feat(rust_common): allow compile actions to declare more outdirs

[alexeagle]

This technique is sometimes needed when a proc_macro derives information from the build, and it needs to be consumed by some other tool.

For example this one generates a JSON file as an intermediate output
https://github.com/napi-rs/napi-rs/blob/main/crates/macro/src/expand/typedef/type_def.rs#L11-L12
and then expects developers to call this via a Node.js binary which wraps rustc and also transforms that file to a TypeScript type definition file.

Under Bazel, this is better modeled as a rust_shared_library that produces the binding file (.so or .dylib for example) along with that JSON output, then run the Node.js binary as a separate target.

[alexeagle]

@UebelAndre ping!

[illicitonion]

This generally looks reasonable - could you add a small test showing this working? Thanks!

[alexeagle]

@illicitonion done, thanks PTAL

[alexeagle]

Test failures do not look related to my change, FWICT

[illicitonion]

Generally looks good, thanks! A couple of small things :)

[alexeagle]

PTAL

[illicitonion]

LGTM! Thanks!

[illicitonion]

Ok we're down to a real test failure!

[alexeagle]

@illicitonion I'm trying to fix, but I don't know either Rust or Windows and don't have local repro. I believe the bug is in the test, not the three-line prod change, can I just tag the test to skip on windows?

[alexeagle]

@illicitonion ping! would like to merge before I give up on contributing...

[illicitonion]

Sorry for the delay here - it looks like even with the test skipping, CI was flaking, but hopefully looks good now!

[alexeagle]

Here's the real-world macro where I use this feature, as an example:

load("@rules_rust//rust:defs.bzl", "rust_shared_library")
load("@bazel_skylib//rules:select_file.bzl", "select_file")
load("@aspect_rules_js//js:defs.bzl", "js_run_binary")

TMP_FOLDER_NAME = "napi_type_def_tmp"

def napi_rust_shared_library(name, deps, **kwargs):
  """Create a NAPI-RS Rust shared library and generate the NAPI type definitions and typegen binary.

  Args:
    name: The name of the target.
    deps: The dependencies for the Rust library. The nodejs headers are added automatically.
    **kwargs: Additional arguments for the rust_shared_library rule.
  """
  lib_target = "_{}_rust_shared_library".format(name)
  bindings_target = "_{}_napi_type_defs".format(name)
  types_target = "_{}_typegen".format(name)
  rust_shared_library(
      name = lib_target,
      extra_outdirs = [TMP_FOLDER_NAME],
      rustc_env = {
          "NAPI_TYPE_DEF_TMP_FOLDER": "$(BINDIR)/{}/{}".format(native.package_name(), TMP_FOLDER_NAME),
      },
      rustc_flags = select({
          "@platforms//os:macos": [
              "--codegen=link-arg=-undefined",
              "--codegen=link-arg=dynamic_lookup",
          ],
          "//conditions:default": [],
      }),
      deps = deps + [
          "@rules_nodejs//nodejs/headers:current_node_cc_headers",
      ],
      **kwargs,
  )

  select_file(
      name = bindings_target,
      srcs = lib_target,
      subpath = TMP_FOLDER_NAME,
      visibility = ["//visibility:public"],
  )

  js_run_binary(
      name = types_target,
      srcs = [bindings_target],
      tool = Label("//tools/napi-rs:typegen_bin"),
      args = [
          "$(rootpath {})".format(bindings_target),
          "$(rootpath index.d.ts)",
      ],
      tags = [
          # TODO(alexeagle): continue the struggle against it finding no bindings in the sandbox
          "local",
      ],
      outs = ["index.d.ts"],
  )

  # Final production is a pair of .so/.dylib rust binding and .d.ts type definitions.
  native.filegroup(
    name = name,
    srcs = [
        lib_target,
        types_target,
    ],
  )

[alexeagle]

I now have to rebase this patch at customer sites to get @blorente fixes, can we merge it please.

[alexeagle]

Ping, it has been another month. Do I need to fork?

[alexeagle]

@UebelAndre is this being held back for some reason? Daniel is good with it, so can he merge?