Improve ros_launch support for launch files

Author: julianadrianheine

bazel_ros2_rules/lib/ament_index.bzl

@@ -47,25 +47,17 @@ Recursively aggregates AmentIndex prefixes from dependencies into one provider.
 """
 
 def _ament_index_share_files_impl(ctx):
-    # declare that a "package" with the given name exists
     package_marker_path = paths.join(
         ctx.attr.prefix,
         "share/ament_index/resource_index/packages/",
         ctx.attr.package_name,
     )
     package_marker_out = ctx.actions.declare_file(package_marker_path)
-    ctx.actions.write(
-        output = package_marker_out,
-        content = "",
-    )
+    ctx.actions.write(output = package_marker_out, content = "")
 
-    # Symlink sources into the share directory
-    runfiles_symlinks = {
-        package_marker_path: package_marker_out,
-    }
+    root_symlinks = {package_marker_path: package_marker_out}
 
     for src in ctx.attr.srcs:
-        # src is a target that could have multiple files
         for file in src.files.to_list():
             sp = file.short_path
             if sp.startswith(ctx.attr.strip_prefix):
@@ -76,21 +68,36 @@ def _ament_index_share_files_impl(ctx):
                 ctx.attr.package_name,
                 sp,
             )
-            runfiles_symlinks[symlink_path] = file
+            root_symlinks[symlink_path] = file
+
+    for exe in ctx.attr.executables:
+        exe_file = exe.files_to_run.executable
+        if exe_file == None:
+            continue
+        symlink_path = paths.join(
+            ctx.attr.prefix,
+            "lib",
+            ctx.attr.package_name,
+            exe_file.basename,
+        )
+        root_symlinks[symlink_path] = exe_file
 
     return [
         AmentIndex(prefix = ctx.attr.prefix),
         DefaultInfo(
-            runfiles = ctx.runfiles(root_symlinks = runfiles_symlinks),
+            runfiles = ctx.runfiles(root_symlinks = root_symlinks),
         ),
     ]
 
 ament_index_share_files = rule(
     attrs = dict(
         package_name = attr.string(mandatory = True),
         srcs = attr.label_list(
-            mandatory = True,
-            allow_empty = False,
+            allow_empty = True,
+            allow_files = True,
+        ),
+        executables = attr.label_list(
+            allow_empty = True,
             allow_files = True,
         ),
         # A prefix is required because the shim can't prepend the runfiles
@@ -103,14 +110,17 @@ ament_index_share_files = rule(
     provides = [AmentIndex],
 )
 """
-Creates an ament resource index and share/ directory for a single package.
+Creates an ament resource index for a single ROS 2 package.
+
+Files in `srcs` are symlinked under `<prefix>/share/<package_name>/`,
+enabling ament_index lookups such as `get_package_share_directory()`.
+
+Executable targets in `executables` are symlinked under
+`<prefix>/lib/<package_name>/`, enabling
+`launch_ros.actions.Node(package=..., executable=...)` to find Bazel-built
+binaries without a colcon install space.
 
-This creates both a package marker for a package, and a share directory
-for that package.
-Files in `srcs` will be added to `share/package_name`.
-A target depending on this one will be able to access the files in the
-share directory using the package's share directory joined with the
-files they expect.
+Both can be used together in a single rule invocation.
 
     d = ament_index_cpp::get_package_share_directory("package_name")
     file = join(d, "short_path of file")
@@ -130,10 +140,11 @@ TODO(sloretz) detect and error when a target is given two ament indexes
 with the same package.
 
