fix: add greater error handling around polars and duckdb csv reader

src/dve/core_engine/backends/exceptions.py

@@ -33,6 +33,33 @@ def __init__(self, *args: object, messages: Messages) -> None:
         """The messages to be returned as part of the error."""
 
 
+class UnableToParseCSVError(MessageBearingError):
+    """An error raised when unable to parse a CSV file"""
+
+    def __init__(
+        self,
+        entity_name: str,
+        field_check_error_message: str,
+        field_check_error_code: str
+    ):
+        super().__init__(
+            messages=[
+                FeedbackMessage(
+                    entity="csv_structure",
+                    record={
+                        entity_name: "Unable to parse file. Please check the structure of the file."
+                    },
+                    failure_type="submission",
+                    is_informational=False,
+                    error_type="csv read",
+                    error_location=entity_name,
+                    error_message=field_check_error_message,
+                    error_code=field_check_error_code,
+                )
+            ]
+        )
+
+
 class BackendErrorMixin(ABC, BackendError):
     """A mixin used to create backend error type."""
 

src/dve/core_engine/backends/implementations/duckdb/readers/csv.py

@@ -6,11 +6,21 @@
 
 import duckdb as ddb
 import polars as pl
-from duckdb import DuckDBPyConnection, DuckDBPyRelation, StarExpression, read_csv
+from duckdb import (
+    DuckDBPyConnection,
+    DuckDBPyRelation,
+    InvalidInputException,
+    StarExpression,
+    read_csv,
+)
 from pydantic import BaseModel
 
 from dve.core_engine.backends.base.reader import read_function
-from dve.core_engine.backends.exceptions import EmptyFileError, MessageBearingError
+from dve.core_engine.backends.exceptions import (
+    EmptyFileError,
+    MessageBearingError,
+    UnableToParseCSVError,
+)
 from dve.core_engine.backends.implementations.duckdb.duckdb_helpers import (
     duckdb_record_index,
     duckdb_write_parquet,
@@ -107,7 +117,14 @@ def read_to_relation(  # pylint: disable=unused-argument
 
         reader_options["columns"] = ddb_schema
 
-        rel = self.add_record_index(read_csv(resource, **reader_options, parallel=False))
+        try:
+            rel = self.add_record_index(read_csv(resource, **reader_options, parallel=False))
+        except InvalidInputException as exc:
+            raise UnableToParseCSVError(
+                entity_name="csv_structure",
+                field_check_error_message=self.field_check_error_message,
+                field_check_error_code=self.field_check_error_code,
+            ) from exc
 
         if self.null_empty_strings:
             cleaned_cols = ",".join(
@@ -156,11 +173,18 @@ def read_to_relation(  # pylint: disable=unused-argument
 
         # there is a raise_if_empty arg for 0.18+. Future reference when upgrading. Makes L85
         # redundant
-        df = self.add_record_index(  # pylint: disable=W0612
-            pl.scan_csv(resource, **reader_options).select(  # type: ignore
-                list(polars_types.keys())
+        try:
+            df = self.add_record_index(  # pylint: disable=W0612
+                pl.scan_csv(resource, **reader_options).select(  # type: ignore
+                    list(polars_types.keys())
+                )
             )
-        )
+        except pl.exceptions.PolarsError as exc:
+            raise UnableToParseCSVError(
+                entity_name="csv_structure",
+                field_check_error_message=self.field_check_error_message,
+                field_check_error_code=self.field_check_error_code,
+            ) from exc
 
         if self.null_empty_strings:
             pl_exprs = [
@@ -170,7 +194,16 @@ def read_to_relation(  # pylint: disable=unused-argument
             ] + [pl.col(RECORD_INDEX_COLUMN_NAME)]
             df = df.select(pl_exprs)
 
