From 0d3132d26681a85c8cc3bc8ff29d3f8737090b96 Mon Sep 17 00:00:00 2001
From: xin700 <xin700@users.noreply.github.com>
Date: Mon, 29 Jun 2026 17:42:37 +0800
Subject: [PATCH] Fix ros2 interface show for msg files in subfolders (humble)

Use rosidl_interfaces resource index instead of get_interface_path()
so interface files under nested directories (e.g. msg-common/Foo.msg)
resolve correctly. Backport of the approach from ros2cli#1205.

Fixes ros2/ros2cli#1186
---
 ros2interface/ros2interface/verb/show.py | 25 +++++++++++++++++++++---
 ros2interface/test/test_cli.py           |  2 +-
 2 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/ros2interface/ros2interface/verb/show.py b/ros2interface/ros2interface/verb/show.py
index d97c713cd..8e4c62a87 100644
--- a/ros2interface/ros2interface/verb/show.py
+++ b/ros2interface/ros2interface/verb/show.py
@@ -13,9 +13,15 @@
 # limitations under the License.
 
 import argparse
+import os
 import sys
 import typing
 
+from ament_index_python.packages import \
+    get_package_share_directory, \
+    PackageNotFoundError
+from ament_index_python.resources import get_resource
+
 from ros2interface.api import type_completer
 from ros2interface.verb import VerbExtension
 from rosidl_adapter.parser import \
@@ -25,7 +31,6 @@
     MessageSpecification, \
     parse_message_string, \
     SERVICE_REQUEST_RESPONSE_SEPARATOR
-from rosidl_runtime_py import get_interface_path
 
 
 class InterfaceTextLine:
@@ -108,9 +113,23 @@ def _get_interface_lines(interface_identifier: str) -> typing.Iterable[Interface
         raise ValueError(
             f"Invalid name '{interface_identifier}'. Expected three parts separated by '/'"
         )
-    pkg_name, _, msg_name = parts
+    pkg_name, msg_type, msg_name = parts
+
+    try:
+        share_dir = get_package_share_directory(pkg_name)
+    except PackageNotFoundError:
+        raise LookupError(f"Unknown package '{pkg_name}'")
+
+    interfaces, _ = get_resource('rosidl_interfaces', pkg_name)
+    interfaces = interfaces.splitlines()
+
+    interface = [f for f in interfaces if f.endswith(msg_name + '.' + msg_type)]
+    if len(interface) == 0:
+        raise LookupError(
+            f"Interface '{msg_type}/{msg_name}' not found in package '{pkg_name}'"
+        )
 
-    file_path = get_interface_path(interface_identifier)
+    file_path = os.path.join(share_dir, interface[0])
     with open(file_path) as file_handler:
         for line in file_handler:
             yield InterfaceTextLine(
diff --git a/ros2interface/test/test_cli.py b/ros2interface/test/test_cli.py
index 8f1c91c5b..698afce86 100644
--- a/ros2interface/test/test_cli.py
+++ b/ros2interface/test/test_cli.py
@@ -479,7 +479,7 @@ def test_show_not_an_interface(self):
         assert interface_command.exit_code == 1
         assert launch_testing.tools.expect_output(
             expected_lines=[re.compile(
-                r"Could not find the interface '.+NotAMessageTypeName\.idl'"
+                r"Interface 'msg/NotAMessageTypeName' not found in package 'test_msgs'"
             )],
             text=interface_command.output,
             strict=True