Show IDL interfaces in their original format

ros2interface/ros2interface/verb/show.py

@@ -104,15 +104,17 @@ def _is_nested(self) -> bool:
             return False
 
 
-def _get_interface_lines(interface_identifier: str) -> typing.Iterable[InterfaceTextLine]:
+def _get_interface_lines(
+    interface_identifier: str,
+    file_path: str,
+) -> typing.Iterable[InterfaceTextLine]:
     parts: typing.List[str] = interface_identifier.split('/')
     if len(parts) != 3:
         raise ValueError(
             f"Invalid name '{interface_identifier}'. Expected three parts separated by '/'"
         )
     pkg_name, _, msg_name = parts
 
-    file_path = get_interface_path(interface_identifier)
     with open(file_path) as file_handler:
         for line in file_handler:
             yield InterfaceTextLine(
@@ -147,7 +149,14 @@ def _show_interface(
     is_show_nested_comments: bool = False,
     indent_level: int = 0
 ):
-    for line in _get_interface_lines(interface_identifier):
+    file_path = get_interface_path(interface_identifier)
+    if file_path.endswith('.idl'):
+        with open(file_path) as file_handler:
+            content = file_handler.read()
+        print(content, end='' if content.endswith('\n') else '\n')
+        return
+
+    for line in _get_interface_lines(interface_identifier, file_path):
 
         _print_interface_line(
             line, is_show_comments=is_show_comments, indent_level=indent_level)

ros2interface/test/test_show.py

@@ -0,0 +1,48 @@
+# Copyright 2026 Old-Ding
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Tests for the interface show verb."""
+
+from ros2interface.verb import show
+
+
+def test_show_msg_interface(tmp_path, monkeypatch, capsys):
+    msg_text = 'uint32 value\n'
+    msg_path = tmp_path / 'Basic.msg'
+    msg_path.write_text(msg_text)
+    monkeypatch.setattr(show, 'get_interface_path', lambda _: str(msg_path))
+
+    show._show_interface('test_interfaces/msg/Basic')
+
+    assert capsys.readouterr().out == msg_text
+
+
+def test_show_idl_interface(tmp_path, monkeypatch, capsys):
+    idl_text = """\
+module test_interfaces {
+  module msg {
+    struct IdlOnly {
+      uint32 value;
+    };
+  };
+};
+"""
+    idl_path = tmp_path / 'IdlOnly.idl'
+    monkeypatch.setattr(show, 'get_interface_path', lambda _: str(idl_path))
+
+    for file_text in (idl_text, idl_text.rstrip('\n')):
+        idl_path.write_text(file_text)
+        show._show_interface('test_interfaces/msg/IdlOnly')
+
+        assert capsys.readouterr().out == idl_text