add support for configuration file (WIP)

Current status:

- break --verbose

- override doesn't work properly, e.g., --case-sensitive in config should be
  overridable with --ignore-case on the CLI, but is not (because we do not
  distinguish between the origin and, when given both on the CLI,
  --case-sensitive wins)

Related #8

pyproject.toml

@@ -28,6 +28,7 @@ classifiers = [
 dependencies = [
     "beancount>=2.3.5",
     "click>=8.1",
+    "pyxdg>=0.28",
 ]
 # version = "0.1.0"
 dynamic = [ "version" ]

src/beangrep/__init__.py

@@ -4,4 +4,4 @@
 __license__ = "GPL-2.0-or-later"
 
 from .beangrep import *  # noqa:F401,F403
-from .cli import cli  # noqa:F401
+from .cli import cli, _cli  # noqa:F401

src/beangrep/cli.py

@@ -6,11 +6,13 @@
 import logging
 import shutil
 import sys
+from pathlib import Path
 from tempfile import NamedTemporaryFile
 
 import beancount.loader  # type: ignore
 import click
 from beancount.parser import printer  # type: ignore
+from xdg.BaseDirectory import xdg_config_home
 
 from .beangrep import (
     INTERNALS_META,
@@ -22,6 +24,38 @@
     filter_entries,
 )
 
+CONFFILE_PATH = Path(xdg_config_home) / "beangreprc"
+
+
+def load_conffile(path: Path) -> list[str]:
+    """Load a configuration file and return its content, as a list of strings (usually
+    CLI flags starting with "-").
+
+    """
+    logging.debug("Reading configuration flags from file: %s ...", path)
+    with open(path) as f:
+        flags = []
+        line_no = 0
+        for line in f.readlines():
+            line_no += 1
+            line = line.strip()
+            if not line:  # empty line, skip
+                continue
+            elif line.startswith("#"):  # comment, skip
+                continue
+            elif line.startswith("-"):  # flag, return it
+                flags.append(line)
+            else:  # invalid line, warn and skip it
+                logging.warning(
+                    'Line %d in configuration file %s is invalid (content: "%s"), '
+                    "ignoring it.",
+                    line_no,
+                    path,
+                    line,
+                )
+
+    return flags
+
 
 @click.command(
     help="""Search for entries matching given criteria in Beancount journals. Pretty
@@ -234,7 +268,7 @@
 )
 @click.version_option(None, "--version", "-V")
 @click.pass_context
-def cli(
+def _cli(
     ctx,
     args,
     accounts,
@@ -256,6 +290,7 @@ def cli(
     invert_match,
     verbose,
 ):
+    """CLI entry point, *after* processing options from configuration file."""
     match verbose:
         case 0:
             log_level = logging.WARNING
@@ -350,5 +385,16 @@ def cli(
     ctx.exit(exit_status)
 
 
+def cli(*args, **kwargs):
+    """CLI entry point, *before* processing options from configuration file."""
+    if CONFFILE_PATH.is_file():
+        conf_flags = load_conffile(CONFFILE_PATH)
+        logging.info("Using configuration flags: %s", conf_flags)
+        if conf_flags:  # patch sys.argv with CLI flags from configuration file
+            sys.argv = [sys.argv[0]] + conf_flags + sys.argv[1:]
+
+    _cli(*args, **kwargs)
+
+
 if __name__ == "__main__":
     cli()

tests/test_cli.py

@@ -6,7 +6,7 @@
 from click.testing import CliRunner
 from test_beangrep import SAMPLE_LEDGER, SAMPLE_LEDGER_SMALL
 
-from beangrep import cli
+from beangrep import _cli as cli
 
 
 def test_basic():