Reland "chromeos: Add only the current SDK version's items to a test's data."

This is a reland of 3a8d37c3

Reland fix:
 - Only adds the needed test data if `cros_sdk_version != ""`

That will prevent ebuild invocations from trying to add non-existant
items to data (since the ebuild doesn't use the cros chrome-sdk cache).

Original change's description:
> chromeos: Add only the current SDK version's items to a test's data.
>
> Instead of adding every version of a given item, this will add only the
> current version's. This is a bit tricky since individual versions of an
> item are keyed by symlink. And since isolate doesn't follow symlinks,
> we have to follow them ourselves.
>
> Bug: 1027382
> Change-Id: I6b3ea4ec15de3804e99fd6af768daac64f490d5b
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1931155
> Commit-Queue: Ben Pastene <bpastene@chromium.org>
> Reviewed-by: Dirk Pranke <dpranke@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#771959}

Bug: 1027382
Change-Id: I2ff8c8452f5f6f43e178d547e963b6f8b7d17166
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2218581Reviewed-by: Nico Weber <thakis@chromium.org>
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Commit-Queue: Ben Pastene <bpastene@chromium.org>
Cr-Commit-Position: refs/heads/master@{#774341}

build/config/chromeos/rules.gni

@@ -14,6 +14,49 @@ declare_args() {
                cros_board == "betty-pi-arc"
 }
 
+# Determine the real paths for various items in the SDK, which may be used
+# in the 'generate_runner_script' template below. We do so outside the template
+# to confine exec_script to a single invocation.
+if (is_chromeos_device && cros_sdk_version != "") {
+  _cache_path_prefix =
+      "//build/cros_cache/chrome-sdk/symlinks/${cros_board}+${cros_sdk_version}"
+  _symlinks = [
+    # Tast harness & test data.
+    rebase_path("${_cache_path_prefix}+chromeos-base/tast-cmd"),
+    rebase_path("${_cache_path_prefix}+chromeos-base/tast-remote-tests-cros"),
+
+    # Binutils (and other toolchain tools) used to deploy Chrome to the device.
+    rebase_path(
+        "${_cache_path_prefix}+environment_chromeos-base_chromeos-chrome.tar.xz"),
+    rebase_path("${_cache_path_prefix}+target_toolchain"),
+  ]
+  if (cros_is_vm) {
+    # VM-related tools.
+    _symlinks += [
+      rebase_path("${_cache_path_prefix}+sys-firmware/seabios"),
+      rebase_path("${_cache_path_prefix}+chromiumos_qemu_image.tar.xz"),
+      rebase_path("${_cache_path_prefix}+app-emulation/qemu"),
+    ]
+  }
+  _symlink_targets =
+      exec_script("//build/get_symlink_targets.py", _symlinks, "list lines")
+  tast_sdk_items = [
+    _symlink_targets[0],
+    _symlink_targets[1],
+  ]
+  toolchain_sdk_items = [
+    _symlink_targets[2],
+    _symlink_targets[3],
+  ]
+  if (cros_is_vm) {
+    vm_sdk_items = [
+      _symlink_targets[4],
+      _symlink_targets[5],
+      _symlink_targets[6],
+    ]
+  }
+}
+
 # Creates a script at $generated_script that can be used to launch a cros VM
 # and optionally run a test within it.
 # Args:
@@ -44,12 +87,6 @@ template("generate_runner_script") {
     deploy_chrome = false
   }
 
-  # These are the only 2 conditions when ${_cache_path_prefix} is used, so
-  # initialize it in a conditional.
-  if (deploy_chrome || cros_is_vm) {
-    _cache_path_prefix = "//build/cros_cache/chrome-sdk/tarballs/"
-  }
-
   assert(defined(generated_script),
          "Must specify where to place generated test launcher script via " +
              "'generated_script'")
@@ -90,24 +127,6 @@ template("generate_runner_script") {
       "//third_party/chromite/",
     ]
 
-    # Add the VM/QEMU-launching bits if needed.
-    if (cros_is_vm) {
-      assert(defined(_cache_path_prefix))
-      _vm_image_path = "${_cache_path_prefix}/chromiumos_qemu_image.tar.xz/"
-      _qemu_dir = "${_cache_path_prefix}/app-emulation/"
-      _firmware_dir = "${_cache_path_prefix}/sys-firmware/"
-      data += [
-        _firmware_dir,
-        _vm_image_path,
-        _qemu_dir,
-      ]
-    }
-    if (is_tast) {
-      data += [
-        "${_cache_path_prefix}/chromeos-base/tast-cmd/",
-        "${_cache_path_prefix}/chromeos-base/tast-remote-tests-cros/",
-      ]
-    }
     if (defined(invoker.data)) {
       deps += invoker.data
     }
@@ -134,15 +153,24 @@ template("generate_runner_script") {
 
     if (deploy_chrome) {
       args += [ "--deploy-chrome" ]
+    }
 
-      # To deploy chrome to the VM, it needs to be stripped down to fit into
-      # the VM. This is done by using binutils in the toolchain. So add the
-      # toolchain to the data.
-      assert(defined(_cache_path_prefix))
-      data += [
-        "${_cache_path_prefix}/environment_chromeos-base_chromeos-chrome.tar.xz",
-        "${_cache_path_prefix}/target_toolchain/",
-      ]
+    # If we're in the cros chrome-sdk (and not the raw ebuild), the test will
+    # need some additional runtime data located in the SDK cache.
+    if (cros_sdk_version != "") {
+      # Add the VM/QEMU-launching bits if needed.
+      if (cros_is_vm) {
+        data += vm_sdk_items
+      }
+      if (is_tast) {
+        data += tast_sdk_items
+      }
+      if (deploy_chrome) {
+        # To deploy chrome to the VM, it needs to be stripped down to fit into
+        # the VM. This is done by using binutils in the toolchain. So add the
+        # toolchain to the data.
+        data += toolchain_sdk_items
+      }
     }
 
     # When --test-exe is specified, test_runner.py will push the exe to the VM

build/dotfile_settings.gni

@@ -10,6 +10,7 @@ build_dotfile_settings = {
     "//build/config/android/config.gni",
     "//build/config/android/internal_rules.gni",
     "//build/config/android/rules.gni",
+    "//build/config/chromeos/rules.gni",
     "//build/config/compiler/BUILD.gn",
     "//build/config/compiler/pgo/BUILD.gn",
     "//build/config/gcc/gcc_version.gni",

build/get_symlink_targets.py

+#!/usr/bin/env python
+# Copyright (c) 2019 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+"""Prints the target paths of the given symlinks.
+
+Prints out each target in the order that the links were passed in.
+"""
+
+import os
+import sys
+
+
+def main():
+  for link_name in sys.argv[1:]:
+    if not os.path.islink(link_name):
+      sys.stderr.write("%s is not a link" % link_name)
+      return 1
+    target = os.readlink(link_name)
+    if not os.path.isabs(target):
+      target = os.path.join(os.path.dirname(link_name), target)
+    print(os.path.realpath(target))
+  return 0
+
+
+if __name__ == '__main__':
+  sys.exit(main())