UseNativeHttpHandler=true is not trimming correctly on mobile apps

[eerhardt]

In a default Maui Android app, I see the following assemblies present in my Release .apk:

The first thing that caught my eye was that System.Net.Quic.dll is there. But on Mobile apps, we are using UseNativeHttpHandler=true, see this Android SDK setting.

Since we are using the native HTTP handler, there should be no reason we are bringing .NET sockets handler (and with it HTTP 2 & 3 support).

The reason this code isn't getting trimmed is because we only have a Linker substitution for when false is specified.

runtime/src/libraries/System.Net.Http/src/ILLink/ILLink.Substitutions.mobile.xml

Lines 1 to 7 in c0d481f

	<linker>
	<assembly fullname="System.Net.Http">
	<type fullname="System.Net.Http.HttpClientHandler">
	<method signature="System.Boolean get_IsNativeHandlerEnabled()" body="stub" value="false" feature="System.Net.Http.UseNativeHttpHandler" featurevalue="false" />
	</type>
	</assembly>
	</linker>

We should add a substitution entry for true as well. This way a bunch of System.Net.* IL can be trimmed from mobile apps by default.

cc @steveisok @jonathanpeppers

Tagging subscribers to 'size-reduction': @eerhardt, @SamMonoRT, @marek-safar
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Issue Details

---

In a default Maui Android app, I see the following assemblies present in my Release .apk:

The first thing that caught my eye was that System.Net.Quic.dll is there. But on Mobile apps, we are using UseNativeHttpHandler=true, see this Android SDK setting.

Since we are using the native HTTP handler, there should be no reason we are bringing .NET sockets handler (and with it HTTP 2 & 3 support).

The reason this code isn't getting trimmed is because we only have a Linker substitution for when false is specified.

runtime/src/libraries/System.Net.Http/src/ILLink/ILLink.Substitutions.mobile.xml

Lines 1 to 7 in c0d481f

	<linker>
	<assembly fullname="System.Net.Http">
	<type fullname="System.Net.Http.HttpClientHandler">
	<method signature="System.Boolean get_IsNativeHandlerEnabled()" body="stub" value="false" feature="System.Net.Http.UseNativeHttpHandler" featurevalue="false" />
	</type>
	</assembly>
	</linker>

We should add a substitution entry for true as well. This way a bunch of System.Net.* IL can be trimmed from mobile apps by default.

cc @steveisok @jonathanpeppers

Author:	eerhardt
Assignees:	-
Labels:	area-System.Net.Http, size-reduction
Milestone:	-

[jonathanpeppers]

Somehow these get trimmed away in this case:

> dotnet new android
# release build and turn off our assembly packing
> dotnet build -c Release -p:AndroidUseAssemblyStore=false
# list the .dll files
> 7z l .\bin\Release\net6.0-android\*.apk | Select-String .dll
1981-01-01 01:01:02 .....        54897        54897  assemblies\Java.Interop.dll
1981-01-01 01:01:02 .....        70259        70259  assemblies\Mono.Android.dll
1981-01-01 01:01:02 .....        10151        10151  assemblies\System.Linq.dll
1981-01-01 01:01:02 .....         2377         2377  assemblies\System.Runtime.dll
1981-01-01 01:01:02 .....       507185       507185  assemblies\arm64-v8a\System.Private.CoreLib.dll
1981-01-01 01:01:02 .....       501601       501601  assemblies\armeabi-v7a\System.Private.CoreLib.dll
1981-01-01 01:01:02 .....         2958         2958  assemblies\foo.dll
1981-01-01 01:01:02 .....       501707       501707  assemblies\x86\System.Private.CoreLib.dll
1981-01-01 01:01:02 .....       511914       511914  assemblies\x86_64\System.Private.CoreLib.dll

So I wonder why these are showing up for MAUI projects? Maybe I should use HttpClient and see what happens.

[jonathanpeppers]

Ok, I added:

var foo = await new System.Net.Http.HttpClient().GetStringAsync ("https://google.com");

And now I get:

