From 4d2274c53f2a46481a25de91f127958af2c2072a Mon Sep 17 00:00:00 2001
From: Simon Willison <swillison@gmail.com>
Date: Sat, 23 Nov 2024 11:39:36 -0800
Subject: [PATCH] Use new TransformError instead of AssertionError

Refs https://github.com/simonw/sqlite-utils/pull/634#discussion_r1835474885
---
 sqlite_utils/db.py      | 28 +++++++++++++++++-----------
 tests/test_transform.py |  6 +++---
 2 files changed, 20 insertions(+), 14 deletions(-)

diff --git a/sqlite_utils/db.py b/sqlite_utils/db.py
index 2d76230..d472242 100644
--- a/sqlite_utils/db.py
+++ b/sqlite_utils/db.py
@@ -156,6 +156,10 @@ XIndexColumn = namedtuple(
 Trigger = namedtuple("Trigger", ("name", "table", "sql"))
 
 
+class TransformError(Exception):
+    pass
+
+
 ForeignKeyIndicator = Union[
     str,
     ForeignKey,
@@ -1974,20 +1978,22 @@ class Table(Queryable):
                     """SELECT sql FROM sqlite_master WHERE type = 'index' AND name = :index_name;""",
                     {"index_name": index.name},
                 ).fetchall()[0][0]
-                assert index_sql is not None, (
-                    f"Index '{index.name}' on table '{self.name}' does not have a "
-                    "CREATE INDEX statement. You must manually drop this index prior to running this "
-                    "transformation and manually recreate the new index after running this transformation."
-                )
+                if index_sql is None:
+                    raise TransformError(
+                        f"Index '{index.name}' on table '{self.name}' does not have a "
+                        "CREATE INDEX statement. You must manually drop this index prior to running this "
+                        "transformation and manually recreate the new index after running this transformation."
+                    )
                 if keep_table:
                     sqls.append(f"DROP INDEX IF EXISTS [{index.name}];")
                 for col in index.columns:
-                    assert col not in rename.keys() and col not in drop, (
-                        f"Index '{index.name}' column '{col}' is not in updated table '{self.name}'. "
-                        f"You must manually drop this index prior to running this transformation "
-                        f"and manually recreate the new index after running this transformation. "
-                        f"The original index sql statement is: `{index_sql}`. No changes have been applied to this table."
-                    )
+                    if col in rename.keys() or col in drop:
+                        raise TransformError(
+                            f"Index '{index.name}' column '{col}' is not in updated table '{self.name}'. "
+                            f"You must manually drop this index prior to running this transformation "
+                            f"and manually recreate the new index after running this transformation. "
+                            f"The original index sql statement is: `{index_sql}`. No changes have been applied to this table."
+                        )
                 sqls.append(index_sql)
         return sqls
 
diff --git a/tests/test_transform.py b/tests/test_transform.py
index f9859f8..7ced9d9 100644
--- a/tests/test_transform.py
+++ b/tests/test_transform.py
@@ -1,4 +1,4 @@
-from sqlite_utils.db import ForeignKey
+from sqlite_utils.db import ForeignKey, TransformError
 from sqlite_utils.utils import OperationalError
 import pytest
 
@@ -625,7 +625,7 @@ def test_transform_with_indexes_errors(fresh_db, transform_params):
 
     dogs.create_index(["name", "age"])
 
-    with pytest.raises(AssertionError) as excinfo:
+    with pytest.raises(TransformError) as excinfo:
         dogs.transform(**transform_params)
 
     assert (
@@ -650,7 +650,7 @@ def test_transform_with_unique_constraint_implicit_index(fresh_db):
     dogs.insert({"id": 1, "name": "Cleo", "age": 5})
 
     # Attempt to transform the table without modifying 'name'
-    with pytest.raises(AssertionError) as excinfo:
+    with pytest.raises(TransformError) as excinfo:
         dogs.transform(types={"age": str})
 
     assert (