util: make inspect more reliable

34a35919e1 added pretty printing for
TypedArray, ArrayBuffer, and DataView. This change allows inspecting
those across different contexts.

Since instanceof does not work across contexts, we can use
v8::Value::IsTypedArray, v8::Value::IsArrayBuffer, and
v8::Value::IsDataView

PR-URL: https://github.com/nodejs/node/pull/4098
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>

lib/util.js

@@ -290,7 +290,7 @@ function formatValue(ctx, value, recurseTimes) {
     }
     // Fast path for ArrayBuffer.  Can't do the same for DataView because it
     // has a non-primitive .buffer property that we need to recurse for.
-    if (value instanceof ArrayBuffer) {
+    if (binding.isArrayBuffer(value)) {
       return `${getConstructorOf(value).name}` +
              ` { byteLength: ${formatNumber(ctx, value.byteLength)} }`;
     }
@@ -328,18 +328,18 @@ function formatValue(ctx, value, recurseTimes) {
       keys.unshift('size');
     empty = value.size === 0;
     formatter = formatMap;
-  } else if (value instanceof ArrayBuffer) {
+  } else if (binding.isArrayBuffer(value)) {
     braces = ['{', '}'];
     keys.unshift('byteLength');
     visibleKeys.byteLength = true;
-  } else if (value instanceof DataView) {
+  } else if (binding.isDataView(value)) {
     braces = ['{', '}'];
     // .buffer goes last, it's not a primitive like the others.
     keys.unshift('byteLength', 'byteOffset', 'buffer');
     visibleKeys.byteLength = true;
     visibleKeys.byteOffset = true;
     visibleKeys.buffer = true;
-  } else if (isTypedArray(value)) {
+  } else if (binding.isTypedArray(value)) {
     braces = ['[', ']'];
     formatter = formatTypedArray;
     if (ctx.showHidden) {
@@ -679,19 +679,6 @@ function reduceToSingleString(output, base, braces) {
 }
 
 
-function isTypedArray(value) {
-  return value instanceof Float32Array ||
-         value instanceof Float64Array ||
-         value instanceof Int16Array ||
-         value instanceof Int32Array ||
-         value instanceof Int8Array ||
-         value instanceof Uint16Array ||
-         value instanceof Uint32Array ||
-         value instanceof Uint8Array ||
-         value instanceof Uint8ClampedArray;
-}
-
-
 // NOTE: These type checking functions intentionally don't use `instanceof`
 // because it is fragile and can be easily faked with `Object.create()`.
 exports.isArray = Array.isArray;

src/node_util.cc

@@ -30,6 +30,24 @@ static void IsPromise(const FunctionCallbackInfo<Value>& args) {
 }
 
 
+static void IsTypedArray(const FunctionCallbackInfo<Value>& args) {
+  CHECK_EQ(1, args.Length());
+  args.GetReturnValue().Set(args[0]->IsTypedArray());
+}
+
+
+static void IsArrayBuffer(const FunctionCallbackInfo<Value>& args) {
+  CHECK_EQ(1, args.Length());
+  args.GetReturnValue().Set(args[0]->IsArrayBuffer());
+}
+
+
+static void IsDataView(const FunctionCallbackInfo<Value>& args) {
+  CHECK_EQ(1, args.Length());
+  args.GetReturnValue().Set(args[0]->IsDataView());
+}
+
+
 static void GetHiddenValue(const FunctionCallbackInfo<Value>& args) {
   Environment* env = Environment::GetCurrent(args);
 
@@ -53,6 +71,9 @@ void Initialize(Local<Object> target,
   env->SetMethod(target, "isMapIterator", IsMapIterator);
   env->SetMethod(target, "isSetIterator", IsSetIterator);
   env->SetMethod(target, "isPromise", IsPromise);
+  env->SetMethod(target, "isTypedArray", IsTypedArray);
+  env->SetMethod(target, "isArrayBuffer", IsArrayBuffer);
+  env->SetMethod(target, "isDataView", IsDataView);
   env->SetMethod(target, "getHiddenValue", GetHiddenValue);
 }
 

test/parallel/test-util-inspect.js

@@ -2,6 +2,7 @@
 var common = require('../common');
 var assert = require('assert');
 var util = require('util');
+const vm = require('vm');
 
 assert.equal(util.inspect(1), '1');
 assert.equal(util.inspect(false), 'false');
@@ -68,6 +69,35 @@ for (const showHidden of [true, false]) {
                '  y: 1337 }');
 }
 
+// Now do the same checks but from a different context
+for (const showHidden of [true, false]) {
+  const ab = vm.runInNewContext('new ArrayBuffer(4)');
+  const dv = vm.runInNewContext('new DataView(ab, 1, 2)', { ab: ab });
+  assert.equal(util.inspect(ab, showHidden), 'ArrayBuffer { byteLength: 4 }');
+  assert.equal(util.inspect(new DataView(ab, 1, 2), showHidden),
+               'DataView {\n' +
+               '  byteLength: 2,\n' +
+               '  byteOffset: 1,\n' +
+               '  buffer: ArrayBuffer { byteLength: 4 } }');
+  assert.equal(util.inspect(ab, showHidden), 'ArrayBuffer { byteLength: 4 }');
+  assert.equal(util.inspect(dv, showHidden),
+               'DataView {\n' +
+               '  byteLength: 2,\n' +
+               '  byteOffset: 1,\n' +
+               '  buffer: ArrayBuffer { byteLength: 4 } }');
+  ab.x = 42;
+  dv.y = 1337;
+  assert.equal(util.inspect(ab, showHidden),
+               'ArrayBuffer { byteLength: 4, x: 42 }');
+  assert.equal(util.inspect(dv, showHidden),
+               'DataView {\n' +
+               '  byteLength: 2,\n' +
+               '  byteOffset: 1,\n' +
+               '  buffer: ArrayBuffer { byteLength: 4, x: 42 },\n' +
+               '  y: 1337 }');
+}
+
+
 [ Float32Array,
   Float64Array,
   Int16Array,
@@ -94,6 +124,38 @@ for (const showHidden of [true, false]) {
     assert.equal(util.inspect(array, false), `${constructor.name} [ 65, 97 ]`);
   });
 
+// Now check that declaring a TypedArray in a different context works the same
+[ Float32Array,
+  Float64Array,
+  Int16Array,
+  Int32Array,
+  Int8Array,
+  Uint16Array,
+  Uint32Array,
+  Uint8Array,
+  Uint8ClampedArray ].forEach(constructor => {
+    const length = 2;
+    const byteLength = length * constructor.BYTES_PER_ELEMENT;
+    const array = vm.runInNewContext('new constructor(new ArrayBuffer(' +
+                                     'byteLength), 0, length)',
+                                     { constructor: constructor,
+                                       byteLength: byteLength,
+                                       length: length
+                                     });
+    array[0] = 65;
+    array[1] = 97;
+    assert.equal(util.inspect(array, true),
+                 `${constructor.name} [\n` +
+                 `  65,\n` +
+                 `  97,\n` +
+                 `  [BYTES_PER_ELEMENT]: ${constructor.BYTES_PER_ELEMENT},\n` +
+                 `  [length]: ${length},\n` +
+                 `  [byteLength]: ${byteLength},\n` +
+                 `  [byteOffset]: 0,\n` +
+                 `  [buffer]: ArrayBuffer { byteLength: ${byteLength} } ]`);
+    assert.equal(util.inspect(array, false), `${constructor.name} [ 65, 97 ]`);
+  });
+
 // Due to the hash seed randomization it's not deterministic the order that
 // the following ways this hash is displayed.
 // See http://codereview.chromium.org/9124004/