[Bug]: js_run_binary is not configured for the execution platform when the use_execroot_entrypoint = True and the target platform != exec platform

[nickschaap]

What happened?

In rules_js v3 support was added for 3p packages which specify optional dependencies that are included based on platform. For example, esbuild specifies various optional dependencies which included pre-compiled binaries for a variety of supported platforms. js_run_binary uses run_binary from bazel_lib and specifically configures its tool label under the exec configuration. However, if you are using use_execroot_entrypoint = True (the default). Only target platform configured sources will be available. This causes issues when you are building a target that transitions to a target that does not match the host.

Ideally the default configuration for js_run_binary would support this use case.

Version

Development (host) and target OS/architectures:

Output of bazel --version:

Bazelisk version: 1.27.0
Aspect CLI version: 2026.7.4-75a8f73d
INFO: Invocation ID: 419c9392-c1cd-417b-8d0a-80a6f2e244e1
Build label: 7.7.1
Build target: @@//src/main/java/com/google/devtools/build/lib/bazel:BazelServer
Build time: Wed Nov 12 17:35:45 2025 (1762968945)
Build timestamp: 1762968945
Build timestamp as int: 1762968945

Version of the Aspect rules, or other relevant rules from your
WORKSPACE or MODULE.bazel file:

aspect_rules_js v3.0.2
rules_nodejs v6.7.3

Language(s) and/or frameworks involved:

How to reproduce

Any other information?

No response

[sallustfire]

This is a pre-existing bug #2121, but v3 now makes it breaking because of logic in npm/private/npm_import.bzl that generates platform constraints for npm package deps like:

deps = {} | select({
    "@aspect_rules_js//platforms/pnpm:linux_x64": {"@esbuild/linux-x64": "..."},
    "@aspect_rules_js//platforms/pnpm:darwin_arm64": {"@esbuild/darwin-arm64": "..."},
    "//conditions:default": {},
})