From ad4aaa64a6a678f2e1c4e2f2b3063056c2d40767 Mon Sep 17 00:00:00 2001
From: Nikolay Govorov <me@govorov.online>
Date: Tue, 28 Oct 2025 06:38:29 +0000
Subject: [PATCH] Provides an PoC of using V8 snapshots

---
 src/browser/js/Env.zig                | 56 ++++++++++++++++++++-------
 src/tests/polyfill/webcomponents.html |  2 +
 2 files changed, 44 insertions(+), 14 deletions(-)

diff --git a/src/browser/js/Env.zig b/src/browser/js/Env.zig
index 370c6f7e5..75480265d 100644
--- a/src/browser/js/Env.zig
+++ b/src/browser/js/Env.zig
@@ -3,6 +3,7 @@ const js = @import("js.zig");
 const v8 = js.v8;
 
 const log = @import("../../log.zig");
+const polyfill = @import("../polyfill/polyfill.zig");
 
 const types = @import("types.zig");
 const Types = types.Types;
@@ -34,6 +35,8 @@ isolate: v8.Isolate,
 // just kept around because we need to free it on deinit
 isolate_params: *v8.CreateParams,
 
+isolate_snaphost: v8.StartupData,
+
 // Given a type, we can lookup its index in TYPE_LOOKUP and then have
 // access to its TunctionTemplate (the thing we need to create an instance
 // of it)
@@ -54,6 +57,21 @@ context_id: usize,
 const Opts = struct {};
 
 pub fn init(allocator: Allocator, platform: *const Platform, _: Opts) !*Env {
+    const env = try allocator.create(Env);
+    errdefer allocator.destroy(env);
+
+    env.* = .{
+        .context_id = 0,
+        .isolate = undefined,
+        .isolate_params = undefined,
+        .isolate_snaphost = undefined,
+        .platform = platform,
+        .templates = undefined,
+        .allocator = allocator,
+        .meta_lookup = undefined,
+        .prototype_lookup = undefined,
+    };
+
     // var params = v8.initCreateParams();
     var params = try allocator.create(v8.CreateParams);
     errdefer allocator.destroy(params);
@@ -63,9 +81,15 @@ pub fn init(allocator: Allocator, platform: *const Platform, _: Opts) !*Env {
     params.array_buffer_allocator = v8.createDefaultArrayBufferAllocator();
     errdefer v8.destroyArrayBufferAllocator(params.array_buffer_allocator.?);
 
+    env.isolate_snaphost = generateIsolateSnaphot(params);
+    params.snapshot_blob = &env.isolate_snaphost;
+
     var isolate = v8.Isolate.init(params);
     errdefer isolate.deinit();
 
+    env.isolate = isolate;
+    env.isolate_params = params;
+
     // This is the callback that runs whenever a module is dynamically imported.
     isolate.setHostImportModuleDynamicallyCallback(Context.dynamicModuleCallback);
     isolate.setPromiseRejectCallback(promiseRejectCallback);
@@ -80,20 +104,6 @@ pub fn init(allocator: Allocator, platform: *const Platform, _: Opts) !*Env {
     v8.HandleScope.init(&temp_scope, isolate);
     defer temp_scope.deinit();
 
-    const env = try allocator.create(Env);
-    errdefer allocator.destroy(env);
-
-    env.* = .{
-        .context_id = 0,
-        .platform = platform,
-        .isolate = isolate,
-        .templates = undefined,
-        .allocator = allocator,
-        .isolate_params = params,
-        .meta_lookup = undefined,
-        .prototype_lookup = undefined,
-    };
-
     // Populate our templates lookup. generateClass creates the
     // v8.FunctionTemplate, which we store in our env.templates.
     // The ordering doesn't matter. What matters is that, given a type
@@ -537,3 +547,21 @@ fn generateUndetectable(comptime Struct: type, template: v8.ObjectTemplate) void
         template.markAsUndetectable();
     }
 }
+
+fn generateIsolateSnaphot(params: *v8.CreateParams) v8.StartupData {
+    var snapshot_creator = v8.SnapshotCreator{};
+    snapshot_creator.init(params);
+    defer snapshot_creator.deinit();
+
+    const isolate = snapshot_creator.getIsolate();
+
+    var temp_scope: v8.HandleScope = undefined;
+    v8.HandleScope.init(&temp_scope, isolate);
+    defer temp_scope.deinit();
+
+    const context = v8.Context.init(isolate, null, null);
+    context.enter();
+    defer context.exit();
+
+    return snapshot_creator.createSnapshotDataBlob("function LightpandaSnapshotPoC() { return 73; }");
+}
diff --git a/src/tests/polyfill/webcomponents.html b/src/tests/polyfill/webcomponents.html
index 5854bc82c..422f54719 100644
--- a/src/tests/polyfill/webcomponents.html
+++ b/src/tests/polyfill/webcomponents.html
@@ -13,6 +13,8 @@
     }
   }
 
+  testing.expectEqual(73, LightpandaSnapshotPoC());
+
   window.customElements.define("lightpanda-test", LightPanda);
   const main = document.getElementById('main');
   main.appendChild(document.createElement('lightpanda-test'));