feat(experimental): Support using --all with node.js ESM (#1320)

This allows `--all` to collect initial coverage from fils which node.js
recognizes as ES modules (`.mjs` files and conditionally `.js` files).
Previously this would cause node.js to produce an `ERR_REQUIRE_ESM`
error.

This does not enable collection of coverage during actual tests, for that
you must use the experimental `@istanbuljs/esm-loader-hook`.

index.js

@@ -20,6 +20,7 @@ const rimraf = promisify(require('rimraf'))
 const SourceMaps = require('./lib/source-maps')
 const TestExclude = require('test-exclude')
 const pMap = require('p-map')
+const getPackageType = require('get-package-type')
 
 const debugLog = debuglog('nyc')
 
@@ -170,14 +171,36 @@ class NYC {
     return source
   }
 
+  _getSourceMap (code, filename, hash) {
+    const sourceMap = {}
+    if (this._sourceMap) {
+      sourceMap.sourceMap = this.sourceMaps.extract(code, filename)
+      sourceMap.registerMap = () => this.sourceMaps.registerMap(filename, hash, sourceMap.sourceMap)
+    } else {
+      sourceMap.registerMap = () => {}
+    }
+
+    return sourceMap
+  }
+
   async addAllFiles () {
     this._loadAdditionalModules()
 
     this.fakeRequire = true
     const files = await this.exclude.glob(this.cwd)
-    files.forEach(relFile => {
+    for (const relFile of files) {
       const filename = path.resolve(this.cwd, relFile)
-      this.addFile(filename)
+      const ext = path.extname(filename)
+      if (ext === '.mjs' || (ext === '.js' && await getPackageType(filename) === 'module')) {
+        const source = await fs.readFile(filename, 'utf8')
+        this.instrumenter().instrumentSync(
+          source,
+          filename,
+          this._getSourceMap(source, filename)
+        )
+      } else {
+        this.addFile(filename)
+      }
       const coverage = coverageFinder()
       const lastCoverage = this.instrumenter().lastFileCoverage()
       if (lastCoverage) {
@@ -187,7 +210,7 @@ class NYC {
           all: true
         }
       }
-    })
+    }
     this.fakeRequire = false
 
     this.writeCoverageFile()
@@ -276,14 +299,7 @@ class NYC {
 
     return (code, metadata, hash) => {
       const filename = metadata.filename
-      const sourceMap = {}
-
-      if (this._sourceMap) {
-        sourceMap.sourceMap = this.sourceMaps.extract(code, filename)
-        sourceMap.registerMap = () => this.sourceMaps.registerMap(filename, hash, sourceMap.sourceMap)
-      } else {
-        sourceMap.registerMap = () => {}
-      }
+      const sourceMap = this._getSourceMap(code, filename, hash)
 
       try {
         instrumented = instrumenter.instrumentSync(code, filename, sourceMap)

package.json

@@ -64,6 +64,7 @@
     "find-cache-dir": "^3.2.0",
     "find-up": "^4.1.0",
     "foreground-child": "^2.0.0",
+    "get-package-type": "^0.1.0",
     "glob": "^7.1.6",
     "istanbul-lib-coverage": "^3.0.0",
     "istanbul-lib-hook": "^3.0.0",

tap-snapshots/test-nyc-integration.js-TAP.test.js

@@ -5,6 +5,18 @@
  * Make sure to inspect the output below.  Do not ignore changes!
  */
 'use strict'
+exports[`test/nyc-integration.js TAP --all does not fail on ERR_REQUIRE_ESM > stdout 1`] = `
+------------|---------|----------|---------|---------|-------------------
+File        | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s 
+------------|---------|----------|---------|---------|-------------------
+All files   |   33.33 |      100 |       0 |   33.33 |                   
+ extra.mjs  |       0 |      100 |       0 |       0 | 2                 
+ index.js   |       0 |      100 |       0 |       0 | 2                 
+ script.cjs |     100 |      100 |     100 |     100 |                   
+------------|---------|----------|---------|---------|-------------------
+
+`
+
 exports[`test/nyc-integration.js TAP --all includes files with both .map files and inline source-maps > stdout 1`] = `
 ----------|---------|----------|---------|---------|-------------------
 File      | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s 

test/fixtures/all-type-module/extra.mjs

@@ -0,0 +1,3 @@
+export default function () {
+	return 'es module';
+}

test/fixtures/all-type-module/index.js

@@ -0,0 +1,3 @@
+export default function () {
+	return 'es module';
+}

test/fixtures/all-type-module/package.json

@@ -0,0 +1,10 @@
+{
+  "name": "all-type-module",
+  "version": "0.1.0",
+  "description": "",
+  "main": "index.js",
+  "type": "module",
+  "nyc": {
+    "all": true
+  }
+}

test/fixtures/all-type-module/script.cjs

@@ -0,0 +1,5 @@
+#!/usr/bin/env node
+'use strict';
+
+// Not doing anything, we just want something to run with `nyc --all`
+process.exit(0);

test/nyc-integration.js

@@ -15,6 +15,7 @@ const nycConfigJS = path.resolve(fixturesCLI, 'nyc-config-js')
 const nycrcDir = path.resolve(fixturesCLI, 'nycrc')
 const fixturesSourceMaps = path.resolve(fixturesCLI, '../source-maps')
 const fixturesENM = path.resolve(fixturesCLI, '../exclude-node-modules')
+const fixturesAllTypeModule = path.resolve(fixturesCLI, '../all-type-module')
 
 const executeNodeModulesArgs = [
   '--all=true',
@@ -436,6 +437,15 @@ t.test('--all uses source-maps to exclude original sources from reports', t => t
   cwd: fixturesSourceMaps
 }))
 
+t.test('--all does not fail on ERR_REQUIRE_ESM', t => testSuccess(t, {
+  args: [
+    '--all',
+    process.execPath,
+    'script.cjs'
+  ],
+  cwd: fixturesAllTypeModule
+}))
+
 t.test('caches source-maps from .map files', async t => {
   await testSuccess(t, {
     args: [