1981-01-01 01:01:02 .....        60054        60054  assemblies\Java.Interop.dll
1981-01-01 01:01:02 .....         3677         3677  assemblies\Microsoft.Win32.Primitives.dll
1981-01-01 01:01:02 .....       132888       132888  assemblies\Mono.Android.dll
1981-01-01 01:01:02 .....         6851         6851  assemblies\System.Collections.NonGeneric.dll
1981-01-01 01:01:02 .....         3034         3034  assemblies\System.Diagnostics.DiagnosticSource.dll
1981-01-01 01:01:02 .....        26850        26850  assemblies\System.Formats.Asn1.dll
1981-01-01 01:01:02 .....        11334        11334  assemblies\System.IO.Compression.Brotli.dll
1981-01-01 01:01:02 .....        18508        18508  assemblies\System.IO.Compression.dll
1981-01-01 01:01:02 .....        10369        10369  assemblies\System.Linq.dll
1981-01-01 01:01:02 .....       221610       221610  assemblies\System.Net.Http.dll
1981-01-01 01:01:02 .....        13159        13159  assemblies\System.Net.NameResolution.dll
1981-01-01 01:01:02 .....        17540        17540  assemblies\System.Net.NetworkInformation.dll
1981-01-01 01:01:02 .....        40562        40562  assemblies\System.Net.Primitives.dll
1981-01-01 01:01:02 .....        47907        47907  assemblies\System.Net.Quic.dll
1981-01-01 01:01:02 .....         3627         3627  assemblies\System.Net.Requests.dll
1981-01-01 01:01:02 .....        57785        57785  assemblies\System.Net.Security.dll
1981-01-01 01:01:02 .....        54520        54520  assemblies\System.Net.Sockets.dll
1981-01-01 01:01:02 .....         1285         1285  assemblies\System.Runtime.CompilerServices.Unsafe.dll
1981-01-01 01:01:02 .....         2912         2912  assemblies\System.Runtime.InteropServices.RuntimeInformation.dll
1981-01-01 01:01:02 .....        21292        21292  assemblies\System.Runtime.Numerics.dll
1981-01-01 01:01:02 .....         2519         2519  assemblies\System.Runtime.dll
1981-01-01 01:01:02 .....        42018        42018  assemblies\System.Security.Cryptography.Algorithms.dll
1981-01-01 01:01:02 .....        13373        13373  assemblies\System.Security.Cryptography.Encoding.dll
1981-01-01 01:01:02 .....         8577         8577  assemblies\System.Security.Cryptography.Primitives.dll
1981-01-01 01:01:02 .....        76491        76491  assemblies\System.Security.Cryptography.X509Certificates.dll
1981-01-01 01:01:02 .....        16762        16762  assemblies\System.Threading.Channels.dll
1981-01-01 01:01:02 .....         9733         9733  assemblies\arm64-v8a\System.Collections.Concurrent.dll
1981-01-01 01:01:02 .....         7284         7284  assemblies\arm64-v8a\System.Collections.dll
1981-01-01 01:01:02 .....       609354       609354  assemblies\arm64-v8a\System.Private.CoreLib.dll
1981-01-01 01:01:02 .....        38431        38431  assemblies\arm64-v8a\System.Private.Uri.dll
1981-01-01 01:01:02 .....         9683         9683  assemblies\armeabi-v7a\System.Collections.Concurrent.dll
1981-01-01 01:01:02 .....         6924         6924  assemblies\armeabi-v7a\System.Collections.dll
1981-01-01 01:01:02 .....       604114       604114  assemblies\armeabi-v7a\System.Private.CoreLib.dll
1981-01-01 01:01:02 .....        38816        38816  assemblies\armeabi-v7a\System.Private.Uri.dll
1981-01-01 01:01:02 .....         3967         3967  assemblies\foo.dll
1981-01-01 01:01:02 .....         9683         9683  assemblies\x86\System.Collections.Concurrent.dll
1981-01-01 01:01:02 .....         6924         6924  assemblies\x86\System.Collections.dll
1981-01-01 01:01:02 .....       604218       604218  assemblies\x86\System.Private.CoreLib.dll
1981-01-01 01:01:02 .....        38817        38817  assemblies\x86\System.Private.Uri.dll
1981-01-01 01:01:02 .....         9733         9733  assemblies\x86_64\System.Collections.Concurrent.dll
1981-01-01 01:01:02 .....         7542         7542  assemblies\x86_64\System.Collections.dll
1981-01-01 01:01:02 .....       614678       614678  assemblies\x86_64\System.Private.CoreLib.dll
1981-01-01 01:01:02 .....        38432        38432  assemblies\x86_64\System.Private.Uri.dll

The MAUI template would use HttpClient because it isn't fully trimmed, and there is support for images from the web like <Image Source="https://someurl" />.

[eerhardt]

Yep - HttpClient stays in a Maui app because of these 2 places:

[eerhardt]

I just tested a prototype fix for this. On a dotnet new maui app with build options:

dotnet build -c Release -t:Run -f net6.0-android -r android-x64 -p:RunAOTCompilation=true -p:AndroidEnableProfiledAot=true

Fixing this takes the profiled AOT .apk from

Before: 14.1 MB (14,787,482 bytes)
After: 13.3 MB (14,040,836 bytes)

Note: Profiled AOT is enabled by default in the latest Xamarin-Android SDK, so I'm just simulating the latest default Release build here. See dotnet/android#6547