Executing node_binary clobbers current working directory

[driveraid]

Hi,
We're using a node binary to implement a small IDL compiler:

node_binary(
    name = "gen",
    srcs = [...]
    ...)

The binary gets used later in a genrule, something like this:

genrule(
    name = "gen_osl",
    srcs = ["example/file.idl"],
    tools = [":gen"],
    cmd = "$(location :gen) ...options... $(location example/file.idl)",
    ...)

However, we find that the generated runner for the gen target has the following content,

#!/usr/bin/env bash
set -e
ROOT=$(dirname $0)
export PATH="$ROOT:$PATH"
cd $ROOT/gen_bundle && exec node node_modules/platform/tools/reaktor/gen_module $@

1. Is there a special reason as to why to chdir into the gen_bundle directory? It destroys our ability to locate the source file.
2. Do you know of some other way I could work around?

[pcj]

Hi @driveraid. In the previous version of rules_node there was a longstanding issue of how to run a node binary in the context of various different execution scenarios (bazel run :foo, ./bazel-bin/foo, bazel test :foo_test) and so forth. Copying over the node binary to the bundle directory and exec`ing there was a way to avoid having to detect where runfiles directory was, etc. Very clever, or so I thought!

Unfortunately as I see now this does not work in a genfile context! It should be possible to redo the create_launcher function to accomodate this use case, hopefully in a non-hacky way.

https://github.com/pubref/rules_node/blob/master/node/internal/node_binary.bzl#L77-L93

As possible short-term workaround might be to adjust the location of the example/file.idl location based on the knowledge of where the script is cd'ing into. You can experiment by putting in ls -al . or find . into your genrule cmd to debug that.

[driveraid]

Thanks @pcj.
For a short term workaround, we realized that in this case we were able to modify the IDL compiler to accept a new --chdir option, enabling bridging of the WD like follows:

genrule(
    name = "gen_osl",
    srcs = ["example/file.idl"],
    tools = [":gen"],
    cmd = "export GEN_WD=$$(pwd) && $(location :gen) --chdir $$GEN_WD ...options... $(location example/file.idl)",
    ...)

It's a bit wierd, we suddenly had to disable sandboxing by issuing --genrule_strategy=standalone because the cd invocation from the runner stopped working (gen_bundle not present in sandbox)... but it's late... could be that too :)

It would be nice with a cleaner solution to this issue!

Thanks

[pcj]

In regard to the sandbox issue, if you write your genrule as an actual build rule, you could access the files property on the node_binary provider and propagate that to the ctx.action.inputs file list.

https://github.com/pubref/rules_node/blob/master/node/internal/node_binary.bzl#L142-L144

But yeah, I get that it deserves a clean solution.

[pcj]

I believe this should be fixed by #41. Please re-open if remains unresolved.

[markushandell]

I can confirm that the CWD issue is fixed with 0.4.1, thanks @pcj! Will now try to go for a sandbox-safe solution as advised.