refactor(Heading): update component to CSS Modules (#4819)

* refactor(Heading): update component to CSS Modules

* test(e2e): add feature flags for Heading test

* chore: fix stylelint errors

* test(e2e): update snapshots for Heading

* refactor(Heading): incorporate variant features into CSS Modules

* chore: add changeset

* test(e2e): remove theme testing

* Fix props here

* Remove examples/nextjs

* Clean up css

---------

Co-authored-by: Josh Black <joshblack@users.noreply.github.com>
Co-authored-by: Jon Rohan <yes@jonrohan.codes>

.changeset/nervous-llamas-ring.md

@@ -0,0 +1,5 @@
+---
+'@primer/react': minor
+---
+
+Update Heading component to use CSS Modules behind feature flag

e2e/components/Heading.test.ts

@@ -1,74 +1,69 @@
 import {test, expect} from '@playwright/test'
 import {visit} from '../test-helpers/storybook'
 
-test.describe('Heading', () => {
-  test.describe('Default', () => {
-    test('default @vrt', async ({page}) => {
-      await visit(page, {
-        id: 'components-heading--default',
-      })
-
-      // Default state
-      expect(await page.screenshot()).toMatchSnapshot(`Heading.Default.png`)
-    })
-
-    test('axe @aat', async ({page}) => {
-      await visit(page, {
-        id: 'components-heading--default',
-      })
-      await expect(page).toHaveNoViolations()
-    })
-  })
-
-  test.describe('Small', () => {
-    test('default @vrt', async ({page}) => {
-      await visit(page, {
-        id: 'components-heading-features--small',
-      })
+const stories = [
+  {
+    title: 'Default',
+    id: 'components-heading--default',
+  },
+  {
+    title: 'Small',
+    id: 'components-heading-features--small',
+  },
+  {
+    title: 'Medium',
+    id: 'components-heading-features--medium',
+  },
+  {
+    title: 'Large',
+    id: 'components-heading-features--large',
+  },
+] as const
 
-      expect(await page.screenshot()).toMatchSnapshot(`Heading.Small.png`)
-    })
+test.describe('Heading', () => {
+  for (const story of stories) {
+    test.describe(story.title, () => {
+      test('default @vrt', async ({page}) => {
+        await visit(page, {
+          id: story.id,
+          globals: {
+            featureFlags: {
+              primer_react_css_modules: true,
+            },
+          },
+        })
 
-    test('axe @aat', async ({page}) => {
-      await visit(page, {
-        id: 'components-heading-features--small',
+        // Default state
+        expect(await page.screenshot()).toMatchSnapshot(`Heading.${story.title}.png`)
       })
-      await expect(page).toHaveNoViolations()
-    })
-  })
 
-  test.describe('Medium', () => {
-    test('default @vrt', async ({page}) => {
-      await visit(page, {
-        id: 'components-heading-features--medium',
-      })
+      test('default (styled-components) @vrt', async ({page}) => {
+        await visit(page, {
+          id: story.id,
+        })
 
-      expect(await page.screenshot()).toMatchSnapshot(`Heading.Medium.png`)
-    })
-
-    test('axe @aat', async ({page}) => {
-      await visit(page, {
-        id: 'components-heading-features--medium',
+        // Default state
+        expect(await page.screenshot()).toMatchSnapshot(`Heading.${story.title}.png`)
       })
-      await expect(page).toHaveNoViolations()
-    })
-  })
 
-  test.describe('Large', () => {
-    test('default @vrt', async ({page}) => {
-      await visit(page, {
-        id: 'components-heading-features--large',
+      test('axe @aat', async ({page}) => {
+        await visit(page, {
+          id: story.id,
+          globals: {
+            featureFlags: {
+              primer_react_css_modules: true,
+            },
+          },
+        })
+        await expect(page).toHaveNoViolations()
       })
 
-      // Default state
-      expect(await page.screenshot()).toMatchSnapshot(`Heading.Large.png`)
-    })
-
-    test('axe @aat', async ({page}) => {
-      await visit(page, {
-        id: 'components-heading-features--large',
+      test('axe (styled-components) @aat', async ({page}) => {
+        await visit(page, {
+          id: story.id,
+        })
+        await expect(page).toHaveNoViolations()
       })
-      await expect(page).toHaveNoViolations()
     })
-  })
+  }
 })

packages/react/src/Heading/Heading.module.css

@@ -0,0 +1,17 @@
+.Heading {
+  margin: 0;
+  font-size: var(--text-title-size-large);
+  font-weight: var(--base-text-weight-semibold);
+
+  &[data-variant='large'] {
+    font: var(--text-title-shorthand-large);
+  }
+
+  &[data-variant='medium'] {
+    font: var(--text-title-shorthand-medium);
+  }
+
+  &[data-variant='small'] {
+    font: var(--text-title-shorthand-small);
+  }
+}

