improve performance on error path in JSON.parse (#90)

* improve performance on SyntaxErrors

* add unit test

* fix resetting stackTraceLimit

* fix lnt error

* use finally block more efficiently

Author: Uzlopak

benchmarks/throw.js

@@ -11,7 +11,7 @@ const internals = {
 const suite = new Benchmark.Suite()
 
 suite
-  .add('JSON.parse', () => {
+  .add('JSON.parse valid', () => {
     JSON.parse(internals.text)
   })
   .add('JSON.parse error', () => {
@@ -21,15 +21,15 @@ suite
   })
   .add('secure-json-parse parse', () => {
     try {
-      sjson.parse(internals.text)
+      sjson.parse(internals.invalid)
     } catch (ignoreErr) { }
   })
   .add('secure-json-parse safeParse', () => {
-    sjson.safeParse(internals.text)
+    sjson.safeParse(internals.invalid)
   })
   .add('reviver', () => {
     try {
-      JSON.parse(internals.text, internals.reviver)
+      JSON.parse(internals.invalid, internals.reviver)
     } catch (ignoreErr) { }
   })
   .on('cycle', (event) => {

index.js

@@ -4,7 +4,7 @@ const hasBuffer = typeof Buffer !== 'undefined'
 const suspectProtoRx = /"(?:_|\\u005[Ff])(?:_|\\u005[Ff])(?:p|\\u0070)(?:r|\\u0072)(?:o|\\u006[Ff])(?:t|\\u0074)(?:o|\\u006[Ff])(?:_|\\u005[Ff])(?:_|\\u005[Ff])"\s*:/
 const suspectConstructorRx = /"(?:c|\\u0063)(?:o|\\u006[Ff])(?:n|\\u006[Ee])(?:s|\\u0073)(?:t|\\u0074)(?:r|\\u0072)(?:u|\\u0075)(?:c|\\u0063)(?:t|\\u0074)(?:o|\\u006[Ff])(?:r|\\u0072)"\s*:/
 
-function parse (text, reviver, options) {
+function _parse (text, reviver, options) {
   // Normalize arguments
   if (options == null) {
     if (reviver !== null && typeof reviver === 'object') {
@@ -97,11 +97,25 @@ function filter (obj, { protoAction = 'error', constructorAction = 'error', safe
   return obj
 }
 
+function parse (text, reviver, options) {
+  const stackTraceLimit = Error.stackTraceLimit
+  Error.stackTraceLimit = 0
+  try {
+    return _parse(text, reviver, options)
+  } finally {
+    Error.stackTraceLimit = stackTraceLimit
+  }
+}
+
 function safeParse (text, reviver) {
+  const stackTraceLimit = Error.stackTraceLimit
+  Error.stackTraceLimit = 0
   try {
-    return parse(text, reviver, { safe: true })
-  } catch (ignoreError) {
+    return _parse(text, reviver, { safe: true })
+  } catch (_e) {
     return null
+  } finally {
+    Error.stackTraceLimit = stackTraceLimit
   }
 }
 

test/index.test.js

@@ -145,6 +145,14 @@ test('parse', t => {
       t.end()
     })
 
+    t.test('should reset stackTraceLimit', t => {
+      const text = '{ "a": 5, "b": 6, "__proto__": { "x": 7 }, "c": { "d": 0, "e": "text", "__proto__": { "y": 8 }, "f": { "g": 2 } } }'
+      Error.stackTraceLimit = 42
+      t.throws(() => j.parse(text))
+      t.same(Error.stackTraceLimit, 42)
+      t.end()
+    })
+
     t.end()
   })
 
@@ -372,6 +380,14 @@ test('safeParse', t => {
     t.end()
   })
 
+  t.test('should reset stackTraceLimit', t => {
+    const text = '{ "a": 5, "b": 6, "__proto__": { "x": 7 }, "c": { "d": 0, "e": "text", "__proto__": { "y": 8 }, "f": { "g": 2 } } }'
+    Error.stackTraceLimit = 42
+    t.same(j.safeParse(text), null)
+    t.same(Error.stackTraceLimit, 42)
+    t.end()
+  })
+
   t.test('sanitizes nested object string', t => {
     const text = '{ "a": 5, "b": 6, "__proto__": { "x": 7 }, "c": { "d": 0, "e": "text", "__proto__": { "y": 8 }, "f": { "g": 2 } } }'