cli: have a hint if fietsboek.ini is not found

1 files changed, 35 insertions, 1 deletions

diff --git a/fietsboek/scripts/__init__.py b/fietsboek/scripts/__init__.py
index c7bbe98..b8a883a 100644
--- a/fietsboek/scripts/__init__.py
+++ b/fietsboek/scripts/__init__.py
@@ -1,5 +1,39 @@
 """Various command line scripts to interact with the fietsboek installation."""
+from typing import Any, Optional
+
 import click
+from click.core import ParameterSource
+
+
+class ConfigOption(click.Path):
+    """Special :class:`~click.Path` subclass to print a more helpful error
+    message.
+
+    This class recognizes if the config option is not given and prints a hint
+    if the file does not exist in this case.
+    """
+
+    def __init__(self):
+        super().__init__(exists=True, dir_okay=False)
+
+    def convert(
+        self,
+        value: Any,
+        param: Optional[click.Parameter],
+        ctx: Optional[click.Context],
+    ) -> Any:
+        try:
+            return super().convert(value, param, ctx)
+        except click.BadParameter as exc:
+            if param is not None and param.name is not None and ctx is not None:
+                source = ctx.get_parameter_source(param.name)
+                if source == ParameterSource.DEFAULT:
+                    exc.message += (
+                        f"\n\nHint: {value!r} is the default, "
+                        "try specifying a configuration file explicitely."
+                    )
+            raise exc
+
 
 # We keep this as a separate option that is added to each subcommand as Click
 # (unlike argparse) cannot handle "--help" without the required arguments of
@@ -10,7 +44,7 @@ import click
 config_option = click.option(
     "-c",
     "--config",
-    type=click.Path(exists=True, dir_okay=False),
+    type=ConfigOption(),
     required=True,
     default="fietsboek.ini",
     help="Path to the Fietsboek configuration file",