ci: size report (#6082)

## Summary

show bundle size info automatically in Pull Request

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-6082-ci-size-report-28e6d73d365081c2bf73ce9919a7c01a)
by [Unito](https://www.unito.io)

scripts/size-report.js

@@ -0,0 +1,162 @@
+// @ts-check
+import { markdownTable } from 'markdown-table'
+import { existsSync } from 'node:fs'
+import { readdir } from 'node:fs/promises'
+import path from 'node:path'
+import prettyBytes from 'pretty-bytes'
+
+import { getCategoryMetadata } from './bundle-categories.js'
+
+/**
+ * @typedef {Object} SizeResult
+ * @property {number} size
+ * @property {number} gzip
+ * @property {number} brotli
+ */
+
+/**
+ * @typedef {SizeResult & { file: string, category?: string }} BundleResult
+ */
+
+const currDir = path.resolve('temp/size')
+const prevDir = path.resolve('temp/size-prev')
+let output = '## Bundle Size Report\n\n'
+const sizeHeaders = ['Size', 'Gzip', 'Brotli']
+
+run()
+
+/**
+ * Main function to generate the size report
+ */
+async function run() {
+  if (!existsSync(currDir)) {
+    console.error('Error: temp/size directory does not exist')
+    console.error('Please run "pnpm size:collect" first')
+    process.exit(1)
+  }
+
+  await renderFiles()
+  process.stdout.write(output)
+}
+
+/**
+ * Renders file sizes and diffs between current and previous versions
+ */
+async function renderFiles() {
+  /**
+   * @param {string[]} files
+   * @returns {string[]}
+   */
+  const filterFiles = (files) => files.filter((file) => file.endsWith('.json'))
+
+  const curr = filterFiles(await readdir(currDir))
+  const prev = existsSync(prevDir) ? filterFiles(await readdir(prevDir)) : []
+  const fileList = new Set([...curr, ...prev])
+
+  // Group bundles by category
+  /** @type {Map<string, Array<{fileName: string, curr: BundleResult | undefined, prev: BundleResult | undefined}>>} */
+  const bundlesByCategory = new Map()
+
+  for (const file of fileList) {
+    const currPath = path.resolve(currDir, file)
+    const prevPath = path.resolve(prevDir, file)
+
+    const curr = await importJSON(currPath)
+    const prev = await importJSON(prevPath)
+    const fileName = curr?.file || prev?.file || ''
+    const category = curr?.category || prev?.category || 'Other'
+
+    if (!bundlesByCategory.has(category)) {
+      bundlesByCategory.set(category, [])
+    }
+
+    // @ts-expect-error - get is valid
+    bundlesByCategory.get(category).push({ fileName, curr, prev })
+  }
+
+  // Sort categories by their order
+  const sortedCategories = Array.from(bundlesByCategory.keys()).sort((a, b) => {
+    const metaA = getCategoryMetadata(a)
+    const metaB = getCategoryMetadata(b)
+    return (metaA?.order ?? 99) - (metaB?.order ?? 99)
+  })
+
+  let totalSize = 0
+  let totalCount = 0
+
+  // Render each category
+  for (const category of sortedCategories) {
+    const bundles = bundlesByCategory.get(category) || []
+    if (bundles.length === 0) continue
+
+    const categoryMeta = getCategoryMetadata(category)
+    output += `### ${category}\n\n`
+    if (categoryMeta?.description) {
+      output += `_${categoryMeta.description}_\n\n`
+    }
+
+    const rows = []
+    let categorySize = 0
+
+    for (const { fileName, curr, prev } of bundles) {
+      if (!curr) {
+        // File was deleted
+        rows.push([`~~${fileName}~~`])
+      } else {
+        rows.push([
+          fileName,
+          `${prettyBytes(curr.size)}${getDiff(curr.size, prev?.size)}`,
+          `${prettyBytes(curr.gzip)}${getDiff(curr.gzip, prev?.gzip)}`,
+          `${prettyBytes(curr.brotli)}${getDiff(curr.brotli, prev?.brotli)}`
+        ])
+        categorySize += curr.size
+        totalSize += curr.size
+        totalCount++
+      }
+    }
+
+    // Sort rows by file name within category
+    rows.sort((a, b) => {
+      const fileA = a[0].replace(/~~/g, '')
+      const fileB = b[0].replace(/~~/g, '')
+      return fileA.localeCompare(fileB)
+    })
+
+    output += markdownTable([['File', ...sizeHeaders], ...rows])
+    output += `\n\n**Category Total:** ${prettyBytes(categorySize)}\n\n`
+  }
+
+  // Add overall summary
+  if (totalCount > 0) {
+    output += '---\n\n'
+    output += `**Overall Total Size:** ${prettyBytes(totalSize)}\n`
+    output += `**Total Bundle Count:** ${totalCount}\n`
+  }
+}
+
+/**
+ * Imports JSON data from a specified path
+ *
+ * @template T
+ * @param {string} filePath - Path to the JSON file
+ * @returns {Promise<T | undefined>} The JSON content or undefined if the file does not exist
+ */
+async function importJSON(filePath) {
+  if (!existsSync(filePath)) return undefined
+  return (await import(filePath, { with: { type: 'json' } })).default
+}
+
+/**
+ * Calculates the difference between the current and previous sizes
+ *
+ * @param {number} curr - The current size
+ * @param {number} [prev] - The previous size
+ * @returns {string} The difference in pretty format
+ */
+function getDiff(curr, prev) {
+  if (prev === undefined) return ''
+  const diff = curr - prev
+  if (diff === 0) return ''
+  const sign = diff > 0 ? '+' : ''
+  return ` (**${sign}${prettyBytes(diff)}**)`
+}