feat: add $(rlocation ...) syntax as a cleaner alternative to $$RUNFILES_DIR/$(rlocationpath ...)

docs/use_execroot_entry_point.md

@@ -104,7 +104,7 @@ bin.rspack(
     fixed_args = [
         "build",
         "--config",
-        "$$RUNFILES_DIR/$(rlocationpath :rspack_config)",
+        "$(rlocation :rspack_config)",
     ],
     use_execroot_entry_point = False,
 )
@@ -128,10 +128,7 @@ Key points:
   `__dirname`, for specifying the output path. This is key, because the config
   file (and therefore `__dirname`) will be in the runfiles directory and not
   the output tree.
-- We refer to `"$$RUNFILES_DIR/$(rlocationpath :rspack_config)"` in
-  `fixed_args`. `$(rlocationpath ...)` is evaluated at analysis time and
-  determines the path to the config file within the runfiles directory. This
-  argument must go in `fixed_args` rather than `args`, to allow `$RUNFILES_DIR`
-  to be evaluated at run time. Note the double dollar sign (`$$`) to prevent
-  the `js_binary` implementation from attempting to evaluate that variable at
-  analysis time.
+- We refer to `"$(rlocation :rspack_config)"` in `fixed_args`. The `js_binary`
+  implementation expands this to the absolute path to the config file in the
+  runfiles directory. Note that this must go in `fixed_args` rather than
+  `args`.

examples/rspack/BUILD.bazel

@@ -27,7 +27,7 @@ bin.rspack(
     fixed_args = [
         "build",
         "--config",
-        "$$RUNFILES_DIR/$(rlocationpath :rspack_config)",
+        "$(rlocation :rspack_config)",
     ],
     use_execroot_entry_point = False,
 )

examples/vite3/BUILD.bazel

@@ -30,7 +30,7 @@ vite_bin.vite(
     fixed_args = [
         "build",
         "--config",
-        "$$RUNFILES_DIR/$(rlocationpath :vite-config)",
+        "$(rlocation :vite-config)",
     ],
     out_dirs = ["build"],
 )

examples/vite6/BUILD.bazel

@@ -30,7 +30,7 @@ vite_bin.vite(
     fixed_args = [
         "build",
         "--config",
-        "$$RUNFILES_DIR/$(rlocationpath :vite-config)",
+        "$(rlocation :vite-config)",
     ],
     out_dirs = ["build"],
 )

examples/webpack_cli/BUILD.bazel

@@ -35,7 +35,7 @@ bin.webpack_cli(
     data = [":webpack-config"],
     fixed_args = [
         "--config",
-        "$$RUNFILES_DIR/$(rlocationpath :webpack-config)",
+        "$(rlocation :webpack-config)",
     ],
     log_level = "debug",
 )

js/libs.bzl

@@ -8,6 +8,7 @@ load(
     "//js/private:js_helpers.bzl",
     _LOG_LEVELS = "LOG_LEVELS",
     _envs_for_log_level = "envs_for_log_level",
+    _expand_rlocation_refs = "expand_rlocation_refs",
     _gather_files_from_js_infos = "gather_files_from_js_infos",
     _gather_npm_package_store_infos = "gather_npm_package_store_infos",
     _gather_npm_sources = "gather_npm_sources",
@@ -25,6 +26,7 @@ js_library_lib = _js_library_lib
 
 js_lib_helpers = struct(
     envs_for_log_level = _envs_for_log_level,
+    expand_rlocation_refs = _expand_rlocation_refs,
     gather_files_from_js_infos = _gather_files_from_js_infos,
     gather_npm_sources = _gather_npm_sources,
     gather_npm_package_store_infos = _gather_npm_package_store_infos,

js/private/coverage/bundle/BUILD.bazel

@@ -27,7 +27,7 @@ rollup_bin.rollup(
     fixed_args = [
         "c8.js",
         "--config",
-        "$$RUNFILES_DIR/$(rlocationpath :config)",
+        "$(rlocation :config)",
         "--format",
         "cjs",
         "--file",

js/private/devserver/src/BUILD.bazel

@@ -22,7 +22,7 @@ rollup_bin.rollup(
     fixed_args = [
         "js_run_devserver.mjs",
         "--config",
-        "$$RUNFILES_DIR/$(rlocationpath :config)",
+        "$(rlocation :config)",
         "--format",
         "es",
         "--file",

js/private/js_binary.bzl

@@ -5,7 +5,7 @@ load("@bazel_lib//lib:directory_path.bzl", "DirectoryPathInfo")
 load("@bazel_lib//lib:expand_make_vars.bzl", "expand_locations", "expand_variables")
 load("@bazel_lib//lib:windows_utils.bzl", "create_windows_native_launcher_script")
 load(":bash.bzl", "BASH_INITIALIZE_RUNFILES")
-load(":js_helpers.bzl", "LOG_LEVELS", "envs_for_log_level", "gather_files_from_js_infos", "gather_runfiles")
+load(":js_helpers.bzl", "LOG_LEVELS", "envs_for_log_level", "expand_rlocation_refs", "gather_files_from_js_infos", "gather_runfiles")
 
