From 2b8724114a3ae9e40ecdbb355df0fb65c1cc8ad1 Mon Sep 17 00:00:00 2001
From: James M Snell <jasnell@gmail.com>
Date: Thu, 21 Apr 2016 10:29:24 -0700
Subject: [PATCH] util: truncate inspect array and typed array

As an alternative to https://github.com/nodejs/node/pull/5070,
set the max length of Arrays/TypedArrays in util.inspect() to
`100` and provide a `maxArrayLength` option to override.
---
 doc/api/util.md                    |  4 +++
 lib/util.js                        | 19 +++++++++--
 test/parallel/test-util-inspect.js | 55 ++++++++++++++++++++++++++++++
 3 files changed, 75 insertions(+), 3 deletions(-)

diff --git a/doc/api/util.md b/doc/api/util.md
index 8ef4b0dfcc564d..178e0cdb082404 100644
--- a/doc/api/util.md
+++ b/doc/api/util.md
@@ -183,6 +183,10 @@ formatted string:
    will be introspected to show their `target` and `hander` objects. Defaults to
    `false`.
 
+ - `maxArrayLength` - specifies the maximum number of Array and TypedArray
+   elements to include when formatting. Defaults to `100`. Set to `null` to
+   show all array elements. Set to `0` or negative to show no array elements.
+
 Example of inspecting all properties of the `util` object:
 
 ```js
diff --git a/lib/util.js b/lib/util.js
index 69df2501997309..d430bfd23df02e 100644
--- a/lib/util.js
+++ b/lib/util.js
@@ -6,6 +6,7 @@ const internalUtil = require('internal/util');
 const binding = process.binding('util');
 
 const isError = internalUtil.isError;
+const kDefaultMaxLength = 100;
 
 var Debug;
 
@@ -141,6 +142,8 @@ function inspect(obj, opts) {
   if (ctx.customInspect === undefined) ctx.customInspect = true;
   if (ctx.showProxy === undefined) ctx.showProxy = false;
   if (ctx.colors) ctx.stylize = stylizeWithColor;
+  if (ctx.maxArrayLength === undefined) ctx.maxArrayLength = kDefaultMaxLength;
+  if (ctx.maxArrayLength === null) ctx.maxArrayLength = Infinity;
   return formatValue(ctx, obj, ctx.depth);
 }
 exports.inspect = inspect;
@@ -579,7 +582,9 @@ function formatObject(ctx, value, recurseTimes, visibleKeys, keys) {
 
 function formatArray(ctx, value, recurseTimes, visibleKeys, keys) {
   var output = [];
-  for (var i = 0, l = value.length; i < l; ++i) {
+  const maxLength = Math.min(Math.max(0, ctx.maxArrayLength), value.length);
+  const remaining = value.length - maxLength;
+  for (var i = 0; i < maxLength; ++i) {
     if (hasOwnProperty(value, String(i))) {
       output.push(formatProperty(ctx, value, recurseTimes, visibleKeys,
           String(i), true));
@@ -587,6 +592,9 @@ function formatArray(ctx, value, recurseTimes, visibleKeys, keys) {
       output.push('');
     }
   }
+  if (remaining > 0) {
+    output.push(`... ${remaining} more item${remaining > 1 ? 's' : ''}`);
+  }
   keys.forEach(function(key) {
     if (typeof key === 'symbol' || !key.match(/^\d+$/)) {
       output.push(formatProperty(ctx, value, recurseTimes, visibleKeys,
@@ -598,9 +606,14 @@ function formatArray(ctx, value, recurseTimes, visibleKeys, keys) {
 
 
 function formatTypedArray(ctx, value, recurseTimes, visibleKeys, keys) {
-  var output = new Array(value.length);
-  for (var i = 0, l = value.length; i < l; ++i)
+  const maxLength = Math.min(Math.max(0, ctx.maxArrayLength), value.length);
+  const remaining = value.length - maxLength;
+  var output = new Array(maxLength);
+  for (var i = 0; i < maxLength; ++i)
     output[i] = formatNumber(ctx, value[i]);
+  if (remaining > 0) {
+    output.push(`... ${remaining} more item${remaining > 1 ? 's' : ''}`);
+  }
   for (const key of keys) {
     if (typeof key === 'symbol' || !key.match(/^\d+$/)) {
       output.push(
diff --git a/test/parallel/test-util-inspect.js b/test/parallel/test-util-inspect.js
index 9e713cf16c542b..d2af5014b241f5 100644
--- a/test/parallel/test-util-inspect.js
+++ b/test/parallel/test-util-inspect.js
@@ -648,3 +648,58 @@ checkAlignment(new Map(big_array.map(function(y) { return [y, null]; })));
   const x = Object.create(null);
   assert.equal(util.inspect(x), '{}');
 }
+
+// The following maxArrayLength tests were introduced after v6.0.0 was released.
+// Do not backport to v5/v4 unless all of
+// https://github.com/nodejs/node/pull/6334 is backported.
+{
+  const x = Array(101);
+  assert(/1 more item/.test(util.inspect(x)));
+}
+
+{
+  const x = Array(101);
+  assert(!/1 more item/.test(util.inspect(x, {maxArrayLength: 101})));
+}
+
+{
+  const x = Array(101);
+  assert(/^\[ ... 101 more items \]$/.test(
+      util.inspect(x, {maxArrayLength: 0})));
+}
+
+{
+  const x = new Uint8Array(101);
+  assert(/1 more item/.test(util.inspect(x)));
+}
+
+{
+  const x = new Uint8Array(101);
+  assert(!/1 more item/.test(util.inspect(x, {maxArrayLength: 101})));
+}
+
+{
+  const x = new Uint8Array(101);
+  assert(/\[ ... 101 more items \]$/.test(
+      util.inspect(x, {maxArrayLength: 0})));
+}
+
+{
+  const x = Array(101);
+  assert(!/1 more item/.test(util.inspect(x, {maxArrayLength: null})));
+}
+
+{
+  const x = Array(101);
+  assert(!/1 more item/.test(util.inspect(x, {maxArrayLength: Infinity})));
+}
+
+{
+  const x = new Uint8Array(101);
+  assert(!/1 more item/.test(util.inspect(x, {maxArrayLength: null})));
+}
+
+{
+  const x = new Uint8Array(101);
+  assert(!/1 more item/.test(util.inspect(x, {maxArrayLength: Infinity})));
+}