[resizetizer] fix a build performance issue

[jonathanpeppers]

I was testing a .NET MAUI project template in Visual Studio on a Windows DevBox, and I noticed a target taking a lot of time:

ResizetizeImages 1.302s
Skipping target "ResizetizeImages" because all output files are up-to-date with respect to the input files.

This is happening on incremental builds with no changes. This is even worse for Android, because it runs twice: one for build and one for deploy.

The ResizetizeImages MSBuild target is skipped, why is it slow?!?

To "debug" this, I added this ugly, one-liner between every <ItemGroup> in the target:

<ItemGroup>
  </ItemGroup><PropertyGroup><_Time>$([System.DateTime]::Now.ToString('THH:mm:ss.fffffffZ'))</_Time></PropertyGroup><ItemGroup>
  <_MauiImageToProcess Include="@(MauiImage)" Exclude="$(DefaultItemExcludes)" />
  </ItemGroup><PropertyGroup><_Time>$([System.DateTime]::Now.ToString('THH:mm:ss.fffffffZ'))</_Time></PropertyGroup><ItemGroup>
  <!-- more item groups -->
  </ItemGroup><PropertyGroup><_Time>$([System.DateTime]::Now.ToString('THH:mm:ss.fffffffZ'))</_Time></PropertyGroup><ItemGroup>
</ItemGroup>

(I found the /profileevaluation switch didn't help me here)

This led me to find the problematic line, is this one:

<_MauiImageToProcess Include="@(MauiImage)" Exclude="$(DefaultItemExcludes)" />

Where $(DefaultItemExcludes) is:

DefaultItemExcludes = ;bin\Debug\/**;obj\Debug\/**;bin\/**;obj\/**;**/*.user;**/*.*proj;**/*.sln;**/*.vssscc;**/.DS_Store

This was introduced in a92fd1d to fix .DS_Store files in the folder:

<MauiImage Include="Resources\Images\*" />

(This is in the .NET MAUI project template).

Here is additinoal timing information, if I try some powershell commands like:

> $files = ls -r -n .\obj\
> $files.Length
5356
> (Measure-Command { $files = ls -r -n .\obj\ }).TotalMilliseconds
715.7382

What is happening is:

• MSBuild expands these 9 wildcards to a lot of files

• MSBuild now has to filter out the files that are in @(MauiImage)

If I simply reduce this to:

<_MauiImageToProcess Include="@(MauiImage)" Exclude="**/.DS_Store" />

It still takes 177ms after this change, because MSBuild has to do a recursive file listing of the current project.

So, we can do better. We can use Condition instead:

<_MauiImageToProcess Include="@(MauiImage)" Condition=" '%(FileName)%(Extension)' != '.DS_Store' " />

After these changes, the target now takes:

ResizetizeImages 6ms

I can't think of what this would break, as I don't think any of these files are in Resources\Images:

DefaultItemExcludes = ;bin\Debug\/**;obj\Debug\/**;bin\/**;obj\/**;**/*.user;**/*.*proj;**/*.sln;**/*.vssscc;**/.DS_Store

The only problem I can think of would be if someone sets $(DefaultItemExcludes) to a custom value, and I think saving the build time is worth it.

[MartinLichtblau]

Damn it! Have been looking into this for far too long and just now I wanted to give up!
Really annoyed me, seeing Android Debug Run being stuck at "Skipping target ResizetizeImages", taking ~7sec of 14sec total build time.
Thank you for finding the culprit!
Hope this will be released soon! Cause, I can't see how to implement a workaround in our app.

[jonathanpeppers]

Hope this will be released soon! Cause, I can't see how to implement a workaround in our app.

@MartinLichtblau the only idea I have as a workaround might be to just clear $(DefaultItemExcludes) like:

<DefaultItemExcludes></DefaultItemExcludes>

But that might cause other issues.

[mattleibow]

How does the SDK do it all over the show and we can't do it this one time? How are they not running a build for 30s with all these usages of the property?

https://github.com/search?q=repo%3Adotnet%2Fsdk%20DefaultItemExcludes&type=code

[jonathanpeppers]

@mattleibow there could be a regression in MSBuild, but I think there is a big difference if it happens during evaluation or inside a target.

[jonathanpeppers]

This one timed out:

Controls (v17.2) TabbedPage,TableView,TimePicker,TitleView,ToolbarItem

But it says I can merge, so going for it. This change shouldn't affect UITests.