[browser][MT] fix calling JS functions from workers

[pavelsavara]

@thaystg said that _mono_wasm_fire_debugger_agent_message_with_data was calling empty function instead of JS implementation.
It's caused by #79466

In the dotnet.js file we have the _mono_wasm_fire_debugger_agent_message_with_data which is replaced in replace_linker_placeholders by the correct one mono_wasm_fire_debugger_agent_message_with_data, which calls the debugger statement.

In a worker replace_linker_placeholders is never called so when we are calling mono_wasm_fire_debugger_agent_message_with_data from mini-wasm-debugger.c file, it's calling the empty version of the JS function and the debugger doesn't work.

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Issue Details

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@thaystg said that _mono_wasm_fire_debugger_agent_message_with_data was calling empty function instead of C implementation.
It's caused by #79466

Author:	pavelsavara
Assignees:	pavelsavara
Labels:	arch-wasm, area-System.Runtime.InteropServices.JavaScript
Milestone:	8.0.0

[lambdageek]

Should we revert #79466?

[pavelsavara]

Should we revert #79466?

We could revert those lines and it will make the dotnet.js slightly bigger again.

Maybe it's rather high time to have our own dotnet.worker.js and call it from there.

[pavelsavara]

I'm surprised it didn't break any MT tests ?

[lambdageek]

Maybe it's rather high time to have our own dotnet.worker.js and call it from there.

I don't think that's a good idea until we do the emscripten upgrade. And maybe not even then. We already have mechanisms to inject our own code into various parts of the worker startup.

For example, can we call replace_linker_placeholders in preInitWorkerAsync (or earlier in mono_wasm_pthread_worker_init)?

[pavelsavara]

it needs to be fed into new WebAssembly.Instance

[lambdageek]

it needs to be fed into new WebAssembly.Instance

I see.

Can we temporarily wrap the changes in dotnet.es6.lib.js in something like "if (threadsEnabled) { [OLD_CODE] } else { [NEW_CODE] }"? I'd like to restore functionality for Preview 1.