Script to install minimum versions of the requirements

Wherever we have a requirement on foo>=N, install foo==N. This is for
testing, to ensure that we don't accidentally depend on features that are
not present in the minimum version we declare support for.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>

scripts/min_requirements.py

@@ -0,0 +1,106 @@
+#!/usr/bin/env python3
+"""Install all the required Python packages, with the minimum Python version.
+"""
+
+# Copyright The Mbed TLS Contributors
+# SPDX-License-Identifier: Apache-2.0
+#
+# 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.
+
+import argparse
+import os
+import re
+import sys
+import typing
+
+from typing import List
+from mbedtls_dev import typing_util
+
+def pylint_doesn_t_notice_that_certain_types_are_used_in_annotations(
+        _list: List[typing.Any],
+) -> None:
+    pass
+
+
+class Requirements:
+    """Collect and massage Python requirements."""
+
+    def __init__(self) -> None:
+        self.requirements = [] #type: List[str]
+
+    def adjust_requirement(self, req: str) -> str:
+        """Adjust a requirement to the minimum specified version."""
+        # allow inheritance #pylint: disable=no-self-use
+        # If a requirement specifies a minimum version, impose that version.
+        req = re.sub(r'>=|~=', r'==', req)
+        return req
+
+    def add_file(self, filename: str) -> None:
+        """Add requirements from the specified file.
+
+        This method supports a subset of pip's requirement file syntax:
+        * One requirement specifier per line, which is passed to
+          `adjust_requirement`.
+        * Comments (``#`` at the beginning of the line or after whitespace).
+        * ``-r FILENAME`` to include another file.
+        """
+        for line in open(filename):
+            line = line.strip()
+            line = re.sub(r'(\A|\s+)#.*', r'', line)
+            if not line:
+                continue
+            m = re.match(r'-r\s+', line)
+            if m:
+                nested_file = os.path.join(os.path.dirname(filename),
+                                           line[m.end(0):])
+                self.add_file(nested_file)
+                continue
+            self.requirements.append(self.adjust_requirement(line))
+
+    def write(self, out: typing_util.Writable) -> None:
+        """List the gathered requirements."""
+        for req in self.requirements:
+            out.write(req + '\n')
+
+    def install(self) -> None:
+        """Call pip to install the requirements."""
+        if not self.requirements:
+            return
+        ret = os.spawnl(os.P_WAIT, sys.executable, 'python', '-m', 'pip',
+                        'install', *self.requirements)
+        if ret != 0:
+            sys.exit(ret)
+
+
+def main() -> None:
+    """Command line entry point."""
+    parser = argparse.ArgumentParser(description=__doc__)
+    parser.add_argument('--no-act', '-n',
+                        action='store_true',
+                        help="Don't act, just print what will be done")
+    parser.add_argument('files', nargs='*', metavar='FILE',
+                        help="Requirement files"
+                             "(default: requirements.txt in the script's directory)")
+    options = parser.parse_args()
+    if not options.files:
+        options.files = [os.path.join(os.path.dirname(__file__),
+                                      'ci.requirements.txt')]
+    reqs = Requirements()
+    for filename in options.files:
+        reqs.add_file(filename)
+    reqs.write(sys.stdout)
+    if not options.no_act:
+        reqs.install()
+
+if __name__ == '__main__':
+    main()