inspector: allow opening inspector when NODE_V8_COVERAGE is set

lib/inspector.js

@@ -168,7 +168,7 @@ class Session extends EventEmitter {
  * @returns {void}
  */
 function inspectorOpen(port, host, wait) {
-  if (isEnabled()) {
+  if (isEnabled() && url()) {
     throw new ERR_INSPECTOR_ALREADY_ACTIVATED();
   }
   // inspectorOpen() currently does not typecheck its arguments and adding

test/fixtures/inspector-open.js

@@ -0,0 +1,14 @@
+const assert = require('assert');
+const inspector = require('inspector');
+
+
+assert.strictEqual(inspector.url(), undefined);
+inspector.open(0, undefined, false);
+assert(inspector.url().startsWith('ws://'));
+assert.throws(() => {
+  inspector.open(0, undefined, false);
+}, {
+  code: 'ERR_INSPECTOR_ALREADY_ACTIVATED'
+});
+inspector.close();
+assert.strictEqual(inspector.url(), undefined);

test/parallel/test-inspector-open-coverage.js

@@ -0,0 +1,21 @@
+'use strict';
+
+const common = require('../common');
+const assert = require('assert');
+const { spawnSync } = require('child_process');
+const fixtures = require('../common/fixtures');
+const tmpdir = require('../common/tmpdir');
+
+common.skipIfInspectorDisabled();
+common.skipIfWorker();
+
+tmpdir.refresh();
+
+
+let output = spawnSync(process.execPath, [fixtures.path('inspector-open.js')]);
+assert.strictEqual(output.status, 0);
+
+output = spawnSync(process.execPath, [fixtures.path('inspector-open.js')], {
+  env: { ...process.env, NODE_V8_COVERAGE: tmpdir.path },
+});
+assert.strictEqual(output.status, 0);