From 2867425874c3903ddc6240e71007cc831d1b2f46 Mon Sep 17 00:00:00 2001
From: Ruben Bridgewater <ruben@bridgewater.de>
Date: Tue, 11 Dec 2018 22:42:34 +0100
Subject: [PATCH 1/2] lib: don't use `util.inspect()` internals

This makes sure the internal `stylize` function is not used to render
anything and instead just uses the regular inspect function in case
of reaching the maximum depth level.
---
 lib/internal/encoding.js                                 | 4 ++--
 lib/internal/url.js                                      | 2 +-
 test/parallel/test-whatwg-encoding-custom-textdecoder.js | 2 +-
 test/parallel/test-whatwg-url-custom-inspect.js          | 2 +-
 4 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/lib/internal/encoding.js b/lib/internal/encoding.js
index 0084c19b904a..3fbbbe1a2fef 100644
--- a/lib/internal/encoding.js
+++ b/lib/internal/encoding.js
@@ -320,7 +320,7 @@ class TextEncoder {
   [inspect](depth, opts) {
     validateEncoder(this);
     if (typeof depth === 'number' && depth < 0)
-      return opts.stylize('[Object]', 'special');
+      return this;
     var ctor = getConstructorOf(this);
     var obj = Object.create({
       constructor: ctor === null ? TextEncoder : ctor
@@ -517,7 +517,7 @@ function makeTextDecoderJS() {
       [inspect](depth, opts) {
         validateDecoder(this);
         if (typeof depth === 'number' && depth < 0)
-          return opts.stylize('[Object]', 'special');
+          return this;
         var ctor = getConstructorOf(this);
         var obj = Object.create({
           constructor: ctor === null ? TextDecoder : ctor
diff --git a/lib/internal/url.js b/lib/internal/url.js
index 6ad7122b8643..816715ab5e6c 100644
--- a/lib/internal/url.js
+++ b/lib/internal/url.js
@@ -343,7 +343,7 @@ class URL {
     }
 
     if (typeof depth === 'number' && depth < 0)
-      return opts.stylize('[Object]', 'special');
+      return this;
 
     var ctor = getConstructorOf(this);
 
diff --git a/test/parallel/test-whatwg-encoding-custom-textdecoder.js b/test/parallel/test-whatwg-encoding-custom-textdecoder.js
index ceee5b9cbbde..63abd2506a57 100644
--- a/test/parallel/test-whatwg-encoding-custom-textdecoder.js
+++ b/test/parallel/test-whatwg-encoding-custom-textdecoder.js
@@ -134,7 +134,7 @@ if (common.hasIntl) {
 // Test TextDecoder inspect with negative depth
 {
   const dec = new TextDecoder();
-  assert.strictEqual(util.inspect(dec, { depth: -1 }), '[Object]');
+  assert.strictEqual(util.inspect(dec, { depth: -1 }), '[TextDecoder]');
 }
 
 {
diff --git a/test/parallel/test-whatwg-url-custom-inspect.js b/test/parallel/test-whatwg-url-custom-inspect.js
index 1083866d86f5..21c13582254e 100644
--- a/test/parallel/test-whatwg-url-custom-inspect.js
+++ b/test/parallel/test-whatwg-url-custom-inspect.js
@@ -63,7 +63,7 @@ assert.strictEqual(
 
 assert.strictEqual(
   util.inspect({ a: url }, { depth: 0 }),
-  '{ a: [Object] }');
+  '{ a: [URL] }');
 
 class MyURL extends URL {}
 assert(util.inspect(new MyURL(url.href)).startsWith('MyURL {'));

From dd1a712079df8eca134c334d02ec668212f64c60 Mon Sep 17 00:00:00 2001
From: Ruben Bridgewater <ruben@bridgewater.de>
Date: Tue, 11 Dec 2018 21:28:45 +0100
Subject: [PATCH 2/2] util: prevent leaking internal properties

This prevents leaking of the internal `inspect()` properties when
using a custom inspect function.