 _ATTRS = {
     "chdir": attr.string(
@@ -78,8 +78,9 @@ _ATTRS = {
     ),
     "expand_args": attr.bool(
         default = True,
-        doc = """Enables [$(location)](https://bazel.build/reference/be/make-variables#predefined_label_variables)
-        and ["Make variable"](https://bazel.build/reference/be/make-variables) substitution for `fixed_args`.
+        doc = """Enables [$(location)](https://bazel.build/reference/be/make-variables#predefined_label_variables),
+        ["Make variable"](https://bazel.build/reference/be/make-variables), and our own custom `$(rlocation)`
+        substitution for `fixed_args`.
 
         This comes at some analysis-time cost even for a set of args that does not have any expansions.""",
     ),
@@ -94,8 +95,14 @@ _ATTRS = {
         doc = """Fixed command line arguments to pass to the Node.js when this
         binary target is executed.
 
-        Subject to [$(location)](https://bazel.build/reference/be/make-variables#predefined_label_variables)
-        and ["Make variable"](https://bazel.build/reference/be/make-variables) substitution if `expand_args` is set to True.
+        Subject to [$(location)](https://bazel.build/reference/be/make-variables#predefined_label_variables),
+        ["Make variable"](https://bazel.build/reference/be/make-variables), and `$(rlocation)` substitution
+        if `expand_args` is set to True.
+
+        The `$(rlocation :label)` syntax is unique to `js_binary` and expands to the
+        absolute path to `:label` in the runfiles. This is supported only in `fixed_args`,
+        because part of the evaluation has to occur at run time, inside the wrapper
+        script.
 
         Unlike the built-in `args`, which are only passed to the target when it is
         executed either by the `bazel run` command or as a test, `fixed_args` are baked
@@ -374,7 +381,7 @@ def _bash_launcher(ctx, nodeinfo, entry_point_path, log_prefix_rule_set, log_pre
         node_options.append(_NODE_OPTION.format(value = "--preserve-symlinks-main"))
 
     if ctx.attr.expand_args:
-        fixed_args = [expand_variables(ctx, expand_locations(ctx, fixed_arg, ctx.attr.data)) for fixed_arg in fixed_args]
+        fixed_args = [expand_variables(ctx, expand_locations(ctx, expand_rlocation_refs(fixed_arg), ctx.attr.data)) for fixed_arg in fixed_args]
 
     toolchain_files = []
     if is_windows:

js/private/js_helpers.bzl

@@ -190,6 +190,36 @@ def gather_runfiles(
         for target in deps
     ])
 
+def expand_rlocation_refs(value):
+    """Pre-processes $(rlocation <label>) into $$RUNFILES_DIR/$(rlocationpath <label>).
+
+    After this transformation, the standard expand_locations/expand_variables chain
+    resolves the rlocationpath and converts $$ to a literal $.
+    """
+    result = []
+    remaining = value
+    prefix = "$(rlocation "
+    for _ in range(len(value)):
+        idx = remaining.find(prefix)
+        if idx == -1:
+            break
+        result.append(remaining[:idx])
+        remaining = remaining[idx + len(prefix):]
+
+        # Parentheses are allowed in Bazel target names and could therefore
+        # theoretically appear in a label. We just look for the first closing
+        # parenthesis without handling that possibility, as this is what Bazel
+        # itself does:
+        # https://github.com/bazelbuild/bazel/blob/b4f16d988ddebc1891d7af57622ec5aff149a838/src/main/java/com/google/devtools/build/lib/analysis/LocationExpander.java#L179
+        end = remaining.find(")")
+        if end == -1:
+            fail("Unclosed $(rlocation ...) in: " + value)
+        label_str = remaining[:end]
+        result.append("$$RUNFILES_DIR/$(rlocationpath " + label_str + ")")
+        remaining = remaining[end + 1:]
+    result.append(remaining)
+    return "".join(result)
+
 LOG_LEVELS = {
     "fatal": 1,
     "error": 2,

js/private/test/BUILD.bazel

@@ -2,6 +2,7 @@ load("@bazel_lib//lib:write_source_files.bzl", "write_source_files")
 load("@bazel_lib_host//:defs.bzl", "host")
 load("@bazel_skylib//rules:write_file.bzl", "write_file")
 load("//js:defs.bzl", "js_binary", "js_library", "js_test")
+load(":js_helpers_test.bzl", "js_helpers_test_suite")
 load(":js_library_test.bzl", "js_library_test_suite")
 load(":run_environment_info_test.bzl", "run_environment_info_test_suite")
 
