Fix: Renovate Config Error - Duplicate Capture Group

Alex Johnson

-Nov 14, 2025

Fix: Renovate Config Error - Duplicate Capture Group

Action Required: Fix Renovate Configuration

Hey there! It looks like we've hit a snag with our Renovate configuration, and it needs a little TLC to get back on track. Specifically, there's an error in one of our regular expressions that's causing Renovate to halt pull requests (PRs) as a precautionary measure. Let's dive into the details and get this sorted out.

Understanding the Issue

At the heart of the problem lies an invalid regular expression within our Renovate configuration. Regular expressions, or regex, are sequences of characters that define a search pattern. They're incredibly powerful for matching specific text formats, but they can also be a bit tricky to get right. In this case, the regex in question is:

^(?<minor>\d+)\.(?<minor>\d+)\.(?<build>\d+)-(?<major>\d+)-bookworm$

The error message, "duplicate capture group name," gives us a crucial clue. Capture groups are parts of the regex enclosed in parentheses () that allow us to extract specific portions of the matched text. The syntax (?<name>...) assigns a name to a capture group, making it easier to refer to the captured value later. However, each capture group name within a single regex must be unique. Here, the name "minor" has been used twice, which is causing the regex engine to throw an error.

Why is this happening? This often occurs due to copy-pasting or accidental duplication when constructing the regular expression. The regex is designed to match a specific versioning pattern, likely related to Debian's "bookworm" release. The intent is to extract the major, minor, and build numbers from a version string like 1.2.3-4-bookworm. However, the duplicated minor capture group is preventing the regex from working correctly.

What's the impact? As a safety measure, Renovate has stopped creating pull requests for this repository. This is to prevent any unintended consequences that might arise from misinterpreting version numbers due to the faulty regex. Until the configuration is fixed, Renovate will remain paused.

How to Resolve the Issue

The solution is straightforward: rename one of the minor capture groups to ensure all capture group names are unique. Here’s how you can approach it:

Identify the Correct Capture Groups: Carefully examine the intended versioning scheme. Determine which parts of the version string should be captured as minor, major, and build.
Rename the Duplicate: Choose a new, descriptive name for one of the minor capture groups. For example, if the first minor group represents the feature version and the second represents the patch version, you could rename them accordingly.
Test the Regex: After making the change, thoroughly test the regular expression with various version strings to ensure it correctly captures the intended values. Tools like regex101.com are invaluable for this purpose. They allow you to input your regex and test strings, showing you exactly which parts of the string are matched by each capture group.

Here's an example of a corrected regex, assuming the first minor refers to a feature version and the second to a patch version:

^(?<feature>\d+)\.(?<patch>\d+)\.(?<build>\d+)-(?<major>\d+)-bookworm$

In this corrected version, minor has been replaced with feature and patch, ensuring each capture group has a unique name. Remember to adjust the names according to the specific versioning scheme used in your project.

Step-by-Step Fix

To fix the renovate configuration follow the steps:

Locate the Renovate Configuration File: The first step is to find the Renovate configuration file in your repository. This is typically named renovate.json, renovate.json5, or .renovaterc.json, and is located in the root directory of your repository. You can use the command line or your code editor to locate the file.
```
find . -name "renovate.json"
find . -name "renovate.json5"
find . -name ".renovaterc.json"
```
Edit the Configuration File: Open the Renovate configuration file in a text editor. Look for the section that contains the invalid regular expression. This might be within a regexManagers or matchStrings section. Identify the line with the problematic regex:
```
"matchStrings": [
  "^(?<minor>\d+)\\.(?<minor>\d+)\\.(?<build>\d+)-(?<major>\d+)-bookworm{{content}}quot;
]
```
Correct the Regular Expression: Modify the regular expression to ensure that all capture group names are unique. For example, rename one of the minor capture groups to feature or patch:
```
"matchStrings": [
  "^(?<feature>\d+)\\.(?<patch>\d+)\\.(?<build>\d+)-(?<major>\d+)-bookworm{{content}}quot;
]
```
Validate the Configuration: After making the changes, validate the Renovate configuration to ensure that it is correct. You can use the Renovate CLI to validate the configuration file. If you don't have the Renovate CLI installed, you can install it using npm:
```
npm install -g renovate
```
Then, run the following command to validate the configuration file:
```
renovate-config-validator ./renovate.json
```
Replace ./renovate.json with the path to your Renovate configuration file. This command will check the configuration file for any syntax errors or other issues.
Commit and Push the Changes: Once you have corrected the regular expression and validated the configuration, commit the changes to your repository and push them to the remote repository.
```
git add .
git commit -m "Fix: Corrected duplicate capture group name in Renovate configuration"
git push origin main
```
Monitor Renovate: After pushing the changes, monitor Renovate to ensure that it resumes creating pull requests as expected. Check the Renovate logs for any errors or warnings. If Renovate does not resume automatically, you may need to manually trigger a run.

Example Scenarios

Consider a few scenarios where this fix might apply:

Scenario 1: Debian Package Versioning: You're using Renovate to keep your dependencies up-to-date, and you've configured it to recognize Debian package version strings. The bookworm suffix indicates the Debian release, and the regex aims to extract the major, minor, and build numbers for comparison.
Scenario 2: Custom Versioning Scheme: Your project uses a custom versioning scheme with a specific format. The regex is designed to parse this format, but a mistake in the capture group names is preventing it from working correctly.

In both cases, identifying the correct capture groups and renaming the duplicate will resolve the issue and allow Renovate to function as intended.

Preventing Future Issues

To avoid similar issues in the future, consider these best practices:

Use a Regex Linter: Integrate a regex linter into your development workflow. Linters can catch common errors, such as duplicate capture group names, during development.
Test Thoroughly: Always test your regular expressions with a variety of inputs to ensure they behave as expected. Tools like regex101.com are invaluable for this purpose.
Document Your Regexes: Add comments to your Renovate configuration to explain the purpose of each regular expression. This will make it easier for others (and your future self) to understand and maintain the configuration.
Code Reviews: Have your Renovate configuration reviewed by another team member before committing changes. A fresh pair of eyes can often spot errors that you might have missed.

By following these practices, you can minimize the risk of introducing errors into your Renovate configuration and ensure that your dependencies stay up-to-date.

Conclusion

Don't worry; fixing this Renovate configuration hiccup is totally manageable. By identifying and correcting the duplicate capture group name in the regular expression, you'll get Renovate back on track, automatically keeping your dependencies up-to-date. Remember to test your changes thoroughly and consider implementing preventative measures to avoid similar issues in the future. Happy Renovating!

For more information on regular expressions, check out this comprehensive guide on MDN Web Docs.