console,doc: add inspector console object

Also, remove undocumented (and unusable without inspector) methods from
the global console object.

Rather than having the undocumented methods on the global console, these
methods are now available on the console.inspector object.

Fixes: nodejs#12675

doc/api/console.md

@@ -417,6 +417,26 @@ added: v0.1.100
 
 The `console.warn()` function is an alias for [`console.error()`][].
 
+### console.inspector
+<!-- YAML
+added: REPLACEME
+-->
+
+V8 contexts provide a `console` global object, but by default it is only useful
+for sending console messages to attached inspectors. This is provided as the
+`inspector` property of the global `console` object (but not of other instances
+of `Console`).
+
+For example, to send a log message, `'hello'` to an attached inspector console:
+
+```js
+console.inspector.log('hello');
+// 'hello' appears in inspector console, but not in node's stdout
+```
+
+When an inspector is connected, logging methods on the global `console` object
+will also send messages to the inspector console.
+
 [`console.error()`]: #console_console_error_data_args
 [`console.group()`]: #console_console_group_label
 [`console.log()`]: #console_console_log_data_args

lib/internal/bootstrap_node.js

@@ -344,11 +344,7 @@
                                              wrappedConsole[key],
                                              config);
     }
-    for (const key of Object.keys(originalConsole)) {
-      if (wrappedConsole.hasOwnProperty(key))
-        continue;
-      wrappedConsole[key] = originalConsole[key];
-    }
+    wrappedConsole.inspector = originalConsole;
   }
 
   function setupProcessFatal() {

test/parallel/test-console.js

@@ -22,6 +22,7 @@
 'use strict';
 const common = require('../common');
 const assert = require('assert');
+const vm = require('vm');
 
 assert.ok(process.stdout.writable);
 assert.ok(process.stderr.writable);
@@ -187,3 +188,16 @@ common.hijackStderr(common.mustCall(function(data) {
     assert.strictEqual(data.includes('no such label'), true);
   });
 }));
+
+const pristineConsole = vm.runInNewContext('this.console');
+for (const name in console.inspector) {
+
+  // No inspector-only functions are available on the global console
+  if (name in console) {
+    assert.notStrictEqual(console[name], console.inspector[name]);
+  }
+
+  // console.inspector should be the same as a pristine console object from a v8
+  // context.
+  assert(name in pristineConsole);
+}