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Code references

Read time: 3 minutes
Last edited: Aug 17, 2020

Overview

This topic explains how to use code references in LaunchDarkly to find and manage references to your feature flags.

The code references feature lets you find references to your feature flags. This makes it easy to determine which projects reference your feature flags, and simplifies removal of technical debt.

We've open-sourced a utility called ld-find-code-refs that scans your code and pushes code reference information to LaunchDarkly. You can integrate this utility into your CI/CD process, or use other trigger mechanisms like GitHub Actions, cron jobs, or commit-triggered Lambda functions.

Integrating ld-find-code-refs with your toolchain

We've designed this feature so that LaunchDarkly services do not need direct access to your source code. The ld-find-code-refs utility is agnostic to where your code is hosted.

Our approach makes it possible to push references to LaunchDarkly whether you're using GitHub, GitHub Enterprise, Bitbucket, Bitbucket Enterprise, GitLab, Azure DevOps, or any other Git code hosting tool.

We offer built-in configurations for common trigger mechanisms and CI/CD providers, including:

You can also invoke the ld-find-code-refs utility from the command line. Run this utility in any custom workflow, such as a bash script or cron job.

Prerequisites

To set up code references in LaunchDarkly, you must have:

  • An API access token with writer-level access or higher. Create an API access token in the Access Tokens page. To learn more, read API access tokens.
  • You must allow ld-find-code-refs to run in environment that has access to your source code.
API access tokens can also use custom roles

Alternatively, you can give the access token access to a custom role with the code-reference-repository resource specifier. To learn more, read Custom roles.

Using code references

You can view existing code references for feature flags in the LaunchDarkly dashboard.

To do so, visit a feature flag's Code references tab.

The screenshot below shows the code references tab displaying an active code reference:

The code references tab for a feature flag.
The code references tab for a feature flag.

Once the code reference has been removed from the codebase, and the scanning tool has been run again, the LaunchDarkly UI will notify you that the flag has been removed from the codebase:

The code references tab for an extinct feature flag
The code references tab for an extinct feature flag

You can toggle a repository on or off to allow or forbid code reference triggers from pushing new data to it.

Managing code references

Manage code references on the Integrations page for your project. Code references are organized into repositories, which the ld-find-code-refs tool creates automatically.

After a repository appears on the Integrations page, you can either temporarily disable it (preventing new code references from being added to LaunchDarkly), or delete all code references associated with the repository.

To disable the repository, click the toggle switch to Off. To delete the repository, click Delete.

If you click Delete, LaunchDarkly purges all data associated with that repository. It will no longer have any record of the code reference or any source context lines. Deleting is permanent and cannot be undone.

Remove code references before you click Delete

If you want to remove a connection permanently, be sure to remove any ld-find-code-refs triggers from your code. If you're not sure how or where the trigger is invoked, you can also delete the access token your trigger uses. If you delete a repository with automated code reference updates enabled, the connection is recreated the next time an automated code reference trigger executes.

The disabling and delete options appear below:

The code reference repositories section of the Integrations page.
The code reference repositories section of the Integrations page.

Configuring context lines

The ld-find-code-refs utility sends two lines of surrounding source context to LaunchDarkly.

Two lines of code appear above, and two lines appear below the actual reference.

The screenshot below shows code references with context lines:

Code references with context lines.
Code references with context lines.

Having a few lines of context can make it easier to understand references to a feature flag. However, these lines are optional. You can disable this feature when you configure ld-find-code-refs.

If context lines are disabled, your code references only show a code location in the form of a filename and line, as well as a link to that location in your Git hosting provider.

The following screenshot shows code references without context lines:

Code references with no context lines.
Code references with no context lines.

Limitations

The LaunchDarkly code references API asserts various limits to limit the number of "false positive" code references. ld-find-code-refs logs warning messages if you exceed any of these limits. Above certain values, LaunchDarkly may ignore some files and references.

These limits include:

  • We do not scan code references for flags with keys that have less than 3 characters.
  • We store up to 10000 files with code references per repository. LaunchDarkly ignores additional files.
  • We allow up to 500 characters is allowed per line of source code stored. LaunchDarkly truncates additional files.
  • We allow up to 25000 code references per file. LaunchDarkly ignores additional references.

If you've encountered any of these limits, or are noticing a large number of false positives being detected by ld-find-code-refs, we'd recommend configuring an .ldignore file in your repository with rules matching the files and directories you'd like to exclude.

To learn more about .ldignore files, read the ld-find-code-refs documentation.

Using ld-find-code-refs with the React SDK

The code references feature scans your source code for occurrences of your flag keys. This process requires your source code to reference flag keys exactly as they appear in LaunchDarkly.

However, by default, the React SDK camel-cases all flag keys for easier access with dot notation. To use the code references feature in conjunction with the React SDK, configure the SDK to disable this camel-casing feature.

To learn more, read Flag keys in the React SDK documentation.