This guide describes how to set up Drake in the JetBrains CLion IDE on Ubuntu.

Using CLion with Bazel

First, you must install Bazel and build Drake with Bazel, following the Drake Bazel instructions.

To use Drake with CLion, your Drake source directory (or git clone) must be named drake.

Installing CLion

1. Go to https://www.jetbrains.com/clion/download/. Look for “Other versions” and download the appropriate version of CLion (see below).
2. Install CLion. Exact steps depend on your platform, but it’s straightforward. Just using defaults for everything is fine. You now have a 30-day trial version of CLion. Either try it out as is, or get a free academic license here.

The most recent versions that we have tested for compatibility are:

• Ubuntu 22.04 (Jammy)
• Bazel 6.4.0
• CLion 2023.3.2
  • Bazel plugin 2023.11.23.0.1-api-version-233

Different CLion versions will normally choose a compatible Bazel plugin.

Current CLion/Bazel problem

We are seeing CLion confused about Drake header files, possibly due to Bazel’s “sandboxing” which uses symbolic links to construct a source tree containing only files that appear in the current workspace. We do not yet have a diagnosis or workaround. CLion is still usable but symbols within header files are not properly recognized, .cc files work fine.

Upgrading CLion

Users upgrading from a previous version of CLion should do the following:

1. To have your Unity launcher CLion icon point to the correct version, run locate jetbrains-clion.desktop and edit the located file. If more than one file is located, you may want to consolidate to a single launch file in your user directory, typically ~/.local/share/applications.
2. Uninstall the previous version of the Bazel plugin and update to the version above (or the most recent version compatible with the CLion version you are upgrading to). See Installing the Bazel Plugin.
3. In CLion, select Bazel->Sync->Non-incrementally Sync Project with BUILD Files
4. You may need to delete cached data in ~/.cache/bazel and ~/.cache/JetBrains/CLion2023.2/caches if you get error messages complaining about old files in the cache (substitute the right version number).

Note: It is not necessary to import your project into a new CLion project. Overwriting the old project is appropriate.

Installing the Bazel Plugin

To use Bazel in CLion, you must install a plugin supplied by Google. To install the plugin, open Settings (either Welcome > Configure > Settings or File > Settings), select Plugins, then choose the Marketplace tab. Locate and install the Bazel plugin. You will be prompted to restart CLion.

To use Drake in CLion you must use Drake’s bazel wrapper. Open Settings > Bazel Settings. For Bazel binary location select the path to drake/tools/clion/bazel_wrapper from any recent Drake source tree (it doesn’t have to match the current project open in CLion).

Setting up Drake in CLion

CLion will invoke Bazel to build Drake, including the external dependencies specified in the WORKSPACE file.

1. File > Import Bazel Project
2. Select Workspace: Use an existing Bazel workspace, and provide the path to your drake directory.
3. Select Project View: choose “Import project view file”, and select the file drake/.bazelproject
4. Project View: Pick a project data directory of your choice for the CLion project files. It must not be a subdirectory of drake.
5. (Advanced) Project View: If you only wish to develop a subset of Drake, you can specify only those files and targets in the project view file. Most users should leave it as-is.
6. Click “Finish”. CLion will begin ingesting the Drake source, building symbols, and compiling Drake. This will take several minutes.

Building and Running Targets

To build all of Drake with default Bazel options, select Bazel > Build > Compile Project.

To build or run a specific target go to Run > Edit Configurations. Click + to create a new Bazel command. Specify the configuration name and Bazel options. The Target expression specifies the actual code (library, binary, and/or test) that you want to run. To learn more about target expressions, see the Bazel manual. Once you’ve created a configuration, you can launch it from the Run menu.

To run a specific target in the debugger, create a configuration as above, using the bazel run command. Then launch it from Run > Debug.

Keeping CLion Up-to-Date with the Bazel Build

Changes to BUILD files can add or remove source files from the Bazel build. To propagate those changes into the CLion project structure, select Bazel > Sync Project With BUILD Files.

