Improve the error message when a configuration override contains an invalid value (#528).

NEWS

@@ -1,4 +1,5 @@
 1.6.1.dev0
+ * #528: Improve the error message when a configuration override contains an invalid value.
  * #532: When a configuration include is a relative path, load it from either the current working
    directory or from the directory containing the file doing the including. (Previously, only the
    working directory was used.)

borgmatic/config/override.py

@@ -52,16 +52,20 @@ def parse_overrides(raw_overrides):
     if not raw_overrides:
         return ()
 
+    parsed_overrides = []
+
+    for raw_override in raw_overrides:
         try:
-        return tuple(
-            (tuple(raw_keys.split('.')), convert_value_type(value))
-            for raw_override in raw_overrides
-            for raw_keys, value in (raw_override.split('=', 1),)
-        )
+            raw_keys, value = raw_override.split('=', 1)
+            parsed_overrides.append((tuple(raw_keys.split('.')), convert_value_type(value),))
         except ValueError:
-        raise ValueError('Invalid override. Make sure you use the form: SECTION.OPTION=VALUE')
+            raise ValueError(
+                f"Invalid override '{raw_override}'. Make sure you use the form: SECTION.OPTION=VALUE"
+            )
         except ruamel.yaml.error.YAMLError as error:
-        raise ValueError(f'Invalid override value: {error}')
+            raise ValueError(f"Invalid override '{raw_override}': {error.problem}")
+
+    return tuple(parsed_overrides)
 
 
 def apply_overrides(config, raw_overrides):

docs/how-to/make-per-application-backups.md

@@ -176,7 +176,14 @@ borgmatic create --override location.repositories=[test1.borg,test2.borg]
 Or even a single list element:
 
 ```bash
-borgmatic create --override location.repositories=[/root/test1.borg]
+borgmatic create --override location.repositories=[/root/test.borg]
+```
+
+If your override value contains special YAML characters like colons, then
+you'll need quotes for it to parse correctly:
+
+```bash
+borgmatic create --override location.repositories="['user@server:test.borg']"
 ```
 
 There is not currently a way to override a single element of a list without