[v5,08/12] iotests: add findtests.py

diff --git a/docs/devel/testing.rst b/docs/devel/testing.rst
index 0c3e79d31c..b2a4f6ce42 100644
--- a/docs/devel/testing.rst
+++ b/docs/devel/testing.rst
@@ -111,7 +111,7 @@  check-block
 -----------
 
 ``make check-block`` runs a subset of the block layer iotests (the tests that
-are in the "auto" group in ``tests/qemu-iotests/group``).
+are in the "auto" group).
 See the "QEMU iotests" section below for more information.
 
 GCC gcov support
@@ -224,6 +224,54 @@  another application on the host may have locked the file, possibly leading to a
 test failure.  If using such devices are explicitly desired, consider adding
 ``locking=off`` option to disable image locking.
 
+Test case groups
+----------------
+
+Test may belong to some groups, you may define it in the comment inside the
+test. By convention, test groups are listed in the second line of the test
+file, after "#!/..." line, like this:
+
+.. code::
+
+  #!/usr/bin/env python3
+  # group: auto quick
+  #
+  ...
+
+Additional way of defining groups is creating tests/qemu-iotests/group.local
+file. This should be used only for downstream (this file should never appear
+in upstream). This file may be used for defining some downstream test groups
+or for temporary disable tests, like this:
+
+.. code::
+
+  # groups for some company downstream process
+  #
+  # ci - tests to run on build
+  # down - our downstream tests, not for upstream
+  #
+  # Format of each line is:
+  # TEST_NAME TEST_GROUP [TEST_GROUP ]...
+
+  013 ci
+  210 disabled
+  215 disabled
+  our-ugly-workaround-test down ci
+
+The (not exhaustive) list of groups:
+
+- quick : Tests in this group should finish within some few seconds.
+
+- auto : Tests in this group are used during "make check" and should be
+  runnable in any case. That means they should run with every QEMU binary
+  (also non-x86), with every QEMU configuration (i.e. must not fail if
+  an optional feature is not compiled in - but reporting a "skip" is ok),
+  work at least with the qcow2 file format, work with all kind of host
+  filesystems and users (e.g. "nobody" or "root") and must not take too
+  much memory and disk space (since CI pipelines tend to fail otherwise).
+
+- disabled : Tests in this group are disabled and ignored by check.
+
 .. _docker-ref:
 
