feat(benchmark): support comparing benchmark result

docs/config/index.md

@@ -312,6 +312,32 @@ By providing an object instead of a string you can define individual outputs whe
 
 To provide object via CLI command, use the following syntax: `--outputFile.json=./path --outputFile.junit=./other-path`.
 
+#### benchmark.outputJson <Version>1.6.0</Version> {#benchmark-outputJson}
+
+- **Type:** `string | undefined`
+- **Default:** `undefined`
+
+A file path to store the benchmark result, which can be used for `--compare` option later.
+
+For example:
+
+```sh
+# save main branch's result
+git checkout main
+vitest bench --outputJson main.json
+
+# change a branch and compare against main
+git checkout feature
+vitest bench --compare main.json
+```
+
+#### benchmark.compare <Version>1.6.0</Version> {#benchmark-compare}
+
+- **Type:** `string | undefined`
+- **Default:** `undefined`
+
+A file path to a previous benchmark result to compare against current runs.
+
 ### alias
 
 - **Type:** `Record<string, string> | Array<{ find: string | RegExp, replacement: string, customResolver?: ResolverFunction | ResolverObject }>`

docs/guide/features.md

@@ -210,6 +210,9 @@ describe('sort', () => {
 })
 ```
 
+<img alt="Benchmark report" img-dark src="https://github.com/vitest-dev/vitest/assets/4232207/6f0383ea-38ba-4f14-8a05-ab243afea01d">
+<img alt="Benchmark report" img-light src="https://github.com/vitest-dev/vitest/assets/4232207/efbcb427-ecf1-4882-88de-210cd73415f6">
+
 ## Type Testing <Badge type="warning">Experimental</Badge> {#type-testing}
 
 Since Vitest 0.25.0 you can [write tests](/guide/testing-types) to catch type regressions. Vitest comes with [`expect-type`](https://github.com/mmkal/expect-type) package to provide you with a similar and easy to understand API.

packages/vitest/src/defaults.ts

@@ -4,7 +4,7 @@ import { isCI } from './utils/env'
 
 export const defaultInclude = ['**/*.{test,spec}.?(c|m)[jt]s?(x)']
 export const defaultExclude = ['**/node_modules/**', '**/dist/**', '**/cypress/**', '**/.{idea,git,cache,output,temp}/**', '**/{karma,rollup,webpack,vite,vitest,jest,ava,babel,nyc,cypress,tsup,build,eslint,prettier}.config.*']
-export const benchmarkConfigDefaults: Required<Omit<BenchmarkUserOptions, 'outputFile'>> = {
+export const benchmarkConfigDefaults: Required<Omit<BenchmarkUserOptions, 'outputFile' | 'compare' | 'outputJson'>> = {
   include: ['**/*.{bench,benchmark}.?(c|m)[jt]s?(x)'],
   exclude: defaultExclude,
   includeSource: [],

packages/vitest/src/node/cli/cac.ts

@@ -1,14 +1,14 @@
 import { normalize } from 'pathe'
-import cac, { type CAC } from 'cac'
+import cac, { type CAC, type Command } from 'cac'
 import c from 'picocolors'
 import { version } from '../../../package.json'
 import { toArray } from '../../utils/base'
 import type { Vitest, VitestRunMode } from '../../types'
 import type { CliOptions } from './cli-api'
-import type { CLIOption } from './cli-config'
-import { cliOptionsConfig } from './cli-config'
+import type { CLIOption, CLIOptions as CLIOptionsConfig } from './cli-config'
+import { benchCliOptionsConfig, cliOptionsConfig } from './cli-config'
 
-function addCommand(cli: CAC, name: string, option: CLIOption<any>) {
+function addCommand(cli: CAC | Command, name: string, option: CLIOption<any>) {
   const commandName = option.alias || name
   let command = option.shorthand ? `-${option.shorthand}, --${commandName}` : `--${commandName}`
   if ('argument' in option)
@@ -56,17 +56,20 @@ interface CLIOptions {
