Goals

The goals for this lab are to:

• Get comfortable with creating, and working with, ROS2 packages.
• Gain experience with submitting code through GitHub Classroom.
• Gain experience creating git repositories and committing changes.

Deliverables

By the end of this Lab you will need to:

• Create a properly-formatted ROS2 Python package.
• Integrate your wander code from the previous lab into that package.
• Modify your code so that it conforms to Python and ROS2 coding standards.
• Create a git repository to store your work (with commits by at least two group members).

Workspace

When you configured your ROS2 environment, you should have executed the script:

ros2_config_account.sh.

In addition to setting up your .bashrc file, this script created a folder named ~/dev_ws that you will use to store your ROS2 files.

Creating and Building a ROS2 Package

1. First, create a src folder in your workspace and cd into it:

   mkdir ~/dev_ws/src/
   cd ~/dev_ws/src/

2. Now create the package:

   ros2 pkg create --build-type ament_python --node-name wander_node wander

   This will populate the wander folder with a properly-formatted ROS2 Python package.

3. If you look inside your wander folder, you should now see the following initial layout:

   wander/                          <-- Folder name matches package name
       package.xml                  <-- ROS2 package information
       setup.cfg                    <-- Python package installation config file
       setup.py                     <-- Python package installation script
       resource/                    <-- Honestly... I'm not sure
           wander
       test/
           test_flake8.py           <-- Tests for Python PEP8 formatting
           test_pep257.py           <-- Tests for docstrings
           test_copyright.py        <-- Test that a copyright is provided
       wander/                      <-- Python package source
           __init__.py              <-- Turns the folder into a Python package
           wander_node.py           <-- Python executable

4. Build your newly created package by changing into your workspace directory and typing:

   colcon build

   Once this command completes, there should be build, install and log directories alongside the existing src directory. Type the following command into the terminal:

   source install/setup.bash

   This command configures your environment so that the ROS2 system is aware of your newly created package.

   You should now be able to interact with your package using ROS2 command line tools:

   $ ros2 run wander wander_node 
   Hi from wander.

Congratulations! You now have a fully-functional, properly built, ROS2 package.

Creating a GitHub Repository

• Copy the URL for the assignment invitation from the course Piazza page. Paste the URL into your browser window and follow the link.

• Click on the link to access the GitHub page for your repository.

• Follow the instructions to select a team name for this assignment. You should see a page with some text like the following:

   Your team’s assignment repository has been created:
          https://github.com/JMU-CS354-F21/ros2-packaging-your-team-name
  

• Complete the following steps in order to add your package to a new git repository. Don't just copy and paste the instructions below! Make sure you understand the meaning of each step. (GIT_URL should be replaced with the URL for your GitHub project. It should look something like: https://github.com/JMU-CS354-F21/ros2-packaging-your-team-name)

  cd ~/dev_ws/src/wander
  git init
  echo "# Packaging Lab" >> README.md
  git add *
  git commit -m "first commit"
  git branch -M master
  git remote add origin GIT_URL
  git push -u origin master

• Reload your repository in GitHub to confirm that your package has been pushed correctly.

Congratulations! You have a git repository on GitHub.

Adding Functionality

At this point SOMEONE ELSE from your group should clone the repository and make the changes described below. Full credit for the lab will require commits from multiple group members.

Note that if you clone the package like this:

git clone GIT_URL

The folder will have the same name as the GitHub repository.

If you clone it like this:

git clone GIT_URL wander

Then the folder name will match the package name, which will be less confusing. Once the repository is cloned into ~/dev_ws/src complete the steps below.

• Copy the contents of your wander.py solution from the previous lab into wander_node.py. Rebuild your package and test that you can use ros2 node run to execute your new node:

  ros2 launch turtlebot3_gazebo  turtlebot3_world.launch.py

  In a separate terminal:

  ros2 run wander wander_node

• Copy your forward.py solution form the last lab into a file named forward_node.py. Update setup.py so that it recognizes forward_node as an entry point, rebuild, and test the result:

  ros2 run wander forward_node

Tidying Up

As you may have noticed above, the skeleton file hierarchy created by ros2 pkg create includes a number of scripts for checking that your source files follow Python and ROS2 coding style guidelines. You can run these tests by using colcon test in the root of your workspace:

cd ~/dev_ws/
colcon test

The output is stored in text files in the log directory. Open the file ~/dev_ws/log/latest_test/wander/stdout_stderr.log to see which style checks your code is failing.

Fix all of the style errors found by test_flake8.

Saving Your Work

Once you are satisfied with your package, commit your work, and push it back to GitHub by completing the following steps:

• Change into your package folder and type:

  git add *

  to add all of your newly created files to the repository.

• Commit your changes by typing:

  git commit -m 'Added wander code. Fixed style issues.'

  Every time you commit your code you MUST provide a reasonably informative commit message.

• Push your changes

  git push

  Your changes are not safe until you complete this step! Once you have completed the previous step, test that everything is OK by accessing your repository through the GitHub web interface. You should be able to see the files you've pushed.

Submitting

There is nothing to submit for this lab. I'll check your work through GitHub.

If You Have Extra Time

Modify your wander_node.py solution so that the wandering is random. Rather than turning until the obstacle is out of range, turn by some randomly determined angle. Push your changes to the GitHub repository.