packages/react/src/Heading/Heading.tsx

@@ -1,3 +1,4 @@
+import cx from 'clsx'
 import React, {forwardRef, useEffect} from 'react'
 import styled from 'styled-components'
 import {get} from '../constants'
@@ -6,6 +7,9 @@ import type {SxProp} from '../sx'
 import sx from '../sx'
 import type {ComponentProps} from '../utils/types'
 import type {ForwardRefComponent as PolymorphicForwardRefComponent} from '../utils/polymorphic'
+import classes from './Heading.module.css'
+import {useFeatureFlag} from '../FeatureFlags'
+import Box from '../Box'
 
 type StyledHeadingProps = {
   as?: 'h1' | 'h2' | 'h3' | 'h4' | 'h5' | 'h6'
@@ -28,9 +32,12 @@ const StyledHeading = styled.h2<StyledHeadingProps>`
   &:where([data-variant='small']) {
     font: var(--text-title-shorthand-small, 600 16px / 1.5 ${get('fonts.normal')});
   }
+
   ${sx};
 `
-const Heading = forwardRef(({as: Component = 'h2', variant, ...props}, forwardedRef) => {
+
+const Heading = forwardRef(({as: Component = 'h2', className, variant, ...props}, forwardedRef) => {
+  const enabled = useFeatureFlag('primer_react_css_modules')
   const innerRef = React.useRef<HTMLHeadingElement>(null)
   useRefObjectAsForwardedRef(forwardedRef, innerRef)
 
@@ -50,13 +57,31 @@ const Heading = forwardRef(({as: Component = 'h2', variant, ...props}, forwarded
     }, [innerRef])
   }
 
+  if (enabled) {
+    if (props.sx) {
+      return (
+        <Box
+          as={Component}
+          className={cx(className, classes.Heading)}
+          data-variant={variant}
+          {...props}
+          // @ts-ignore shh
+          ref={innerRef}
+        />
+      )
+    }
+    return <Component className={cx(className, classes.Heading)} data-variant={variant} {...props} ref={innerRef} />
+  }
+
   return (
     <StyledHeading
       as={Component}
+      className={className}
+      data-variant={variant}
+      sx={sx}
       {...props}
       // @ts-ignore shh
       ref={innerRef}
-      data-variant={variant}
     />
   )
 }) as PolymorphicForwardRefComponent<'h2', StyledHeadingProps>

packages/react/src/Heading/__tests__/Heading.test.tsx

@@ -1,9 +1,10 @@
 import React from 'react'
 import {Heading} from '../..'
 import {render, behavesAsComponent, checkExports} from '../../utils/testing'
-import {render as HTMLRender} from '@testing-library/react'
+import {render as HTMLRender, screen} from '@testing-library/react'
 import axe from 'axe-core'
 import ThemeProvider from '../../ThemeProvider'
+import {FeatureFlags} from '../../FeatureFlags'
 
 const theme = {
   breakpoints: ['400px', '640px', '960px', '1280px'],
@@ -140,4 +141,55 @@ describe('Heading', () => {
       ),
     ).toHaveStyleRule('font-style', 'italic')
   })
+
+  describe('with primer_react_css_modules enabled', () => {
+    it('should only include css modules class', () => {
+      HTMLRender(
+        <FeatureFlags
+          flags={{
+            primer_react_css_modules: true,
+          }}
+        >
+          <Heading>test</Heading>
+        </FeatureFlags>,
+      )
+      expect(screen.getByText('test')).toHaveClass('Heading')
+      // Note: this is the generated class name when styled-components is used
+      // for this component
+      expect(screen.getByText('test')).not.toHaveClass(/^Heading__StyledHeading/)
+    })
+
+    it('should support `className` on the outermost element', () => {
+      const {container} = HTMLRender(
+        <FeatureFlags
+          flags={{
+            primer_react_css_modules: true,
+          }}
+        >
+          <Heading className="test">test</Heading>
+        </FeatureFlags>,
+      )
+      expect(container.firstChild).toHaveClass('test')
+    })
+
+    it('should support overrides with sx if provided', () => {
+      HTMLRender(
+        <FeatureFlags
+          flags={{
+            primer_react_css_modules: true,
+          }}
+        >
+          <Heading
+            sx={{
+              fontWeight: '900',
+            }}
+          >
+            test
+          </Heading>
+        </FeatureFlags>,
+      )
+
+      expect(screen.getByText('test')).toHaveStyle('font-weight: 900')
+    })
+  })
 })