Added database support for finding empty fields

spoolman/database/utils.py

@@ -1,9 +1,11 @@
 """Utility functions for the database module."""
 
 from enum import Enum
-from typing import Any
+from typing import Any, Optional, TypeVar
 
 import sqlalchemy
+from sqlalchemy import Select
+from sqlalchemy.orm import attributes
 
 from spoolman.database import models
 
@@ -13,7 +15,7 @@ class SortOrder(Enum):
     DESC = 2
 
 
-def parse_nested_field(base_obj: type[models.Base], field: str) -> sqlalchemy.Column[Any]:
+def parse_nested_field(base_obj: type[models.Base], field: str) -> attributes.InstrumentedAttribute[Any]:
     """Parse a nested field string into a sqlalchemy field object."""
     fields = field.split(".")
     if not hasattr(base_obj, fields[0]):
@@ -33,3 +35,45 @@ def parse_nested_field(base_obj: type[models.Base], field: str) -> sqlalchemy.Co
         raise ValueError(f"Field '{fields[0]}' does not have any nested fields")
 
     return getattr(base_obj, fields[0])
+
+
+def add_where_clause_str_opt(
+    stmt: Select,
+    field: attributes.InstrumentedAttribute[Optional[str]],
+    value: Optional[str],
+) -> Select:
+    """Add a where clause to a select statement for an optional string field."""
+    if value is not None:
+        if len(value) == 0:
+            stmt = stmt.where(sqlalchemy.or_(field.is_(None), field == ""))
+        else:
+            stmt = stmt.where(field.ilike(f"%{value}%"))
+    return stmt
+
+
+def add_where_clause_str(
+    stmt: Select,
+    field: attributes.InstrumentedAttribute[str],
+    value: Optional[str],
+) -> Select:
+    """Add a where clause to a select statement for a string field."""
+    if value is not None:
+        if len(value) == 0:
+            stmt = stmt.where(field == "")
+        else:
+            stmt = stmt.where(field.ilike(f"%{value}%"))
+    return stmt
+
+
+T = TypeVar("T")
+
+
+def add_where_clause(
+    stmt: Select,
+    field: attributes.InstrumentedAttribute[T],
+    value: Optional[T],
+) -> Select:
+    """Add a where clause to a select statement for a field."""
+    if value is not None:
+        stmt = stmt.where(field == value)
+    return stmt