cliutil: Better implementation of is_main_script.

The old one could return True if you called accrual.main()
directly from one-off test scripts.

conservancy_beancount/cliutil.py

@@ -28,6 +28,8 @@ import sys
 import traceback
 import types
 
+from pathlib import Path
+
 from typing import (
     Any,
     Iterable,
@@ -134,10 +136,14 @@ def add_version_argument(parser: argparse.ArgumentParser) -> argparse.Action:
         help="Show program version and license information",
     )
 
-def is_main_script() -> bool:
+def is_main_script(prog_name: str) -> bool:
     """Return true if the caller is the "main" program."""
-    stack = inspect.stack(context=False)
-    return len(stack) <= 3 and stack[-1].function.startswith('<')
+    stack = iter(inspect.stack(context=False))
+    next(stack)  # Discard the frame for calling this function
+    caller_filename = next(stack).filename
+    return all(frame.filename == caller_filename
+               or Path(frame.filename).stem == prog_name
+               for frame in stack)
 
 def setup_logger(logger: Union[str, logging.Logger]='',
                  loglevel: int=logging.INFO,

conservancy_beancount/reports/accrual.py

@@ -391,7 +391,7 @@ def main(arglist: Optional[Sequence[str]]=None,
          stderr: TextIO=sys.stderr,
          config: Optional[configmod.Config]=None,
 ) -> int:
-    if cliutil.is_main_script():
+    if cliutil.is_main_script(PROGNAME):
         global logger
         logger = logging.getLogger(PROGNAME)
         sys.excepthook = cliutil.ExceptHook(logger)

tests/test_cliutil.py

@@ -27,6 +27,11 @@ import pytest
 
 from conservancy_beancount import cliutil
 
+class AlwaysEqual:
+    def __eq__(self, other):
+        return True
+
+
 class MockTraceback:
     def __init__(self, stack=None, index=0):
         if stack is None:
@@ -91,8 +96,12 @@ def test_excepthook_traceback(caplog):
     assert caplog.records
     assert caplog.records[-1].message == ''.join(traceback.format_exception(*args))
 
-def test_is_main_script():
-    assert not cliutil.is_main_script()
+@pytest.mark.parametrize('prog_name,expected', [
+    ('', False),
+    (AlwaysEqual(), True),
+])
+def test_is_main_script(prog_name, expected):
+    assert cliutil.is_main_script(prog_name) == expected
 
 @pytest.mark.parametrize('arg,expected', [
     ('debug', logging.DEBUG),