refactor: move xmodule folder to root

- Moving xmodule folder to root as we're dissolving sub-projects of common folder in edx-platform
    - More info: https://openedx.atlassian.net/browse/BOM-2579
- -e common/lib/xmodule has been removed from the requirements as xmodule has itself become the part of edx-platform and not being installed through requirements
- The test files common/lib/xmodule/test_files/ have been removed as they are not being used anymore

xmodule/validation.py

@@ -0,0 +1,128 @@
+"""
+Extension of XBlock Validation class to include information for presentation in Studio.
+"""
+from xblock.validation import Validation, ValidationMessage
+
+
+class StudioValidationMessage(ValidationMessage):
+    """
+    A message containing validation information about an xblock, extended to provide Studio-specific fields.
+    """
+
+    # A special message type indicating that the xblock is not yet configured. This message may be rendered
+    # in a different way within Studio.
+    NOT_CONFIGURED = "not-configured"
+
+    TYPES = [ValidationMessage.WARNING, ValidationMessage.ERROR, NOT_CONFIGURED]
+
+    def __init__(self, message_type, message_text, action_label=None, action_class=None, action_runtime_event=None):
+        """
+        Create a new message.
+
+        Args:
+            message_type (str): The type associated with this message. Most be `WARNING` or `ERROR`.
+            message_text (unicode): The textual message.
+            action_label (unicode): Text to show on a "fix-up" action (optional). If present, either `action_class`
+                or `action_runtime_event` should be specified.
+            action_class (str): A class to link to the "fix-up" action (optional). A click handler must be added
+                for this class, unless it is "edit-button", "duplicate-button", or "delete-button" (which are all
+                handled in general for xblock instances.
+            action_runtime_event (str): An event name to be triggered on the xblock client-side runtime when
+                the "fix-up" action is clicked (optional).
+        """
+        super().__init__(message_type, message_text)
+        if action_label is not None:
+            if not isinstance(action_label, str):
+                raise TypeError("Action label must be unicode.")
+            self.action_label = action_label
+        if action_class is not None:
+            if not isinstance(action_class, str):
+                raise TypeError("Action class must be a string.")
+            self.action_class = action_class
+        if action_runtime_event is not None:
+            if not isinstance(action_runtime_event, str):
+                raise TypeError("Action runtime event must be a string.")
+            self.action_runtime_event = action_runtime_event
+
+    def to_json(self):
+        """
+        Convert to a json-serializable representation.
+
+        Returns:
+            dict: A dict representation that is json-serializable.
+        """
+        serialized = super().to_json()
+        if hasattr(self, "action_label"):
+            serialized["action_label"] = self.action_label
+        if hasattr(self, "action_class"):
+            serialized["action_class"] = self.action_class
+        if hasattr(self, "action_runtime_event"):
+            serialized["action_runtime_event"] = self.action_runtime_event
+        return serialized
+
+
+class StudioValidation(Validation):
+    """
+    Extends `Validation` to add Studio-specific summary message.
+    """
+
+    @classmethod
+    def copy(cls, validation):
+        """
+        Copies the `Validation` object to a `StudioValidation` object. This is a shallow copy.
+
+        Args:
+            validation (Validation): A `Validation` object to be converted to a `StudioValidation` instance.
+
+        Returns:
+            StudioValidation: A `StudioValidation` instance populated with the messages from supplied
+                `Validation` object
+        """
+        if not isinstance(validation, Validation):
+            raise TypeError("Copy must be called with a Validation instance")
+        studio_validation = cls(validation.xblock_id)
+        studio_validation.messages = validation.messages
+        return studio_validation
+
+    def __init__(self, xblock_id):
+        """
+        Create a `StudioValidation` instance.
+
+        Args:
+            xblock_id (object): An identification object that must support conversion to unicode.
+        """
+        super().__init__(xblock_id)
+        self.summary = None
+
+    def set_summary(self, message):
+        """
+        Sets a summary message on this instance. The summary is optional.
+
+        Args:
+            message (ValidationMessage): A validation message to set as this instance's summary.
+        """
+        if not isinstance(message, ValidationMessage):
+            raise TypeError("Argument must of type ValidationMessage")
+        self.summary = message
+
+    @property
+    def empty(self):
+        """
+        Is this object empty (contains no messages and no summary)?
+
+        Returns:
+            bool: True iff this instance has no validation issues and therefore has no messages or summary.
+        """
+        return super().empty and not self.summary
+
+    def to_json(self):
+        """
+        Convert to a json-serializable representation.
+
+        Returns:
+            dict: A dict representation that is json-serializable.
+        """
+        serialized = super().to_json()
+        if self.summary:
+            serialized["summary"] = self.summary.to_json()
+        return serialized