[PATCH v2 4/5] qemu-iotests: let "check" spawn an arbitrary test command

[Paolo Bonzini <pbonzini@redhat.com>]

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>
---
 tests/qemu-iotests/check         | 15 ++++++++++++++-
 tests/qemu-iotests/testenv.py    |  3 ++-
 tests/qemu-iotests/testrunner.py |  1 -
 3 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/tests/qemu-iotests/check b/tests/qemu-iotests/check
index d1c87ceaf1..478d74e509 100755
--- a/tests/qemu-iotests/check
+++ b/tests/qemu-iotests/check
@@ -19,6 +19,7 @@
 import os
 import sys
 import argparse
+import shutil
 from findtests import TestFinder
 from testenv import TestEnv
 from testrunner import TestRunner
@@ -101,7 +102,7 @@ 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
 
@@ -114,6 +115,18 @@ 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_path = shutil.which(cmd[0])
+        if exec_path is None:
+            sys.exit('command not found: ' + cmd[0])
+        cmd[0] = exec_path
+        full_env = env.prepare_subprocess(cmd)
+        os.execve(cmd[0], cmd, full_env)
+
     testfinder = TestFinder(test_dir=env.source_iotests)
 
     groups = args.groups.split(',') if args.groups else None
diff --git a/tests/qemu-iotests/testenv.py b/tests/qemu-iotests/testenv.py
index 341a4af4e9..6767eeeb25 100644
--- a/tests/qemu-iotests/testenv.py
+++ b/tests/qemu-iotests/testenv.py
@@ -283,7 +283,8 @@ 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())
 
diff --git a/tests/qemu-iotests/testrunner.py b/tests/qemu-iotests/testrunner.py
index 519924dc81..2f56ac545d 100644
--- a/tests/qemu-iotests/testrunner.py
+++ b/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
 
-- 
2.30.1