Add cli options to output lookml

lkml/__init__.py

@@ -84,7 +84,7 @@ def parse_args(args: Sequence) -> argparse.Namespace:
         )
     )
     parser.add_argument(
-        "file", type=argparse.FileType("r"), help="path to the LookML file to parse"
+        "file", type=argparse.FileType("r+"), help="path to the LookML file to parse"
     )
     parser.add_argument(
         "-v",
@@ -96,6 +96,27 @@ def parse_args(args: Sequence) -> argparse.Namespace:
         help="increase logging verbosity to debug",
     )
 
+    group = parser.add_mutually_exclusive_group()
+    group.add_argument(
+        "--json",
+        action="store_true",
+        default=True,
+        help="return a JSON string (default)",
+    )
+    group.add_argument(
+        "--lookml",
+        action="store_true",
+        default=False,
+        help="return a LookML string",
+    )
+    group.add_argument(
+        "-w",
+        "--write",
+        action="store_true",
+        default=False,
+        help="parse and write back to file",
+    )
+
     return parser.parse_args(args)
 
 
@@ -116,8 +137,19 @@ def cli():
 
     logging.getLogger().setLevel(args.log_level)
 
-    result: dict = load(args.file)
-    args.file.close()
-
-    json_string = json.dumps(result, indent=2)
-    print(json_string)
+    try:
+        result: dict = load(args.file)
+
+        if args.write:
+            args.file.seek(0)
+            dump(result, args.file)
+            args.file.truncate()
+        elif args.lookml:
+            lookml_string = dump(result)
+            print(lookml_string)
+        elif args.json:
+            json_string = json.dumps(result, indent=2)
+            print(json_string)
+
+    finally:
+        args.file.close()

tests/test_cli.py

@@ -25,6 +25,25 @@ def test_absence_of_debug_flag_is_parsed_to_log_level_warn(lookml_path):
     assert args.log_level == logging.WARN
 
 
+def test_default_option(lookml_path):
+    args = lkml.parse_args([lookml_path])
+    assert args.json is True
+    assert args.lookml is args.write is False
+
+
+def test_options(lookml_path):
+    args = lkml.parse_args([lookml_path, "--json"])
+    assert args.json is True
+    args = lkml.parse_args([lookml_path, "--lookml"])
+    assert args.lookml is True
+    args = lkml.parse_args([lookml_path, "--write"])
+    assert args.write is True
+    args = lkml.parse_args([lookml_path, "-w"])
+    assert args.write is True
+    with pytest.raises(SystemExit):
+        args = lkml.parse_args([lookml_path, "--json", "--lookml"])
+
+
 @patch("lkml.load")
 @patch("lkml.parse_args")
 def test_run_cli(mock_parse_args, mock_load, lookml_path):