Inherit from BaseLinter for HTML class checking

BaseLinter already has class checking and exception count functionality.

We did have to modify BaseLinter to allow an empty `TAGS` array
constant, thereby checking all tags.

lib/primer/view_components/linters/base_linter.rb

@@ -40,7 +40,7 @@ def run(processed_source)
 
         tags.each do |tag|
           next if tag.closing?
-          next unless self.class::TAGS&.include?(tag.name)
+          next if self.class::TAGS&.none?(tag.name)
 
           classes = tag.attributes["class"]&.value&.split(" ") || []
           tag_tree[tag][:offense] = false

lib/primer/view_components/linters/view_component_html_classes_counter.rb

@@ -0,0 +1,30 @@
+# frozen_string_literal: true
+
+require_relative "base_linter"
+
+# Load all the other linters so we can filter out their restricted
+# CLASSES—they will be responsible for complaining about the use of
+# those HTML classes.
+Dir[File.join(__dir__, "*.rb")].sort.each do |file|
+  require file unless file == __FILE__
+end
+
+module ERBLint
+  module Linters
+    # Counts the number of times a class reserved for ViewComponents is used
+    class ViewComponentHtmlClassesCounter < BaseLinter
+      CLASSES = (
+        JSON.parse(
+          File.read(
+            File.join(__dir__, "..", "..", "..", "..", "static", "classes.json")
+          )
+        ) - BaseLinter.subclasses.reduce([]) do |html_classes, klass|
+          html_classes.concat(klass.const_get(:CLASSES))
+        end
+      ).freeze
+
+      TAGS = nil
+      MESSAGE = "Primer ViewComponents defines some HTML classes with associated styles that should not be used outside those components. (These classes might have their styles changed or even disappear in the future.) Instead of using this class directly, please use its component if appropriate or define the styles you need some other way."
+    end
+  end
+end

package.json

@@ -53,15 +53,14 @@
     "@github/mini-throttle": "^2.1.0",
     "@github/relative-time-element": "^4.0.0",
     "@github/tab-container-element": "^3.1.2",
-    "@primer/behaviors": "^1.2.0",
-    "css-what": "^6.1.0"
+    "@primer/behaviors": "^1.2.0"
   },
   "devDependencies": {
     "@changesets/changelog-github": "^0.4.6",
     "@changesets/cli": "^2.24.1",
     "@github/browserslist-config": "^1.0.0",
-    "@github/markdownlint-github": "^0.2.2",
     "@github/prettier-config": "0.0.4",
+    "@github/markdownlint-github": "^0.2.2",
     "@playwright/test": "^1.27.1",
     "@primer/css": "20.4.7",
     "@primer/primitives": "^7.9.0",