child_process: allow 'http_parser' monkey patching again

Lazy load _http_common and HTTPParser so that the 'http_parser' binding
can be monkey patched before any internal modules require it. This also
probably improves startup performance minimally for programs that never
require the HTTP stack.

Fixes: nodejs#23716
Fixes: creationix/http-parser-js#57

PR-URL: nodejs#24006
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

lib/internal/child_process.js

@@ -38,8 +38,6 @@ const { owner_symbol } = require('internal/async_hooks').symbols;
 const { convertToValidSignal } = require('internal/util');
 const { isArrayBufferView } = require('internal/util/types');
 const spawn_sync = internalBinding('spawn_sync');
-const { HTTPParser } = internalBinding('http_parser');
-const { freeParser } = require('_http_common');
 const { kStateSymbol } = require('internal/dgram');
 
 const {
@@ -57,6 +55,10 @@ const { SocketListSend, SocketListReceive } = SocketList;
 
 // Lazy loaded for startup performance.
 let StringDecoder;
+// Lazy loaded for startup performance and to allow monkey patching of
+// internalBinding('http_parser').HTTPParser.
+let freeParser;
+let HTTPParser;
 
 const MAX_HANDLE_RETRANSMISSIONS = 3;
 
@@ -121,6 +123,12 @@ const handleConversion = {
         handle.onread = nop;
         socket._handle = null;
         socket.setTimeout(0);
+
+        if (freeParser === undefined)
+          freeParser = require('_http_common').freeParser;
+        if (HTTPParser === undefined)
+          HTTPParser = internalBinding('http_parser').HTTPParser;
+
         // In case of an HTTP connection socket, release the associated
         // resources
         if (socket.parser && socket.parser instanceof HTTPParser) {

test/parallel/test-http-parser-lazy-loaded.js

@@ -0,0 +1,37 @@
+// Flags: --expose-internals
+
+'use strict';
+
+const { internalBinding } = require('internal/test/binding');
+
+// Monkey patch before requiring anything
+class DummyParser {
+  constructor(type) {
+    this.test_type = type;
+  }
+}
+DummyParser.REQUEST = Symbol();
+internalBinding('http_parser').HTTPParser = DummyParser;
+
+const common = require('../common');
+const assert = require('assert');
+const { spawn } = require('child_process');
+const { parsers } = require('_http_common');
+
+// Test _http_common was not loaded before monkey patching
+const parser = parsers.alloc();
+assert.strictEqual(parser instanceof DummyParser, true);
+assert.strictEqual(parser.test_type, DummyParser.REQUEST);
+
+if (process.argv[2] !== 'child') {
+  // Also test in a child process with IPC (specific case of https://github.com/nodejs/node/issues/23716)
+  const child = spawn(process.execPath, [
+    '--expose-internals', __filename, 'child'
+  ], {
+    stdio: ['inherit', 'inherit', 'inherit', 'ipc']
+  });
+  child.on('exit', common.mustCall((code, signal) => {
+    assert.strictEqual(code, 0);
+    assert.strictEqual(signal, null);
+  }));
+}