"Failed to read accessWidener" in 0.10

I just started to conver some mods to 21w40a. Everything appears to compile fine, but when I start the client (using gradlew runClient or starting it from IntelliJ) I get the following error:

Exception in thread “main” java.lang.RuntimeException: Failed to read accessWidener file from mod fabric-screen-handler-api-v1 at net.fabricmc.loader.impl.FabricLoaderImpl.loadAccessWideners(FabricLoaderImpl.java:443) at net.fabricmc.loader.impl.launch.knot.Knot.init(Knot.java:122) at net.fabricmc.loader.impl.launch.knot.Knot.launch(Knot.java:68) at net.fabricmc.loader.launch.knot.KnotClient.main(KnotClient.java:28) at net.fabricmc.devlaunchinjector.Main.main(Main.java:86) Caused by: net.fabricmc.accesswidener.AccessWidenerFormatException: line 1: Namespace (intermediary) does not match current runtime namespace (named) at net.fabricmc.accesswidener.AccessWidenerReader.error(AccessWidenerReader.java:281) at net.fabricmc.accesswidener.AccessWidenerReader.read(AccessWidenerReader.java:90) at net.fabricmc.loader.impl.FabricLoaderImpl.loadAccessWideners(FabricLoaderImpl.java:441)

The Mod I am working on does not use any accessWideners. I alsow cleared my entire build environment to make sure that it is not related to cached data or any game-config. Is this a Bug or something I am missing?

[Juuxel]

Using the local project does work when using Loom 0.9 or earlier.

This is the key here. (Warning: heavy Gradle-ese ahead.) 0.10 made the default outgoing configurations (or “variants”), meaning apiElements and runtimeElements, export the remapped mods so that publishing would work as expected. This has the side effect of forwarding intermediary dep jars, which is causing your crash.

This means that you either need to use a custom outgoing configuration with dev/unmapped jars and depend on that, or modSomething project('theproject') (this one is a bit cursed with the useless remapping).

[quiqueck]

Sorry for the delay and thanks for the sample (which appears to work as it is supposed to). And thanks again for the really fast and in depth help!