util: support inspecting Map, Set, and Promise

lib/util.js

@@ -276,12 +276,24 @@ function formatValue(ctx, value, recurseTimes) {
     }
   }
 
-  var base = '', array = false, braces = ['{', '}'];
+  var base = '', braces;
 
-  // Make Array say that they are Array
   if (Array.isArray(value)) {
-    array = true;
     braces = ['[', ']'];
+  } else if (value instanceof Set) {
+    braces = ['Set {', '}'];
+    // With `showHidden`, `length` will display as a hidden property for
+    // arrays. For consistency's sake, do the same for `size`, even though this
+    // property isn't selected by Object.getOwnPropertyNames().
+    if (ctx.showHidden)
+      keys.unshift('size');
+  } else if (value instanceof Map) {
+    braces = ['Map {', '}'];
+    // ditto
+    if (ctx.showHidden)
+      keys.unshift('size');
+  } else {
+    braces = ['{', '}'];
   }
 
   // Make functions say that they are functions
@@ -323,7 +335,10 @@ function formatValue(ctx, value, recurseTimes) {
     base = ' ' + '[Boolean: ' + formatted + ']';
   }
 
-  if (keys.length === 0 && (!array || value.length === 0)) {
+  if (keys.length === 0 &&
+      (!Array.isArray(value) || value.length === 0) &&
+      (!(value instanceof Set) || value.size === 0) &&
+      (!(value instanceof Map) || value.size === 0)) {
     return braces[0] + base + braces[1];
   }
 
@@ -338,11 +353,15 @@ function formatValue(ctx, value, recurseTimes) {
   ctx.seen.push(value);
 
   var output;
-  if (array) {
+  if (Array.isArray(value)) {
     output = formatArray(ctx, value, recurseTimes, visibleKeys, keys);
+  } else if (value instanceof Set) {
+    output = formatSet(ctx, value, recurseTimes, visibleKeys, keys);
+  } else if (value instanceof Map) {
+    output = formatMap(ctx, value, recurseTimes, visibleKeys, keys);
   } else {
     output = keys.map(function(key) {
-      return formatProperty(ctx, value, recurseTimes, visibleKeys, key, array);
+      return formatProperty(ctx, value, recurseTimes, visibleKeys, key, false);
     });
   }
 
@@ -417,6 +436,38 @@ function formatArray(ctx, value, recurseTimes, visibleKeys, keys) {
 }
 
 
+function formatSet(ctx, value, recurseTimes, visibleKeys, keys) {
+  var output = [];
+  value.forEach(function(v) {
+    var str = formatValue(ctx, v,
+                          recurseTimes === null ? null : recurseTimes - 1);
+    output.push(str);
+  });
+  keys.forEach(function(key) {
+    output.push(formatProperty(ctx, value, recurseTimes, visibleKeys,
+                               key, false));
+  });
+  return output;
+}
+
+
+function formatMap(ctx, value, recurseTimes, visibleKeys, keys) {
+  var output = [];
+  value.forEach(function(v, k) {
+    var str = formatValue(ctx, k,
+                          recurseTimes === null ? null : recurseTimes - 1);
+    str += ' => ';
+    str += formatValue(ctx, v, recurseTimes === null ? null : recurseTimes - 1);
+    output.push(str);
+  });
+  keys.forEach(function(key) {
+    output.push(formatProperty(ctx, value, recurseTimes, visibleKeys,
+                               key, false));
+  });
+  return output;
+}
+
+
 function formatProperty(ctx, value, recurseTimes, visibleKeys, key, array) {
   var name, str, desc;
   desc = Object.getOwnPropertyDescriptor(value, key) || { value: value[key] };
@@ -488,7 +539,10 @@ function reduceToSingleString(output, base, braces) {
 
   if (length > 60) {
     return braces[0] +
-           (base === '' ? '' : base + '\n ') +
+           // If the opening "brace" is too large, like in the case of "Set {",
+           // we need to force the first item to be on the next line or the
+           // items will not line up correctly.
+           (base === '' && braces[0].length === 1 ? '' : base + '\n ') +
            ' ' +
            output.join(',\n  ') +
            ' ' +

test/parallel/test-util-inspect.js

@@ -235,3 +235,17 @@ if (typeof Symbol !== 'undefined') {
   assert.equal(util.inspect(subject, options), '[ 1, 2, 3, [length]: 3, [Symbol(symbol)]: 42 ]');
 
 }
+
+// test Set
+assert.equal(util.inspect(new Set), 'Set {}')
+assert.equal(util.inspect(new Set([1, 2, 3])), 'Set { 1, 2, 3 }')
+var set = new Set(["foo"])
+set.bar = 42
+assert.equal(util.inspect(set, true), 'Set { \'foo\', [size]: 1, bar: 42 }')
+
+// test Map
+assert.equal(util.inspect(new Map), 'Map {}')
+assert.equal(util.inspect(new Map([[1, 'a'], [2, 'b'], [3, 'c']])), 'Map { 1 => \'a\', 2 => \'b\', 3 => \'c\' }')
+var map = new Map([["foo", null]])
+map.bar = 42
+assert.equal(util.inspect(map, true), 'Map { \'foo\' => null, [size]: 1, bar: 42 }')