 Docker based tests
diff --git a/tests/qemu-iotests/findtests.py b/tests/qemu-iotests/findtests.py
new file mode 100755
index 0000000000..b053db48e8
--- /dev/null
+++ b/tests/qemu-iotests/findtests.py
@@ -0,0 +1,229 @@ 
+#!/usr/bin/env python3
+#
+# Parse command line options to define set of tests to run.
+#
+# Copyright (c) 2020 Virtuozzo International GmbH
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+
+import os
+import sys
+import glob
+import argparse
+import re
+from collections import defaultdict
+from contextlib import contextmanager
+from typing import Optional, List, Tuple, Iterator, Set
+
+
+@contextmanager
+def chdir(path: Optional[str] = None) -> Iterator:
+    if path is None:
+        yield
+        return
+
+    saved_dir = os.getcwd()
+    os.chdir(path)
+    try:
+        yield
+    finally:
+        os.chdir(saved_dir)
+
+
+class TestFinder:
+    _argparser = None
+    @classmethod
+    def get_argparser(cls) -> argparse.ArgumentParser:
+        if cls._argparser is not None:
+            return cls._argparser
+
+        p = argparse.ArgumentParser(description="= test selecting options =",
+                                    add_help=False, usage=argparse.SUPPRESS)
+
+        p.add_argument('-g', '--groups', metavar='group1,...',
+                       help='include tests from these groups')
+        p.add_argument('-x', '--exclude-groups', metavar='group1,...',
+                       help='exclude tests from these groups')
+        p.add_argument('--start-from', metavar='TEST',
+                       help='Start from specified test: make sorted sequence '
+                       'of tests as usual and then drop tests from the first '
+                       'one to TEST (not inclusive). This may be used to '
+                       'rerun failed ./check command, starting from the '
+                       'middle of the process.')
+        p.add_argument('tests', metavar='TEST_FILES', nargs='*',
+                       help='tests to run')
+
+        cls._argparser = p
+        return p
+
+    def __init__(self, test_dir: Optional[str] = None) -> None:
+        self.groups = defaultdict(set)
+
+        with chdir(test_dir):
+            self.all_tests = glob.glob('[0-9][0-9][0-9]')
+            self.all_tests += [f for f in glob.iglob('tests/*')
+                               if not f.endswith('.out') and
+                               os.path.isfile(f + '.out')]
+
+            for t in self.all_tests:
+                with open(t) as f:
+                    for line in f:
+                        if line.startswith('# group: '):
+                            for g in line.split()[2:]:
+                                self.groups[g].add(t)
+
+    def add_group_file(self, fname: str):
+        with open(fname) as f:
+            for line in f:
+                line = line.strip()
+
+                if (not line) or line[0] == '#':
+                    continue
+
+                words = line.split()
+                test_file = words[0]
+                groups = words[1:]
+
+                if test_file not in self.all_tests:
+                    print(f'Warning: {fname}: "{test_file}" test is not found.'
+                          ' Skip.')
+                    continue
+
+                for g in groups:
+                    self.groups[g].add(test_file)
+
+    def parse_test_name(self, name: str) -> str:
+        if '/' in name:
+            raise ValueError('Paths are unsupported for test selecting, '
+                             f'requiring "{name}" is wrong')
+
+        if re.fullmatch(r'\d+', name):
+            # Numbered tests are old naming convetion. We should convert them
+            # to three-digit-length, like 1 --> 001.
+            name = f'{int(name):03}'
+        else:
+            # Named tests all should be in tests/ subdirectory
+            name = os.path.join('tests', name)
+
+        if name not in self.all_tests:
+            raise ValueError(f'Test "{name}" is not found')
+
+        return name
+
+    def find_tests(self, groups: Optional[List[str]] = None,
+                   exclude_groups: Optional[List[str]] = None,
+                   tests: Optional[List[str]] = None,
+                   start_from: Optional[str] = None) -> List[str]:
+        """Find tests
+
+        Algorithm:
+
+        1. a. if some @groups specified
+             a.1 Take all tests from @groups
+             a.2 Drop tests, which are in at least one of @exclude_groups or in
+                 'disabled' group (if 'disabled' is not listed in @groups)
+             a.3 Add tests from @tests (don't exclude anything from them)
+
+           b. else, if some @tests specified:
+             b.1 exclude_groups must be not specified, so just take @tests
+
+           c. else (only @exclude_groups list is non-empty):
+             c.1 Take all tests
+             c.2 Drop tests, which are in at least one of @exclude_groups or in
+                 'disabled' group
+
+        2. sort
+
+        3. If start_from specified, drop tests from first one to @start_from
+           (not inclusive)
+        """
+        if groups is None:
+            groups = []
+        if exclude_groups is None:
+            exclude_groups = []
+        if tests is None:
+            tests = []
+
+        res: Set[str] = set()
+        if groups:
+            # Some groups specified. exclude_groups supported, additionally
+            # selecting some individual tests supported as well.
+            res.update(*(self.groups[g] for g in groups))
+        elif tests:
+            # Some individual tests specified, but no groups. In this case
+            # we don't support exclude_groups.
+            if exclude_groups:
+                raise ValueError("Can't exclude from individually specified "
+                                 "tests.")
+        else:
+            # No tests no groups: start from all tests, exclude_groups
+            # supported.
+            res.update(self.all_tests)
+
+        if 'disabled' not in groups and 'disabled' not in exclude_groups:
+            exclude_groups.append('disabled')
+
+        res = res.difference(*(self.groups[g] for g in exclude_groups))
+
+        # We want to add @tests. But for compatibility with old test names,
+        # we should convert any number < 100 to number padded by
+        # leading zeroes, like 1 -> 001 and 23 -> 023.
+        for t in tests:
+            res.add(self.parse_test_name(t))
+
+        sequence = sorted(res)
+
+        if start_from is not None:
+            del sequence[:sequence.index(self.parse_test_name(start_from))]
+
+        return sequence
+
+    def find_tests_argv(self, argv: List[str]) -> Tuple[List[str], List[str]]:
+        """Returns tuple of tests list and remaining arguments list"""
+        args, remaining = self.get_argparser().parse_known_args(argv)
+
+        if args.groups is not None:
+            args.groups = args.groups.split(',')
+
+        if args.exclude_groups is not None:
+            args.exclude_groups = args.exclude_groups.split(',')
+
+        return self.find_tests(**vars(args)), remaining
+
+
+def find_tests(argv, test_dir: Optional[str] = None) -> Tuple[List[str],
+                                                              List[str]]:
+    """Returns tuple of tests list and remaining arguments list"""
+    tf = TestFinder(test_dir)
+
+    if test_dir is None:
+        group_local = 'group.local'
+    else:
+        group_local = os.path.join(test_dir, 'group.local')
+    if os.path.isfile(group_local):
+        tf.add_group_file(group_local)
+
+    return tf.find_tests_argv(argv)
+
+
+if __name__ == '__main__':
+    if len(sys.argv) == 2 and sys.argv[1] in ['-h', '--help']:
+        TestFinder.get_argparser().print_help()
+        exit()
+
+    tests, remaining_argv = find_tests(sys.argv[1:])
+    print('\n'.join(tests))
+    if remaining_argv:
+        print('\nUnhandled options: ', remaining_argv)