Tox: Add GPL license checker

A common mistage is to add a file into GPL directory,
with Apache license only.
This adds a tox checker to vote -1 on such changes,
gpl_license.log contains the list of affected files.

There are TODOs related to unlicensed files
or unconventional GPL licenses.

Change-Id: I267e4fb98afd199d5acc7d211068b28c97b31dc9
Signed-off-by: Vratko Polak <vrpolak@cisco.com>

3 files changed, 81 insertions, 3 deletions

diff --git a/resources/libraries/bash/entry/check/copyright_year.sh b/resources/libraries/bash/entry/check/copyright_year.sh
index 66667b96ca..2f9bc1fbeb 100644
--- a/resources/libraries/bash/entry/check/copyright_year.sh
+++ b/resources/libraries/bash/entry/check/copyright_year.sh
@@ -18,7 +18,7 @@ set -exuo pipefail
 # This file does not have executable flag nor shebang,
 # to dissuade non-tox callers.
 
-# This script runs a few grep-based command and fails
+# This script runs a few grep-based commands and fails
 # if it detects any file edited or added since HEAD~
 # containing a copyright notice in first 3 lines,
 # but not the current year (in the same line).
diff --git a/resources/libraries/bash/entry/check/gpl_license.sh b/resources/libraries/bash/entry/check/gpl_license.sh
new file mode 100644
index 0000000000..a1c46a0e90
--- /dev/null
+++ b/resources/libraries/bash/entry/check/gpl_license.sh
@@ -0,0 +1,73 @@
+# Copyright (c) 2020 Cisco and/or its affiliates.
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at:
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+set -exuo pipefail
+
+# This file should be executed from tox, as the assumed working directory
+# is different from where this file is located.
+# This file does not have executable flag nor shebang,
+# to dissuade non-tox callers.
+
+# This script runs a few grep-based commands and fails
+# if it detects any file edited or added since HEAD~
+# containing a copyright notice in first 3 lines,
+# but not GPL-based license.
+# The offending files are stored to gpl_license.log (overwriting).
+
+# "set -eu" handles failures from the following two lines.
+BASH_CHECKS_DIR="$(dirname $(readlink -e "${BASH_SOURCE[0]}"))"
+BASH_FUNCTION_DIR="$(readlink -e "${BASH_CHECKS_DIR}/../../function")"
+source "${BASH_FUNCTION_DIR}/common.sh" || {
+    echo "Source failed." >&2
+    exit 1
+}
+
+IFS=$'\n'
+gpl_files=($(git diff --name-only HEAD~ | grep '^GPL/' || true))
+unset IFS
+logfile="gpl_license.log"
+truncate -s 0 "${logfile}" || die
+# A change can have thousands of files, supress console output in the cycle.
+set +x
+for fil in "${gpl_files[@]}"; do
+    if head -n 3 "${fil}" | fgrep -iq 'Copyright'; then
+        # Copyrighted file, processed below.
+        true
+    else
+        # Uncopyrighted files are allowed.
+        # TODO: Should we have list of extesions that require Copyright?
+        continue
+    fi
+    if fgrep -q 'GNU General Public License v2.0 or later' "${fil}"; then
+        # This can be GPL only or the OR license, we accept both.
+        # TODO: Should we require "Apache-2.0 OR GPL-2.0-or-later"?
+        continue
+    else
+        echo "GPL license not detected: ${fil}" >> "${logfile}"
+    fi
+done
+set -x
+lines="$(< "${logfile}" wc -l)"
+if [ "${lines}" != "0" ]; then
+    # TODO: Decide which text goes to stdout and which to stderr.
+    warn "Wrong licensed files in GPL directory detected: ${lines}"
+    # TODO: Disable when output size does more harm than good.
+    pwd
+    cat "${logfile}" >&2
+    warn
+    warn "GPL license checker: FAIL"
+    exit 1
+fi
+
+warn
+warn "GPL license checker: PASS"
diff --git a/tox.ini b/tox.ini
index b19d07e978..4eff6ac124 100644
--- a/tox.ini
+++ b/tox.ini
@@ -26,8 +26,8 @@
 
 [tox]
 # Fast and brief checkers to front, slow or verbose checkers to back.
-envlist = tc_naming, tc_coverage, copyright_year, new_line_length, line_length,
-    autogen, pylint, doc_verify
+envlist = tc_naming, tc_coverage, copyright_year, gpl_license, new_line_length,
+    line_length, autogen, pylint, doc_verify
 
 # The following is needed as tox requires setup.py by default.
 skipsdist = true
@@ -53,6 +53,11 @@ commands = bash {[tox]checker_dir}/copyright_year.sh
 whitelist_externals = /bin/bash
 commands = bash -c "bash {[tox]checker_dir}/doc_verify.sh || true"
 
+[testenv:gpl_license]
+whitelist_externals = /bin/bash
+setenv = PYTHONPATH = {toxinidir}
+commands = bash {[tox]checker_dir}/gpl_license.sh
+
 [testenv:line_length]
 whitelist_externals = /bin/bash
 # Fix all transgressions and remove the " || true" workaround.