util: add an option for configuring break length

This commit adds a breakLength option to util.inspect(). This
option allows users to control the length at which object keys
are split across multiple lines. For backwards compatibility,
this option defaults to 60.

Fixes: #7305
PR-URL: #7499
Reviewed-By: Evan Lucas <evanlucas@me.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>

Author: cjihrig

doc/api/util.md

@@ -187,6 +187,9 @@ stream.write('It works!'); // Received data: "It works!"
     `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.
+  * `breakLength` {number} The length at which an object's keys are split
+    across multiple lines. Set to `Infinity` to format an object as a single
+    line. Defaults to 60 for legacy compatibility.
 
 The `util.inspect()` method returns a string representation of `object` that is
 primarily useful for debugging. Additional `options` may be passed that alter

lib/util.js

@@ -194,6 +194,7 @@ function inspect(obj, opts) {
   if (ctx.colors) ctx.stylize = stylizeWithColor;
   if (ctx.maxArrayLength === undefined) ctx.maxArrayLength = kDefaultMaxLength;
   if (ctx.maxArrayLength === null) ctx.maxArrayLength = Infinity;
+  if (ctx.breakLength === undefined) ctx.breakLength = 60;
   return formatValue(ctx, obj, ctx.depth);
 }
 exports.inspect = inspect;
@@ -575,7 +576,7 @@ function formatValue(ctx, value, recurseTimes) {
 
   ctx.seen.pop();
 
-  return reduceToSingleString(output, base, braces);
+  return reduceToSingleString(output, base, braces, ctx.breakLength);
 }
 
 
@@ -807,12 +808,12 @@ function formatProperty(ctx, value, recurseTimes, visibleKeys, key, array) {
 }
 
 
-function reduceToSingleString(output, base, braces) {
+function reduceToSingleString(output, base, braces, breakLength) {
   var length = output.reduce(function(prev, cur) {
     return prev + cur.replace(/\u001b\[\d\d?m/g, '').length + 1;
   }, 0);
 
-  if (length > 60) {
+  if (length > breakLength) {
     return braces[0] +
            // 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

test/parallel/test-util-inspect.js

@@ -709,3 +709,16 @@ checkAlignment(new Map(big_array.map(function(y) { return [y, null]; })));
   const x = new Uint8Array(101);
   assert(!/1 more item/.test(util.inspect(x, {maxArrayLength: Infinity})));
 }
+
+{
+  const obj = {foo: 'abc', bar: 'xyz'};
+  const oneLine = util.inspect(obj, {breakLength: Infinity});
+  // Subtract four for the object's two curly braces and two spaces of padding.
+  // Add one more to satisfy the strictly greater than condition in the code.
+  const breakpoint = oneLine.length - 5;
+  const twoLines = util.inspect(obj, {breakLength: breakpoint});
+
+  assert.strictEqual(oneLine, '{ foo: \'abc\', bar: \'xyz\' }');
+  assert.strictEqual(oneLine, util.inspect(obj, {breakLength: breakpoint + 1}));
+  assert.strictEqual(twoLines, '{ foo: \'abc\',\n  bar: \'xyz\' }');
+}