add-column --ignore option, refs #450

docs/cli-reference.rst

@@ -1031,6 +1031,7 @@ See :ref:`cli_add_column`.
       --fk-col TEXT            Referenced column on that foreign key table - if
                                omitted will automatically use the primary key
       --not-null-default TEXT  Add NOT NULL DEFAULT 'TEXT' constraint
+      --ignore                 If column already exists, do nothing
       --load-extension TEXT    SQLite extensions to load
       -h, --help               Show this message and exit.
 

sqlite_utils/cli.py

@@ -418,9 +418,22 @@ def dump(path, load_extension):
     required=False,
     help="Add NOT NULL DEFAULT 'TEXT' constraint",
 )
+@click.option(
+    "--ignore",
+    is_flag=True,
+    help="If column already exists, do nothing",
+)
 @load_extension_option
 def add_column(
-    path, table, col_name, col_type, fk, fk_col, not_null_default, load_extension
+    path,
+    table,
+    col_name,
+    col_type,
+    fk,
+    fk_col,
+    not_null_default,
+    ignore,
+    load_extension,
 ):
     """Add a column to the specified table
 
@@ -431,9 +444,13 @@ def add_column(
     """
     db = sqlite_utils.Database(path)
     _load_extensions(db, load_extension)
-    db[table].add_column(
+    try:
-        col_name, col_type, fk=fk, fk_col=fk_col, not_null_default=not_null_default
+        db[table].add_column(
-    )
+            col_name, col_type, fk=fk, fk_col=fk_col, not_null_default=not_null_default
+        )
+    except OperationalError as ex:
+        if not ignore:
+            raise click.ClickException(str(ex))
 
 
 @cli.command(name="add-foreign-key")

tests/test_cli.py

@@ -271,6 +271,19 @@ def test_add_column(db_path, col_name, col_type, expected_schema):
     assert expected_schema == collapse_whitespace(db["dogs"].schema)
 
 
+@pytest.mark.parametrize("ignore", (True, False))
+def test_add_column_ignore(db_path, ignore):
+    db = Database(db_path)
+    db.create_table("dogs", {"name": str})
+    args = ["add-column", db_path, "dogs", "name"] + (["--ignore"] if ignore else [])
+    result = CliRunner().invoke(cli.cli, args)
+    if ignore:
+        assert result.exit_code == 0
+    else:
+        assert result.exit_code == 1
+        assert result.output == "Error: duplicate column name: name\n"
+
+
 def test_add_column_not_null_default(db_path):
     db = Database(db_path)
     db.create_table("dogs", {"name": str})