Add source visibility support for lazy and S/D

Summary:
The tricky case was to support `toString` on lazy function that
haven't been invoked once (hence not parsed/compiled yet). Luckily,
previous diffs had already set up everything.

Before this diff, we already recorded directives from the
preParse pass and restore the directive nodes for lazy function in
lazyParse, and SemanticValidator will compute sourceVisibility
for lazy functions no different with any other non-lazy functions.
That means, lazy function with non-normal sources have already been
reserved ahead of time in the "root" bytecode module.

So the only thing this diff is doing is to make the `toString`
implementation looking for lazy root bc module instead.

To make sure source visibility works for S/D, we also need to
specialize `getLazyRootModule` return the root RM under S/D.
Note that lazy and S/D are not intended to work together.

Reviewed By: avp

Differential Revision: D26796465

fbshipit-source-id: e847422ba5a177124d763b00690176d10350b2fb

include/hermes/VM/RuntimeModule.h

@@ -208,8 +208,10 @@ class RuntimeModule final : public llvh::ilist_node<RuntimeModule> {
   /// file's global function (i.e. the first RM created when we started
   /// interpreting and lazily compiling the source code). For other RMs,
   /// e.g. those loaded from precompiled bytecode, this is just itself.
+  /// We also return this for RM created from serialization/deserialization.
+  /// Note that lazy and serialization are not intended to work together.
   RuntimeModule *getLazyRootModule() {
-#ifdef HERMESVM_LEAN
+#if defined(HERMESVM_LEAN) || defined(HERMESVM_SERIALIZE)
     return this;
 #else
     return lazyRoot_;

lib/VM/CodeBlock.cpp

@@ -255,8 +255,13 @@ OptValue<hbc::DebugSourceLocation> CodeBlock::getSourceLocation(
 }
 
 OptValue<uint32_t> CodeBlock::getFunctionSourceID() const {
+  // Note that for the case of lazy compilation, the function sources had been
+  // reserved into the function source table of the root bytecode module.
+  // For non-lazy module, the lazy root module is itself.
   llvh::ArrayRef<std::pair<uint32_t, uint32_t>> table =
-      runtimeModule_->getBytecode()->getFunctionSourceTable();
+      runtimeModule_->getLazyRootModule()
+          ->getBytecode()
+          ->getFunctionSourceTable();
 
   // Performs a binary search since the function source table is sorted by the
   // 1st value. We could further optimize the lookup by loading it as a map in

lib/VM/JSLib/Function.cpp

@@ -127,6 +127,7 @@ functionPrototypeToString(void *, Runtime *runtime, NativeArgs args) {
       StringPrimitive *source =
           jsFunc->getCodeBlock()
               ->getRuntimeModule()
+              ->getLazyRootModule()
               ->getStringPrimFromStringIDMayAllocate(*sourceID);
       // Empty source marks implementation-hidden function, fabricate a source
       // code string that imitate a NativeFunction.

test/hermes/function-toString.js

@@ -7,8 +7,10 @@
 
 // RUN: %hermes %s | %FileCheck --match-full-lines %s
 // RUN: %hermes -O %s | %FileCheck --match-full-lines %s
+// RUN: %hermes -lazy %s | %FileCheck --match-full-lines %s
 // RUN: %hermes -O -target=HBC %s | %FileCheck --match-full-lines %s
 // RUN: %hermes -O -target=HBC -emit-binary -out %t.hbc %s && %hermes %t.hbc | %FileCheck --match-full-lines %s
+// UNSUPPORTED: serializer
 
 print('Function.prototype.toString');
 // CHECK-LABEL: Function.prototype.toString
@@ -42,11 +44,14 @@ print((function now() { 'hide source' }).toString());
 // CHECK-NEXT: function now() { [native code] }
 
 
-/// --- Function Expression / Arrow / Anonymous ---
+/// --- Function Expression ---
 
 print((function fe() { 'show source' }).toString());
 // CHECK-NEXT: function fe() { 'show source' }
 
+
+/// --- Arrow Function Expression ---
+
 print((() => { 'show source' }).toString());
 // CHECK-NEXT: () => { 'show source' }
 

test/hermes/lazy-function-toString.js

@@ -0,0 +1,18 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+// RUN: %hermes -non-strict -O0 %s 2>&1 | %FileCheck --match-full-lines %s
+// RUN: %hermes -lazy -non-strict -O0 %s 2>&1 | %FileCheck --match-full-lines %s
+// UNSUPPORTED: serializer
+
+// foo is never called, but its source needs to be reserved ahead of time.
+function foo(x) { "show source"; }
+
+(function bar() {
+    print(foo.toString());
+    // CHECK: function foo(x) { "show source"; }
+})()

test/hermes/source-visibility/global-hide-source.js

@@ -6,6 +6,8 @@
  */
 
 // RUN: %hermes -O %s | %FileCheck --match-full-lines %s
+// RUN: %hermes -lazy %s | %FileCheck --match-full-lines %s
+// UNSUPPORTED: serializer
 
 'hide source';
 

test/hermes/source-visibility/global-show-source.js

@@ -6,6 +6,8 @@
  */
 
 // RUN: %hermes -O %s | %FileCheck --match-full-lines %s
+// RUN: %hermes -lazy %s | %FileCheck --match-full-lines %s
+// UNSUPPORTED: serializer
 
 'show source';
 

test/hermes/source-visibility/override.js

@@ -6,6 +6,8 @@
  */
 
 // RUN: %hermes -O %s | %FileCheck --match-full-lines %s
+// RUN: %hermes -lazy %s | %FileCheck --match-full-lines %s
+// UNSUPPORTED: serializer
 
 // Inner HideSource can override outer ShowSource
 function showSource1() {

test/hermes/source-visibility/with-eval.js

@@ -6,6 +6,7 @@
  */
 
 // RUN: %hermes -O %s | %FileCheck --match-full-lines %s
+// RUN: %hermes -lazy %s | %FileCheck --match-full-lines %s
 
 print("with eval");
 // CHECK-LABEL: with eval

test/serialize/function-usercode.js

@@ -15,6 +15,7 @@ var F = function(x) { return x; };
 var f = new F(1);
 var F2 = function(a,b,c,d,e,f,g,h,i,j,k){}
 var foo = function badlength(a, b, c){};
+var bar = function showSource(a, b, c){"show source"};
 Object.defineProperty(foo, "length", {value:"aa"});
 var f2 = function(a, b) {
   print(arguments.length, this, a, b);
@@ -60,6 +61,10 @@ serializeVM(function() {
   print(foo);
   // CHECK-NEXT: function badlength() { [bytecode] }
 
+  // Source visibility directives
+  print(bar);
+  // CHECK-NEXT: function showSource(a, b, c){"show source"}
+
   print('call');
   // CHECK-LABEL: call
   print(f2.length);