Git Integration

CLion provides a user interface for Git, which you can enable in the VCS menu. It automatically detects all Git roots within the workspace. This will include bazel-drake, which is a Bazel-internal detail. Bazel edits the contents of that directory for its own purposes, and those changes will spuriously appear in the CLion UI as changes that need to be committed. To make CLion ignore bazel-drake, enable Git integration under the VCS tab, then go to File > Settings. Select the Version Control menu item directly (not one of the subtopics displayed when that item is expanded). You will see a list of all the Git root directories. Look for bazel-drake on that list and select it. On the right hand side are + and - buttons; click - to remove the spurious root directory. After that you should be able to go to VCS > Commit Changes and there should be no changes seen.

Integrating External Tools with CLion

CLion provides a mechanism for invoking external binaries/scripts/etc. with parameters derived from the CLion GUI. Below, we outline a number of common tools to aid with compliance with the Drake style guide. The work to create a new external tool is the same in all cases; only the specific tool settings differ from tool to tool. We’ll outline the general work here and provide per-tool details below. The GUI description applies to version 2018.1.6 and may be slightly different in previous versions.

1. Open the Settings dialog (File > Settings) or Alt+Ctrl+S.
2. Navigate to Tools > External Tools.
3. Click the + sign to add a new tool.
4. Set the appropriate fields in the Edit Tool. See the following tools for details.
5. Click Ok.

There are several ways to use an External Tool. One is to right-click on a file and select External Tools > Tool Name. Another is to select Tools > External Tools > Tool Name. For tools that operate on a selected file, make sure that file is “active” by clicking on it. The Tool Name will be the value set in the Name field outlined below.

Formatting files

You can use clang format to modify the formatting of your file in the GUI. We’ll introduce three variants:

• Apply clang-format to a whole file.
• Apply clang-format to selected lines.
• Apply clang-format to correct #include ordering.

These tools modify the selected file. There is a synchronization issue with CLion such that the modification may not be immediately apparent. When in doubt, select away from the target file and back; this will cause the file to refresh and you can confirm that the file has been modified as expected.

First, make sure you have installed clang-format-15 (see Tools for Code Style Compliance).

Clang format selected file

Open the Edit Tool for external tools as outlined above and enter the following values for the fields:

• Name: Clang Format Full File
• Description: Apply clang-format to the active file
• Program: clang-format-15
• Arguments: -i $FileName$
• Working directory: $FileDir$
• Advanced Options: Uncheck Open console for tool output

Leave the checkbox options in their default state.

Clang format selected lines

Open the Edit Tool for external tools as outlined above and enter the following values for the fields:

• Name: Clang Format Selected Lines
• Description: Apply clang-format to the selected lines
• Program: clang-format-15
• Arguments: -lines $SelectionStartLine$:$SelectionEndLine$ -i $FileName$
• Working directory: $FileDir$
• Advanced Options: Uncheck Open console for tool output

Leave the checkbox options in their default state.

Correct #include ordering

Open the Edit Tool for external tools as outlined above and enter the following values for the fields:

• Name: Clang Format Include Ordering
• Description: Runs the clang format for correcting includes on the current file
• Program: bazel
• Arguments: run //tools/lint:clang-format-includes -- $FilePath$
• Working directory: $Projectpath$
• Advanced Options: Uncheck Open console for tool output

Leave the checkbox options in their default state.

“Linting” files

“Linting” refers to using tools to find aspects of code which don’t conform to specified coding practices. You can apply Drake’s linting tools in CLion to find such issues. We’ll define two tools:

• General linting (via cpplint) which captures most of the Drake style guide.
• Drake extended linting which captures aspects of the Drake style guide not captured by the general linting tool. This includes detecting out-of-order #include directives.

These tools produce reports. In some cases, the reports can be automatically converted into clickable links so that you can click on a message and be taken to the file and line indicated in the message. The configuration instructions include the details of how to configure these clickable links.

