refactor: rename flag to _hoist_runfiles_to_exec_cfg to signal it is internal

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

Author: acozzette

.github/workflows/ci.yaml

@@ -143,7 +143,7 @@ jobs:
                   bazel test \
                     --test_tag_filters=-skip-on-bazel7 \
                     --build_tag_filters=-skip-on-bazel7 \
-                    --@aspect_rules_js//js:hoist_runfiles_to_exec_cfg=true \
+                    --@aspect_rules_js//js:_hoist_runfiles_to_exec_cfg=true \
                     //...
 
     # Mac/Windows smoke tests - only e2e/bzlmod

js/BUILD.bazel

@@ -3,15 +3,18 @@
 load("@bazel_skylib//:bzl_library.bzl", "bzl_library")
 load("@bazel_skylib//rules:common_settings.bzl", "bool_flag")
 
+# Underscore prefix signals this is internal — do not rely on it.
+# It exists temporarily to allow opt-in to the new default (False) while
+# the ecosystem migrates, and will be removed once the default is flipped.
 bool_flag(
-    name = "hoist_runfiles_to_exec_cfg",
+    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"},
+    name = "_hoist_runfiles_to_exec_cfg_true",
+    flag_values = {"_hoist_runfiles_to_exec_cfg": "True"},
 )
 
 bzl_library(

js/private/js_run_binary.bzl

@@ -157,8 +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.
+            When set to `None` (the default), the value of the internal `//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. This flag is temporary and will be removed once the default is changed to `True`.
 
         copy_srcs_to_bin: When True, all srcs files are copied to the output tree that are not already there.
 
@@ -399,11 +400,11 @@ See https://github.com/aspect-build/rules_js/tree/main/docs#using-binaries-publi
             extra_srcs.append(runfiles_label)
         else:
             tools = tools + select({
-                "//js:hoist_runfiles_to_exec_cfg_true": [runfiles_label],
+                "//js:_hoist_runfiles_to_exec_cfg_true": [runfiles_label],
                 "//conditions:default": [],
             })
             extra_srcs = extra_srcs + select({
-                "//js:hoist_runfiles_to_exec_cfg_true": [],
+                "//js:_hoist_runfiles_to_exec_cfg_true": [],
                 "//conditions:default": [runfiles_label],
             })