It also aligns the indentation to the way it was in v8.0.0 since
that changed unintentionally. All strings returned by the custom
inspect function will now be indented appropriately to the current
depth.
---
 doc/api/util.md                    |  4 ++++
 lib/internal/util/inspect.js       |  8 ++++++--
 test/parallel/test-util-inspect.js | 20 ++++++++++++++++----
 3 files changed, 26 insertions(+), 6 deletions(-)

diff --git a/doc/api/util.md b/doc/api/util.md
index 9db263632e0a..b1d4854997f0 100644
--- a/doc/api/util.md
+++ b/doc/api/util.md
@@ -388,6 +388,10 @@ stream.write('With ES6');
 <!-- YAML
 added: v0.3.0
 changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/24971
+    description: Internal properties no longer appear in the context argument
+                 of a custom inspection function.
   - version: v11.7.0
     pr-url: https://github.com/nodejs/node/pull/25006
     description: ArrayBuffers now also show their binary contents.
diff --git a/lib/internal/util/inspect.js b/lib/internal/util/inspect.js
index 94d6ef8706f7..7f016794dd27 100644
--- a/lib/internal/util/inspect.js
+++ b/lib/internal/util/inspect.js
@@ -516,10 +516,14 @@ function formatValue(ctx, value, recurseTimes, typedArray) {
         maybeCustom !== inspect &&
         // Also filter out any prototype objects using the circular check.
         !(value.constructor && value.constructor.prototype === value)) {
+      // Remove some internal properties from the options before passing it
+      // through to the user function. This also prevents option manipulation.
+      // eslint-disable-next-line no-unused-vars
+      const { budget, seen, indentationLvl, ...plainCtx } = ctx;
       // This makes sure the recurseTimes are reported as before while using
       // a counter internally.
       const depth = ctx.depth === null ? null : ctx.depth - recurseTimes;
-      const ret = maybeCustom.call(value, depth, ctx);
+      const ret = maybeCustom.call(value, depth, plainCtx);
 
       // If the custom inspection method returned `this`, don't go into
       // infinite recursion.
@@ -527,7 +531,7 @@ function formatValue(ctx, value, recurseTimes, typedArray) {
         if (typeof ret !== 'string') {
           return formatValue(ctx, ret, recurseTimes);
         }
-        return ret;
+        return ret.replace(/\n/g, `\n${' '.repeat(ctx.indentationLvl)}`);
       }
     }
   }
diff --git a/test/parallel/test-util-inspect.js b/test/parallel/test-util-inspect.js
index 76f8caa31a88..2e55da2faa03 100644
--- a/test/parallel/test-util-inspect.js
+++ b/test/parallel/test-util-inspect.js
@@ -775,9 +775,21 @@ util.inspect({ hasOwnProperty: null });
 
   assert.strictEqual(util.inspect(subject), "{ foo: 'bar' }");
 
-  subject[util.inspect.custom] = (depth, opts) => {
-    assert.strictEqual(opts.customInspectOptions, true);
-  };
+  subject[util.inspect.custom] = common.mustCall((depth, opts) => {
+    const clone = { ...opts };
+    // This might change at some point but for now we keep the stylize function.
+    // The function should either be documented or an alternative should be
+    // implemented.
+    assert.strictEqual(typeof opts.stylize, 'function');
+    assert.strictEqual(opts.seen, undefined);
+    assert.strictEqual(opts.budget, undefined);
+    assert.strictEqual(opts.indentationLvl, undefined);
+    assert.strictEqual(opts.showHidden, false);
+    opts.showHidden = true;
+    return { [util.inspect.custom]: common.mustCall((depth, opts2) => {
+      assert.deepStrictEqual(clone, opts2);
+    }) };
+  });
 
   util.inspect(subject, { customInspectOptions: true });
 
@@ -1584,7 +1596,7 @@ util.inspect(process);
   );
   const longList = util.inspect(list, { depth: Infinity });
   const match = longList.match(/next/g);
-  assert(match.length > 1000 && match.length < 10000);
+  assert(match.length > 500 && match.length < 10000);
   assert(longList.includes('[Object: Inspection interrupted ' +
     'prematurely. Maximum call stack size exceeded.]'));
 }