implement error accumulation

This way, multiple ConfigurationErrors are caught during setup, accumulated and printed all at once

configurations/base.py

@@ -4,6 +4,7 @@ import re
 from django.conf import global_settings
 from django.core.exceptions import ImproperlyConfigured
 
+from .errors import ConfigurationError, SetupError
 from .utils import uppercase_attributes
 from .values import Value, setup_value
 
@@ -142,6 +143,13 @@ class Configuration(metaclass=ConfigurationBase):
 
     @classmethod
     def setup(cls):
+        exceptions = []
         for name, value in uppercase_attributes(cls).items():
             if isinstance(value, Value):
-                setup_value(cls, name, value)
+                try:
+                    setup_value(cls, name, value)
+                except ConfigurationError as err:
+                    exceptions.append(err)
+
+        if len(exceptions) > 0:
+            raise SetupError(f"Couldn't setup values of configuration {cls.__name__}", exceptions)

configurations/errors.py

@@ -13,6 +13,20 @@ class TermStyles:
     END = "\033[0m" if os.isatty(sys.stderr.fileno()) else ""
 
 
+class SetupError(Exception):
+    """
+    Exception that gets raised when a configuration class cannot be set up by the importer
+    """
+    def __init__(self, msg: str, child_errors: List['ConfigurationError'] = None) -> None:
+        """
+        :param step_verb: Which step the importer tried to perform (e.g. import, setup)
+        :param configuration_path: The full module path of the configuration that was supposed to be set up
+        :param child_errors: Optional child configuration errors that caused this error
+        """
+        super().__init__(msg)
+        self.child_errors = child_errors or []
+
+
 class ConfigurationError(ValueError):
     """
     Base error class that is used to indicate that something went wrong during configuration.
@@ -95,10 +109,13 @@ def with_error_handler(callee: Callable) -> Callable:
     def wrapper(*args, **kwargs):
         try:
             return callee(*args, **kwargs)
-        except ConfigurationError as e:
-            msg = "{}{}{}".format(TermStyles.RED + TermStyles.BOLD, e, TermStyles.END)
-            for line in e.explanation_lines:
-                msg += f"\n    {line}"
+        except SetupError as e:
+            msg = f"{str(e)}"
+            for child_error in e.child_errors:
+                msg += f"\n    * {child_error.main_error_msg}"
+                for explanation_line in child_error.explanation_lines:
+                    msg += f"\n        - {explanation_line}"
+
             print(msg, file=sys.stderr)
 
     return wrapper

configurations/importer.py

@@ -8,6 +8,7 @@ from django.conf import ENVIRONMENT_VARIABLE as SETTINGS_ENVIRONMENT_VARIABLE
 from django.core.exceptions import ImproperlyConfigured
 from django.core.management import base
 
+from .errors import SetupError, ConfigurationError
 from .utils import uppercase_attributes, reraise
 from .values import Value, setup_value
 
@@ -149,10 +150,10 @@ class ConfigurationLoader:
 
         try:
             cls = getattr(mod, self.name)
-        except AttributeError as err:  # pragma: no cover
-            reraise(err, "Couldn't find configuration '{0}' "
-                         "in module '{1}'".format(self.name,
-                                                  mod.__package__))
+        except AttributeError:  # pragma: no cover
+            raise SetupError(f"Couldn't find configuration '{self.name}' in module {mod.__package__}.\n"
+                             f"Hint: '{self.name}' is taken from the environment variable '{CONFIGURATION_ENVIRONMENT_VARIABLE}'"
+                             f"and '{mod.__package__}' from the environment variable '{SETTINGS_ENVIRONMENT_VARIABLE}'.")
         try:
             cls.pre_setup()
             cls.setup()
@@ -172,6 +173,10 @@ class ConfigurationLoader:
                                                            self.name))
             cls.post_setup()
 
+        except SetupError:
+            raise
+        except ConfigurationError as err:
+            raise SetupError(f"Couldn't setup configuration '{cls_path}'", [err])
         except Exception as err:
             reraise(err, "Couldn't setup configuration '{0}'".format(cls_path))