Rework native code function toString.

Summary: Tools such as Babel rely on the format of function toString. In particular, they check for the substring `[native code]`, as opposed to the future standard `[ native code ]` which Hermes supports. We want to avoid pretending every single function is a native function, so we switch bytecode functions to say `[bytecode]` instead. Reviewed By: ridiculousfish Differential Revision: D17102765 fbshipit-source-id: e81f63a066b1ddcae9c8e26cfd48221a86dd2b75
BiBoyang · Sep 5, 2019 · d5ad9be · d5ad9be
1 parent a29c955
commit d5ad9be
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Showing 7 changed files with 31 additions and 21 deletions.
diff --git a/lib/VM/JSLib/Function.cpp b/lib/VM/JSLib/Function.cpp
@@ -138,8 +138,16 @@ functionPrototypeToString(void *, Runtime *runtime, NativeArgs args) {
   }
 
   // The rest of the body.
-  // http://tc39.github.io/Function-prototype-toString-revision
-  strBuf.append(") { [ native code ] }");
+  if (vmisa<NativeFunction>(*func)) {
+    // Use [native code] here because we want to work with tools like
+    // Babel which detect the string [native code] and use it to alter
+    // behavior during the class transform.
+    strBuf.append(") { [native code] }");
+  } else {
+    // Avoid using the [native code] string to prevent extra wrapping overhead
+    // in, e.g., Babel's class extension mechanism.
+    strBuf.append(") { [bytecode] }");
+  }
 
   // Finally allocate a StringPrimitive.
   return StringPrimitive::create(runtime, strBuf);

diff --git a/test/debugger/vars-for.js b/test/debugger/vars-for.js
@@ -29,14 +29,14 @@ func1();
 // CHECK-NEXT: 0: elem = a
 // CHECK-NEXT: 1: var1_0 = 10
 // CHECK-NEXT: 1: var1_1 = 11
-// CHECK-NEXT: 1: func2 = function func2(a0) { [ native code ] }
+// CHECK-NEXT: 1: func2 = function func2(a0) { [bytecode] }
 // CHECK-NEXT: Selected frame 1
 // CHECK-NEXT: this = a,b
 // CHECK-NEXT: Selected frame 2
 // CHECK-NEXT: this = undefined
 // CHECK-NEXT: 0: var1_0 = 10
 // CHECK-NEXT: 0: var1_1 = 11
-// CHECK-NEXT: 0: func2 = function func2(a0) { [ native code ] }
+// CHECK-NEXT: 0: func2 = function func2(a0) { [bytecode] }
 // CHECK-NEXT: Continuing execution
 // CHECK-NEXT: Break on 'debugger' statement in func2: {{.*}}
 // CHECK-NEXT: Selected frame 0
@@ -45,12 +45,12 @@ func1();
 // CHECK-NEXT: 0: elem = b
 // CHECK-NEXT: 1: var1_0 = 10
 // CHECK-NEXT: 1: var1_1 = 11
-// CHECK-NEXT: 1: func2 = function func2(a0) { [ native code ] }
+// CHECK-NEXT: 1: func2 = function func2(a0) { [bytecode] }
 // CHECK-NEXT: Selected frame 1
 // CHECK-NEXT: this = a,b
 // CHECK-NEXT: Selected frame 2
 // CHECK-NEXT: this = undefined
 // CHECK-NEXT: 0:     var1_0 = 10
 // CHECK-NEXT: 0:     var1_1 = 11
-// CHECK-NEXT: 0: func2 = function func2(a0) { [ native code ] }
+// CHECK-NEXT: 0: func2 = function func2(a0) { [bytecode] }
 // CHECK-NEXT: Continuing execution
diff --git a/test/debugger/vars-this.js b/test/debugger/vars-this.js
@@ -26,10 +26,10 @@ foo.f1();
 // CHECK-NEXT: Break on 'debugger' statement in f3: {{.*}}
 // CHECK-NEXT: Selected frame 0
 // CHECK-NEXT: this = 412
-// CHECK-NEXT: 1: f3 = function f3() { [ native code ] }
+// CHECK-NEXT: 1: f3 = function f3() { [bytecode] }
 // CHECK-NEXT: Selected frame 2
 // CHECK-NEXT: this = [object Object]
-// CHECK-NEXT: 0: f3 = function f3() { [ native code ] }
+// CHECK-NEXT: 0: f3 = function f3() { [bytecode] }
 // CHECK-NEXT: Selected frame 3
 // CHECK-NEXT: this = [object Object]
 // CHECK-NEXT: Selected frame 4

