temp repro

BUILD

@@ -1,6 +1,6 @@
 load("@io_bazel_rules_go//go:def.bzl", "go_binary", "go_library")
 load("@bazel_tools//tools/build_defs/pkg:pkg.bzl", "pkg_tar")
-load("//src/undocker:rules.bzl", "rootfs")
+load("//src/undocker:rules.bzl", "rootfs", "temp")
 load(
     "@io_bazel_rules_docker//container:container.bzl",
     "container_bundle",
@@ -34,3 +34,15 @@ rootfs(
     #src = "@alpine//image:image",
     src = ":alpine-container-plus",
 )
+
+filegroup(
+    name = "maingo",
+    srcs = ["main.go"],
+    visibility = ["//visibility:public"],
+)
+
+temp(
+    name = "temp",
+    data = ":maingo",
+    out = "maingo.txt",
+)

rules.bzl

@@ -33,3 +33,19 @@ rootfs = rule(
         ),
     },
 )
+
+def _temp_impl(ctx):
+    for f in ctx.files.data:
+        print(f.path)
+    ctx.actions.run_shell(
+        outputs = [ctx.outputs.out],
+        command = "find $@",
+    )
+
+temp = rule(
+    implementation = _temp_impl,
+    attrs = {
+        "data": attr.label(mandatory = True, allow_single_file = True),
+        "out": attr.output(mandatory = True)
+    },
+)