   allowUnknownOptions?: boolean
 }
 
+function addCliOptions(cli: CAC | Command, options: CLIOptionsConfig<any>) {
+  for (const [optionName, option] of Object.entries(options)) {
+    if (option)
+      addCommand(cli, optionName, option)
+  }
+}
+
 export function createCLI(options: CLIOptions = {}) {
   const cli = cac('vitest')
 
   cli
     .version(version)
 
-  for (const optionName in cliOptionsConfig) {
-    const option = (cliOptionsConfig as any)[optionName] as CLIOption<any> | null
-    if (option)
-      addCommand(cli, optionName, option)
-  }
+  addCliOptions(cli, cliOptionsConfig)
 
   cli.help((info) => {
     const helpSection = info.find(current => current.title?.startsWith('For more info, run any command'))
@@ -158,9 +161,12 @@ export function createCLI(options: CLIOptions = {}) {
     .command('dev [...filters]', undefined, options)
     .action(watch)
 
-  cli
-    .command('bench [...filters]', undefined, options)
-    .action(benchmark)
+  addCliOptions(
+    cli
+      .command('bench [...filters]', undefined, options)
+      .action(benchmark),
+    benchCliOptionsConfig,
+  )
 
   // TODO: remove in Vitest 2.0
   cli

packages/vitest/src/node/cli/cli-config.ts

@@ -638,4 +638,17 @@ export const cliOptionsConfig: VitestCLIOptions = {
   name: null,
   includeTaskLocation: null,
   snapshotEnvironment: null,
+  compare: null,
+  outputJson: null,
+}
+
+export const benchCliOptionsConfig: Pick<VitestCLIOptions, 'compare' | 'outputJson'> = {
+  compare: {
+    description: 'benchmark output file to compare against',
+    argument: '<filename>',
+  },
+  outputJson: {
+    description: 'benchmark output file',
+    argument: '<filename>',
+  },
 }

packages/vitest/src/node/config.ts

@@ -381,6 +381,12 @@ export function resolveConfig(
 
     if (options.outputFile)
       resolved.benchmark.outputFile = options.outputFile
+
+    // --compare from cli
+    if (options.compare)
+      resolved.benchmark.compare = options.compare
+    if (options.outputJson)
+      resolved.benchmark.outputJson = options.outputJson
   }
 
   resolved.setupFiles = toArray(resolved.setupFiles || []).map(file =>

packages/vitest/src/node/reporters/benchmark/index.ts

@@ -1,10 +1,8 @@
 import { VerboseReporter } from '../verbose'
-import { JsonReporter } from './json'
 import { TableReporter } from './table'
 
 export const BenchmarkReportsMap = {
   default: TableReporter,
   verbose: VerboseReporter,
-  json: JsonReporter,
 }
 export type BenchmarkBuiltinReporters = keyof typeof BenchmarkReportsMap

packages/vitest/src/node/reporters/benchmark/table/index.ts

@@ -1,8 +1,11 @@
+import fs from 'node:fs'
 import c from 'picocolors'
+import * as pathe from 'pathe'
 import type { TaskResultPack } from '@vitest/runner'
 import type { UserConsoleLog } from '../../../../types/general'
 import { BaseReporter } from '../../base'
-import { getFullName } from '../../../../utils'
+import type { BenchmarkResult, File } from '../../../../types'
+import { getFullName, getTasks } from '../../../../utils'
 import { getStateSymbol } from '../../renderers/utils'
 import { type TableRendererOptions, createTableRenderer, renderTree } from './tableRender'
 
@@ -20,11 +23,24 @@ export class TableReporter extends BaseReporter {
     super.onWatcherStart()
   }
 
-  onCollected() {
+  async onCollected() {
+    this.rendererOptions.logger = this.ctx.logger
+    this.rendererOptions.showHeap = this.ctx.config.logHeapUsage
+    this.rendererOptions.slowTestThreshold = this.ctx.config.slowTestThreshold
