> For the complete documentation index, see [llms.txt](https://docs.vale.sh/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.vale.sh/checks/conditional.md). # conditional Learn about the conditional extension point. | Name | Type | Description | | ------------ | -------- | ------------------------------------------------------------------------------------------------------------------------------ | | `ignorecase` | `bool` | Makes all matches case-insensitive. | | `first` | `string` | The antecedent of the statement. | | `second` | `string` | The consequent of the statement. | | `vocab` | `bool` | If false, disables all active vocabularies for this rule (default: true). | | `exceptions` | `array` | An array of strings to be ignored. | | `in` | `string` | The [View](/topics/views.md) scope `second` is looked for in. Without it, `second` is looked for in the same scope as `first`. | ```yaml extends: conditional message: "'%s' has no definition" level: error scope: text ignorecase: false # Ensures that the existence of 'first' # implies the existence of 'second'. first: '\b([A-Z]{3,5})\b' second: '(?:\b[A-Z][a-z]+ )+\(([A-Z]{3,5})\)' # ... with the exception of these: exceptions: - ABC - ADD ``` For example, consider the following text: > According to Wikipedia, the World Health Organization (WHO) is a specialized agency of the United Nations that is concerned with international public health. We can now use WHO because it has been defined, but we can’t use DAFB because people may not know what it represents. We can use `DAFB` when it’s presented as code, though. Using the above text with our example rule yields the following: ```bash test.md:1:224:style.UnexpandedAcronyms:'DAFB' has no definition ``` A definition has to come before the use: a match of `second` covers every `first` after it in the file, in any later paragraph, and a `first` before it is flagged. Every undefined use is flagged, not only the first one. ## [Several definition forms](#several-definition-forms) Every capture group in `second` counts, so a pattern with an alternation accepts more than one way of defining a term. The rule below is satisfied by `WHO: World Health Organization` and by `World Health Organization (WHO)` alike: ```yaml extends: conditional message: "'%s' has no definition" level: error scope: text first: '\b([A-Z]{3,5})\b' second: '\b([A-Z]{3,5}): (?:[A-Z][a-z]+ ?)+|(?:\b[A-Z][a-z]+ )+\(([A-Z]{3,5})\)' ``` > WHO: World Health Organization. The Central Intelligence Agency (CIA) is next. But FBI is never defined, so FBI is flagged both times. ```bash test.md:1:84:style.UnexpandedAcronyms:'FBI' has no definition test.md:1:109:style.UnexpandedAcronyms:'FBI' has no definition ``` ## [Exceptions and vocabulary](#exceptions-and-vocabulary) A `first` match listed in `exceptions` is never flagged. The project's [vocabulary](/keys/vocabularies.md) is added to that list, so a term in `accept.txt` needs no definition either, and a multi-word entry covers the terms inside it: with `AWS CLI` accepted, `AWS` and `CLI` pass when they appear together and are flagged when they appear alone. ```yaml extends: conditional message: "'%s' has no definition" level: error scope: text first: '\b([A-Z]{3,5})\b' second: '(?:\b[A-Z][a-z]+ )+\(([A-Z]{3,5})\)' exceptions: - ABC - ADD ``` > The API is fine. The AWS CLI is fine. AWS alone is not. ```bash test.md:1:39:style.UnexpandedAcronyms:'AWS' has no definition ``` Set `vocab: false` to ignore the vocabulary and use only the rule's own `exceptions`. ## [Presence checks](#presence-checks) When `second` has a capture group, a `first` match is allowed only if its captured value was also captured by a `second` match—the acronym-definition pattern above. When `second` has *no* capture group, the rule is a plain presence check: any `first` match requires `second` to appear somewhere in the same scope. ```yaml extends: conditional message: "A 'Section' requires a 'Summary:' line." level: error scope: raw first: '\bSection\b' second: 'Summary:' ``` ## [Lookarounds](#lookarounds) Regular expression lookarounds can be used to restrict the capture of the rule, allowing for more complex conditional statements. For example, the following rule will flag any MDX-style import that is not used: ```yaml extends: conditional message: "'%s' has been imported but not used." level: error scope: raw first: '(?<=import )(\w+)(?= from)' second: '(?<=<)(\w+)' ``` See the [regex guide](/guides/regex.md) for more information. ## [Across a View's scopes](#across-a-views-scopes) When a [View](/topics/views.md) names the parts of a file, `in` looks for `second` in one part while `first` is matched in another. A commit whose subject is marked with `!` needs a `BREAKING CHANGE:` footer: ```yaml extends: conditional message: "A '!' in the subject needs a 'BREAKING CHANGE:' footer." level: error scope: subject first: '^\w+(?:\([^)]*\))?!:' second: '^BREAKING CHANGE: ' in: trailer ``` The alert lands on the subject's `!`. The reverse, a footer that needs the `!`, is the same rule with `scope` and `in` swapped. An `in` that no View defines is an error when the rule loads. --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter: ``` GET https://docs.vale.sh/checks/conditional.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.