util: recover from maximum call stack size

Using util.inspect should still return values in case the maximum call stack size is reached. This is important to inspect linked lists and similar.
nodejs · BridgeAR · May 14, 2018 · Jun 11, 2018 · Jun 11, 2018 · ef4e8d39457ab6a1e62918e89982405e68e3ff57
commit ef4e8d39457ab6a1e62918e89982405e68e3ff57
diff --git a/doc/api/util.md b/doc/api/util.md
@@ -360,6 +360,10 @@ stream.write('With ES6');
 <!-- YAML
 added: v0.3.0
 changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/REPLACEME
+    description: Inspecting linked lists and similar objects is now possible
+                 up to the maximum call stack size.
   - version: v10.0.0
     pr-url: https://github.com/nodejs/node/pull/19259
     description: The `WeakMap` and `WeakSet` entries can now be inspected
@@ -388,8 +392,9 @@ changes:
     properties will be included in the formatted result as well as [`WeakMap`][]
     and [`WeakSet`][] entries. **Default:** `false`.
   * `depth` {number} Specifies the number of times to recurse while formatting
-    the `object`. This is useful for inspecting large complicated objects.
-    To make it recurse indefinitely pass `null`. **Default:** `2`.
+    the `object`. This is useful for inspecting large complicated objects. To
+    make it recurse up to the maximum call stack size pass `Infinity` or `null`.
+    **Default:** `2`.
   * `colors` {boolean} If `true`, the output will be styled with ANSI color
     codes. Colors are customizable, see [Customizing `util.inspect` colors][].
     **Default:** `false`.

diff --git a/lib/util.js b/lib/util.js
@@ -701,14 +701,32 @@ function formatValue(ctx, value, recurseTimes) {
   }
 
   ctx.seen.push(value);
-  const output = formatter(ctx, value, recurseTimes, keys);
-
+  let output;
+  // This corresponds to a depth of at least 333 and likely 500.
+  if (ctx.indentationLvl < 1000) {
+    output = formatter(ctx, value, recurseTimes, keys);
+  } else {
+    try {
+      output = formatter(ctx, value, recurseTimes, keys);
+    } catch (err) {
+      if (errors.isStackOverflowError(err)) {
+        ctx.seen.pop();
+        process.emitWarning(
+          'Inspection reached the maximum call stack size. Incomplete ' +
+          'inspected object returned.'
+        );
+        return ctx.stylize(`[${constructor || tag || 'Object'}]`, 'special');
+      }
+      throw err;
+    }
+  }
   if (extra !== undefined)
     output.unshift(extra);
 
   for (var i = 0; i < symbols.length; i++) {
     output.push(formatProperty(ctx, value, recurseTimes, symbols[i], 0));
   }
+
   ctx.seen.pop();
 
   return reduceToSingleString(ctx, output, base, braces);

diff --git a/test/parallel/test-util-inspect.js b/test/parallel/test-util-inspect.js
@@ -1410,10 +1410,23 @@ util.inspect(process);
   // Test that a long linked list can be inspected without throwing an error.
   const list = {};
   let head = list;
-  // The real cutoff value is closer to 1400 stack frames as of May 2018,
-  // but let's be generous here – even a linked listed of length 100k should be
-  // inspectable in some way.
+  // A linked list of length 100k should be inspectable in some way, even though
+  // the real cutoff value is much lower than 100k.
   for (let i = 0; i < 100000; i++)
     head = head.next = {};
-  util.inspect(list);
+  assert.strictEqual(
+    util.inspect(list),
+    '{ next: { next: { next: [Object] } } }'
+  );
+  common.expectWarning({
+    Warning: [
+      'Inspection reached the maximum call stack size. ' +
+        'Incomplete inspected object returned.',
+      common.noWarnCode
+    ]
+  });
+  const longList = util.inspect(list, { depth: Infinity });
+  const match = longList.match(/next/g);
+  assert(match.length > 1000 && match.length < 10000);
+  assert(longList.includes('[Object]'));
 }