Stop using anonymous functions in ResolverUtility.FindLibraryByVersionAsync to reduce memory allocations

[kartheekp-ms]

Bug

Fixes: NuGet/Home#11409

Regression? Last working version:

Description

I added a few details about the memory allocations in the linked issue. After reading Use local function instead of lambda (IDE0039) doc and https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/local-functions#heap-allocations, I modified the code path to use local function instead of lambda expressions. The reason I chose static local function is because of If you know that your local function won't be converted to a delegate and none of the variables captured by it are captured by other lambdas or local functions that are converted to delegates, you can guarantee that your local function avoids being allocated on the heap by declaring it as a static local function. Note that this feature is available in C# 8.0 and newer. in the doc.

This method has ~880 MB allocations during solution restore for OrchardCore solution https://github.com/OrchardCMS/OrchardCore/tree/75923732c36d2785cb869affb805f0ff19d1847c

After code modifications the heap allocations of ResolverUtility.FindLibraryByVersionAsync method have reduced by ~200 MB. for the same solution.

PR Checklist

• PR has a meaningful title

• PR has a linked issue.

• Described changes

• Tests

  • N/A No functional change to the product.

• Documentation

  • N/A

[zivkan]

Firstly, I think "Stop using anonymous functions in ResolverUtility.FindLibraryByVersionAsync" would be a better PR title (and easier to understand when looking at the commit history after this is merged), since 200MB depends on the solution and the current title doesn't say much about how it was fixed. I think pull requests should be about the technicalities of what changed, while linked issues should be the customer friendly explanation/high level of what changed.

Secondly, on the topic of customer friendly titles, the linked issue is currently a private issue in Client.Engineering, and therefore won't appear in release notes. Shouldn't perf improvements like this be listed in the release notes, and therefore the linked issue should be in Home?