chore: add test coverage for run_binary & expand_variables makevars

lib/private/expand_variables.bzl

@@ -5,6 +5,11 @@ load("@bazel_skylib//lib:paths.bzl", _spaths = "paths")
 def expand_variables(ctx, s, outs = [], output_dir = False, attribute_name = "args"):
     """Expand make variables and substitute like genrule does.
 
+    Bazel [pre-defined variables](https://bazel.build/reference/be/make-variables#predefined_variables)
+    are expanded however only `$@`, `$(@D)` and `$(RULEDIR)` of
+    [pre-defined genrule variables](https://bazel.build/reference/be/make-variables#predefined_genrule_variables)
+    are supported.
+
     This function is the same as ctx.expand_make_variables with the additional
     genrule-like substitutions of:
 

lib/private/run_binary.bzl

@@ -141,11 +141,17 @@ def run_binary(
 
         args: Command line arguments of the binary.
 
-            Subject to `$(location)` and makevar expansions.
+            Subject to `$(location)` and make variable expansions via
+            [expand_location](https://docs.aspect.build/rules/aspect_bazel_lib/docs/expand_make_vars#expand_locations)
+            and
+            [expand_make_vars](https://docs.aspect.build/rules/aspect_bazel_lib/docs/expand_make_vars).
 
         env: Environment variables of the action.
 
-            Subject to `$(location)` and makevar expansions.
+            Subject to `$(location)` and make variable expansions via
+            [expand_location](https://docs.aspect.build/rules/aspect_bazel_lib/docs/expand_make_vars#expand_locations)
+            and
+            [expand_make_vars](https://docs.aspect.build/rules/aspect_bazel_lib/docs/expand_make_vars).
 
         outs: Output files generated by the action.
 

lib/tests/run_binary_expansions/BUILD.bazel

@@ -0,0 +1,56 @@
+"tests for run_binary"
+
+load("@aspect_bazel_lib//lib:write_source_files.bzl", "write_source_file")
+load("@bazel_skylib//rules:write_file.bzl", "write_file")
+load("//lib:run_binary.bzl", "run_binary")
+
+sh_binary(
+    name = "expansions_sh",
+    srcs = [":expansions.sh"],
+)
+
+write_file(
+    name = "gen_src_1",
+    out = "src_1",
+    content = ["src1"],
+)
+
+# target-under-test
+run_binary(
+    name = "expansions",
+    srcs = [
+        ":gen_src_1",
+    ],
+    outs = ["expansions_out"],
+    args = [
+        "$@",
+        "$(@D)",
+        "$(rootpath :gen_src_1)",
+        "$(execpath :gen_src_1)",
+        # Bazel built-in pre-defined variables
+        # https://bazel.build/reference/be/make-variables#predefined_variables
+        "$(COMPILATION_MODE)",
+        "$(BINDIR)",
+        "$(GENDIR)",
+        "$(TARGET_CPU)",
+        # Additional variables handled by aspect_bazel_lib expand_variables
+        # used by run_binary
+        # https://docs.aspect.build/rules/aspect_bazel_lib/docs/expand_expansions#expand_variables
+        "$(BUILD_FILE_PATH)",
+        "$(VERSION_FILE)",
+        "$(INFO_FILE)",
+        "$(TARGET)",
+        "$(WORKSPACE)",
+    ],
+    execution_requirements = {
+        "no-cache": "1",
+    },
+    progress_message = "doing some work to make %{output}",
+    tool = ":expansions_sh",
+)
+
+write_source_file(
+    name = "write_expansions_golden",
+    in_file = "expansions_out",
+    out_file = "expansions_golden",
+)

lib/tests/run_binary_expansions/expansions.sh

@@ -0,0 +1,12 @@
+#!/usr/bin/env bash
+set -o errexit -o nounset -o pipefail
+
+mkdir -p $(dirname $1)
+outfile=$1
+rm -f $outfile
+for each in $@
+do
+  sanitized=${each/darwin/PLATFORM}
+  sanitized=${sanitized/k8/PLATFORM}
+  echo $sanitized >> $outfile
+done

lib/tests/run_binary_expansions/expansions_golden

@@ -0,0 +1,13 @@
+bazel-out/PLATFORM-fastbuild/bin/lib/tests/run_binary_expansions/expansions_out
+bazel-out/PLATFORM-fastbuild/bin/lib/tests/run_binary_expansions
+lib/tests/run_binary_expansions/src_1
+bazel-out/PLATFORM-fastbuild/bin/lib/tests/run_binary_expansions/src_1
+fastbuild
+bazel-out/PLATFORM-fastbuild/bin
+bazel-out/PLATFORM-fastbuild/bin
+PLATFORM
+lib/tests/run_binary_expansions/BUILD.bazel
+bazel-out/volatile-status.txt
+bazel-out/stable-status.txt
+//lib/tests/run_binary_expansions:expansions
+aspect_bazel_lib