util: pass opts to custom inspect functions

Objects with custom inpsect functions should get the options that were
passed to `util.inspect()`

fixes #5822
fixes #6098

doc/api/util.markdown

@@ -98,8 +98,8 @@ formatted string:
  - `colors` - if `true`, then the output will be styled with ANSI color codes.
    Defaults to `false`. Colors are customizable, see below.
 
- - `customInspect` - if `false`, then custom `inspect()` functions defined on the
-   objects being inspected won't be called. Defaults to `true`.
+ - `customInspect` - if `false`, then custom `inspect(depth, opts)` functions
+   defined on the objects being inspected won't be called. Defaults to `true`.
 
 Example of inspecting all properties of the `util` object:
 
@@ -107,6 +107,10 @@ Example of inspecting all properties of the `util` object:
 
     console.log(util.inspect(util, { showHidden: true, depth: null }));
 
+Values may supply their own custom `inspect(depth, opts)` functions, when
+called they receive the current depth in the recursive inspection, as well as
+the options object passed to `util.inspect()`.
+
 ### Customizing `util.inspect` colors
 
 <!-- type=misc -->

lib/util.js

@@ -218,7 +218,7 @@ function formatValue(ctx, value, recurseTimes) {
       value.inspect !== exports.inspect &&
       // Also filter out any prototype objects using the circular check.
       !(value.constructor && value.constructor.prototype === value)) {
-    var ret = value.inspect(recurseTimes);
+    var ret = value.inspect(recurseTimes, ctx);
     if (!isString(ret)) {
       ret = formatValue(ctx, ret, recurseTimes);
     }

test/simple/test-util-inspect.js

@@ -161,6 +161,12 @@ subject.inspect = function() { return { foo: 'bar' }; };
 
 assert.equal(util.inspect(subject), '{ foo: \'bar\' }');
 
+subject.inspect = function(depth, opts) {
+  assert.strictEqual(opts.customInspectOptions, true);
+};
+
+util.inspect(subject, { customInspectOptions: true });
+
 // util.inspect with "colors" option should produce as many lines as without it
 function test_lines(input) {
   var count_lines = function(str) {