diff --git a/test/debugger/vars.js b/test/debugger/vars.js
@@ -34,12 +34,12 @@ func1();
 // CHECK-NEXT: 0: var333 = c
 // CHECK-NEXT: 1: var1 = 5
 // CHECK-NEXT: 1: var22 = 17
-// CHECK-NEXT: 1: func2 = function func2() { [ native code ] }
+// CHECK-NEXT: 1: func2 = function func2() { [bytecode] }
 // CHECK-NEXT: Selected frame 1
 // CHECK-NEXT: this = undefined
 // CHECK-NEXT: 0: var1 = 5
 // CHECK-NEXT: 0: var22 = 17
-// CHECK-NEXT: 0: func2 = function func2() { [ native code ] }
+// CHECK-NEXT: 0: func2 = function func2() { [bytecode] }
 // CHECK-NEXT: Selected frame 2
 // CHECK-NEXT: this = [object global]
 // CHECK-NEXT: Stepped to func2: {{.*}}
@@ -48,13 +48,13 @@ func1();
 // CHECK-NEXT: this = undefined
 // CHECK-NEXT: 0: var1 = 5
 // CHECK-NEXT: 0: var22 = 17
-// CHECK-NEXT: 0: func2 = function func2() { [ native code ] }
+// CHECK-NEXT: 0: func2 = function func2() { [bytecode] }
 // CHECK-NEXT: Selected frame 1
 // CHECK-NEXT: this = undefined
 // CHECK-NEXT: 0: var333 = c
 // CHECK-NEXT: 1: var1 = 5
 // CHECK-NEXT: 1: var22 = 17
-// CHECK-NEXT: 1: func2 = function func2() { [ native code ] }
+// CHECK-NEXT: 1: func2 = function func2() { [bytecode] }
 // CHECK-NEXT: Selected frame 0
 // CHECK-NEXT: this = undefined
 // CHECK-NEXT: 0: var0 = undefined

diff --git a/test/hermes/function-constructor.js b/test/hermes/function-constructor.js
@@ -46,19 +46,21 @@ print(f.__proto__ === F.prototype, f.constructor === F, f.prop1);
 print('toString');
 // CHECK-LABEL: toString
 print(function (){});
-// CHECK-NEXT: function () { [ native code ] }
+// CHECK-NEXT: function () { [bytecode] }
 print(function foo(){});
-// CHECK-NEXT: function foo() { [ native code ] }
+// CHECK-NEXT: function foo() { [bytecode] }
 print(function(a,b,c){});
-// CHECK-NEXT: function (a0, a1, a2) { [ native code ] }
+// CHECK-NEXT: function (a0, a1, a2) { [bytecode] }
 print(function(a,b,c,d,e,f,g,h,i,j,k){});
-// CHECK-NEXT: function (a0, a1, a2, a3, a4, a5, a6, a7, a8, a9, a10) { [ native code ] }
+// CHECK-NEXT: function (a0, a1, a2, a3, a4, a5, a6, a7, a8, a9, a10) { [bytecode] }
+print(Map.toString());
+// CHECK-NEXT: function Map() { [native code] }
 
 // Non-string .length
 var foo = function badlength(a, b, c){};
 Object.defineProperty(foo, "length", {value:"aa"});
 print(foo);
-// CHECK-NEXT: function badlength() { [ native code ] }
+// CHECK-NEXT: function badlength() { [bytecode] }
 
 print('call');
 // CHECK-LABEL: call

diff --git a/test/repl/pretty.js b/test/repl/pretty.js
@@ -18,7 +18,7 @@ null
 "asdf"
 // CHECK-NEXT: "asdf"
 (function(){})
-// CHECK-NEXT: function () { [ native code ] }
+// CHECK-NEXT: function () { [bytecode] }
 
 a = [1,2, function(){}, null]
 // CHECK-NEXT: [ 1, 2, [Function], null, [length]: 4 ]
@@ -61,7 +61,7 @@ a.arr.cycle = a;
 // CHECK-NEXT: { x: 1, [z]: 3, arr: [ "foo", 4, [length]: 2, cycle: [cyclic] ] }
 
 a = function foo() {}
-// CHECK-NEXT: function foo() { [ native code ] }
+// CHECK-NEXT: function foo() { [bytecode] }
 a = [function foo() {}]
 // CHECK-NEXT: [ [Function foo], [length]: 1 ]
 

diff --git a/test/serialize/function-usercode.js b/test/serialize/function-usercode.js
@@ -52,11 +52,11 @@ serializeVM(function() {
   print('toString');
   // CHECK-LABEL: toString
   print(F2);
-  // CHECK-NEXT: function F2(a0, a1, a2, a3, a4, a5, a6, a7, a8, a9, a10) { [ native code ] }
+  // CHECK-NEXT: function F2(a0, a1, a2, a3, a4, a5, a6, a7, a8, a9, a10) { [bytecode] }
 
   // Non-string .length
   print(foo);
-  // CHECK-NEXT: function badlength() { [ native code ] }
+  // CHECK-NEXT: function badlength() { [bytecode] }
 
   print('call');
   // CHECK-LABEL: call