feat: improve error handling and validation (#34)

Author: edgardevo

dataform2looker/database_mappers.py

@@ -4,7 +4,11 @@
 
 from google.cloud import bigquery
 
-from dataform2looker.exceptions import UnsupportedDatabaseTypeError
+from dataform2looker.exceptions import (
+    InvalidFieldTypeError,
+    TableNotFoundError,
+    UnsupportedDatabaseTypeError,
+)
 
 
 class Column:
@@ -48,6 +52,9 @@ def __init__(
             data_type: The original database data type of the column.
             time_frames: A list of timeframes for time dimension groups (optional).
 
+        Raises:
+            InvalidFieldTypeError: If an unsupported field type is provided.
+
         Sets the attributes and constructs the `column_dictionary` for Looker integration.
         If the column is a time dimension group, it adds `timeframes` and `datatype` to the dictionary.
         """  # noqa: E501
@@ -56,10 +63,11 @@ def __init__(
         self.field_type = field_type
         self.data_type = data_type
         self.time_frames = time_frames
-        assert (
-            self.field_type in self._DIMENSION_TYPE_MAP
-        ), f"Invalid field type, use one of {self._DIMENSION_TYPE_MAP.keys()},\
-            got {self.field_type}"
+        if self.field_type not in self._DIMENSION_TYPE_MAP:
+            raise InvalidFieldTypeError(
+                field_type=self.field_type,
+                allowed_types=list(self._DIMENSION_TYPE_MAP.keys()),
+            )
         self.dimension_type = self._DIMENSION_TYPE_MAP[self.field_type]
         self.column_dictionary = {
             "name": self.name,
@@ -224,11 +232,19 @@ def __get_columns(self) -> list[Column]:
         This method connects to BigQuery, fetches the schema of the table identified by `self.table_id`,
         and constructs a list of `Column` objects representing each field in the table.
 
+        Raises:
+            TableNotFoundError: If the table is not found or cannot be retrieved.
+
         Returns:
             list[Column]: A list of `Column` objects, each representing a column in the BigQuery table.
         """  # noqa: E501
         client = bigquery.Client()
-        table = client.get_table(self.table_id)
+        try:
+            table = client.get_table(self.table_id)
+        except Exception as e:
+            logging.error(f"Failed to retrieve table '{self.table_id}': {e}")
+            raise TableNotFoundError(self.table_id) from e
+
         logging.debug(f"Got table schema from table {self.table_id}")
         columns = [
             Column(

dataform2looker/exceptions.py

@@ -16,3 +16,35 @@ def __init__(self, db_type: str) -> None:
         """  # noqa: E501
         self.msg_template = f"'{db_type}' is not a supported database type"
         super().__init__(self.msg_template)
+
+
+class InvalidFieldTypeError(Exception):
+    """Exception raised when an invalid field type is encountered."""
+
+    def __init__(self, field_type: str, allowed_types: list) -> None:
+        """Initializes the `InvalidFieldTypeError` exception.
+
+        Args:
+            field_type (str): The unsupported field type.
+            allowed_types (list): The list of allowed types.
+        """
+        self.msg_template = (
+            f"Invalid field type, use one of {allowed_types}, got {field_type}"
+        )
+        super().__init__(self.msg_template)
+
+
+class TableNotFoundError(Exception):
+    """Exception raised when a table is not found in the database."""
+
+    def __init__(self, table_id: str) -> None:
+        """Initializes the `TableNotFoundError` exception.
+
+        Args:
+            table_id (str): The ID of the table that was not found.
+        """
+        self.msg_template = (
+            f"Table '{table_id}' was not found, check permissions "
+            f"or if the table exists"
+        )
+        super().__init__(self.msg_template)