+    if (this.ctx.config.benchmark?.compare) {
+      const compareFile = pathe.resolve(this.ctx.config.root, this.ctx.config.benchmark?.compare)
+      try {
+        this.rendererOptions.compare = flattenFormattedBenchamrkReport(
+          JSON.parse(
+            await fs.promises.readFile(compareFile, 'utf-8'),
+          ),
+        )
+      }
+      catch (e) {
+        this.ctx.logger.error(`Failed to read '${compareFile}'`, e)
+      }
+    }
     if (this.isTTY) {
-      this.rendererOptions.logger = this.ctx.logger
-      this.rendererOptions.showHeap = this.ctx.config.logHeapUsage
-      this.rendererOptions.slowTestThreshold = this.ctx.config.slowTestThreshold
       const files = this.ctx.state.getFiles(this.watchFilters)
       if (!this.renderer)
         this.renderer = createTableRenderer(files, this.rendererOptions).start()
@@ -56,6 +72,18 @@ export class TableReporter extends BaseReporter {
     await this.stopListRender()
     this.ctx.logger.log()
     await super.onFinished(files, errors)
+
+    // write output for future comparison
+    let outputFile = this.ctx.config.benchmark?.outputJson
+    if (outputFile) {
+      outputFile = pathe.resolve(this.ctx.config.root, outputFile)
+      const outputDirectory = pathe.dirname(outputFile)
+      if (!fs.existsSync(outputDirectory))
+        await fs.promises.mkdir(outputDirectory, { recursive: true })
+      const output = createFormattedBenchamrkReport(files)
+      await fs.promises.writeFile(outputFile, JSON.stringify(output, null, 2))
+      this.ctx.logger.log(`Benchmark report written to ${outputFile}`)
+    }
   }
 
   async onWatcherStart() {
@@ -80,3 +108,70 @@ export class TableReporter extends BaseReporter {
     super.onUserConsoleLog(log)
   }
 }
+
+export interface FormattedBenchamrkReport {
+  files: {
+    filepath: string
+    groups: FormattedBenchmarkGroup[]
+  }[]
+}
+
+// flat results with TaskId as a key
+export interface FlatBenchmarkReport {
+  [id: string]: FormattedBenchmarkResult
+}
+
+interface FormattedBenchmarkGroup {
+  fullName: string
+  benchmarks: FormattedBenchmarkResult[]
+}
+
+export type FormattedBenchmarkResult = Omit<BenchmarkResult, 'samples'> & {
+  id: string
+  sampleCount: number
+}
+
+function createFormattedBenchamrkReport(files: File[]) {
+  const report: FormattedBenchamrkReport = { files: [] }
+  for (const file of files) {
+    const groups: FormattedBenchmarkGroup[] = []
+    for (const task of getTasks(file)) {
+      if (task && task.type === 'suite') {
+        const benchmarks: FormattedBenchmarkResult[] = []
+        for (const t of task.tasks) {
+          const benchmark = t.meta.benchmark && t.result?.benchmark
+          if (benchmark) {
+            const { samples, ...rest } = benchmark
+            benchmarks.push({
+              id: t.id,
+              sampleCount: samples.length,
+              ...rest,
+            })
+          }
+        }
+        if (benchmarks.length) {
+          groups.push({
+            fullName: getFullName(task, ' > '),
+            benchmarks,
+          })
+        }
+      }
+    }
+    report.files.push({
+      filepath: file.filepath,
+      groups,
+    })
+  }
+  return report
+}
+
+function flattenFormattedBenchamrkReport(report: FormattedBenchamrkReport): FlatBenchmarkReport {
+  const flat: FlatBenchmarkReport = {}
+  for (const file of report.files) {
+    for (const group of file.groups) {
+      for (const t of group.benchmarks)
+        flat[t.id] = t
+    }
+  }
+  return flat
+}