Bazel windows support

[zaucy]

closes #814

• Updated scripts/update_bazel_workspace.sh to calculate sha from .zip archive for windows
• Adds .bat file equivalent scripts for use on windows
• Removes use of cp and file commands in favour of python modules
  • Introduces filetype dependency for wasm_binary.py instead of relying on file

[sbc100]

Nice one!

Mostly makes sense to me. The pip install thing seems a little heavy weight, but if its just one once on first use I guess its fine.

Will leave the final lgtm to @walkingeyerobot

[walkingeyerobot]

Haven't had a chance to dig into this fully yet, but looks good so far! I'll submit a full review later this week.

[walkingeyerobot]

Overall I'm happy with this. I'd like to eliminate the filetype dep, not because I think adding such a dep is bad, but because we shouldn't actually need to check the mimetype of the file. I'll try to get a PR that eliminates the need to check the mimetype entirely in the next day or two, which will eliminate the need for the dep.

For a bit more context, a long time ago this was purely an asmjs toolchain. As such, it would only output a single file, which was a js file. When wasm support was added, suddenly we needed to output the .wasm and the .js files, but cc_binary wouldn't support that, so we decided to roll them into a tar, leaving in place the logic that if only a single file had been outputted we would simply copy it. Looking back, it would have been simpler and better to just always tar the result.

[walkingeyerobot]

Ok, I made #936 to remove the need to add the filetype dep. Once that's merged you can integrate it with this PR.

I think link_wrapper.py also needs to be updated in this PR to be cross-platform. link_wrapper.py is always run as part of the toolchain and is what creates the tarball in the first place. wasm_binary.py is only run when using the wasm_cc_binary rule. After that's done and we resolve @trybka 's concerns this will be good to go.

[walkingeyerobot]

oh, and we need a test-bazel-windows on circleci

[walkingeyerobot]

Sorry for the delay, but you should be able to get away without the python dep now that #936 is merged

[zaucy]

@walkingeyerobot I've rebased against the latest main branch and added a (untested) circle CI job for windows with bazel.

I didn't change link_wrapper.py to use the tarfile module only because I didn't have any trouble with it on my local windows machine, but I can make that change.

[walkingeyerobot]

This is almost certainly stuck on circleci. @zaucy I think you have to log in to circleci (no paid account required or anything) and then rebase, and that should be enough of a kick to actually run the tests.

[walkingeyerobot]

Looks like the windows test can't find python. maybe it's pointing to the wrong path somewhere?

[zaucy]

I couldn't seem to find if there was a python3.exe somewhere in the windows vm. I was planning on looking again this weekend sometime.

[zaucy]

@walkingeyerobot The bazel CI is passing now. I used py -3 instead of python3 which should be available for most windows python users. I also removed a hardcoded python3 subprocess call and used sys.executable instead.

Hope those changes are acceptable :)

[walkingeyerobot]

Thanks very much for this, and I appreciate your patience with the lengthy review!