feat(coverage): automatic threshold updating

docs/config/index.md

@@ -767,6 +767,16 @@ Do not show files with 100% statement, branch, and function coverage.
 Check thresholds per file.
 See `lines`, `functions`, `branches` and `statements` for the actual thresholds.
 
+#### thresholdAutoUpdate
+
+- **Type:** `boolean`
+- **Default:** `false`
+- **Available for providers:** `'c8' | 'istanbul'`
+- **CLI:** `--coverage.thresholdAutoUpdate=<boolean>`
+
+Update threshold values `lines`, `functions`, `branches` and `statements` to configuration file when current coverage is above the configured thresholds.
+This option helps to maintain thresholds when coverage is improved.
+
 #### lines
 
 - **Type:** `number`

packages/coverage-c8/src/provider.ts

@@ -177,5 +177,18 @@ export class C8CoverageProvider extends BaseCoverageProvider implements Coverage
 
     await report.run()
     await checkCoverages(options, report)
+
+    if (this.options.thresholdAutoUpdate && allTestsRun) {
+      this.updateThresholds({
+        coverageMap: await report.getCoverageMapFromAllCoverageFiles(),
+        thresholds: {
+          branches: this.options.branches,
+          functions: this.options.functions,
+          lines: this.options.lines,
+          statements: this.options.statements,
+        },
+        configurationFile: this.ctx.server.config.configFile,
+      })
+    }
   }
 }

packages/coverage-istanbul/src/provider.ts

@@ -154,6 +154,19 @@ export class IstanbulCoverageProvider extends BaseCoverageProvider implements Co
         statements: this.options.statements,
       })
     }
+
+    if (this.options.thresholdAutoUpdate && allTestsRun) {
+      this.updateThresholds({
+        coverageMap,
+        thresholds: {
+          branches: this.options.branches,
+          functions: this.options.functions,
+          lines: this.options.lines,
+          statements: this.options.statements,
+        },
+        configurationFile: this.ctx.server.config.configFile,
+      })
+    }
   }
 
   checkThresholds(coverageMap: CoverageMap, thresholds: Record<Threshold, number | undefined>) {

packages/vitest/src/types/coverage.ts

@@ -186,6 +186,13 @@ export interface BaseCoverageOptions {
    * @default undefined
    */
   statements?: number
+
+  /**
+   * Update threshold values automatically when current coverage is higher than earlier thresholds
+   *
+   * @default false
+   */
+  thresholdAutoUpdate?: boolean
 }
 
 export interface CoverageIstanbulOptions extends BaseCoverageOptions {

packages/vitest/src/utils/coverage.ts

@@ -1,6 +1,61 @@
+import { readFileSync, writeFileSync } from 'node:fs'
+import type { CoverageMap } from 'istanbul-lib-coverage'
 import type { BaseCoverageOptions, ResolvedCoverageOptions } from '../types'
 
+type Threshold = 'lines' | 'functions' | 'statements' | 'branches'
+
+const THRESHOLD_KEYS: Readonly<Threshold[]> = ['lines', 'functions', 'statements', 'branches']
+
 export class BaseCoverageProvider {
+  /**
+   * Check if current coverage is above configured thresholds and bump the thresholds if needed
+   */
+  updateThresholds({ configurationFile, coverageMap, thresholds }: {
+    coverageMap: CoverageMap
+    thresholds: Record<Threshold, number | undefined>
+    configurationFile?: string
+  }) {
+    // Thresholds cannot be updated if there is no configuration file and
+    // feature was enabled by CLI, e.g. --coverage.thresholdAutoUpdate
+    if (!configurationFile)
+      throw new Error('Missing configurationFile. The "coverage.thresholdAutoUpdate" can only be enabled when configuration file is used.')
+
+    const summary = coverageMap.getCoverageSummary()
+    const thresholdsToUpdate: Threshold[] = []
+
+    for (const key of THRESHOLD_KEYS) {
+      const threshold = thresholds[key] || 100
+      const actual = summary[key].pct
+
+      if (actual > threshold)
+        thresholdsToUpdate.push(key)
+    }
+
+    if (thresholdsToUpdate.length === 0)
+      return
+
+    const originalConfig = readFileSync(configurationFile, 'utf8')
+    let updatedConfig = originalConfig
+
+    for (const threshold of thresholdsToUpdate) {
+      // Find the exact match from the configuration file and replace the value
+      const previousThreshold = (thresholds[threshold] || 100).toString()
+      const pattern = new RegExp(`(${threshold}\\s*:\\s*)${previousThreshold.replace('.', '\\.')}`)
+      const matches = originalConfig.match(pattern)
+
+      if (matches)
+        updatedConfig = updatedConfig.replace(matches[0], matches[1] + summary[threshold].pct)
+      else
+        console.error(`Unable to update coverage threshold ${threshold}. No threshold found using pattern ${pattern}`)
+    }
+
+    if (updatedConfig !== originalConfig) {
+      // eslint-disable-next-line no-console
+      console.log('Updating thresholds to configuration file. You may want to push with updated coverage thresholds.')
+      writeFileSync(configurationFile, updatedConfig, 'utf-8')
+    }
+  }
+
   /**
    * Resolve reporters from various configuration options
    */

test/coverage-test/coverage-report-tests/generic.report.test.ts

@@ -63,3 +63,20 @@ test('files should not contain a setup file', () => {
 
   expect(srcFiles).not.toContain('another-setup.ts.html')
 })
+
+test('thresholdAutoUpdate updates thresholds', async () => {
+  const configFilename = resolve('./vitest.config.ts')
+  const configContents = fs.readFileSync(configFilename, 'utf-8')
+
+  for (const threshold of ['functions', 'branches', 'lines', 'statements']) {
+    const match = configContents.match(new RegExp(`${threshold}: (?<coverage>[\\d|\\.]+)`))
+    const coverage = match?.groups?.coverage || '0'
+
+    // Configuration has fixed value of 1.01 set for each threshold
+    expect(parseInt(coverage)).toBeGreaterThan(1.01)
+  }
+
+  // Update thresholds back to fixed values
+  const updatedConfig = configContents.replace(/(branches|functions|lines|statements): ([\d|\.])+/g, '$1: 1.01')
+  fs.writeFileSync(configFilename, updatedConfig)
+})

test/coverage-test/vitest.config.ts

@@ -25,6 +25,13 @@ export default defineConfig({
         ['lcov', {}],
         ['json', { file: 'custom-json-report-name.json' }],
       ],
+
+      // These will be updated by tests and reseted back by generic.report.test.ts
+      thresholdAutoUpdate: true,
+      functions: 1.01,
+      branches: 1.01,
+      lines: 1.01,
+      statements: 1.01,
     },
     setupFiles: [
       resolve(__dirname, './setup.ts'),