config example is raising a wasm error

[fliepeltje]

I'm getting the following output when running the configs example from the readme:

Error: wasm error: unreachable
wasm stack trace:
        .$10486(i32,i32,i32,i32,i32)
        .$10772(i32,i32)
        .$10792(i32,i32,i32,i32,i32)
        .$10827(i32,i32) i32
        .$10846() i32
returned non-zero exit code: 1

I figured out that it is because it should in fact be a get_str call:

import extism

@extism.plugin_fn
def greet():
  user = extism.Config.get_str("user")
  extism.output_str(f"Hello, {user}!")

But I find the output of this mistake quite scary; I'm unsure if it is somehow possible to throw up something a bit friendlier when you try to access a non-existent method or var?

[bhelx]

I figured out that it is because it should in fact be a get_str call:

do you have an example of the broken program? Maybe we are not handling an error condition properly. if you had a python syntax or type error, this should not have caused a panic. if it was something deeper in the code, it might cause a panic.

But I find the output of this mistake quite scary; I'm unsure if it is somehow possible to throw up something a bit friendlier when you try to access a non-existent method or var?

unreachable is kind of the equivalent of a segfault. Sometimes it can be tricky to get context to show the user. the numbers are because, i assume, the python implementation is compiled without debug info. Maybe we can compile it with the debug info? @zshipko should know.

[zshipko]

It's been tricky to make debug info work correctly with all the different layers but I'll look into that a bit more.

One trick I've been using to debug Python plugins is using the EXTISM_ENABLE_WASI_OUTPUT environment variable, which will print the original Python exception to stdout.

[fliepeltje]

do you have an example of the broken program

It is literally the docs example - I'll make a PR for it.

using the EXTISM_ENABLE_WASI_OUTPUT environment variable

This does indeed give more info, for now that is all I need :)

In the PR for this I will also incorporate this nugget of knowledge into the readme :)