feat: add bool_flag to control hoist_runfiles_to_exec_cfg default

Introduces `//js:hoist_runfiles_to_exec_cfg` as a `bool_flag` (default
`False`) to control the default value of `js_run_binary`'s
`hoist_runfiles_to_exec_cfg` parameter. The parameter's default changes
from `True` to `None`, deferring to the flag when not set explicitly.

The launcher script now auto-detects which configuration the entry point
was built in (exec vs target) by checking file existence, removing the
need for the `JS_BINARY__HOIST_RUNFILES_TO_EXEC_CFG` env var entirely.

CI is updated to run `e2e/bzlmod` with `--@aspect_rules_js//js:hoist_runfiles_to_exec_cfg=true`
to verify the opt-in path continues to work.

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

Author: acozzette

.github/workflows/ci.yaml

@@ -120,6 +120,32 @@ jobs:
                     echo "No test.sh in ${PWD}; skipping"
                   fi
 
+    # Ubuntu smoke test for e2e/bzlmod with hoist_runfiles_to_exec_cfg=true to verify
+    # that the flag-controlled opt-in path works correctly.
+    test-hoist-runfiles:
+        runs-on: ubuntu-22.04
+        defaults:
+            run:
+                working-directory: e2e/bzlmod
+        env:
+            ASPECT_RULES_JS_FROZEN_PNPM_LOCK: 1
+        steps:
+            - uses: actions/checkout@v6
+
+            - uses: bazel-contrib/[email protected]
+              with:
+                  bazelisk-cache: true
+                  disk-cache: hoist-runfiles-bzlmod
+                  repository-cache: true
+
+            - name: bazel test //... with hoist_runfiles_to_exec_cfg=true
+              run: |
+                  bazel test \
+                    --test_tag_filters=-skip-on-bazel7 \
+                    --build_tag_filters=-skip-on-bazel7 \
+                    --@aspect_rules_js//js:hoist_runfiles_to_exec_cfg=true \
+                    //...
+
     # Mac/Windows smoke tests - only e2e/bzlmod
     # Only run on main branch (not PRs) to minimize minutes (billed at 10X and 2X respectively)
     # https://docs.github.com/en/billing/managing-billing-for-github-actions/about-billing-for-github-actions#included-storage-and-minutes
@@ -155,12 +181,12 @@ jobs:
     # For branch protection settings, this job provides a "stable" name that can be used to gate PR merges
     # on "all matrix jobs were successful".
     conclusion:
-        needs: [test, smoke]
+        needs: [test, smoke, test-hoist-runfiles]
         runs-on: ubuntu-latest
         if: always()
         steps:
             - run: |
-                  if [[ "${{ needs.test.result }}" == "success" && ("${{ needs.smoke.result }}" == "success" || "${{ needs.smoke.result }}" == "skipped") ]]; then
+                  if [[ "${{ needs.test.result }}" == "success" && ("${{ needs.smoke.result }}" == "success" || "${{ needs.smoke.result }}" == "skipped") && "${{ needs.test-hoist-runfiles.result }}" == "success" ]]; then
                     exit 0
                   else
                     exit 1

js/BUILD.bazel

@@ -1,6 +1,18 @@
 "Public API"
 
 load("@bazel_skylib//:bzl_library.bzl", "bzl_library")
+load("@bazel_skylib//rules:common_settings.bzl", "bool_flag")
+
+bool_flag(
+    name = "hoist_runfiles_to_exec_cfg",
+    build_setting_default = False,
+    visibility = ["//visibility:public"],
+)
+
+config_setting(
+    name = "hoist_runfiles_to_exec_cfg_true",
+    flag_values = {":hoist_runfiles_to_exec_cfg": "True"},
+)
 
 bzl_library(
     name = "defs",

js/private/js_binary.sh.tpl

@@ -96,16 +96,19 @@ function logf_debug {
 }
 
 function resolve_execroot_bin_path {
-    if [ "${JS_BINARY__HOIST_RUNFILES_TO_EXEC_CFG:-}" ]; then
-        local bindir="$JS_BINARY__EXECROOT/$JS_BINARY__BINDIR"
-    else
-        local bindir="$JS_BINARY__EXECROOT/$BAZEL_BINDIR"
-    fi
     local short_path="$1"
+    local suffix
     if [[ "$short_path" == ../* ]]; then
-        echo "$bindir/external/${short_path:3}"
+        suffix="external/${short_path:3}"
+    else
+        suffix="$short_path"
+    fi
+    local exec_path="$JS_BINARY__EXECROOT/$JS_BINARY__BINDIR/$suffix"
+    local target_path="$JS_BINARY__EXECROOT/${BAZEL_BINDIR:-$JS_BINARY__BINDIR}/$suffix"
+    if [ "$exec_path" = "$target_path" ] || [ -e "$exec_path" ]; then
+        echo "$exec_path"
     else
-        echo "$bindir/$short_path"
+        echo "$target_path"
     fi
 }
 

js/private/js_run_binary.bzl

@@ -31,7 +31,7 @@ def js_run_binary(
         exit_code_out = None,
         silent_on_success = True,
         use_execroot_entry_point = True,
-        hoist_runfiles_to_exec_cfg = True,
+        hoist_runfiles_to_exec_cfg = None,
         copy_srcs_to_bin = True,
         include_sources = True,
         include_types = False,
@@ -157,6 +157,9 @@ def js_run_binary(
             results in a more correct build by ensuring that code that is executed during a build action is built for the
             execution platform, which may not be the same as the target platform.
 
+            When set to `None` (the default), the value of the `//js:hoist_runfiles_to_exec_cfg` build flag is used.
+            Pass `--//js:hoist_runfiles_to_exec_cfg=true` on the command line or in `.bazelrc` to enable globally.
+
         copy_srcs_to_bin: When True, all srcs files are copied to the output tree that are not already there.
 
         include_sources: see `js_info_files` documentation
@@ -389,11 +392,20 @@ See https://github.com/aspect-build/rules_js/tree/main/docs#using-binaries-publi
             # Always propagate the testonly attribute
             testonly = kwargs.get("testonly", False),
         )
-        if hoist_runfiles_to_exec_cfg:
-            fixed_env["JS_BINARY__HOIST_RUNFILES_TO_EXEC_CFG"] = "1"
-            tools.append(":{}".format(js_runfiles_name))
+        runfiles_label = ":{}".format(js_runfiles_name)
+        if hoist_runfiles_to_exec_cfg == True:
+            tools.append(runfiles_label)
+        elif hoist_runfiles_to_exec_cfg == False:
+            extra_srcs.append(runfiles_label)
         else:
-            extra_srcs.append(":{}".format(js_runfiles_name))
+            tools = tools + select({
+                "//js:hoist_runfiles_to_exec_cfg_true": [runfiles_label],
+                "//conditions:default": [],
+            })
+            extra_srcs = extra_srcs + select({
+                "//js:hoist_runfiles_to_exec_cfg_true": [],
+                "//conditions:default": [runfiles_label],
+            })
 
     if allow_execroot_entry_point_with_no_copy_data_to_bin:
         fixed_env["JS_BINARY__ALLOW_EXECROOT_ENTRY_POINT_WITH_NO_COPY_DATA_TO_BIN"] = "1"