 Args:
-    package_name: name of a ROS 2 package to which these share files belong
+    package_name: name of a ROS 2 package
     srcs: files to put into the share directory
+    executables: executable targets to expose under lib/
     prefix: optional prefix to give to the generated runfiles.
-    strip_prefix: optional prefix to strip from the short_path of the files
+    strip_prefix: optional prefix to strip from the short_path of srcs files
 
 Provides:
     AmentIndex: a prefix path where the ament resource index was generated.

bazel_ros2_rules/lib/private/ros_py.bzl

@@ -1,5 +1,9 @@
 # -*- python -*-
 
+load(
+    "@bazel_ros2_rules//lib:ament_index.bzl",
+    "ament_index_share_files",
+)
 load(
     "@bazel_ros2_rules//lib:kwargs.bzl",
     "filter_to_only_common_kwargs",
@@ -198,6 +202,16 @@ def ros_launch(
         # runfiles.py to use "this repository" in a way that doesn't require
         # bespoke information.
         workspace_name = None,
+        # dict mapping ROS 2 package name to a list of executable
+        # targets to expose via the ament resource index, enabling
+        # launch_ros.actions.Node(package=..., executable=...) to find
+        # Bazel-built binaries without a colcon install space.
+        # Example:
+        #   executables = {
+        #       "my_pkg": [":talker", ":listener"],
+        #       "other_pkg": ["//other_pkg:some_node"],
+        #   }
+        executables = {},
         **kwargs):
     main = "{}_roslaunch_main.py".format(name)
     launch_respath = _make_respath(launch_file, workspace_name)
@@ -218,6 +232,17 @@ def ros_launch(
             REPOSITORY_ROOT + ":ros2",
         ],
     )
+
+    for pkg_name, pkg_executables in executables.items():
+        index_target = "_{}_ament_index_{}".format(name, pkg_name)
+        ament_index_share_files(
+            name = index_target,
+            package_name = pkg_name,
+            executables = pkg_executables,
+            visibility = ["//visibility:private"],
+        )
+        data = data + pkg_executables + [":" + index_target]
+
     data = data + [launch_file]
 
     if "tags" not in kwargs:

ros2_example_bazel_installed/ros2_example_apps/BUILD.bazel

@@ -233,15 +233,19 @@ ros_cc_binary(
 # See bazel_ros2_rules/ros2/README.md, Launch Files, for notes on
 # features and limitations.
 
-# Uses a python launch file to spawn the talker and listener.
 workspace_name = "ros2_example_bazel_installed"
 
+# Uses a python launch file to spawn the talker and listener.
+# Note: it also uses launch_ros.actions.Node, the natural ROS 2 pattern,
+# by registering the Bazel-built binaries in a fake ament prefix.
 ros_launch(
     name = "roslaunch_eg_py",
-    data = [
-        ":eg_listener",
-        ":eg_talker",
-    ],
+    executables = {
+        "ros2_example_apps": [
+            ":eg_listener",
+            ":eg_talker",
+        ],
+    },
     launch_file = "eg_launch.py",
     workspace_name = workspace_name,
 )

ros2_example_bazel_installed/ros2_example_apps/eg_launch.py

@@ -1,21 +1,17 @@
 from launch import LaunchDescription
-from launch.actions import ExecuteProcess
-from python.runfiles import runfiles
+import launch_ros.actions
 
 
 def generate_launch_description():
-    # See bazel_ros2_rules/ros2/README.md, Launch Files, for notes on
-    # features and limitations.
-    r = runfiles.Create()
-    prefix = "ros2_example_bazel_installed/ros2_example_apps"
-    talker_bin = r.Rlocation(f"{prefix}/eg_talker")
-    listener_bin = r.Rlocation(f"{prefix}/eg_listener")
-
     return LaunchDescription(
         [
-            # Running a talker written in python.
-            ExecuteProcess(cmd=[talker_bin]),
-            # Running a listener written in cpp.
-            ExecuteProcess(cmd=[listener_bin]),
+            launch_ros.actions.Node(
+                package="ros2_example_apps",
+                executable="eg_talker",
+            ),
+            launch_ros.actions.Node(
+                package="ros2_example_apps",
+                executable="eg_listener",
+            ),
         ]
     )