vm: add Script.createCodeCache()

PR-URL: #20300
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: John-David Dalton <john.david.dalton@gmail.com>
Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com>
Reviewed-By: Yang Guo <yangguo@chromium.org>

doc/api/deprecations.md

@@ -1005,6 +1005,14 @@ accepted by the legacy `url.parse()` API. The mentioned APIs now use the WHATWG
 URL parser that requires strictly valid URLs. Passing an invalid URL is
 deprecated and support will be removed in the future.
 
+<a id="DEP00XX"></a>
+### DEP00XX: vm.Script cached data
+
+Type: Documentation-only
+
+The option `produceCachedData` has been deprecated. Use
+[`script.createCachedData()`][] instead.
+
 [`--pending-deprecation`]: cli.html#cli_pending_deprecation
 [`Buffer.allocUnsafeSlow(size)`]: buffer.html#buffer_class_method_buffer_allocunsafeslow_size
 [`Buffer.from(array)`]: buffer.html#buffer_class_method_buffer_from_array
@@ -1055,6 +1063,7 @@ deprecated and support will be removed in the future.
 [`process.env`]: process.html#process_process_env
 [`punycode`]: punycode.html
 [`require.extensions`]: modules.html#modules_require_extensions
+[`script.createCachedData()`]: vm.html#vm_script_create_cached_data
 [`setInterval()`]: timers.html#timers_setinterval_callback_delay_args
 [`setTimeout()`]: timers.html#timers_settimeout_callback_delay_args
 [`tls.CryptoStream`]: tls.html#tls_class_cryptostream

doc/api/vm.md

@@ -411,6 +411,10 @@ changes:
     pr-url: https://github.com/nodejs/node/pull/4777
     description: The `cachedData` and `produceCachedData` options are
                  supported now.
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/20300
+    description: The `produceCachedData` is deprecated in favour of
+                 `script.createCachedData()`
 -->
 
 * `code` {string} The JavaScript code to compile.
@@ -431,11 +435,39 @@ changes:
     `cachedData` property of the returned `vm.Script` instance.
     The `cachedDataProduced` value will be set to either `true` or `false`
     depending on whether code cache data is produced successfully.
+    This option is deprecated in favor of `script.createCachedData`.
 
 Creating a new `vm.Script` object compiles `code` but does not run it. The
 compiled `vm.Script` can be run later multiple times. The `code` is not bound to
 any global object; rather, it is bound before each run, just for that run.
 
+### script.createCachedData()
+<!-- YAML
+added: REPLACEME
+-->
+
+* Returns: {Buffer}
+
+Creates a code cache that can be used with the Script constructor's
+`cachedData` option. Returns a Buffer. This method may be called at any
+time and any number of times.
+
+```js
+const script = new vm.Script(`
+function add(a, b) {
+  return a + b;
+}
+
+const x = add(1, 2);
+`);
+
+const cacheWithoutX = script.createCachedData();
+
+script.runInThisContext();
+
+const cacheWithX = script.createCachedData();
+```
+
 ### script.runInContext(contextifiedSandbox[, options])
 <!-- YAML
 added: v0.3.1

src/node_contextify.cc

@@ -25,6 +25,7 @@
 #include "base_object-inl.h"
 #include "node_contextify.h"
 #include "node_context_data.h"
+#include "node_errors.h"
 
 namespace node {
 namespace contextify {
@@ -596,6 +597,7 @@ class ContextifyScript : public BaseObject {
     Local<FunctionTemplate> script_tmpl = env->NewFunctionTemplate(New);
     script_tmpl->InstanceTemplate()->SetInternalFieldCount(1);
     script_tmpl->SetClassName(class_name);
+    env->SetProtoMethod(script_tmpl, "createCachedData", CreateCachedData);
     env->SetProtoMethod(script_tmpl, "runInContext", RunInContext);
     env->SetProtoMethod(script_tmpl, "runInThisContext", RunInThisContext);
 
@@ -637,7 +639,7 @@ class ContextifyScript : public BaseObject {
     Local<Context> parsing_context = context;
 
     if (argc > 2) {
-      // new ContextifyScript(code, filename, lineOffset, columnOffset
+      // new ContextifyScript(code, filename, lineOffset, columnOffset,
       //                      cachedData, produceCachedData, parsingContext)
       CHECK_EQ(argc, 7);
       CHECK(args[2]->IsNumber());
@@ -719,7 +721,7 @@ class ContextifyScript : public BaseObject {
           Boolean::New(isolate, source.GetCachedData()->rejected));
     } else if (produce_cached_data) {
       const ScriptCompiler::CachedData* cached_data =
-        ScriptCompiler::CreateCodeCache(v8_script.ToLocalChecked(), code);
+        ScriptCompiler::CreateCodeCache(v8_script.ToLocalChecked());
       bool cached_data_produced = cached_data != nullptr;
       if (cached_data_produced) {
         MaybeLocal<Object> buf = Buffer::Copy(
@@ -745,6 +747,26 @@ class ContextifyScript : public BaseObject {
   }
 
 
+  static void CreateCachedData(const FunctionCallbackInfo<Value>& args) {
+    Environment* env = Environment::GetCurrent(args);
+    ContextifyScript* wrapped_script;
+    ASSIGN_OR_RETURN_UNWRAP(&wrapped_script, args.Holder());
+    Local<UnboundScript> unbound_script =
+        PersistentToLocal(env->isolate(), wrapped_script->script_);
+    std::unique_ptr<ScriptCompiler::CachedData> cached_data(
+        ScriptCompiler::CreateCodeCache(unbound_script));
+    if (!cached_data) {
+      args.GetReturnValue().Set(Buffer::New(env, 0).ToLocalChecked());
+    } else {
+      MaybeLocal<Object> buf = Buffer::Copy(
+          env,
+          reinterpret_cast<const char*>(cached_data->data),
+          cached_data->length);
+      args.GetReturnValue().Set(buf.ToLocalChecked());
+    }
+  }
+
+
   static void RunInThisContext(const FunctionCallbackInfo<Value>& args) {
     Environment* env = Environment::GetCurrent(args);
 

test/parallel/test-vm-createcacheddata.js

@@ -0,0 +1,22 @@
+'use strict';
+
+require('../common');
+
+const { Script } = require('vm');
+const assert = require('assert');
+
+const source = 'function x() {} const y = x();';
+
+const script = new Script(source);
+let cachedData = script.createCachedData();
+assert(cachedData instanceof Buffer);
+
+assert(!new Script(source, { cachedData }).cachedDataRejected);
+
+script.runInNewContext();
+
+for (let i = 0; i < 10; i += 1) {
+  cachedData = script.createCachedData();
+
+  assert(!new Script(source, { cachedData }).cachedDataRejected);
+}