[baronfel]

Summary

• reuse exact compatible tool versions from the global NuGet cache without contacting configured feeds
• probe feeds briefly for floating versions, then fall back to the best compatible cached version when feeds are unavailable
• preserve cache-bypass behavior for --no-cache and NO_CACHE

Testing

• built src\Cli\dotnet\dotnet.csproj
• passed 6 focused dnx and dotnet tool exec cache fallback tests

Fixes #50579

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[Copilot]

Pull request overview

This PR updates dotnet tool exec / dnx tool resolution to better support offline (or partially offline) scenarios by reusing already-downloaded tool packages from the global NuGet cache and only probing feeds briefly when a floating version is requested.

Changes:

• Add cache-first resolution logic for ToolExecuteCommand, including a short, configurable feed probe and honoring NO_CACHE.
• Add ToolPackageDownloader helpers to select the best matching cached tool and to resolve versions with cancellation support.
• Extend NuGetPackageDownloader to accept cancellation and treat HttpRequestException similarly to FatalProtocolException when IgnoreFailedSources is enabled.
• Add end-to-end regression tests covering cached fallback behavior and cache bypass.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 1 comment.

File	Description
test/Microsoft.DotNet.PackageInstall.Tests/EndToEndToolTests.cs	Adds end-to-end tests for cached tool fallback and cache-bypass behavior.
src/Cli/dotnet/ToolPackage/ToolPackageDownloader.cs	Adds cached-tool selection and cancellable version/source lookup.
src/Cli/dotnet/NugetPackageDownloader/NuGetPackageDownloader.cs	Adds cancellable version+source resolution and improved handling of HttpRequestException with IgnoreFailedSources.
src/Cli/dotnet/Commands/Tool/Execute/ToolExecuteCommand.cs	Implements cache-first tool execution logic with feed probing, timeout, and NO_CACHE support.

[baronfel]

@dsplaisted this PR allows dnx to work in offline scenarios, should be hopefully straightforward!

[lbussell]

A good follow-up might be to make async commands more first-class in the .NET CLI / in CommandBase. As far as I can tell, I don't think the synchronous version of ToolExecuteCommand.Execute() is called from anywhere.

[baronfel]

A good follow-up might be to make async commands more first-class in the .NET CLI / in CommandBase. As far as I can tell, I don't think the synchronous version of ToolExecuteCommand.Execute() is called from anywhere.

I do agree, but pre-LLMs didn't want to do all of the grunt work myself.