re-write rules.bzl

rules.bzl

@@ -1,46 +1,40 @@
-# From: 
+# From:
 # https://stackoverflow.com/questions/47192668/idiomatic-retrieval-of-the-bazel-execution-path#
 
 def _dirname(path):
   prefix, _, _ = path.rpartition("/")
   return prefix.rstrip("/")
 
+def _test_files(bats, srcs):
+  return '"{bats_bin}" {test_paths}'.format(
+      bats_bin = bats.short_path,
+      test_paths = " ".join(['"{}"'.format(s.short_path) for s in srcs]),
+  )
 
 def _bats_test_impl(ctx):
-  runfiles = ctx.runfiles(
-      files = ctx.files.srcs,
-      collect_data = True,
-  )
-  tests = ["\"{}\"".format(f.short_path) for f in ctx.files.srcs]
   path = ["$PWD/" + _dirname(b.short_path) for b in ctx.files.deps]
-  l = ['export {}="{}"'.format(
-        key, ctx.expand_location(val, ctx.attr.deps)) for key, val in ctx.attr.env.items()]
-  env = "\n".join(l)
-
   sep = ctx.configuration.host_path_separator
 
-  BASH_TEMPLATE = """#!/usr/bin/env bash
-set -e
-export TMPDIR="$TEST_TMPDIR"
-export PATH="{bats_bins_path}":$PATH
-{env}
-"{bats}" {test_paths}
-"""
-  content = BASH_TEMPLATE.format(
-      bats = ctx.executable._bats.short_path,
-      bats_bins_path = sep.join(path),
-      env=env,
-      test_paths = " ".join(tests),
+  content = "\n".join(
+      ["#!/usr/bin/env bash"] +
+      ["set -e"] +
+      ["export TMPDIR=\"$TEST_TMPDIR\""] +
+      ["export PATH=\"{bats_bins_path}\":$PATH".format(bats_bins_path = sep.join(path))] +
+      [
+          'export {}="{}"'.format(key, ctx.expand_location(val, ctx.attr.deps))
+          for key, val in ctx.attr.env.items()
+      ] +
+      [_test_files(ctx.executable._bats, ctx.files.srcs)]
   )
   ctx.actions.write(
       output = ctx.outputs.executable,
-      is_executable = True,
       content = content,
   )
-  runfiles = runfiles.merge(ctx.attr._bats.default_runfiles)
-  return DefaultInfo(
-      runfiles = runfiles,
-  )
+  runfiles = ctx.runfiles(
+      files = ctx.files.srcs,
+      collect_data = True,
+  ).merge(ctx.attr._bats.default_runfiles)
+  return [DefaultInfo(runfiles = runfiles)]
 
 
 bats_test = rule(
@@ -57,7 +51,7 @@ bats_test = rule(
       "_bats": attr.label(
          default = Label("@bats_core//:bats"),
          executable = True,
-         cfg = "host",
+         cfg = "exec",
       ),
     },
     test = True,