client_server_test find .exe on Windows

bazel_tools/client_server/client_server_test.bzl

@@ -59,10 +59,10 @@ def client_server_test(
         # Deduplicate in case any of runner, client, server are identical.
         data = depset([runner, client, server]).to_list() + data,
         cmd = """\
-runner=$$(canonicalize_rlocation "$(rootpaths {runner})")
+runner=$$(canonicalize_rlocation $$(get_exe $(rootpaths {runner})))
 runner_args="{runner_args}"
-client=$$(canonicalize_rlocation "$(rootpaths {client})")
-server=$$(canonicalize_rlocation "$(rootpaths {server})")
+client=$$(canonicalize_rlocation $$(get_exe $(rootpaths {client})))
+server=$$(canonicalize_rlocation $$(get_exe $(rootpaths {server})))
 server_args="{server_args}"
 for file in {server_files}; do
     server_args+=" $$(canonicalize_rlocation $$file)"

bazel_tools/sh/sh.bzl

@@ -1,6 +1,8 @@
 # Copyright (c) 2020 Digital Asset (Switzerland) GmbH and/or its affiliates. All rights reserved.
 # SPDX-License-Identifier: Apache-2.0
 
+load("@os_info//:os_info.bzl", "os_name")
+
 def _sh_inline_script_impl(ctx):
     cmd = ctx.attr.cmd
     cmd = ctx.expand_location(cmd, ctx.attr.data)
@@ -11,6 +13,7 @@ def _sh_inline_script_impl(ctx):
         is_executable = True,
         substitutions = {
             "%cmd%": cmd,
+            "%os%": os_name,
         },
     )
 

bazel_tools/sh/test.sh.tpl

@@ -19,6 +19,38 @@ canonicalize_rlocation() {
   # or rlocation will fail to find the path in the manifest file.
   rlocation $(realpath -L -s -m --relative-to=$PWD $TEST_WORKSPACE/$1)
 }
+get_exe() {
+  # Usage: get_exe FILE...
+  #
+  # On Windows: Return the FILE ending on .exe or the first argument.
+  # On Unix: Return the first argument.
+
+  # Note (AH): Bazel `sh_binary` targets produce multiple outputs.
+  # On Unix `script`, and `script.sh`.
+  # On Windows `script`, `script.exe`, and `script.sh`.
+  # Assuming `srcs = ["script.sh"]`.
+  # This is an issue for macros like `client_server_test` which would like
+  # to determine the path to executables such as.
+  # `$$(canonicalize_rlocation $(rootpath {client}))`.
+  # For a `sh_binary` generated `{client}` this fails since `$(rootpath )` is
+  # not applicable to a target with multiple outputs and we have to use
+  # `$(rootpaths )` instead. This happens to work on Unix because the first
+  # item returned by `$(rootpaths )` is correctly executable. However, on
+  # Windows the required `.exe` wrapper is only the second item returned by
+  # `$(rootpaths )` and consequently the obtained `$client` path cannot be
+  # executed on Windows.
+  if [[ %os% = windows ]]; then
+    for arg in "$@"; do
+      if [[ $arg = *.exe ]]; then
+        echo "$arg"
+        return
+      fi
+    done
+    echo "$1"
+  else
+    echo "$1"
+  fi
+}
 set -e
 %cmd%
 # vim: ft=sh