Repro: .NET 7 Preview 4 breaks HarmonyX

[danielcweber]

This PR shows that building and running on .NET SDK 7.0.100-preview.4.22252.9 breaks HarmonyX.
I found .NET 7 Preview 1 to work. I will, in subsequent commits, downgrade to preview 3, 2 and 1 to identify where the breaking change occured.

EDIT:
For Preview 1 and 2, there's 2 failing tests. Preview 1 works for us, but we're probably not using a broken feature.
For Preview 3 on, there's 56 failing tests.

EDIT:
Find the Github Actions runs here:

Preview 4
Preview 3
Preview 2
Preview 1

[ghorsington]

Greetings!

Thank you for your report! From a quick look, it seems like the CI runs tests meant for mono and older corefx runtimes only. Right now the code has some preprocessors for NET_6, for example here and some in HarmonyTests. All of them are directly taken from upstream pardeike/Harmony and haven't been altered if I recall correctly. From a quick look, I'd assume some tests might be fixed by simply adjusting the preprocessor to NET6_0_OR_GREATER or just NET.

[danielcweber]

Thanks for having a look into it. I'll try to identify the directives and give it a try.

[danielcweber]

It seems the line you references is the only one that mentions .NET6 but given the only core-target of the main library is netstandard, the NET6 directive doesn't do that much anyway. Also, thinking about it, it doesn't explain why there is a bigger break from preview 2 to preview 3.

Another finding: Some tests don't fail when you step into them in Visual Studio.

[ghorsington]

Searching for all preprocessors gives some problematic places

@ rg "#if"
HarmonyTests\Traverse\TestTraverse_Types.cs
58:#if !NET6_0 // writing to static fields after init not allowed in NET6

HarmonyTests\Tools\TestAccessTools.cs
59:#if NETCOREAPP
75:#if NETCOREAPP

HarmonyTests\TestTools.cs
6:#if NETCOREAPP
190:#if NETCOREAPP
197:#if NETCOREAPP
265:#if NET35

HarmonyTests\Patching\Transpiling.cs
16:#if DEBUG

HarmonyTests\Patching\Specials.cs
486:#if !NETCOREAPP3_0 || NETCOREAPP3_1 || NET5_0

HarmonyTests\Patching\Assets\PatchClasses.cs
572:#if NETCOREAPP2_0

HarmonyTests\IL\Instructions.cs
118:#if DEBUG
270:#if NETFRAMEWORK

Harmony\Tools\Shims.net.cs
1:#if NET35 || NET45

Harmony\Tools\AccessTools.cs
1684:#if NET35
1695:#if NET35
1781:#if NET35
1832:#if NET35
1846:#if NET35
1858:#if NET35
1882:#if NET35

HarmonyTests\Extras\PatchSerialization.cs
30:#if NET50_OR_GREATER

Harmony\Internal\PatchTools.cs
40:#if NETCOREAPP2_0 || NETCOREAPP3_0 || NETCOREAPP3_1 || NETSTANDARD2_0 || NET6_0

The ones targeting .NET Core or .NET 5 all seem to be fixed (and not for example NET5_0_OR_GREATER) which seems like one of the problems. There are a few of those for tests, e.g. one in TestTraverse_Types which seems to fail based on your CI.

I'll check a bit later locally if cleaning all those up helps.

[danielcweber]

Just wildly guessing here: If it's got something to do with tiered compilation, there was a reimplementation in .NET 7 Preview 3.

Complete changelog of preview 3.

[ghorsington]

On a closer look, it appears that all hooking fails without any errors. As such, this is most likely the issue with MonoMod, the library that HarmonyX uses for runtime patching.

I posted an issue about this in MonoMod/MonoMod#94. I think it's best the problem is further tracked there since there isn't a direct issue with HarmonyX (sans the few tests that break in Preview 2, those can be fixed by adjusting some preprocessor tags from the looks of it).

[danielcweber]

Thanks a lot @ghorsington!

[danielcweber]

Closing here, see MonoMod/MonoMod#94 for further tracking.