Help with conditional rule: Check whether variable is unused

[wilhelmer]

I'm having trouble understanding the conditional extension point syntax.

I want to create a rule that notifies me when a variable has been defined via import <variable> from, but the variable is never used.

Example

import Profile from "@site/static/img/icons/profile.svg";
import Admonition from '@theme-original/Admonition';
import Notif from "@site/static/img/icons/notification.svg";

Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. 

1. On the left-side menu, click <Profile className="icon"/> **Profile** > <Profile className="icon"/> **Profile**.
2. Click <Notif className="icon"/> **Email Notifications**.

In the example above, Vale should report that "Admonition" was defined, but never used.

I feel like this should be possible with the conditional extension point, but I can't get it to work.

extends: conditional
message: "'%s' has no definition"
level: error
scope: raw
ignorecase: false
first: 'import (.*?) from'
second: '\<\0 className' # what to use here? Can I use back references? 

[jdkato]

While this feels like something that shouldn't be done using Vale (it's more appropriate for an MDX syntax linter), it is possible:

extends: conditional
message: "'%s' has been imported but not used."
level: error
scope: raw
first: "(?<=import )(.*)(?= from)"
second: '(?<=<)(\w+)'

[wilhelmer]

Thanks for that! You're right, probably not meant for Vale, but still interesting how this works.

So you're using the lookaheads and lookbehinds to "exclude" these parts from match, so that only (.*) and (\w+) are compared? Clever stuff.