From 69c0b05f7ab72f957ce7685998d3f424fb7e812c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bartek=20Iwa=C5=84czuk?= <biwanczuk@gmail.com>
Date: Tue, 21 Feb 2023 21:12:22 +0100
Subject: refactor(core): More efficient serde for ES modules in snapshot
 (#17856)
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Instead of relying on "serde_v8" which is very inefficient in
serializing enums, I'm hand rolling serde for "ModuleMap" data
that is stored in the V8 snapshot to make ES modules
snapshottable.

```
// this branch
Benchmark #2: ./target/release/deno run empty.js

  Time (mean ± σ):      21.4 ms ±   0.9 ms    [User: 15.6 ms, System: 6.4 ms]

  Range (min … max):    20.2 ms …  24.4 ms

// main branch
Benchmark #2: ./target/release/deno run empty.js

  Time (mean ± σ):      23.1 ms ±   1.2 ms    [User: 17.0 ms, System: 6.2 ms]

  Range (min … max):    21.0 ms …  26.0 ms

```
---
 core/runtime.rs | 14 +++++---------
 1 file changed, 5 insertions(+), 9 deletions(-)

(limited to 'core/runtime.rs')

diff --git a/core/runtime.rs b/core/runtime.rs
index d098c25b1..9c6b7afea 100644
--- a/core/runtime.rs
+++ b/core/runtime.rs
@@ -438,7 +438,7 @@ impl JsRuntime {
     fn get_context_data(
       scope: &mut v8::HandleScope<()>,
       context: v8::Local<v8::Context>,
-    ) -> (Vec<v8::Global<v8::Module>>, v8::Global<v8::Object>) {
+    ) -> (Vec<v8::Global<v8::Module>>, v8::Global<v8::Array>) {
       fn data_error_to_panic(err: v8::DataError) -> ! {
         match err {
           v8::DataError::BadType { actual, expected } => {
@@ -457,15 +457,11 @@ impl JsRuntime {
       // The 0th element is the module map itself, followed by X number of module
       // handles. We need to deserialize the "next_module_id" field from the
       // map to see how many module handles we expect.
-      match scope.get_context_data_from_snapshot_once::<v8::Object>(0) {
+      match scope.get_context_data_from_snapshot_once::<v8::Array>(0) {
         Ok(val) => {
           let next_module_id = {
-            let info_str = v8::String::new(&mut scope, "info").unwrap();
-            let info_data: v8::Local<v8::Array> = val
-              .get(&mut scope, info_str.into())
-              .unwrap()
-              .try_into()
-              .unwrap();
+            let info_data: v8::Local<v8::Array> =
+              val.get_index(&mut scope, 1).unwrap().try_into().unwrap();
             info_data.length()
           };
 
@@ -3648,7 +3644,7 @@ pub mod tests {
         main,
         name: specifier.to_string(),
         requests: vec![crate::modules::ModuleRequest {
-          specifier: crate::resolve_url(&format!("file:///{prev}.js")).unwrap(),
+          specifier: format!("file:///{prev}.js"),
           asserted_module_type: AssertedModuleType::JavaScriptOrWasm,
         }],
         module_type: ModuleType::JavaScript,
-- 
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