[v5,15/44] tests/functional: enable pre-emptive caching of assets

diff --git a/tests/Makefile.include b/tests/Makefile.include
index 66c8cc3123..010369bd3a 100644
--- a/tests/Makefile.include
+++ b/tests/Makefile.include
@@ -161,7 +161,8 @@  $(FUNCTIONAL_TARGETS):
 
 .PHONY: check-functional
 check-functional:
-	@$(MAKE) SPEED=thorough check-func check-func-quick
+	@$(NINJA) precache-functional
+	@QEMU_TEST_NO_DOWNLOAD=1 $(MAKE) SPEED=thorough check-func check-func-quick
 
 # Consolidated targets
 
diff --git a/tests/functional/meson.build b/tests/functional/meson.build
index f1f344f860..df79775df3 100644
--- a/tests/functional/meson.build
+++ b/tests/functional/meson.build
@@ -39,6 +39,7 @@  tests_x86_64_system_quick = [
 tests_x86_64_system_thorough = [
 ]
 
+precache_all = []
 foreach speed : ['quick', 'thorough']
   foreach dir : target_dirs
 
@@ -78,11 +79,35 @@  foreach speed : ['quick', 'thorough']
                                meson.current_source_dir())
 
     foreach test : target_tests
-      test('func-@0@/@1@'.format(target_base, test),
+      testname = '@0@-@1@'.format(target_base, test)
+      testfile = 'test_' + test + '.py'
+      testpath = meson.current_source_dir() / testfile
+      teststamp = testname + '.tstamp'
+      test_precache_env = environment()
+      test_precache_env.set('QEMU_TEST_PRECACHE', meson.current_build_dir() / teststamp)
+      test_precache_env.set('PYTHONPATH', meson.project_source_root() / 'python:' +
+                                          meson.current_source_dir())
+      precache = custom_target('func-precache-' + testname,
+                               output: teststamp,
+                               command: [python, testpath],
+                               depend_files: files(testpath),
+                               build_by_default: false,
+                               env: test_precache_env)
+      precache_all += precache
+
+      # Ideally we would add 'precache' to 'depends' here, such that
+      # 'build_by_default: false' lets the pre-caching automatically
+      # run immediately before the test runs. In practice this is
+      # broken in meson, with it running the pre-caching in the normal
+      # compile phase https://github.com/mesonbuild/meson/issues/2518
+      # If the above bug ever gets fixed, when QEMU changes the min
+      # meson version, add the 'depends' and remove the custom
+      # 'run_target' logic below & in Makefile.include
+      test('func-' + testname,
            python,
            depends: [test_deps, test_emulator, emulator_modules],
            env: test_env,
-           args: [meson.current_source_dir() / 'test_' + test + '.py'],
+           args: [testpath],
            protocol: 'tap',
            timeout: test_timeouts.get(test, 60),
            priority: test_timeouts.get(test, 60),
@@ -90,3 +115,7 @@  foreach speed : ['quick', 'thorough']
     endforeach
   endforeach
 endforeach
+
+run_target('precache-functional',
+           depends: precache_all,
+           command: ['true'])
diff --git a/tests/functional/qemu_test/asset.py b/tests/functional/qemu_test/asset.py
index c0e675d847..b329ab7dbe 100644
--- a/tests/functional/qemu_test/asset.py
+++ b/tests/functional/qemu_test/asset.py
@@ -9,6 +9,8 @@ 
 import logging
 import os
 import subprocess
+import sys
+import unittest
 import urllib.request
 from pathlib import Path
 from shutil import copyfileobj
@@ -62,6 +64,9 @@  def fetch(self):
                            self.cache_file, self.url)
             return str(self.cache_file)
 
+        if os.environ.get("QEMU_TEST_NO_DOWNLOAD", False):
+            raise Exception("Asset cache is invalid and downloads disabled")
+
         self.log.info("Downloading %s to %s...", self.url, self.cache_file)
         tmp_cache_file = self.cache_file.with_suffix(".download")
 
@@ -95,3 +100,32 @@  def fetch(self):
 
         self.log.info("Cached %s at %s" % (self.url, self.cache_file))
         return str(self.cache_file)
+
+    def precache_test(test):
+        log = logging.getLogger('qemu-test')
+        log.setLevel(logging.DEBUG)
+        handler = logging.StreamHandler(sys.stdout)
+        handler.setLevel(logging.DEBUG)
+        formatter = logging.Formatter(
+            '%(asctime)s - %(name)s - %(levelname)s - %(message)s')
+        handler.setFormatter(formatter)
+        log.addHandler(handler)
+        for name, asset in vars(test.__class__).items():
+            if name.startswith("ASSET_") and type(asset) == Asset:
+                log.info("Attempting to cache '%s'" % asset)
+                asset.fetch()
+        log.removeHandler(handler)
+
+    def precache_suite(suite):
+        for test in suite:
+            if isinstance(test, unittest.TestSuite):
+                Asset.precache_suite(test)
+            elif isinstance(test, unittest.TestCase):
+                Asset.precache_test(test)
+
+    def precache_suites(path, cacheTstamp):
+        loader = unittest.loader.defaultTestLoader
+        tests = loader.loadTestsFromNames([path], None)
+
+        with open(cacheTstamp, "w") as fh:
+            Asset.precache_suite(tests)
diff --git a/tests/functional/qemu_test/testcase.py b/tests/functional/qemu_test/testcase.py
index b2dd863c6e..18314be9d1 100644
--- a/tests/functional/qemu_test/testcase.py
+++ b/tests/functional/qemu_test/testcase.py
@@ -21,6 +21,7 @@ 
 from qemu.machine import QEMUMachine
 from qemu.utils import kvm_available, tcg_available
 
+from .asset import Asset
 from .cmd import run_cmd
 from .config import BUILD_DIR
 
@@ -58,6 +59,12 @@  def tearDown(self):
 
     def main():
         path = os.path.basename(sys.argv[0])[:-3]
+
+        cache = os.environ.get("QEMU_TEST_PRECACHE", None)
+        if cache is not None:
+            Asset.precache_suites(path, cache)
+            return
+
         tr = pycotap.TAPTestRunner(message_log = pycotap.LogMode.LogToError,
                                    test_output_log = pycotap.LogMode.LogToError)
         unittest.main(module = None, testRunner = tr, argv=["__dummy__", path])