-        return self._connection.sql("SELECT * FROM df")
+        entity = self._connection.sql("SELECT * FROM df")
+
+        if entity.pl().shape[0] == 0:
+            raise UnableToParseCSVError(
+                entity_name="csv_structure",
+                field_check_error_message=self.field_check_error_message,
+                field_check_error_code=self.field_check_error_code,
+            )
+
+        return entity
 
 
 class DuckDBCSVRepeatingHeaderReader(PolarsToDuckDBCSVReader):

tests/test_core_engine/test_backends/test_readers/test_csv.py

@@ -5,12 +5,18 @@
 import csv
 from pathlib import Path
 from typing import Dict, Iterator, Optional
+from uuid import uuid4
 
 import pandas as pd
 import pytest
 from pydantic import BaseModel
 
-from dve.core_engine.backends.exceptions import EmptyFileError, FieldCountMismatch, MessageBearingError
+from dve.core_engine.backends.exceptions import (
+    EmptyFileError,
+    FieldCountMismatch,
+    MessageBearingError,
+    UnableToParseCSVError,
+)
 from dve.core_engine.backends.readers import CSVFileReader
 from dve.core_engine.backends.readers.utilities import get_all_model_fields
 from dve.core_engine.constants import RECORD_INDEX_COLUMN_NAME

tests/test_core_engine/test_backends/test_readers/test_duckdb/test_ddb_csv.py

@@ -2,14 +2,19 @@
 from datetime import date, datetime
 from pathlib import Path
 from tempfile import TemporaryDirectory
+from uuid import uuid4
 
 import duckdb
 import polars as pl
 import pytest
 from duckdb import DuckDBPyRelation
 from pydantic import BaseModel
 
-from dve.core_engine.backends.exceptions import EmptyFileError, MessageBearingError
+from dve.core_engine.backends.exceptions import (
+    EmptyFileError,
+    MessageBearingError,
+    UnableToParseCSVError,
+)
 from dve.core_engine.backends.implementations.duckdb.duckdb_helpers import (
     get_duckdb_type_from_annotation,
 )
@@ -21,7 +26,7 @@
 from dve.core_engine.backends.utilities import stringify_model
 from dve.core_engine.constants import RECORD_INDEX_COLUMN_NAME
 
-# pylint: disable=C0115,C0116,W0621
+# pylint: disable=C0103,C0115,C0116,W0621
 
 
 class SimpleModel(BaseModel):
@@ -164,6 +169,25 @@ def test_DuckDBCSVReader_with_null_empty_strings(self, temp_dir):
         assert entity.shape[0] == 3
         assert entity.filter("test_col IS NULL").shape[0] == 2
 
+    def test_DuckDBCSVReader_with_malformed_header(self, temp_dir):
+        test_data_headers = '"varchar_field,bigint_field,date_field,timestamp_field"'
+        row_data = "hello,1,2023-04-01,2023-04-01T12:30:00"
+        temp_id = uuid4().hex
+        fqp = Path(temp_dir, f"{temp_id}.csv")
+
+        with open(fqp, mode="w", encoding="utf-8") as f:
+            f.write(f"{test_data_headers}\n{row_data}")
+
+        reader = DuckDBCSVReader(
+            header=True,
+            delim=",",
+            connection=duckdb.connect(),
+        )
+
+        with pytest.raises(UnableToParseCSVError) as err:
+            reader.read_to_relation(fqp.as_posix(), "test", SimpleModel)
+            assert len(err.messages) == 1
+
 
 class TestPolarsToDuckDBCSVReader:
     """Test PolarsToDuckDBCSVReader"""
@@ -199,6 +223,26 @@ def test_PolarsToDuckDBCSVReader_with_null_empty_strings(self, temp_dir):
         assert entity.shape[0] == 3
         assert entity.filter("test_col IS NULL").shape[0] == 2
 
+    def test_PolarsToDuckDBCSVReader_with_malformed_header(self, temp_dir):
+        test_data_headers = '"varchar_field,bigint_field,date_field,timestamp_field"'
+        row_data = "hello,1,2023-04-01,2023-04-01T12:30:00"
+        temp_id = uuid4().hex
+        fqp = Path(temp_dir, f"{temp_id}.csv")
+
+        with open(fqp, mode="w", encoding="utf-8") as f:
+            f.write(f"{test_data_headers}\n{row_data}")
+
+        reader = PolarsToDuckDBCSVReader(
+            header=True,
+            delim=",",
+            connection=duckdb.connect(),
+        )
+
+        with pytest.raises(UnableToParseCSVError) as err:
+            reader.read_to_relation(fqp.as_posix(), "test", SimpleModel)
+            assert len(err.messages) == 1
+
+
 class TestDuckDBCSVRepeatingHeaderReader:
     """Test DuckDBCSVRepeatingHeaderReader"""