<!--- Please read this! Before opening a new issue, make sure to search for keywords in the issues filtered by the "regression" or "type::bug" label: - https://gitlab.com/gitlab-org/gitlab/issues?label_name%5B%5D=regression - https://gitlab.com/gitlab-org/gitlab/issues?label_name%5B%5D=type::bug and verify the issue you're about to submit isn't a duplicate. ---> ### Summary There is a potential bug in the `match?` method of the `::Gitlab::UntrustedRegexp` class that is preventing the validation of empty strings as the default value for a component's input, even when the regular expression allows for empty strings. This issue can cause false negatives across GitLab, as many components use this function. ### Steps to reproduce 1. Create a component in GitLab that takes an optional string input. 2. Use a regex for validation that allows for empty strings (e.g., `^(\/[\w-]+){0,2}$`). 3. Set the component input to an empty string (default value). ``` # component.yml spec: inputs: registry_subpath: default: "" regex: ^(\/[\w-]+){0,2}$ --- job: script: - echo push container to $CI_REGISTRY_IMAGE$[[ inputs.registry_subpath ]] ``` ``` # gitlab-ci.yml include: - local: component.yml ``` ### Example Project [hicksca/testing-gl-bug](https://gitlab.com/hicksca/testing-gl-bug) ### What is the current *bug* behavior? This bug prevents valid regex checks for optional inputs in GitLab pipelines. For instance, a default empty string value fails validation even when the regex allows for empty strings. Resulting in in an error: `"component.yml: registry_subpath input: default value does not match required RegEx pattern"` ### What is the expected *correct* behavior? The `match?` method should return `true` for empty strings if the regex pattern allows for empty values. ### Relevant logs and/or screenshots {width=755 height=128} ### Output of checks <!-- If you are reporting a bug on GitLab.com, uncomment below --> This bug happens on GitLab.com ### Possible fixes The bug is caused by checking `text.present?` before even calling the regex and by calling `.present?` on the output of the regex scan. Both of these checks cause all `nil` or falsey values (including empty and whitespace strings) to result in an immediate match failure. The check should either be removed entirely or replaced with a check that only prevents `nil`, assuming that was the intended purpose. **Related Code:** - [Bug Implementation](https://gitlab.com/gitlab-org/gitlab/-/blob/master/lib/gitlab/ci/config/interpolation/inputs/string_input.rb#L50) - [Method for Validating String Component Inputs Against Regex](https://gitlab.com/gitlab-org/gitlab/-/blob/master/lib/gitlab/untrusted_regexp.rb#L72) **References:** - Description of `.present?`: https://api.rubyonrails.org/classes/Object.html#method-i-present-3F - Description of `.empty?`: https://api.rubyonrails.org/classes/Object.html#method-i-blank-3F