Test suite: Fix small numbers of Python tests being run in incorrect environment

Also fix env reporting. Fixes #10478

kitty_tests/__init__.py

@@ -4,3 +4,8 @@
 import os
 
 is_ci = os.environ.get('CI') == 'true'
+
+
+def in_isolated_test_env() -> bool:
+    """Whether HOME and the XDG dirs point at the throwaway directory created by env_for_python_tests()."""
+    return 'KT_ORIGINAL_HOME' in os.environ

kitty_tests/datatypes.py

@@ -41,9 +41,19 @@ from kitty.utils import (
     shlex_split_with_positions,
 )
 
+from . import in_isolated_test_env
 from .base import BaseTest, filled_cursor, filled_history_buf, filled_line_buf
 
 
+def rmtree_in_test_home(path):
+    # Guard against destroying the invoking user's data if the test suite is ever
+    # run without the isolated $HOME set up by env_for_python_tests()
+    if not in_isolated_test_env():
+        raise AssertionError(f'Refusing to delete {path} as the test suite is not running with an isolated HOME')
+    if os.path.exists(path):
+        shutil.rmtree(path)
+
+
 def create_lbuf(*lines):
     maxw = max(map(len, lines))
     ans = LineBuf(len(lines), maxw)
@@ -692,8 +702,7 @@ class TestDataTypes(BaseTest):
         saved = {x: os.environ.get(x) for x in 'KITTY_CONFIG_DIRECTORY XDG_CONFIG_DIRS XDG_CONFIG_HOME'.split()}
         try:
             dot_config = os.path.expanduser('~/.config')
-            if os.path.exists(dot_config):
-                shutil.rmtree(dot_config)
+            rmtree_in_test_home(dot_config)
             with tempfile.TemporaryDirectory() as tdir:
                 with open(tdir + '/macos-launch-services-cmdline', 'w') as f:
                     print('kitty --title from-file', file=f)
@@ -736,8 +745,7 @@ class TestDataTypes(BaseTest):
                         os.environ[k] = v
                     self.assertEqual(x[-1], get_config_dir(), str(x))
         finally:
-            if os.path.exists(dot_config):
-                shutil.rmtree(dot_config)
+            rmtree_in_test_home(dot_config)
             for k in saved:
                 os.environ.pop(k, None)
                 if saved[k] is not None:

kitty_tests/main.py

@@ -225,21 +225,29 @@ def env_vars(**kw: str) -> Iterator[None]:
                 os.environ[k] = v
 
 
-@contextmanager
-def env_for_python_tests(report_env: bool = False) -> Iterator[None]:
-    gohome = os.path.expanduser('~/go')
-    slangc = os.environ.get('SLANGC') or shutil.which('slangc') or 'slangc'
+def path_for_python_tests() -> str:
+    """The PATH used by tests: the built launcher dir followed by all entries not under the real home dir."""
     current_home = os.path.expanduser('~') + os.sep
     paths = os.environ.get('PATH', '/usr/local/sbin:/usr/local/bin:/usr/bin').split(os.pathsep)
     path = os.pathsep.join(x for x in paths if not x.startswith(current_home))
     launcher_dir = os.path.join(os.path.dirname(os.path.abspath(__file__)), 'kitty', 'launcher')
-    path = f'{launcher_dir}{os.pathsep}{path}'
-    if report_env:
-        print('Running under CI:', is_ci)
-        print('Using PATH in test environment:', path)
-        from kitty.fast_data_types import has_avx2, has_avx512, has_sse4_2
+    return f'{launcher_dir}{os.pathsep}{path}'
 
-        print(f'Intrinsics: {has_avx512=} {has_avx2=} {has_sse4_2=}')
+
+def report_test_env() -> None:
+    """Print details of the environment tests will run in. Called once in the master process as workers have their stdout captured."""
+    print('Running under CI:', is_ci)
+    print('Using PATH in test environment:', path_for_python_tests())
+    from kitty.fast_data_types import has_avx2, has_avx512, has_sse4_2
+
+    print(f'Intrinsics: {has_avx512=} {has_avx2=} {has_sse4_2=}')
+
+
+@contextmanager
+def env_for_python_tests() -> Iterator[None]:
+    gohome = os.path.expanduser('~/go')
+    slangc = os.environ.get('SLANGC') or shutil.which('slangc') or 'slangc'
+    path = path_for_python_tests()
     with (
         TemporaryDirectory() as tdir,
         env_vars(
@@ -759,8 +767,11 @@ def run_tests(report_env: bool = False) -> None:
     if args.name and not tests_list and not has_go:
         raise SystemExit('No test named %s found' % ' '.join(args.name))
 
-    # Start Python workers before modifying the main-process env; each worker
-    # calls env_for_python_tests independently for full HOME/XDG isolation.
+    if report_env:
+        report_test_env()
+
+    # Start Python workers; each worker calls env_for_python_tests independently
+    # for full HOME/XDG isolation, as does the serial path below.
     # On macOS fork()+threading is unsafe, so use subprocess workers there.
     use_parallel = len(tests_list) > PARALLEL_THRESHOLD
     worker_pids: list[int] = []
@@ -795,7 +806,15 @@ def run_tests(report_env: bool = False) -> None:
         if use_parallel:
             python_ok, go_ok = collect_worker_results(worker_pids, worker_procs, read_fds, len(tests_list), go_proc=go_proc)
         elif tests_list:
-            python_ok = run_cli(all_tests, args.verbosity)
+            # we need fonts installed in the user home directory as well, so initialize
+            # fontconfig before nuking $HOME and friends
+            from kitty.fonts.common import all_fonts_map
+
+            all_fonts_map(True)
+            # Tests must never run against the real $HOME, some of them delete
+            # files/directories in it. See run_test_worker() for the parallel equivalent.
+            with env_for_python_tests():
+                python_ok = run_cli(all_tests, args.verbosity)
             if go_proc is not None:
                 _, go_ok = collect_worker_results([], [], [], 0, go_proc=go_proc)
             else: