/work/aspire/aspire/.dotnet/dotnet test tests/Aspire.Cli.Tests/Aspire.Cli.Tests.csproj --filter FullyQualifiedName~InteractionServiceTests|FullyQualifiedName~AddCommand_EmptyPackageList|FullyQualifiedName~NewCommand_EmptyPackageList (dns block)
  • Triggering command: /home/REDACTED/work/_temp/ghcca-node/node/bin/node /home/REDACTED/work/_temp/copilot-developer-action-main/dist/index.js (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to my firewall allow list

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[Copilot]

Pull Request Overview

Adds graceful handling of offline scenarios for aspire new and aspire add by throwing and catching a dedicated exception when no templates or packages are available.

• Introduces EmptyChoicesException and guards prompts against empty collections
• Updates InteractionService to throw on empty choices and enhances NewCommand/AddCommand with checks and catch blocks
• Adds unit tests covering empty-choice scenarios in the interaction layer and the two commands

Reviewed Changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
tests/Aspire.Cli.Tests/TestServices/TestInteractionService.cs	test stub that throws EmptyChoicesException for empty prompts
tests/Aspire.Cli.Tests/Interaction/InteractionServiceTests.cs	new test for PromptForSelectionAsync with no choices
tests/Aspire.Cli.Tests/Commands/NewCommandTests.cs	new test for empty-template error handling in NewCommand
tests/Aspire.Cli.Tests/Commands/AddCommandTests.cs	new test for empty-package error handling in AddCommand
src/Aspire.Cli/Interaction/InteractionService.cs	added empty-check and throw in PromptForSelectionAsync
src/Aspire.Cli/Interaction/EmptyChoicesException.cs	introduced EmptyChoicesException class
src/Aspire.Cli/Commands/NewCommand.cs	added empty-list guard and catch in NewCommand
src/Aspire.Cli/Commands/AddCommand.cs	added empty-list guard and catch in AddCommand

[mitchdenny]

I think this is good to go.