refactor - use ValitationError exception subclass to handle & format …

…list of errors in message

Signed-off-by: David Martin <[email protected]>

chaoslib/exceptions.py

@@ -3,7 +3,7 @@
 __all__ = ["ChaosException", "InvalidExperiment", "InvalidActivity",
            "ActivityFailed", "DiscoveryFailed", "InvalidSource",
            "InterruptExecution", "ControlPythonFunctionLoadingError",
-           "InvalidControl"]
+           "InvalidControl", "ValidationError"]
 
 
 class ChaosException(Exception):
@@ -44,3 +44,30 @@ class InterruptExecution(ChaosException):
 
 class InvalidControl(ChaosException):
     pass
+
+
+class ValidationError(ChaosException):
+    def __init__(self, msg, errors, *args, **kwargs):
+        """
+        :param msg: exception message
+        :param errors: single error as string or list of errors/exceptions
+        """
+        if isinstance(errors, str):
+            errors = [errors]
+        self.errors = errors
+        super().__init__(msg, *args, **kwargs)
+
+    def __str__(self) -> str:
+        errors = self.errors
+        nb_errors = len(errors)
+        err_msg = super().__str__()
+        return (
+            "{msg}{dot} {nb} validation error{plural}:\n"
+            " - {errors}".format(
+                msg=err_msg,
+                dot="" if err_msg.endswith(".") else ".",
+                nb=nb_errors,
+                plural="" if nb_errors == 1 else "s",
+                errors="\n - ".join([str(err) for err in errors])
+            )
+        )

chaoslib/experiment.py

@@ -15,7 +15,7 @@
     cleanup_global_controls
 from chaoslib.deprecation import warn_about_deprecated_features
 from chaoslib.exceptions import ActivityFailed, ChaosException, \
-    InterruptExecution, InvalidActivity, InvalidExperiment
+    InterruptExecution, InvalidActivity, InvalidExperiment, ValidationError
 from chaoslib.extension import validate_extensions
 from chaoslib.configuration import load_configuration
 from chaoslib.hypothesis import ensure_hypothesis_is_valid, \
@@ -55,10 +55,14 @@ def ensure_experiment_is_valid(experiment: Experiment):
     """
     logger.info("Validating the experiment's syntax")
 
+    full_validation_msg = 'Experiment is not valid, ' \
+                          'please fix the following errors'
     errors = []
 
     if not experiment:
-        raise InvalidExperiment("an empty experiment is not an experiment")
+        # empty experiment, cannot continue validation any further
+        raise ValidationError(full_validation_msg,
+                              "an empty experiment is not an experiment")
 
     if not experiment.get("title"):
         errors.append(InvalidExperiment("experiment requires a title"))
@@ -103,11 +107,7 @@ def ensure_experiment_is_valid(experiment: Experiment):
     errors.extend(validate_controls(experiment))
 
     if errors:
-        full_validation_msg = 'Experiment is not valid, ' \
-                              'please fix the following errors:'
-        for error in errors:
-            full_validation_msg += '\n- {}'.format(error)
-        raise InvalidExperiment(full_validation_msg)
+        raise ValidationError(full_validation_msg, errors)
 
     logger.info("Experiment looks valid")