basic code coverage support

Signed-off-by: Matteo Collina <hello@matteocollina.com>

borp.js

@@ -2,7 +2,11 @@
 
 import { parseArgs } from 'node:util'
 import { tap, spec } from 'node:test/reporters'
+import { mkdtemp, rm } from 'node:fs/promises'
+import { finished } from 'node:stream/promises'
+import { join } from 'node:path'
 import runWithTypeScript from './lib/run.js'
+import { Report } from 'c8'
 
 let reporter
 if (process.stdout.isTTY) {
@@ -18,7 +22,8 @@ const args = parseArgs({
     only: { type: 'boolean', short: 'o' },
     watch: { type: 'boolean', short: 'w' },
     pattern: { type: 'string', short: 'p' },
-    concurrency: { type: 'string', short: 'c' }
+    concurrency: { type: 'string', short: 'c' },
+    coverage: { type: 'boolean', short: 'C' }
   },
   allowPositionals: true
 })
@@ -27,13 +32,38 @@ if (args.values.concurrency) {
   args.values.concurrency = parseInt(args.values.concurrency)
 }
 
+
+let covDir
+if (args.values.coverage) {
+  covDir = await mkdtemp(join(process.cwd(), 'coverage-'))
+  process.env.NODE_V8_COVERAGE = covDir
+}
+
 const config = {
   ...args.values,
   files: args.positionals,
   pattern: args.values.pattern,
   cwd: process.cwd()
 }
 
-;(await runWithTypeScript(config))
-  .compose(reporter)
+const stream = await runWithTypeScript(config)
+
+stream.compose(reporter)
   .pipe(process.stdout)
+
+await finished(stream)
+
+if (covDir) {
+  const report = Report({
+    reporter: ['text'],
+    tempDirectory: covDir
+  })
+
+  try {
+    await report.run()
+  } catch (err) {
+    console.error(err)
+  } finally {
+    await rm(covDir, { recursive: true })
+  }
+}

lib/run.js

@@ -3,7 +3,7 @@ import { glob } from 'glob'
 import { findUp } from 'find-up'
 import { createRequire } from 'node:module'
 import { resolve, join, dirname } from 'node:path'
-import { access, readFile } from 'node:fs/promises'
+import { access, readFile, mkdtemp } from 'node:fs/promises'
 import { execa } from 'execa'
 
 async function isFileAccessible (filename, directory) {
@@ -17,7 +17,7 @@ async function isFileAccessible (filename, directory) {
 }
 
 export default async function runWithTypeScript (config) {
-  const { cwd } = config
+  const { cwd, coverage } = config
   const tsconfigPath = await findUp('tsconfig.json', { cwd })
 
   let prefix = ''

package.json

@@ -19,6 +19,7 @@
     "typescript": "^5.3.2"
   },
   "dependencies": {
+    "c8": "^8.0.1",
     "execa": "^8.0.1",
     "find-up": "^7.0.0",
     "glob": "^10.3.10"