git-hooks: support linting outside of the source tree

We appear to have workflows and committers that prefer to `push` from
outside of the CrOS source tree.

It's relatively straightforward to have fallbacks to support that, so I
don't see why not.

If you want to interact with this repository from outside of a CrOS
source tree, you now have two options:
- If you have a source tree somewhere on your machine, you can set
  CHROMEOS_ROOT_DIRECTORY to that path. If `check-lint` detects a usable
  `cros` in there, it'll function as usual.
- If you don't have a source tree on your machine, `check-lint` will
  fall back to pylint-only linting (with a warning). This isn't ideal
  (we miss shell linting, as well as a few other nits in Python,
  somehow), but should get us most of the way to happiness.

This also includes a refactor of `test` to `[[`

BUG=chromium:918755
TEST=Ran check-lint on some python files in a checkout outside and
     inside of the source tree

Change-Id: I101c4c8b142f0c8f78819779adcfd0b3b0e1d614
Reviewed-on: https://chromium-review.googlesource.com/1412682
Commit-Ready: George Burgess <gbiv@chromium.org>
Tested-by: George Burgess <gbiv@chromium.org>
Reviewed-by: Caroline Tice <cmtice@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>

1 files changed, 62 insertions, 3 deletions

diff --git a/toolchain_utils_githooks/check-lint b/toolchain_utils_githooks/check-lint
index 5b9ade37..a9345a7e 100755
--- a/toolchain_utils_githooks/check-lint
+++ b/toolchain_utils_githooks/check-lint
@@ -1,11 +1,11 @@
-#!/bin/bash -u
+#!/bin/bash -ue
 # Copyright 2019 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 #
 # This script runs `cros lint` on everything it's handed.
 
-if test $# -eq 0; then
+if [[ $# -eq 0 ]]; then
   echo "No files were given to lint." >&2
   echo "Usage: $0 file1 file2 ..." >&2
   exit 1
@@ -19,4 +19,63 @@ if ! type "${cros}" >&/dev/null; then
   exit 1
 fi
 
-"${cros}" lint -- $@
+lint_args=( "$@" )
+
+# Trys to lint our sources. If `cros` tooling isn't properly found, returns. If
+# anything else happens, this will exit the script with the exit code of
+# `cros`.
+try_lint() {
+  local output last_exit_code cros_binary
+
+  cros_binary="$1"
+
+  set +e
+  output="$("${cros_binary}" lint -- "${lint_args[@]}" 2>&1)"
+  last_exit_code="$?"
+  set -e
+
+  # `cros` exits with 127 specifically if it failed due to not finding a Chrome
+  # OS checkout.
+  if [[ "${last_exit_code}" -ne 127 ]]; then
+    if [[ -n "${output}" ]]; then
+      echo "${output}"
+    fi
+    exit "${last_exit_code}"
+  fi
+}
+
+try_lint "${cros}"
+
+# If the user's given us a root directory to fall back on, try that
+if [[ -n "${CHROMEOS_ROOT_DIRECTORY:-}" ]]; then
+  user_cros="${CHROMEOS_ROOT_DIRECTORY}/chromite/bin/cros"
+  if [[ -x "${user_cros}" ]]; then
+    try_lint "${user_cros}"
+  fi
+fi
+
+# So, `cros` outside of the chroot defers to other tools inside of Chromite. If
+# `cros` couldn't find the real `cros` tool, we fall back to pylint on each
+# Python file. It appears that `cros` uses depot_tools' pylint configuration, so
+# this should get us most of the way there, and is probably the best we can
+# reasonably expect to do for users who want to develop without the source
+# tree.
+echo "WARNING: No Chrome OS checkout detected, and no viable CrOS tree" >&2
+echo "found; falling back to python-only linting. If you have a Chrome OS" >&2
+echo "checkout, please either develop from inside of the source tree, or" >&2
+echo "set \$CHROMEOS_ROOT_DIRECTORY to the root of it." >&2
+
+python_files=()
+for file in "$@"; do
+  if [[ "${file}" == *.py ]]; then
+    python_files+=( "${file}" )
+  fi
+done
+
+if [[ "${#python_files[@]}" -eq 0 ]]; then
+  exit 0
+fi
+
+# We saw `cros` above, so assume that `pylint` is in our PATH (depot_tools
+# packages it, and provides a reasonable default config).
+pylint "${python_files[@]}"