Fix transform() corrupting TRUE/FALSE/NULL column defaults into strings

* Fix transform() corrupting TRUE/FALSE/NULL column defaults

quote_default_value() passed keyword-literal defaults (TRUE, FALSE, NULL)
through self.quote(), wrapping them in quotes. So transform() rebuilt a
column declared "INTEGER DEFAULT TRUE" as "INTEGER DEFAULT 'TRUE'", and a
later default insert stored the text 'TRUE' instead of the integer 1
(likewise 'FALSE' for 0 and 'NULL' for null) - silent value corruption.

Return these keyword literals unquoted, as already done for the
CURRENT_TIME/DATE/TIMESTAMP literals.

PR #764

docs/changelog.rst

@@ -42,6 +42,10 @@ Column names passed to Python API methods are now matched against the table sche
 - Foreign key columns are validated and recorded using the casing of the actual schema columns, in ``foreign_keys=`` when creating tables, ``db.add_foreign_keys()``, ``table.add_foreign_key()`` and ``table.add_column(fk_col=...)``. Duplicate foreign key detection is also case-insensitive.
 - ``table.create()`` with ``pk=``, ``not_null=``, ``defaults=`` or ``column_order=`` referencing columns using different casing no longer creates an unwanted extra primary key column or raises a ``ValueError``.
 
+Everything else:
+
+- Fixed a bug where ``table.transform()`` could convert ``DEFAULT TRUE``, ``DEFAULT FALSE`` and ``DEFAULT NULL`` column defaults into quoted string defaults when rebuilding a table. Thanks, `Vincent Gao <https://github.com/gaoflow>`__. (`#764 <https://github.com/simonw/sqlite-utils/pull/764>`__)
+
 .. _v4_0rc2:
 
 4.0rc2 (2026-07-04)

sqlite_utils/db.py

@@ -983,6 +983,11 @@ class Database:
         if str(value).upper() in ("CURRENT_TIME", "CURRENT_DATE", "CURRENT_TIMESTAMP"):
             return value
 
+        if isinstance(value, str) and value.upper() in ("TRUE", "FALSE", "NULL"):
+            # Keyword literals must stay unquoted; quoting them would turn the
+            # default into a string ('TRUE' instead of 1, 'NULL' instead of null).
+            return value
+
         if str(value).endswith(")"):
             # Expr
             return "({})".format(value)

tests/test_default_value.py

@@ -21,6 +21,11 @@ EXAMPLES = [
     # Strings
     ("TEXT DEFAULT 'CURRENT_TIMESTAMP'", "'CURRENT_TIMESTAMP'", "'CURRENT_TIMESTAMP'"),
     ('TEXT DEFAULT "CURRENT_TIMESTAMP"', '"CURRENT_TIMESTAMP"', '"CURRENT_TIMESTAMP"'),
+    # Boolean and null keyword literals must stay unquoted
+    ("INTEGER DEFAULT TRUE", "TRUE", "TRUE"),
+    ("INTEGER DEFAULT FALSE", "FALSE", "FALSE"),
+    ("INTEGER DEFAULT true", "true", "true"),
+    ("TEXT DEFAULT NULL", "NULL", "NULL"),
 ]
 
 

tests/test_transform.py

@@ -224,6 +224,40 @@ def test_transform_rename_pk(fresh_db):
     )
 
 
+def test_transform_preserves_keyword_literal_defaults(fresh_db):
+    # transform() used to requote keyword-literal defaults (DEFAULT TRUE became
+    # DEFAULT 'TRUE'), so a default insert stored the text 'TRUE' instead of the
+    # integer 1 -- silent value corruption on every rebuilt table.
+    fresh_db.execute(
+        "CREATE TABLE t ("
+        " id INTEGER PRIMARY KEY,"
+        " is_active INTEGER DEFAULT TRUE,"
+        " flag INTEGER DEFAULT FALSE,"
+        " note TEXT DEFAULT NULL"
+        ")"
+    )
+    table = fresh_db["t"]
+    table.insert({"id": 1})
+    before = fresh_db.execute("SELECT is_active, flag, note FROM t").fetchone()
+    assert before == (1, 0, None)
+
+    # Rebuild the table via an unrelated change.
+    table.transform(rename={"note": "note2"})
+
+    # The keyword literals stay unquoted in the schema ...
+    assert "DEFAULT TRUE" in table.schema
+    assert "DEFAULT FALSE" in table.schema
+    assert "DEFAULT NULL" in table.schema
+    assert "'TRUE'" not in table.schema
+
+    # ... and a fresh default insert still yields 1 / 0 / NULL, not strings.
+    table.insert({"id": 2})
+    after = fresh_db.execute(
+        "SELECT is_active, flag, note2 FROM t WHERE id = 2"
+    ).fetchone()
+    assert after == (1, 0, None)
+
+
 def test_transform_not_null(fresh_db):
     dogs = fresh_db["dogs"]
     dogs.insert({"id": 1, "name": "Cleo", "age": "5"}, pk="id")