You can also set the general coding style for CLion through the following steps

1. Go to File > Settings > Editor > Code Style
2. On the right panel, Go to Default Options > Right margin (columns): Set it to 80
3. Go to File > Settings > Editor > Code Style > C/C++
4. On the right panel, choose Set from > Predefined Style > Google

Lint selected file for google style guide

Open the Edit Tool for external tools as outlined above and enter the following values for the fields:

• Name: Cpplint File
• Description: Apply cpplint to the current file
• Program: bazel
• Arguments: run @styleguide//:cpplint -- --output=eclipse $FilePath$
• Working directory: $Projectpath$
• Advanced Options: Confirm Open console for tool output is checked

To configure the clickable links, enter the following string in the Advanced Options > Output filters window:

    $FILE_PATH$:$LINE$

Lint selected file for Drake style addenda

This tool is a supplement to the google style cpplint. It tests for additional style requirements which are otherwise missed by the general tool. The primary reason to run this is to confirm that the order of the #include statements is correct.

Open the Edit Tool for external tools as outlined above and enter the following values for the fields:

• Name: Drake Lint File
• Description: Apply drake lint to the current file
• Program: bazel
• Arguments: run //tools/lint:drakelint -- $FilePath$
• Working directory: $Projectpath$
• Advanced Options: Confirm Open console for tool output is checked

In the event of finding a lint problem (e.g., out-of-order include files), the CLion output will contain a single clickable link. This link is only the first error encountered in the include section; there may be more. The link merely provides a hint to the developer to see the problem area. Rather than fixing by hand, we strongly recommend executing the Clang Format Include Ordering external tool on the file.

Alternative linting configuration

The linting tools have been configured to use the bazel system. The advantage in doing so is that it guarantees that the tools are built prior to being used. However, bazel only allows one instance of bazel to run at a time. For example, if building Drake in a command-line window, it would be impossible to lint files at the same time.

The work around is to change the configurations to execute the binaries directly. This approach generally works but will fail if the corresponding bazel targets have not been built. The tools would need to be built prior to execution.

With this warning in place, you can make the following modifications to the linting tools to be able to lint and compile simultaneously.

Google style guide linting

Change the following fields in the instructions given above:

• Program: bazel-bin/external/styleguide/cpplint_binary
• Arguments: --output=eclipse $FilePath$

Building the google styleguide lint tool:

bazel build @styleguide//:cpplint

Drake style addenda

Change the following fields in the instructions given above:

• Program: bazel-bin/tools/lint/drakelint
• Arguments: $FilePath$

Building the drake addenda lint tool:

bazel build //tools/lint:drakelint

Debugging an arbitrary program in Drake with CLion

Apparently CLion (or perhaps the Bazel plugin) has a certain amount of auto-configuration of run/debug targets. It appears to hinge on the presence of the gtest.h header in source files. This is convenient, but only further mystifies the process of debugging a non-gtest program. This section explains how to configure debugging support for arbitrary programs in a Drake/CLion project.

This section assumes all of the Drake-recommended installation and configuration is done.

Get the bazel target string

Find the source file of the program in the file tree view. Right-click on the file, and select “Copy BUILD Target String”. This will put the Bazel target name into the clipboard.

Start a run configuration

From the top menu, select “Run/Edit Configurations…”. Select the “+” at the upper left of the dialog to add a new configuration. From the list, select “Bazel Command”.

Fill in the configuration

Now it’s time to fill in the new blank configuration. Give it a name, then select the “+” at the right side to add the target expression. Once the edit box appears, paste the contents of the clipboard there. Hit “Enter” or “Tab” to confirm the setting; a port number value should appear in the “Port number” field below. In “Bazel command”, select either “run” (for an arbitrary program), or “test” (for a Bazel test target). Everything else can be left at default values. Click OK to finish.

Launch the debugger

At this point, the top menu “Run” should have entries to run or debug the new configuration. Select the debug entry there, or use the controls at the upper right to launch the debugger.