Lint for reserved HTML classes

.changeset/ten-ravens-camp.md

@@ -0,0 +1,5 @@
+---
+'@primer/view-components': patch
+---
+
+Add general reserved-class-checking linter

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/disallow_component_css_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 DisallowComponentCssCounter < 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

@@ -59,8 +59,8 @@
     "@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",

script/export-css-selectors

@@ -1,37 +1,83 @@
 #!/usr/bin/env node
 
-const postcss = require('postcss');
-const glob = require('glob');
-const fs = require('fs');
+const postcss = require('postcss')
+const { readFile, writeFile } = require('node:fs/promises')
+const { promisify } = require('util')
+const glob = promisify(require('glob'))
+const CSSwhat = require('css-what')
 
-console.log('Exporting CSS selectors...');
+console.log('Exporting CSS selectors...')
 
-const export_selectors = (folder) => {
+const exportSelectors = (folder) => {
   const folder_glob = folder + '/**/*.css'
+  const componentNameRegex = new RegExp(`${folder.replace('/','\\/')}\\/(.*).css`)
 
-  glob(folder_glob, (_err, files) => {
-    files.forEach(file => {
-      console.log(`Processing ${file}`)
-      const css = fs.readFileSync(file, 'utf8')
-      const root = postcss.parse(css)
-      const componentNameRegex = new RegExp(`${folder.replace('/','\\/')}\\/(.*).css`)
-      const componentName = componentNameRegex.exec(file)[1]
-      const selectors = []
-
-      root.walkRules(rule => {
-        if (rule.parent.type === 'atrule' && rule.parent.name === 'keyframes') {
-          return
-        }
-
-        rule.selectors.forEach(ruleSelector => {
-          selectors.push(ruleSelector)
+  return glob(folder_glob).then(files =>
+    Promise.all(
+      files.map(async (file) => {
+        console.log(`Processing ${file}`)
+        const css = await readFile(file, 'utf8')
+        const root = postcss.parse(css)
+        const componentName = componentNameRegex.exec(file)[1]
+
+        const selectors = []
+        const classes = []
+
+        root.walkRules(rule => {
+          // @keyframes at-rules have children that look like they have normal
+          // CSS selectors, but they're each just "from", "to", or a percentage.
+          // Either way, we don't have to worry about them as selectors and they
+          // don't include any classes.
+          if (rule.parent?.type === 'atrule' && rule.parent?.name === 'keyframes') {
+            return
+          }
+
+          rule.selectors.forEach(ruleSelector => {
+            selectors.push(ruleSelector)
+            CSSwhat.parse(ruleSelector)[0].forEach(ruleObj => {
+              if (ruleObj.type === 'attribute' && ruleObj.name === 'class') {
+                classes.push(ruleObj.value)
+              }
+            })
+          })
         })
-      })
 
-      fs.writeFileSync(`${file}.json`, JSON.stringify({ 'name': componentName, 'selectors': [...new Set(selectors)] }, null, 2))
-    })
-  })
+        console.log(`Writing ${file}.json`)
+        writeFile(
+          `${file}.json`,
+          JSON.stringify({
+            name: componentName,
+            selectors: [...new Set(selectors)],
+            classes: [...new Set(classes)]
+          }, null, 2)
+        ).catch(error => console.error(`Failed to write ${file}.json`, { error }))
+
+        return classes
+      })
+    )
+  )
 }
 
-export_selectors('app/components/primer')
-export_selectors('app/lib/primer/css')
+// stylesheets under app/lib/primer/css need their individual
+// json files generated
+exportSelectors('app/lib/primer/css')
+
+// class names referenced under app/components/primer might need
+// to be reserved in addition to getting individual json files
+const classShouldBeReserved = className =>
+  (className[0].toUpperCase() === className[0])
+exportSelectors('app/components/primer')
+  .then(classLists => {
+    console.log(`Writing static/classes.json`)
+    return writeFile(
+      'static/classes.json',
+      JSON.stringify(
+        [...new Set(classLists.reduce((a, b) => a.concat(b)))]
+          .filter(classShouldBeReserved)
+          .sort(),
+        null,
+        2
+      )
+    )
+  })
+  .catch(error => console.error("failed to write static/classes.json", { error }))