add support for adding help_text to values

Now Value classes accept a 'help_text' keyword which will get printed when a
ValueRetrievalError or ValueProcessingError occurs

configurations/errors.py

@@ -13,10 +13,24 @@ class TermStyles:
     END = "\033[0m" if os.isatty(sys.stderr.fileno()) else ""
 
 
+def extract_explanation_lines_from_value(value_instance: 'Value') -> List[str]:
+    result = []
+
+    if value_instance.help_text is not None:
+        result.append(f"Help: {value_instance.help_text}")
+
+    if value_instance.destination_name is not None:
+        result.append(f"{value_instance.destination_name} is taken from the environment variable "
+                      f"{value_instance.full_environ_name} as a {type(value_instance).__name__}")
+
+    return result
+
+
 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)
@@ -60,14 +74,9 @@ class ValueRetrievalError(ConfigurationError):
         :param extra_explanation_lines: Extra lines that will be appended to `ConfigurationError.explanation_lines`
             in addition the ones automatically generated from the provided *value_instance*.
         """
-        explanation_lines = list(extra_explanation_lines)
-        if value_instance.destination_name is not None:
-            explanation_lines.append(f"{value_instance.destination_name} is taken from the environment variable "
-                                     f"{value_instance.full_environ_name} as a {type(value_instance).__name__}")
-
         super().__init__(
             f"Value of {value_instance.destination_name} could not be retrieved from environment",
-            explanation_lines
+            list(extra_explanation_lines) + extract_explanation_lines_from_value(value_instance)
         )
 
 
@@ -89,11 +98,7 @@ class ValueProcessingError(ConfigurationError):
         if hasattr(value_instance, "message"):
             error += ": " + value_instance.message.format(raw_value)
 
-        explanation_lines = list(extra_explanation_lines)
-        if value_instance.destination_name is not None:
-            explanation_lines.append(f"{value_instance.destination_name} is taken from the environment variable "
-                                     f"{value_instance.full_environ_name} as a {type(value_instance).__name__}")
-
+        explanation_lines = list(extra_explanation_lines) + extract_explanation_lines_from_value(value_instance)
         explanation_lines.append(f"'{raw_value}' was received but that is invalid")
 
         super().__init__(error, explanation_lines)

configurations/values.py

@@ -58,7 +58,7 @@ class Value:
         return instance
 
     def __init__(self, default=None, environ=True, environ_name=None,
-                 environ_prefix='DJANGO', environ_required=False,
+                 environ_prefix='DJANGO', environ_required=False, help_text=None,
                  *args, **kwargs):
         if isinstance(default, Value) and default.default is not None:
             self.default = copy.copy(default.default)
@@ -71,6 +71,7 @@ class Value:
         self.environ_name = environ_name
         self.environ_required = environ_required
         self.destination_name = None
+        self.help_text = help_text
 
     def __str__(self):
         return str(self.value)

test_project/test_project/settings.py

@@ -4,7 +4,7 @@ from configurations import Configuration, values
 class Base(Configuration):
     # Django settings for test_project project.
 
-    DEBUG = values.BooleanValue(True, environ=True)
+    DEBUG = values.BooleanValue(True, environ=True, help_text="Enables or disables django debug mode")
 
     ADMINS = (
         # ('Your Name', 'your_email@example.com'),