books: Add Loader.load_none() method.

conservancy_beancount/books.py

@@ -30,6 +30,8 @@ from typing import (
     Union,
 )
 from .beancount_types import (
+    Error,
+    Errors,
     LoadResult,
 )
 
@@ -171,3 +173,22 @@ class Loader:
         fy_range = self.fiscal_year.range(from_fy, to_fy)
         fy_paths = self._iter_fy_books(fy_range)
         return self._load_paths(fy_paths)
+
+    @classmethod
+    def load_none(cls, config_path: Optional[PathLike]=None, lineno: int=0) -> LoadResult:
+        """Load no books and generate an error about it
+
+        This is a convenience method for reporting tools that already handle
+        general Beancount errors. If a configuration problem prevents them from
+        loading the books, they can call this method in place of a regular
+        loading method, and then continue on their normal code path.
+
+        The path and line number given in the arguments will be named as the
+        source of the error.
+        """
+        source = {
+            'filename': str(config_path or 'conservancy_beancount.ini'),
+            'lineno': lineno,
+        }
+        errors: Errors = [Error(source, "no books to load in configuration", None)]
+        return [], errors, {}

conservancy_beancount/reports/accrual.py

@@ -113,6 +113,7 @@ import rt
 from beancount.parser import printer as bc_printer
 
 from . import core
+from .. import books
 from .. import cliutil
 from .. import config as configmod
 from .. import data
@@ -693,12 +694,7 @@ def main(arglist: Optional[Sequence[str]]=None,
 
     books_loader = config.books_loader()
     if books_loader is None:
-        entries: Entries = []
-        source = {
-            'filename': str(config.config_file_path()),
-            'lineno': 1,
-        }
-        load_errors: Errors = [Error(source, "no books to load in configuration", None)]
+        entries, load_errors, _ = books.Loader.load_none(config.config_file_path())
     elif args.report_type is ReportType.AGING:
         entries, load_errors, _ = books_loader.load_all()
     else:

tests/test_books_loader.py

@@ -107,3 +107,17 @@ def test_load_all_from_date(conservancy_loader, from_date):
     actual_years = txn_years(entries)
     assert actual_years.issuperset(range(from_year, 2021))
     assert min(actual_years) == from_year
+
+def test_load_none_full_args():
+    entries, errors, options_map = books.Loader.load_none('test.cfg', 42)
+    assert not entries
+    assert errors
+    assert all(err.source['filename'] == 'test.cfg' for err in errors)
+    assert all(err.source['lineno'] == 42 for err in errors)
+
+def test_load_none_no_args():
+    entries, errors, options_map = books.Loader.load_none()
+    assert not entries
+    assert errors
+    assert all(isinstance(err.source['filename'], str) for err in errors)
+    assert all(isinstance(err.source['lineno'], int) for err in errors)

tests/test_reports_accrual.py

@@ -737,7 +737,7 @@ def test_main_aging_report(tmp_path, arglist):
 
 def test_main_no_books():
     check_main_fails([], testutil.TestConfig(), 1 | 8, [
-        r':1: +no books to load in configuration\b',
+        r':[01]: +no books to load in configuration\b',
     ])
 
 @pytest.mark.parametrize('arglist', [