@@ -39,6 +40,8 @@ write_source_files(
     },
 )
 
+js_helpers_test_suite(name = "js_helpers_test")
+
 js_library_test_suite(name = "js_library_test")
 
 run_environment_info_test_suite(name = "run_environment_info_tests")

js/private/test/js_helpers_test.bzl

@@ -0,0 +1,61 @@
+"""Tests for js_helpers utility functions"""
+
+load("@bazel_skylib//lib:unittest.bzl", "asserts", "unittest")
+load("//js/private:js_helpers.bzl", "expand_rlocation_refs")
+
+def _no_rlocation_refs_test(ctx):
+    env = unittest.begin(ctx)
+    asserts.equals(env, "build", expand_rlocation_refs("build"))
+    return unittest.end(env)
+
+def _single_rlocation_ref_test(ctx):
+    env = unittest.begin(ctx)
+    asserts.equals(
+        env,
+        "$$RUNFILES_DIR/$(rlocationpath :rspack_config)",
+        expand_rlocation_refs("$(rlocation :rspack_config)"),
+    )
+    return unittest.end(env)
+
+def _rlocation_ref_with_surrounding_text_test(ctx):
+    env = unittest.begin(ctx)
+    asserts.equals(
+        env,
+        "--config=$$RUNFILES_DIR/$(rlocationpath :my_config)",
+        expand_rlocation_refs("--config=$(rlocation :my_config)"),
+    )
+    return unittest.end(env)
+
+def _multiple_rlocation_refs_test(ctx):
+    env = unittest.begin(ctx)
+    asserts.equals(
+        env,
+        "$$RUNFILES_DIR/$(rlocationpath :foo):$$RUNFILES_DIR/$(rlocationpath :bar)",
+        expand_rlocation_refs("$(rlocation :foo):$(rlocation :bar)"),
+    )
+    return unittest.end(env)
+
+def _absolute_label_rlocation_ref_test(ctx):
+    env = unittest.begin(ctx)
+    asserts.equals(
+        env,
+        "$$RUNFILES_DIR/$(rlocationpath //some/pkg:target)",
+        expand_rlocation_refs("$(rlocation //some/pkg:target)"),
+    )
+    return unittest.end(env)
+
+no_rlocation_refs_test = unittest.make(_no_rlocation_refs_test)
+single_rlocation_ref_test = unittest.make(_single_rlocation_ref_test)
+rlocation_ref_with_surrounding_text_test = unittest.make(_rlocation_ref_with_surrounding_text_test)
+multiple_rlocation_refs_test = unittest.make(_multiple_rlocation_refs_test)
+absolute_label_rlocation_ref_test = unittest.make(_absolute_label_rlocation_ref_test)
+
+def js_helpers_test_suite(name):
+    unittest.suite(
+        name,
+        no_rlocation_refs_test,
+        single_rlocation_ref_test,
+        rlocation_ref_with_surrounding_text_test,
+        multiple_rlocation_refs_test,
+        absolute_label_rlocation_ref_test,
+    )

js/private/test/node-patches/BUILD.bazel

@@ -69,7 +69,7 @@ babel_bin.babel(
     data = [":babel_config"],
     fixed_args = [
         "--config-file",
-        "$$RUNFILES_DIR/$(rlocationpath :babel_config)",
+        "$(rlocation :babel_config)",
         "--extensions",
         ".mjs",
         "--out-file-extension",

js/private/worker/src/BUILD.bazel

@@ -32,7 +32,7 @@ rollup_bin.rollup(
     fixed_args = [
         "index.ts",
         "--config",
-        "$$RUNFILES_DIR/$(rlocationpath :config)",
+        "$(rlocation :config)",
         "--format",
         "cjs",
         "--file",

npm/private/lifecycle/src/BUILD.bazel

@@ -26,7 +26,7 @@ rollup_bin.rollup(
     fixed_args = [
         "lifecycle-hooks.js",
         "--config",
-        "$$RUNFILES_DIR/$(rlocationpath //npm/private/lifecycle:rollup_config)",
+        "$(rlocation //npm/private/lifecycle:rollup_config)",
         "--format",
         "cjs",
         "--file",