inspector: throw error when activating an already active inspector

doc/api/errors.md

@@ -1210,6 +1210,13 @@ time.
 The `--input-type` flag was used to attempt to execute a file. This flag can
 only be used with input via `--eval`, `--print` or `STDIN`.
 
+<a id="ERR_INSPECTOR_ALREADY_ACTIVATED"></a>
+### `ERR_INSPECTOR_ALREADY_ACTIVATED`
+
+While using the `inspector` module, an attempt was made to activate the
+inspector when it already started to listen on a port. Use `inspector.close()`
+before activating it on a different address.
+
 <a id="ERR_INSPECTOR_ALREADY_CONNECTED"></a>
 ### `ERR_INSPECTOR_ALREADY_CONNECTED`
 

lib/inspector.js

@@ -8,6 +8,7 @@ const {
 } = primordials;
 
 const {
+  ERR_INSPECTOR_ALREADY_ACTIVATED,
   ERR_INSPECTOR_ALREADY_CONNECTED,
   ERR_INSPECTOR_CLOSED,
   ERR_INSPECTOR_COMMAND,
@@ -33,6 +34,7 @@ const {
   MainThreadConnection,
   open,
   url,
+  isEnabled,
   waitForDebugger
 } = internalBinding('inspector');
 
@@ -131,6 +133,9 @@ class Session extends EventEmitter {
 }
 
 function inspectorOpen(port, host, wait) {
+  if (isEnabled()) {
+    throw new ERR_INSPECTOR_ALREADY_ACTIVATED();
+  }
   open(port, host);
   if (wait)
     waitForDebugger();

lib/internal/errors.js

@@ -920,6 +920,10 @@ E('ERR_INCOMPATIBLE_OPTION_PAIR',
   'Option "%s" cannot be used in combination with option "%s"', TypeError);
 E('ERR_INPUT_TYPE_NOT_ALLOWED', '--input-type can only be used with string ' +
   'input via --eval, --print, or STDIN', Error);
+E('ERR_INSPECTOR_ALREADY_ACTIVATED',
+  'Inspector is already activated. Close it with inspector.close() ' +
+  'before activating it again.',
+  Error);
 E('ERR_INSPECTOR_ALREADY_CONNECTED', '%s is already connected', Error);
 E('ERR_INSPECTOR_CLOSED', 'Session was closed', Error);
 E('ERR_INSPECTOR_COMMAND', 'Inspector error %d: %s', Error);

test/sequential/test-inspector-already-activated-cli.js

@@ -0,0 +1,19 @@
+// Flags: --inspect=0
+'use strict';
+
+const common = require('../common');
+common.skipIfInspectorDisabled();
+common.skipIfWorker();
+
+const assert = require('assert');
+const inspector = require('inspector');
+const wsUrl = inspector.url();
+assert(wsUrl.startsWith('ws://'));
+assert.throws(() => {
+  inspector.open(0, undefined, false);
+}, {
+  code: 'ERR_INSPECTOR_ALREADY_ACTIVATED'
+});
+assert.strictEqual(inspector.url(), wsUrl);
+inspector.close();
+assert.strictEqual(inspector.url(), undefined);

test/sequential/test-inspector-open.js

@@ -10,6 +10,10 @@ const fork = require('child_process').fork;
 const net = require('net');
 const url = require('url');
 
+const kFirstOpen = 0;
+const kOpenWhileOpen = 1;
+const kReOpen = 2;
+
 if (process.env.BE_CHILD)
   return beChild();
 
@@ -19,7 +23,7 @@ const child = fork(__filename,
 child.once('message', common.mustCall((msg) => {
   assert.strictEqual(msg.cmd, 'started');
 
-  child.send({ cmd: 'open', args: [0] });
+  child.send({ cmd: 'open', args: [kFirstOpen] });
   child.once('message', common.mustCall(firstOpen));
 }));
 
@@ -31,7 +35,7 @@ function firstOpen(msg) {
   ping(port, (err) => {
     assert.ifError(err);
     // Inspector is already open, and won't be reopened, so args don't matter.
-    child.send({ cmd: 'open', args: [] });
+    child.send({ cmd: 'open', args: [kOpenWhileOpen] });
     child.once('message', common.mustCall(tryToOpenWhenOpen));
     firstPort = port;
   });
@@ -62,7 +66,7 @@ function closeWhenOpen(msg) {
 function tryToCloseWhenClosed(msg) {
   assert.strictEqual(msg.cmd, 'url');
   assert.strictEqual(msg.url, undefined);
-  child.send({ cmd: 'open', args: [] });
+  child.send({ cmd: 'open', args: [kReOpen] });
   child.once('message', common.mustCall(reopenAfterClose));
 }
 
@@ -93,7 +97,17 @@ function beChild() {
 
   process.on('message', (msg) => {
     if (msg.cmd === 'open') {
-      inspector.open(...msg.args);
+      if (msg.args[0] === kFirstOpen) {
+        inspector.open(0, false, undefined);
+      } else if (msg.args[0] === kOpenWhileOpen) {
+        assert.throws(() => {
+          inspector.open(0, false, undefined);
+        }, {
+          code: 'ERR_INSPECTOR_ALREADY_ACTIVATED'
+        });
+      } else if (msg.args[0] === kReOpen) {
+        inspector.open(0, false, undefined);
+      }
     }
     if (msg.cmd === 'close') {
       inspector.close();