Fix #705: Clarify ensure_autocommit_off() naming and documentation

sqlite_utils/cli.py

@@ -1176,7 +1176,7 @@ def insert_upsert_implementation(
                 )
             else:
                 raise
-        if tracker is not None:
+        if tracker is not None and db.table(table).exists():
             db.table(table).transform(types=tracker.types)
 
         # Clean up open file-like objects
@@ -2033,7 +2033,7 @@ def memory(
                 rows = (_flatten(row) for row in rows)
 
             db.table(file_table).insert_all(rows, alter=True)
-            if tracker is not None:
+            if tracker is not None and db.table(file_table).exists():
                 db.table(file_table).transform(types=tracker.types)
             # Add convenient t / t1 / t2 views
             view_names = ["t{}".format(i + 1)]

sqlite_utils/db.py

@@ -40,6 +40,7 @@
     Tuple,
 )
 import uuid
+import warnings
 from sqlite_utils.plugins import pm
 
 try:
@@ -401,13 +402,16 @@ def close(self) -> None:
         self.conn.close()
 
     @contextlib.contextmanager
-    def ensure_autocommit_off(self) -> Generator[None, None, None]:
+    def ensure_autocommit_on(self) -> Generator[None, None, None]:
         """
-        Ensure autocommit is off for this database connection.
+        Ensure autocommit is on for this database connection.
+
+        In SQLite's Python module, ``isolation_level = None`` enables autocommit mode,
+        where each statement is committed immediately.
 
         Example usage::
 
-            with db.ensure_autocommit_off():
+            with db.ensure_autocommit_on():
                 # do stuff here
 
         This will reset to the previous autocommit state at the end of the block.
@@ -419,6 +423,21 @@ def ensure_autocommit_off(self) -> Generator[None, None, None]:
         finally:
             self.conn.isolation_level = old_isolation_level
 
+    @contextlib.contextmanager
+    def ensure_autocommit_off(self) -> Generator[None, None, None]:
+        """
+        Deprecated alias for :meth:`ensure_autocommit_on`.
+
+        This method name is confusing - ``isolation_level = None`` actually enables
+        autocommit mode in SQLite, not disables it. Use :meth:`ensure_autocommit_on` instead.
+        """
+        warnings.warn(
+            "ensure_autocommit_off() is deprecated, use ensure_autocommit_on() instead",
+            DeprecationWarning,
+        )
+        with self.ensure_autocommit_on():
+            yield
+
     @contextlib.contextmanager
     def tracer(
         self, tracer: Optional[Callable[[str, Optional[Sequence]], None]] = None
@@ -781,13 +800,13 @@ def enable_wal(self) -> None:
         Sets ``journal_mode`` to ``'wal'`` to enable Write-Ahead Log mode.
         """
         if self.journal_mode != "wal":
-            with self.ensure_autocommit_off():
+            with self.ensure_autocommit_on():
                 self.execute("PRAGMA journal_mode=wal;")
 
     def disable_wal(self) -> None:
         "Sets ``journal_mode`` back to ``'delete'`` to disable Write-Ahead Log mode."
         if self.journal_mode != "delete":
-            with self.ensure_autocommit_off():
+            with self.ensure_autocommit_on():
                 self.execute("PRAGMA journal_mode=delete;")
 
     def _ensure_counts_table(self) -> None:

tests/test_cli_insert.py

@@ -597,3 +597,21 @@ def try_until(expected):
     proc.stdin.close()
     proc.wait()
     assert proc.returncode == 0
+
+
+def test_insert_csv_headers_only(tmpdir):
+    """Test that CSV with only header row (no data) works with --detect-types (issue #702)"""
+    db_path = str(tmpdir / "test.db")
+    csv_path = str(tmpdir / "headers_only.csv")
+    with open(csv_path, "w") as fp:
+        fp.write("id,name,age\n")
+    # Should not crash with --detect-types (which is now the default)
+    result = CliRunner().invoke(
+        cli.cli,
+        ["insert", db_path, "data", csv_path, "--csv"],
+        catch_exceptions=False,
+    )
+    assert result.exit_code == 0
+    # Table should not exist since there were no data rows
+    db = Database(db_path)
+    assert not db["data"].exists()