Replace require.main with ES module compatible code

lib/find-main-script.js

@@ -0,0 +1,12 @@
+'use strict';
+
+// Node.js should provide an API for this
+function mainScript(defaultName) {
+  if (typeof repl !== 'undefined' || '_eval' in process) {
+    return defaultName
+  }
+
+  return process.argv[1] || defaultName
+}
+
+module.exports = mainScript;

lib/test.js

@@ -41,6 +41,7 @@ const stack = require('./stack.js')
 const settings = require('../settings.js')
 const Snapshot = require('./snapshot.js')
 const Waiter = require('./waiter.js')
+const findMainScript = require('./find-main-script.js')
 
 const formatSnapshotDefault = obj => format(obj, { sort: true })
 const cwd = process.cwd()
@@ -1149,9 +1150,7 @@ class Test extends Base {
   get testdirName () {
     const re = /[^a-z0-9]+/ig
     if (!this.parent) {
-      const main = (require.main ||
-        /* istanbul ignore next: only tested in node -p, where
-           NYC cannot reach */ { filename: 'TAP' }).filename
+      const main = findMainScript('TAP')
       const dir = path.dirname(main)
       const base = (path.basename(main).replace(/\.[^.]+$/, '')
         + ' ' + process.argv.slice(2).join(' ')).trim()

test/find-main-script.js

@@ -0,0 +1,27 @@
+'use strict'
+const t = require('../')
+const findMainScript = require('../lib/find-main-script.js')
+
+t.equal(findMainScript(), __filename)
+
+// Simulate REPL
+global.repl = {}
+t.type(findMainScript(), 'undefined')
+t.equal(findMainScript('default'), 'default')
+
+// Clear REPL flag
+delete global.repl
+t.equal(findMainScript(), __filename)
+
+// Simulate `node -p`, `node -e` or `node --eval`
+process._eval = 'testing'
+t.type(findMainScript(), 'undefined')
+t.equal(findMainScript('default'), 'default')
+
+// Clear eval flag
+delete process._eval
+t.equal(findMainScript(), __filename)
+
+// This is likely impossible but test it anyways
+process.argv = [process.argv[0]]
+t.equal(findMainScript('default'), 'default')

test/find-main-script.mjs

@@ -0,0 +1,29 @@
+import {fileURLToPath} from 'url'
+import t from 'libtap'
+import findMainScript from '../lib/find-main-script.js'
+
+const __filename = fileURLToPath(import.meta.url)
+
+t.equal(findMainScript(), __filename)
+
+// Simulate REPL
+global.repl = {}
+t.type(findMainScript(), 'undefined')
+t.equal(findMainScript('default'), 'default')
+
+// Clear REPL flag
+delete global.repl
+t.equal(findMainScript(), __filename)
+
+// Simulate `node -p`, `node -e` or `node --eval`
+process._eval = 'testing'
+t.type(findMainScript(), 'undefined')
+t.equal(findMainScript('default'), 'default')
+
+// Clear eval flag
+delete process._eval
+t.equal(findMainScript(), __filename)
+
+// This is likely impossible but test it anyways
+process.argv = [process.argv[0]]
+t.equal(findMainScript('default'), 'default')