qemu-iotests: let "check" spawn an arbitrary test command

Right now there is no easy way for "check" to print a reproducer command.
Because such a reproducer command line would be huge, we can instead teach
check to start a command of our choice.  This can be for example a Python
unit test with arguments to only run a specific subtest.

Move the trailing empty line to print_env(), since it always looks better
and one caller was not adding it.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Tested-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Message-Id: <20210323181928.311862-5-pbonzini@redhat.com>
Message-Id: <20210503110110.476887-5-pbonzini@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>

tests/qemu-iotests/check

@@ -19,6 +19,9 @@
 import os
 import sys
 import argparse
+import shutil
+from pathlib import Path
+
 from findtests import TestFinder
 from testenv import TestEnv
 from testrunner import TestRunner
@@ -100,7 +103,7 @@ def make_argparser() -> argparse.ArgumentParser:
                        'rerun failed ./check command, starting from the '
                        'middle of the process.')
     g_sel.add_argument('tests', metavar='TEST_FILES', nargs='*',
-                       help='tests to run')
+                       help='tests to run, or "--" followed by a command')
 
     return p
 
@@ -113,6 +116,20 @@ if __name__ == '__main__':
                   imgopts=args.imgopts, misalign=args.misalign,
                   debug=args.debug, valgrind=args.valgrind)
 
+    if len(sys.argv) > 1 and sys.argv[-len(args.tests)-1] == '--':
+        if not args.tests:
+            sys.exit("missing command after '--'")
+        cmd = args.tests
+        env.print_env()
+        exec_pathstr = shutil.which(cmd[0])
+        if exec_pathstr is None:
+            sys.exit('command not found: ' + cmd[0])
+        exec_path = Path(exec_pathstr).resolve()
+        cmd[0] = str(exec_path)
+        full_env = env.prepare_subprocess(cmd)
+        os.chdir(exec_path.parent)
+        os.execve(cmd[0], cmd, full_env)
+
     testfinder = TestFinder(test_dir=env.source_iotests)
 
     groups = args.groups.split(',') if args.groups else None

tests/qemu-iotests/testenv.py

@@ -284,7 +284,8 @@ def print_env(self) -> None:
 PLATFORM      -- {platform}
 TEST_DIR      -- {TEST_DIR}
 SOCK_DIR      -- {SOCK_DIR}
-SOCKET_SCM_HELPER -- {SOCKET_SCM_HELPER}"""
+SOCKET_SCM_HELPER -- {SOCKET_SCM_HELPER}
+"""
 
         args = collections.defaultdict(str, self.get_env())
 

tests/qemu-iotests/testrunner.py

@@ -316,7 +316,6 @@ def run_tests(self, tests: List[str]) -> bool:
 
         if not self.makecheck:
             self.env.print_env()
-            print()
 
         test_field_width = max(len(os.path.basename(t)) for t in tests) + 2