benchmark: use options.filename when, for esm, require.main.filename is undefined

Author: bumblehead

benchmark/common.js

@@ -19,7 +19,16 @@ class Benchmark {
     this._time = 0n;
 
     // Use the file name as the name of the benchmark
-    this.name = require.main.filename.slice(__dirname.length + 1);
+    // For esm, require.main is undefined so probe filename from error stack
+    this.mainfilename = require.main
+      ? require.main.filename
+      : (new Error).stack.split('\n')[3]
+        .match(/^.*(\(|at )(.*):[\d]*:[\d]*.*$/)[2]
+        .replace(/^file:\/\//, '')
+
+    this.name = require.main
+      ? require.main.filename.slice(__dirname.length + 1)
+      : this.mainfilename.match(/[^\/]*$/)[0]
 
     // Execution arguments i.e. flags used to run the jobs
     this.flags = process.env.NODE_BENCHMARK_FLAGS?.split(/\s+/) ?? [];
@@ -224,7 +233,7 @@ class Benchmark {
         childArgs.push(`${key}=${value}`);
       }
 
-      const child = child_process.fork(require.main.filename, childArgs, {
+      const child = child_process.fork(this.mainfilename, childArgs, {
         env: childEnv,
         execArgv: this.flags.concat(process.execArgv),
       });