unittest.bzl: supports Windows (#84)

In this commit:

- change unittest.bzl to declare a named output
  file instead of relying on the deprecated [1]
  default output name (ctx.outputs.executable).

- define a new toolchain_type and toolchain rules
  for cmd.exe and for Bash (basically Windows and
  non-Windows)

- register the new toolchains in workspace.bzl

- let unittest.make-created test rules require the
  new toolchain_type

- write the test output script as a Windows batch
  script or as a Shell script, depending on the
  selected toolchain

This PR enables the Bazel team to break the Bash
dependency (for test execution) on Windows, and
can run Starlark unittests with the new,
Windows-native test wrapper (still under
development).

See https://github.com/bazelbuild/bazel/issues/5508

1 files changed, 47 insertions, 0 deletions

diff --git a/toolchains/unittest/BUILD b/toolchains/unittest/BUILD
new file mode 100644
index 0000000..195bbb6
--- /dev/null
+++ b/toolchains/unittest/BUILD
@@ -0,0 +1,47 @@
+load("//lib:unittest.bzl", "TOOLCHAIN_TYPE", "unittest_toolchain")
+
+toolchain_type(
+    name = "toolchain_type",
+    visibility = ["//visibility:public"],
+)
+
+unittest_toolchain(
+    name = "cmd",
+    failure_templ = """@echo off
+echo %s
+exit /b 1
+""",
+    file_ext = ".bat",
+    join_on = "\necho ",
+    success_templ = "@exit /b 0",
+    visibility = ["//visibility:public"],
+)
+
+unittest_toolchain(
+    name = "bash",
+    failure_templ = """#!/bin/sh
+cat <<'EOF'
+%s
+EOF
+exit 1
+""",
+    file_ext = ".sh",
+    join_on = "\n",
+    success_templ = "#!/bin/sh\nexit 0",
+    visibility = ["//visibility:public"],
+)
+
+toolchain(
+    name = "cmd_toolchain",
+    exec_compatible_with = [
+        "@bazel_tools//platforms:windows",
+    ],
+    toolchain = ":cmd",
+    toolchain_type = TOOLCHAIN_TYPE,
+)
+
+toolchain(
+    name = "bash_toolchain",
+    toolchain = ":bash",
+    toolchain_type = TOOLCHAIN_TYPE,
+)