create-table --ignore and --replace, refs #27

docs/cli.rst

@@ -399,6 +399,8 @@ You can specify foreign key relationships between the tables you are creating us
                 [author_id] INTEGER REFERENCES [authors]([id])
              )
 
+If a table with the same name already exists, you will get an error. You can choose to silently ignore this error with ``--ignore``, or you can replace the existing table with a new, empty table using ``--replace``.
+
 .. _cli_add_column:
 
 Adding columns

docs/python-api.rst

@@ -262,6 +262,8 @@ The first argument here is a dictionary specifying the columns you would like to
 
 This method takes optional arguments ``pk=``, ``column_order=``, ``foreign_keys=``, ``not_null=set()`` and ``defaults=dict()`` - explained below.
 
+You can pass ``ignore=True`` to silently ignore an existing table and do nothing, or ``replace=True`` to replace that table with a new, empty table.
+
 .. _python_api_compound_primary_keys:
 
 Compound primary keys

sqlite_utils/cli.py

@@ -554,7 +554,13 @@ def upsert(
     type=(str, str, str),
     help="Column, other table, other column to set as a foreign key",
 )
-def create_table(path, table, columns, pk, not_null, default, fk):
+@click.option(
+    "--ignore", is_flag=True, help="If table already exists, do nothing",
+)
+@click.option(
+    "--replace", is_flag=True, help="If table already exists, replace it",
+)
+def create_table(path, table, columns, pk, not_null, default, fk, ignore, replace):
     "Add an index to the specified table covering the specified columns"
     db = sqlite_utils.Database(path)
     if len(columns) % 2 == 1:
@@ -571,6 +577,18 @@ def create_table(path, table, columns, pk, not_null, default, fk):
                 "column types must be one of {}".format(VALID_COLUMN_TYPES)
             )
         coltypes[name] = ctype.upper()
+    # Does table already exist?
+    if table in db.table_names():
+        if ignore:
+            return
+        elif replace:
+            db[table].drop()
+        else:
+            raise click.ClickException(
+                'Table "{}" already exists. Use --replace to delete and replace it.'.format(
+                    table
+                )
+            )
     db[table].create(
         coltypes, pk=pk, not_null=not_null, defaults=dict(default), foreign_keys=fk
     )

tests/test_cli.py

@@ -960,3 +960,42 @@ def test_create_table_foreign_key():
             "   [author_id] INTEGER REFERENCES [authors]([id])\n"
             ")"
         ) == db["books"].schema
+
+
+def test_create_table_error_if_table_exists():
+    runner = CliRunner()
+    with runner.isolated_filesystem():
+        db = Database("test.db")
+        db["dogs"].insert({"name": "Cleo"})
+        result = runner.invoke(
+            cli.cli, ["create-table", "test.db", "dogs", "id", "integer"]
+        )
+        assert 1 == result.exit_code
+        assert (
+            'Error: Table "dogs" already exists. Use --replace to delete and replace it.'
+            == result.output.strip()
+        )
+
+
+def test_create_table_ignore():
+    runner = CliRunner()
+    with runner.isolated_filesystem():
+        db = Database("test.db")
+        db["dogs"].insert({"name": "Cleo"})
+        result = runner.invoke(
+            cli.cli, ["create-table", "test.db", "dogs", "id", "integer", "--ignore"]
+        )
+        assert 0 == result.exit_code
+        assert "CREATE TABLE [dogs] (\n   [name] TEXT\n)" == db["dogs"].schema
+
+
+def test_create_table_replace():
+    runner = CliRunner()
+    with runner.isolated_filesystem():
+        db = Database("test.db")
+        db["dogs"].insert({"name": "Cleo"})
+        result = runner.invoke(
+            cli.cli, ["create-table", "test.db", "dogs", "id", "integer", "--replace"]
+        )
+        assert 0 == result.exit_code
+        assert "CREATE TABLE [dogs] (\n   [id] INTEGER\n)" == db["dogs"].schema