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Document how to run code under WASI #100956
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fwiw, I have a devcontainer here: https://github.com/dev-wasm/dev-wasm-python that makes it easy to do this in GitHub codespaces or VS Code.
I would be happy to expand that documentation via PR if there is an interest.
I'm happy to take a PR! I'm honestly not looking at anything fancy, just something simple like, "To run code under wasmtime, you probably want to run the command
wasmtime run --dir . --." Maybe something similar for iwasm, but that's just a bonus.The only thing that may need checking is whether any specific directory mapping is necessary for e.g.
/tmpin case some code somewhere in pytest or something is making some bad assumption about that directory always existing.Ok, I will send a PR.
Reacted by Brett CannonMostly for me to not forget,
wasmtime run --mapdir .::Python-3.11.0-wasm32-wasi-16 Python-3.11.0-wasm32-wasi-16/python.wasmgets the REPL up and running, as doeswasmtime run --dir . python.wasmwhen in the same directory aslib/(at least when grabbed from https://github.com/tiran/cpython-wasm-test/releases).Here's the script I use (and which I put in the docs)
#!/bin/bash if [ $# -eq 0 ]; then FILE="" HOST_DIR=$PWD GUEST_DIR=$PWD elif [[ "$1" = /* ]]; then REAL_PATH=$(realpath $1) HOST_DIR=$(dirname $REAL_PATH) GUEST_DIR=$HOST_DIR FILE=${REAL_PATH} else HOST_DIR=$PWD GUEST_DIR=$PWD FILE="/$PWD/${@#}" fi PYTHON_WASI_ROOT=/Python-3.11.0-wasm32-wasi-16 wasmtime run --dir ${PYTHON_WASI_ROOT} \ --mapdir /::${PYTHON_WASI_ROOT} \ --dir ${HOST_DIR} \ --mapdir ${GUEST_DIR}::${HOST_DIR} \ -- ${PYTHON_WASI_ROOT}/python.wasm $FILE
Note that the one weirdness is that the working directory is the working directory of
python.wasmnot the directory of the script. That's a little unfortunate, but doesn't seem to be settable in wasmtime right now. I would wish for a flag that I could use inwasmtimeto set the working directory, but I can't seem to find one.Note that the one weirdness is that the working directory is the working directory of
python.wasmnot the directory of the script. That's a little unfortunate, but doesn't seem to be settable in wasmtime right now. I would wish for a flag that I could use inwasmtimeto set the working directory, but I can't seem to find one.Yeah, it's a bit annoying. We can actually compile in the bytecode for the
.pyfiles in the stdlib into the binary (it's called freezing), but it does make the tracebacks less useful since the actual source code won't be shown (the line numbers and file paths are still there, though). I think we have a mechanism right now that lets us manually specify the paths back to the source for frozen code; @ericsnowcurrently , is that right?I think we have a mechanism right now that lets us manually specify the paths back to the source for frozen code; @ericsnowcurrently , is that right?
There is no manual step. Currently when freezing the stdlib, the tools record the relative path for each frozen stdlib module as part of the frozen data. During import we then make that path absolute (using
sys._stdlib_dir) and use the result for__file__. I'm not sure how that works with WASM though.Reacted by Brett Cannon
https://github.com/python/cpython/tree/main/Tools/wasm doesn't cover how to take a WASI build and actually use it. We can probably just snag the instructions from https://github.com/tiran/cpython-wasm-test for wasmtime, maybe something for https://github.com/bytecodealliance/wasm-micro-runtime . Key thing is to probably show how to run something like pytest with a WASI build.
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