Do not create tables when in read-only mode

sqlitedict.py

@@ -168,10 +168,14 @@ def __init__(self, filename=None, tablename='unnamed', flag='c',
         self.decode = decode
 
         logger.info("opening Sqlite table %r in %r" % (tablename, filename))
-        MAKE_TABLE = 'CREATE TABLE IF NOT EXISTS "%s" (key TEXT PRIMARY KEY, value BLOB)' % self.tablename
         self.conn = self._new_conn()
-        self.conn.execute(MAKE_TABLE)
-        self.conn.commit()
+        if self.flag == 'r':
+            if not self.tablename in SqliteDict.get_tablenames(self.filename):
+                raise RuntimeError('Refusing to create a new table "%s" in read-only DB mode' % tablename)
+        else:
+            MAKE_TABLE = 'CREATE TABLE IF NOT EXISTS "%s" (key TEXT PRIMARY KEY, value BLOB)' % self.tablename
+            self.conn.execute(MAKE_TABLE)
+            self.conn.commit()
         if flag == 'w':
             self.clear()
 

tests/test_core.py

@@ -143,6 +143,26 @@ def attempt_terminate():
             with self.assertRaises(RuntimeError):
                 func()
 
+    def test_readonly_table(self):
+        """
+        Read-only access on a non-existant tablename should raise RuntimeError,
+        and not create a new (empty) table.
+        """
+        fname = norm_file('tests/db/sqlitedict-override-test.sqlite')
+        dummy_tablename = 'table404'
+        orig_db = SqliteDict(filename=fname)
+        orig_db['key'] = 'value'
+        orig_db['key_two'] = 2
+        orig_db.commit()
+        orig_db.close()
+
+        self.assertFalse(dummy_tablename in SqliteDict.get_tablenames(fname))
+
+        with self.assertRaises(RuntimeError):
+            SqliteDict(filename=fname, tablename=dummy_tablename, flag='r')
+
+        self.assertFalse(dummy_tablename in SqliteDict.get_tablenames(fname))
+
     def test_irregular_tablenames(self):
         """Irregular table names need to be quoted"""
         def __test_irregular_tablenames(tablename):