forked from vercel/next.js
/
loader.ts
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/
loader.ts
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import type { AdjustFontFallback, FontLoader } from 'next/font'
// @ts-ignore
import { calculateSizeAdjustValues } from 'next/dist/server/font-utils'
// @ts-ignore
import * as Log from 'next/dist/build/output/log'
// @ts-ignore
import chalk from 'next/dist/compiled/chalk'
// @ts-ignore
import {
fetchCSSFromGoogleFonts,
fetchFontFile,
getFontAxes,
getUrl,
validateData,
} from './utils'
const cssCache = new Map<string, Promise<string>>()
const fontCache = new Map<string, any>()
const downloadGoogleFonts: FontLoader = async ({
functionName,
data,
config,
emitFontFile,
isServer,
}) => {
const subsets = config?.subsets || []
const {
fontFamily,
weights,
styles,
display,
preload,
selectedVariableAxes,
fallback,
adjustFontFallback,
variable,
subsets: callSubsets,
} = validateData(functionName, data)
if (isServer && preload && !callSubsets && !config?.subsets) {
Log.warn(
`The ${chalk.bold('@next/font/google')} font ${chalk.bold(
fontFamily
)} has no selected subsets. Please specify subsets in the function call or in your ${chalk.bold(
'next.config.js'
)}, otherwise no fonts will be preloaded. Read more: https://nextjs.org/docs/messages/google-fonts-missing-subsets`
)
}
const fontAxes = getFontAxes(
fontFamily,
weights,
styles,
selectedVariableAxes
)
const url = getUrl(fontFamily, fontAxes, display)
let cachedCssRequest = cssCache.get(url)
const fontFaceDeclarations =
cachedCssRequest ?? (await fetchCSSFromGoogleFonts(url, fontFamily))
if (!cachedCssRequest) {
cssCache.set(url, fontFaceDeclarations)
} else {
cssCache.delete(url)
}
// Find font files to download
const fontFiles: Array<{
googleFontFileUrl: string
preloadFontFile: boolean
}> = []
let currentSubset = ''
for (const line of fontFaceDeclarations.split('\n')) {
// Each @font-face has the subset above it in a comment
const newSubset = /\/\* (.+?) \*\//.exec(line)?.[1]
if (newSubset) {
currentSubset = newSubset
} else {
const googleFontFileUrl = /src: url\((.+?)\)/.exec(line)?.[1]
if (googleFontFileUrl) {
fontFiles.push({
googleFontFileUrl,
preloadFontFile:
!!preload && (callSubsets ?? subsets).includes(currentSubset),
})
}
}
}
// Download font files
const downloadedFiles = await Promise.all(
fontFiles.map(async ({ googleFontFileUrl, preloadFontFile }) => {
let cachedFontRequest = fontCache.get(googleFontFileUrl)
const fontFileBuffer =
cachedFontRequest ?? (await fetchFontFile(googleFontFileUrl))
if (!cachedFontRequest) {
fontCache.set(googleFontFileUrl, fontFileBuffer)
} else {
fontCache.delete(googleFontFileUrl)
}
const ext = /\.(woff|woff2|eot|ttf|otf)$/.exec(googleFontFileUrl)![1]
// Emit font file to .next/static/fonts
const selfHostedFileUrl = emitFontFile(
fontFileBuffer,
ext,
preloadFontFile
)
return {
googleFontFileUrl,
selfHostedFileUrl,
}
})
)
// Replace @font-face sources with self-hosted files
let updatedCssResponse = fontFaceDeclarations
for (const { googleFontFileUrl, selfHostedFileUrl } of downloadedFiles) {
updatedCssResponse = updatedCssResponse.replace(
googleFontFileUrl,
selfHostedFileUrl
)
}
// Add fallback font
let adjustFontFallbackMetrics: AdjustFontFallback | undefined
if (adjustFontFallback) {
try {
const { ascent, descent, lineGap, fallbackFont, sizeAdjust } =
calculateSizeAdjustValues(
require('next/dist/server/google-font-metrics.json')[fontFamily]
)
adjustFontFallbackMetrics = {
fallbackFont,
ascentOverride: `${ascent}%`,
descentOverride: `${descent}%`,
lineGapOverride: `${lineGap}%`,
sizeAdjust: `${sizeAdjust}%`,
}
} catch {
Log.error(
`Failed to find font override values for font \`${fontFamily}\``
)
}
}
return {
css: updatedCssResponse,
fallbackFonts: fallback,
weight:
weights.length === 1 && weights[0] !== 'variable'
? weights[0]
: undefined,
style: styles.length === 1 ? styles[0] : undefined,
variable,
adjustFontFallback: adjustFontFallbackMetrics,
}
}
export default downloadGoogleFonts