feat: restore --passthrough option (#70)

Allow processing all messages even without decodable LiDAR packet topics.
Previously available in #40 but dropped during the v0.6.0 rearchitecture.

Also add a documentation-update rule to AGENTS.md.

Author: otenim

AGENTS.md

@@ -7,6 +7,7 @@
 - When creating commits and pull requests, always use `tier4/bag_converter` (origin) as the base repository. Never push commits or create PRs against the upstream fork (`0x126/bag_converter`).
 - Do not push directly to the main branch without permission. Always create a pull request first.
 - Always write source code and documentation in English.
+- When modifying source code, always update the corresponding documentation (e.g. README.md, help text) to reflect the changes.
 - Write PR descriptions that are comprehensive and detailed, but concise. Cover the problem, solution, and test plan without unnecessary verbosity.
 - When writing code or documentation, be mindful of the GitHub Actions workflows configured in this repository and ensure changes do not cause them to fail.
 - When investigating GitHub Actions workflow failures, always use the `gh` command (e.g. `gh run view`, `gh run view --log-failed`) to retrieve and read the actual workflow logs. Base your bug fixes on evidence from those logs, not on assumptions.

README.md

@@ -58,6 +58,7 @@ If the input path is a directory, all bag files (`.mcap`, `.db3`, `.sqlite3`) in
 | `--keep-original`             | Keep original packet topics in output bag                                                                                                                            |
 | `--base-frame <frame>`        | Transform PointCloud2 to the specified TF frame                                                                                                                      |
 | `--tf-mode <static\|dynamic>` | TF mode: `static` (default) or `dynamic`                                                                                                                             |
+| `--passthrough`               | Process all messages even without decodable LiDAR packet topics                                                                                                      |
 | `--comp-algo <algo>`          | Output compression algorithm: `none`, `lz4`, or `zstd` (default: `zstd`). Applies to mcap output only.                                                               |
 | `--comp-level <level>`        | Output compression level: `fastest`, `fast`, `default`, `slow`, or `slowest` (default: `default`). Ignored when `--comp-algo none`.                                  |
 | `--merge`                     | Merge bag files from distributed log modules and convert in a single pass. Accepts multiple input directories. The last positional argument is the output directory. |

src/bag_converter/include/bag_converter.hpp

@@ -111,6 +111,9 @@ struct BagConverterConfig
   std::string comp_algo = "zstd";
   std::string comp_level = "default";
 
+  // Passthrough mode (process all messages even without decodable topics)
+  bool passthrough = false;
+
   // Delete source files after successful conversion
   bool delete_sources = false;
 

src/bag_converter/src/bag_converter.cpp

@@ -128,6 +128,7 @@ void print_usage()
     << "                            after point cloud messages in the bag.\n"
     << "  --merge                   Merge bag files from distributed log modules, then\n"
     << "                            convert. Accepts multiple input directories.\n"
+    << "  --passthrough             Process all messages even without decodable topics\n"
     << "  --comp-algo <none|lz4|zstd>  Output compression algorithm (default: zstd)\n"
     << "  --comp-level <fastest|fast|default|slow|slowest>\n"
     << "                            Output compression level (default: default)\n"
@@ -290,6 +291,8 @@ std::optional<int> parse_arguments(int argc, char ** argv, BagConverterConfig &
                   << "'. Must be 'fastest', 'fast', 'default', 'slow', or 'slowest'.\n";
         return 1;
       }
+    } else if (arg == "--passthrough") {
+      config.passthrough = true;
     } else if (arg == "--merge" || arg == "--delete") {
       // Already processed in pre-scan
     } else if (arg == "--help" || arg == "-h" || arg == "--version" || arg == "-v") {
@@ -541,13 +544,18 @@ BagConverterResultStatus run_impl(const BagConverterConfig & config)
     }
   }
 
-  if (!has_decodable_topics) {
+  if (!has_decodable_topics && !config.passthrough) {
     RCLCPP_WARN(
       g_logger, "Skipping conversion: no decodable topics found in %s",
       config.src_bag_path.c_str());
     return BagConverterResultStatus::kSkipped;
   }
 
+  if (!has_decodable_topics && config.passthrough) {
+    RCLCPP_INFO(
+      g_logger, "Passthrough mode: no decodable topics, all messages will be passed through");
+  }
+
   if (transformer && !has_tf_topic) {
     RCLCPP_ERROR(
       g_logger, "No TF topics found in %s. Cannot transform to frame '%s'",