Fixing transformations

Author: pydanny

sqlite_minutils/db.py

@@ -954,6 +954,15 @@ def create_table(
         if transform and self[name].exists():
             table = cast(Table, self[name])
             should_transform = False
+            # Has the primary key changed?
+            current_pks = table.pks
+            desired_pk = None
+            if isinstance(pk, str):
+                desired_pk = [pk]
+            elif pk:
+                desired_pk = list(pk)
+            if desired_pk and current_pks != desired_pk:
+                should_transform = True            
             # First add missing columns and figure out columns to drop
             existing_columns = table.columns_dict
             missing_columns = dict(
@@ -964,6 +973,14 @@ def create_table(
             columns_to_drop = [
                 column for column in existing_columns if column not in columns
             ]
+            # If no primary key was specified and id was added automatically, we prevent
+            # it from being deleted here or Sqlite will complain that a primary key is
+            # being dropped. We delete the ID column once a new PK has been set.
+            delete_id_column = False
+            if table.pks == ['id'] and 'id' in columns_to_drop:
+                columns_to_drop.remove('id')
+                delete_id_column = True
+
             if columns_to_drop:
                 for col_name in columns_to_drop: table.drop_column(col_name)
             if missing_columns:
@@ -977,15 +994,6 @@ def create_table(
                 and list(existing_columns)[: len(column_order)] != column_order
             ):
                 should_transform = True
-            # Has the primary key changed?
-            current_pks = table.pks
-            desired_pk = None
-            if isinstance(pk, str):
-                desired_pk = [pk]
-            elif pk:
-                desired_pk = list(pk)
-            if desired_pk and current_pks != desired_pk:
-                should_transform = True
             # Any not-null changes?
             current_not_null = {c.name for c in table.columns if c.notnull}
             desired_not_null = set(not_null) if not_null else set()
@@ -1003,6 +1011,9 @@ def create_table(
                     defaults=defaults,
                     pk=pk,
                 )
+            # Now it is safe to drop the ID column.
+            if delete_id_column:
+                table.drop_column('id')
             return table
         sql = self.create_table_sql(
             name=name,

tests/test_create.py

@@ -1368,3 +1368,4 @@ def test_create_strict(fresh_db, strict):
     table = fresh_db["t"]
     table.create({"id": int}, strict=strict)
     assert table.strict == strict or not fresh_db.supports_strict
+    

tests/test_transform.py

@@ -1,4 +1,4 @@
-from sqlite_minutils.db import ForeignKey
+from sqlite_minutils.db import ForeignKey, Database
 from sqlite_minutils.utils import OperationalError
 from sqlite3 import IntegrityError
 import pytest
@@ -521,3 +521,15 @@ def test_transform_strict(fresh_db, strict):
     assert dogs.strict == strict or not fresh_db.supports_strict
     dogs.transform(not_null={"name"})
     assert dogs.strict == strict or not fresh_db.supports_strict
+
+
+def test_create_twice(fresh_db):
+    columns = {'name': str}
+    fresh_db['demo'].create(columns=columns)
+    fresh_db['demo'].create(columns=columns, transform=True)
+
+def test_create_twice_with_pk_change(fresh_db):
+    columns = {'name': str}
+    fresh_db['demo'].create(columns=columns)
+    new_columns = {'name': str, 'age': int}
+    fresh_db['demo'].create(columns=new_columns, transform=True, pk='age')