bpo-44859: Raise more accurate exceptions in sqlite3 (GH-27695)

* Improve exception compliance with PEP 249
* Raise InterfaceError instead of ProgrammingError for SQLITE_MISUSE.
  If SQLITE_MISUSE is raised, it is a sqlite3 module bug. Users of the
  sqlite3 module are not responsible for using the SQLite C API correctly.
* Don't overwrite BufferError with ValueError when conversion to BLOB fails.
* Raise ProgrammingError instead of Warning if user tries to execute() more
  than one SQL statement.
* Raise ProgrammingError instead of ValueError if an SQL query contains null characters.
* Make sure `_pysqlite_set_result` raises an exception if it returns -1.

Lib/test/test_sqlite3/test_dbapi.py

@@ -652,8 +652,9 @@ class CursorTests(unittest.TestCase):
             self.cu.execute("select asdf")
 
     def test_execute_too_much_sql(self):
-        with self.assertRaises(sqlite.Warning):
-            self.cu.execute("select 5+4; select 4+5")
+        self.assertRaisesRegex(sqlite.ProgrammingError,
+                               "You can only execute one statement at a time",
+                               self.cu.execute, "select 5+4; select 4+5")
 
     def test_execute_too_much_sql2(self):
         self.cu.execute("select 5+4; -- foo bar")

Lib/test/test_sqlite3/test_regression.py

@@ -319,12 +319,15 @@ class RegressionTests(unittest.TestCase):
 
     def test_null_character(self):
         # Issue #21147
-        con = sqlite.connect(":memory:")
-        self.assertRaises(ValueError, con, "\0select 1")
-        self.assertRaises(ValueError, con, "select 1\0")
-        cur = con.cursor()
-        self.assertRaises(ValueError, cur.execute, " \0select 2")
-        self.assertRaises(ValueError, cur.execute, "select 2\0")
+        cur = self.con.cursor()
+        queries = ["\0select 1", "select 1\0"]
+        for query in queries:
+            with self.subTest(query=query):
+                self.assertRaisesRegex(sqlite.ProgrammingError, "null char",
+                                       self.con.execute, query)
+            with self.subTest(query=query):
+                self.assertRaisesRegex(sqlite.ProgrammingError, "null char",
+                                       cur.execute, query)
 
     def test_surrogates(self):
         con = sqlite.connect(":memory:")

Lib/test/test_sqlite3/test_userfunctions.py

@@ -196,6 +196,8 @@ class FunctionTests(unittest.TestCase):
         self.con.create_function("returnlonglong", 0, func_returnlonglong)
         self.con.create_function("returnnan", 0, lambda: float("nan"))
         self.con.create_function("returntoolargeint", 0, lambda: 1 << 65)
+        self.con.create_function("return_noncont_blob", 0,
+                                 lambda: memoryview(b"blob")[::2])
         self.con.create_function("raiseexception", 0, func_raiseexception)
         self.con.create_function("memoryerror", 0, func_memoryerror)
         self.con.create_function("overflowerror", 0, func_overflowerror)
@@ -340,10 +342,17 @@ class FunctionTests(unittest.TestCase):
                                "select spam(?)", (1 << 65,))
 
     def test_non_contiguous_blob(self):
-        self.assertRaisesRegex(ValueError, "could not convert BLOB to buffer",
+        self.assertRaisesRegex(BufferError,
+                               "underlying buffer is not C-contiguous",
                                self.con.execute, "select spam(?)",
                                (memoryview(b"blob")[::2],))
 
+    @with_tracebacks(BufferError, regex="buffer.*contiguous")
+    def test_return_non_contiguous_blob(self):
+        with self.assertRaises(sqlite.OperationalError):
+            cur = self.con.execute("select return_noncont_blob()")
+            cur.fetchone()
+
     def test_param_surrogates(self):
         self.assertRaisesRegex(UnicodeEncodeError, "surrogates not allowed",
                                self.con.execute, "select spam(?)",
@@ -466,6 +475,12 @@ class FunctionTests(unittest.TestCase):
             with self.assertRaises(sqlite.DataError):
                 cur.execute("select largeblob()")
 
+    def test_func_return_illegal_value(self):
+        self.con.create_function("badreturn", 0, lambda: self)
+        msg = "user-defined function raised exception"
+        self.assertRaisesRegex(sqlite.OperationalError, msg,
+                               self.con.execute, "select badreturn()")
+
 
 class AggregateTests(unittest.TestCase):
     def setUp(self):

Misc/NEWS.d/next/Library/2021-08-10-00-05-53.bpo-44859.9e9_3V.rst

@@ -0,0 +1,10 @@
+Raise more accurate and :pep:`249` compatible exceptions in :mod:`sqlite3`.
+
+* Raise :exc:`~sqlite3.InterfaceError` instead of
+  :exc:`~sqlite3.ProgrammingError` for ``SQLITE_MISUSE`` errors.
+* Don't overwrite :exc:`BufferError` with :exc:`ValueError` when conversion to
+  BLOB fails.
+* Raise :exc:`~sqlite3.ProgrammingError` instead of :exc:`~sqlite3.Warning` if
+  user tries to :meth:`~sqlite3.Cursor.execute()` more than one SQL statement.
+* Raise :exc:`~sqlite3.ProgrammingError` instead of :exc:`ValueError` if an SQL
+  query contains null characters.

Modules/_sqlite/connection.c

@@ -578,8 +578,6 @@ _pysqlite_set_result(sqlite3_context* context, PyObject* py_val)
     } else if (PyObject_CheckBuffer(py_val)) {
         Py_buffer view;
         if (PyObject_GetBuffer(py_val, &view, PyBUF_SIMPLE) != 0) {
-            PyErr_SetString(PyExc_ValueError,
-                            "could not convert BLOB to buffer");
             return -1;
         }
         if (view.len > INT_MAX) {
@@ -591,6 +589,11 @@ _pysqlite_set_result(sqlite3_context* context, PyObject* py_val)
         sqlite3_result_blob(context, view.buf, (int)view.len, SQLITE_TRANSIENT);
         PyBuffer_Release(&view);
     } else {
+        callback_context *ctx = (callback_context *)sqlite3_user_data(context);
+        PyErr_Format(ctx->state->ProgrammingError,
+                     "User-defined functions cannot return '%s' values to "
+                     "SQLite",
+                     Py_TYPE(py_val)->tp_name);
         return -1;
     }
     return 0;

Modules/_sqlite/statement.c

@@ -67,7 +67,7 @@ pysqlite_statement_create(pysqlite_Connection *connection, PyObject *sql)
         return NULL;
     }
     if (strlen(sql_cstr) != (size_t)size) {
-        PyErr_SetString(PyExc_ValueError,
+        PyErr_SetString(connection->ProgrammingError,
                         "the query contains a null character");
         return NULL;
     }
@@ -85,7 +85,7 @@ pysqlite_statement_create(pysqlite_Connection *connection, PyObject *sql)
     }
 
     if (pysqlite_check_remaining_sql(tail)) {
-        PyErr_SetString(connection->Warning,
+        PyErr_SetString(connection->ProgrammingError,
                         "You can only execute one statement at a time.");
         goto error;
     }
@@ -190,7 +190,6 @@ int pysqlite_statement_bind_parameter(pysqlite_Statement* self, int pos, PyObjec
         case TYPE_BUFFER: {
             Py_buffer view;
             if (PyObject_GetBuffer(parameter, &view, PyBUF_SIMPLE) != 0) {
-                PyErr_SetString(PyExc_ValueError, "could not convert BLOB to buffer");
                 return -1;
             }
             if (view.len > INT_MAX) {