Merge pull request #4 from OCHA-DAP/reflection

Table names in snake case

documentation/main.md

@@ -17,6 +17,9 @@ Additional postgresql functionality is available if this library is installed wi
 
 ## Breaking changes
 
+From 1.2.7, default table names are no longer plural. The camel case class name 
+is converted to snake case, for example `MyTable` becomes `my_table`.
+
 From 1.2.3, Base must be chosen from `hdx.database.no_timezone` 
 (`db_has_tz=False`: the default) or `hdx.database.with_timezone` 
 (`db_has_tz=True`).
@@ -46,7 +49,10 @@ Your SQLAlchemy database tables must inherit from `Base` in
 
     from hdx.database.no_timezone import Base
     class MyTable(Base):
-        my_col = Column(Integer, ForeignKey(MyTable2.col2), primary_key=True)
+        my_col: Mapped[int] = mapped_column(Integer, ForeignKey(MyTable2.col2), primary_key=True)
+
+A default table name is set which can be overridden: it is the camel case class 
+name to converted to snake case, for example `MyTable` becomes `my_table`.
 
 Then a connection can be made to a database as follows including through an SSH
 tunnel:

src/hdx/database/no_timezone.py

@@ -5,6 +5,8 @@
 from sqlalchemy import DateTime, TypeDecorator
 from sqlalchemy.orm import DeclarativeBase, declared_attr
 
+from .utils import camel_to_snake_case
+
 
 class ConversionNoTZ(TypeDecorator):
     """Convert from/to datetime with timezone from database columns that don't
@@ -37,4 +39,4 @@ class Base(DeclarativeBase):
 
     @declared_attr.directive
     def __tablename__(cls):
-        return f"{cls.__name__.lower()}s"
+        return camel_to_snake_case(cls.__name__)

src/hdx/database/utils.py

@@ -0,0 +1,19 @@
+"""Other utilities"""
+
+import re
+
+
+def camel_to_snake_case(string: str) -> str:
+    """Convert a ``CamelCase`` name to ``snake_case``.
+    (Taken from flask-sqlalchemy code.)
+
+    Args:
+        string (str): String to convert
+
+    Returns:
+        str: String in snake case
+    """
+    string = re.sub(
+        r"((?<=[a-z0-9])[A-Z]|(?!^)[A-Z](?=[a-z]))", r"_\1", string
+    )
+    return string.lower().lstrip("_")

src/hdx/database/with_timezone.py

@@ -1,7 +1,9 @@
 from sqlalchemy.orm import DeclarativeBase, declared_attr
 
+from .utils import camel_to_snake_case
+
 
 class Base(DeclarativeBase):
     @declared_attr.directive
     def __tablename__(cls):
-        return f"{cls.__name__.lower()}s"
+        return camel_to_snake_case(cls.__name__)

tests/hdx/database/test_database.py

@@ -81,6 +81,7 @@ def close(self):
         monkeypatch.setattr(Database, "get_session", get_session)
 
     def test_get_session(self, nodatabase):
+        assert DBTestDate.__tablename__ == "db_test_date"
         with Database(
             database=TestDatabase.dbpath, port=None, dialect="sqlite"
         ) as dbsession: