Add rule no-conditional-css-prop

.changeset/ninety-flowers-promise.md

@@ -0,0 +1,5 @@
+---
+'eslint-config-widen-react': minor
+---
+
+Add a new rule that detects conditional statements used on a css prop.

packages/eslint-config-widen-react/src/react.ts

@@ -1,6 +1,7 @@
 import jsxA11y from 'eslint-plugin-jsx-a11y'
 import react from 'eslint-plugin-react'
 import reactHooks from 'eslint-plugin-react-hooks'
+import noConditionalCssProp from './rules/no-conditional-css-prop.js'
 import sharedGlobals from './sharedGlobals.js'
 
 const languageOptions = {
@@ -71,6 +72,7 @@ export default [
     files: ['*.tsx', '*.{spec,test}.{js,jsx}'],
     languageOptions,
     rules: {
+      'custom/no-conditional-css-prop': noConditionalCssProp,
       'jsx-a11y/click-events-have-key-events': 'warn',
       'jsx-a11y/label-has-associated-control': [
         'error',

packages/eslint-config-widen-react/src/rules/no-conditional-css-prop.ts

@@ -0,0 +1,35 @@
+import { Rule } from 'eslint'
+
+export default {
+  create(context) {
+    return {
+      // eslint-disable-next-line @typescript-eslint/no-explicit-any
+      JSXAttribute(node: any) {
+        if (
+          node.name.name === 'css' &&
+          node.value &&
+          node.value.type === 'JSXExpressionContainer' &&
+          (node.value.expression.type === 'ConditionalExpression' ||
+            (node.value.expression.type === 'LogicalExpression' &&
+              (node.value.expression.operator === '&&' ||
+                node.value.expression.operator === '||')))
+        ) {
+          context.report({
+            message:
+              'Avoid using conditionals within the css prop, move them to style.',
+            node,
+          })
+        }
+      },
+    }
+  },
+  meta: {
+    docs: {
+      category: 'Best Practices',
+      description: 'Disallow conditionals within the css prop in components',
+      recommended: false,
+    },
+    schema: [],
+    type: 'suggestion',
+  },
+} as Rule.RuleModule

packages/eslint-config-widen-react/src/types.d.ts

@@ -2,3 +2,4 @@ declare module 'eslint-plugin-jsx-a11y'
 declare module 'eslint-plugin-react'
 declare module 'eslint-plugin-react-hooks'
 declare module 'globals'
+declare module 'no-conditional-css-prop'

packages/eslint-config-widen-react/test/no-conditional-css-prop.test.js

@@ -0,0 +1,57 @@
+import { RuleTester } from 'eslint'
+import rule from '../src/rules/no-conditional-css-prop'
+import sharedGlobals from '../src/sharedGlobals'
+
+const ruleTester = new RuleTester({
+  languageOptions: {
+    globals: sharedGlobals,
+    parserOptions: {
+      ecmaFeatures: {
+        jsx: true,
+      },
+    },
+  },
+})
+
+ruleTester.run('no-conditional-css-prop', rule, {
+  invalid: [
+    {
+      code: '<div css={condition ? { color: "red" } : { color: "blue" }} />',
+      errors: [
+        {
+          message:
+            'Avoid using conditionals within the css prop, move them to style.',
+        },
+      ],
+    },
+    {
+      code: '<div css={condition && { color: "red" }} />',
+      errors: [
+        {
+          message:
+            'Avoid using conditionals within the css prop, move them to style.',
+        },
+      ],
+    },
+    {
+      code: '<div css={condition || { color: "blue" }} />',
+      errors: [
+        {
+          message:
+            'Avoid using conditionals within the css prop, move them to style.',
+        },
+      ],
+    },
+  ],
+  valid: [
+    {
+      code: '<div css={{ color: "red" }} />',
+    },
+    {
+      code: '<div css={someVariable} />',
+    },
+    {
+      code: '<div css={`color: ${someVariable}`} />',
+    },
+  ],
+})