From 4e0639c2dceef3feca273cf0dadfd4f045826f77 Mon Sep 17 00:00:00 2001
From: Mofei Zhang <feifei0@fb.com>
Date: Mon, 3 Oct 2022 14:37:23 -0400
Subject: [PATCH] Add makeReadOnly codegen into the compiler

---
 compiler/forget/src/BackEnd/JS.ts                   | 13 +++++++++++++
 compiler/forget/src/BackEnd/JSGen.ts                |  5 +++++
 compiler/forget/src/CompilerFlags.ts                |  6 ++++++
 .../forget/src/__tests__/CompilerOptions-test.ts    |  1 +
 4 files changed, 25 insertions(+)

diff --git a/compiler/forget/src/BackEnd/JS.ts b/compiler/forget/src/BackEnd/JS.ts
index 33f22aa77b..4baebb3d10 100644
--- a/compiler/forget/src/BackEnd/JS.ts
+++ b/compiler/forget/src/BackEnd/JS.ts
@@ -188,6 +188,19 @@ export class Func {
     ]);
   }
 
+  // Generate calls to utility function that freezes immut objects
+  emitMakeReadOnly(val: IR.BindingVal) {
+    if (this.context.opts.flags.addFreeze === true) {
+      this.code.push(
+        t.expressionStatement(
+          t.callExpression(t.identifier("useMemoCache.makeReadOnly"), [
+            val.binding.identifier,
+          ])
+        )
+      );
+    }
+  }
+
   /**
    * Generate code materializing reactions
    * @returns
diff --git a/compiler/forget/src/BackEnd/JSGen.ts b/compiler/forget/src/BackEnd/JSGen.ts
index b0f66c9a2e..1a97c4872c 100644
--- a/compiler/forget/src/BackEnd/JSGen.ts
+++ b/compiler/forget/src/BackEnd/JSGen.ts
@@ -85,6 +85,8 @@ export function runFunc(
    */
   function genPrologue(): void {
     for (const param of irFunc.params) {
+      // params are immut
+      jsFunc.emitMakeReadOnly(param);
       if (IR.isReactiveVal(param)) {
         jsFunc.emitReactiveVal(param);
       }
@@ -102,6 +104,9 @@ export function runFunc(
       jsFunc.emit(instr.ast.node);
 
       for (const decl of instr.ir.decls) {
+        if (decl.immutable) {
+          jsFunc.emitMakeReadOnly(decl);
+        }
         if (IR.isReactiveVal(decl)) {
           jsFunc.emitReactiveVal(decl);
         }
diff --git a/compiler/forget/src/CompilerFlags.ts b/compiler/forget/src/CompilerFlags.ts
index 91f3333754..e92b6ea789 100644
--- a/compiler/forget/src/CompilerFlags.ts
+++ b/compiler/forget/src/CompilerFlags.ts
@@ -81,6 +81,10 @@ export type CompilerFlags = {
    * can remove this flag.
    */
   guardThrows: boolean;
+  /**
+   * Experimental runtime logging to collect data
+   */
+  addFreeze: boolean;
 };
 
 export function createCompilerFlags(): CompilerFlags {
@@ -95,6 +99,7 @@ export function createCompilerFlags(): CompilerFlags {
     guardReads: false,
     guardHooks: false,
     guardThrows: false,
+    addFreeze: false,
   };
 }
 
@@ -115,6 +120,7 @@ export function parseCompilerFlags(
       case "guardReads":
       case "guardHooks":
       case "guardThrows":
+      case "addFreeze":
         if (typeof value !== "boolean") {
           throw `Expected boolean for flag '${key}': ${value}`;
         }
diff --git a/compiler/forget/src/__tests__/CompilerOptions-test.ts b/compiler/forget/src/__tests__/CompilerOptions-test.ts
index 74780cea17..9a2dc859ec 100644
--- a/compiler/forget/src/__tests__/CompilerOptions-test.ts
+++ b/compiler/forget/src/__tests__/CompilerOptions-test.ts
@@ -49,6 +49,7 @@ describe("CompilerOptions", () => {
     const fullInput = {
       outputKinds: [OutputKind.JS, OutputKind.LIR],
       flags: {
+        addFreeze: true,
         condCache: true,
         guardReads: true,
         guardHooks: true,