Python support

[bstrie]

Python programs need to be well-supported on Enarx. cc #1646

[rjzak]

This may help: https://github.com/kateinoigakukun/wasi-vfs. Specifically if compiling Python (or something else) with the resulting ./target/wasm32-unknown-unknown/debug/libwasi_vfs.a, then using the wasi-vfs tool.

[rjzak]

There's an issue with Python where it needs to get it's current working directory:

enarx run python.wasm 
Exception ignored error evaluating path:
Traceback (most recent call last):
  File "<frozen getpath>", line 353, in <module>
OSError: [Errno 76] Capabilities insufficient
Fatal Python error: error evaluating path
Python runtime state: core initialized

Related: WebAssembly/wasi-filesystem#24

[bstrie]

After reaching out to some of the people involved in improving Python on WASM, they pointed me to two high-priority issues:

1. In wasmtime CLI, passing --tcplisten argument breaks --dir bytecodealliance/wasmtime#3936
2. wasmtime run -g fails with 'assertion failed: (left < right) bytecodealliance/wasmtime#4669

The first already has a patch from harald, but the maintainers need convincing that it's the proper fix. The second issue needs some investigation, which I'll be working on next.

[rjzak]

LPython is an LLVM-based Python compiler and it supports WebAssembly as a target. Unfortunately, it only supports WebAssembly for the browser at the moment.

[nickvidal]

Observations from @rjzak:

Nick Vidal, Oct 12, 4:32 PM
Were you able to get it working with Enarx?

Richard Zak, Oct 12, 4:32 PM
Doesn't work with Enarx because Python tries to open its current working directory and is unable to do so due to lacking filesystem support

Nick Vidal, Oct 12, 4:33 PM
Yes, I had trouble with that as well
But the packed wasm creates a VFS that is loaded in memory, right?

Richard Zak, Oct 12, 4:34 PM
Yes, but only for the library directory, not the directory the user is in

Nick Vidal, Oct 12, 4:34 PM
Ah, I see
Thanks for the clarification

Richard Zak, Oct 12, 4:35 PM
Nathaniel says the finished VFS support in Enarx will resolve this issue