util: show Weak(Set|Map) entries in inspect

This adds support for WeakMap and WeakSet entries in `util.inspect`.
The output is limited to a maximum entry length of `maxArrayLength`.

PR-URL: https://github.com/nodejs/node/pull/19259
Fixes: https://github.com/nodejs/node/issues/19001:
Reviewed-By: Yosuke Furukawa <yosuke.furukawa@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

1 files changed, 67 insertions, 1 deletions

diff --git a/lib/util.js b/lib/util.js
index 774b185095..a9be7cbda4 100644
--- a/lib/util.js
+++ b/lib/util.js
@@ -32,7 +32,9 @@ const { isBuffer } = require('buffer').Buffer;
 
 const {
   previewMapIterator,
-  previewSetIterator
+  previewSetIterator,
+  previewWeakMap,
+  previewWeakSet
 } = require('internal/v8');
 
 const {
@@ -54,6 +56,8 @@ const {
   isPromise,
   isSet,
   isSetIterator,
+  isWeakMap,
+  isWeakSet,
   isRegExp,
   isDate,
   isTypedArray
@@ -291,6 +295,8 @@ function inspect(value, opts) {
     colors: inspectDefaultOptions.colors,
     customInspect: inspectDefaultOptions.customInspect,
     showProxy: inspectDefaultOptions.showProxy,
+    // TODO(BridgeAR): Deprecate `maxArrayLength` and replace it with
+    // `maxEntries`.
     maxArrayLength: inspectDefaultOptions.maxArrayLength,
     breakLength: inspectDefaultOptions.breakLength,
     indentationLvl: 0,
@@ -328,6 +334,8 @@ Object.defineProperty(inspect, 'defaultOptions', {
     if (options === null || typeof options !== 'object') {
       throw new ERR_INVALID_ARG_TYPE('options', 'Object', options);
     }
+    // TODO(BridgeAR): Add input validation and make sure `defaultOptions` are
+    // not configurable.
     return _extend(inspectDefaultOptions, options);
   }
 });
@@ -465,6 +473,7 @@ function formatValue(ctx, value, recurseTimes, ln) {
   let braces;
   let noIterator = true;
   let raw;
+  let extra;
 
   // Iterators and the rest are split to reduce checks
   if (value[Symbol.iterator]) {
@@ -562,6 +571,20 @@ function formatValue(ctx, value, recurseTimes, ln) {
     } else if (isPromise(value)) {
       braces[0] = `${prefix}{`;
       formatter = formatPromise;
+    } else if (isWeakSet(value)) {
+      braces[0] = `${prefix}{`;
+      if (ctx.showHidden) {
+        formatter = formatWeakSet;
+      } else {
+        extra = '[items unknown]';
+      }
+    } else if (isWeakMap(value)) {
+      braces[0] = `${prefix}{`;
+      if (ctx.showHidden) {
+        formatter = formatWeakMap;
+      } else {
+        extra = '[items unknown]';
+      }
     } else {
       // Check boxed primitives other than string with valueOf()
       // NOTE: `Date` has to be checked first!
@@ -616,6 +639,9 @@ function formatValue(ctx, value, recurseTimes, ln) {
   ctx.seen.push(value);
   const output = formatter(ctx, value, recurseTimes, keys);
 
+  if (extra !== undefined)
+    output.unshift(extra);
+
   for (var i = 0; i < symbols.length; i++) {
     output.push(formatProperty(ctx, value, recurseTimes, symbols[i], 0));
   }
@@ -839,6 +865,46 @@ function formatMap(ctx, value, recurseTimes, keys) {
   return output;
 }
 
+function formatWeakSet(ctx, value, recurseTimes, keys) {
+  const maxArrayLength = Math.max(ctx.maxArrayLength, 0);
+  const entries = previewWeakSet(value, maxArrayLength + 1);
+  const maxLength = Math.min(maxArrayLength, entries.length);
+  let output = new Array(maxLength);
+  for (var i = 0; i < maxLength; ++i)
+    output[i] = formatValue(ctx, entries[i], recurseTimes);
+  // Sort all entries to have a halfway reliable output (if more entries than
+  // retrieved ones exist, we can not reliably return the same output).
+  output = output.sort();
+  if (entries.length > maxArrayLength)
+    output.push('... more items');
+  for (i = 0; i < keys.length; i++)
+    output.push(formatProperty(ctx, value, recurseTimes, keys[i], 0));
+  return output;
+}
+
+function formatWeakMap(ctx, value, recurseTimes, keys) {
+  const maxArrayLength = Math.max(ctx.maxArrayLength, 0);
+  const entries = previewWeakMap(value, maxArrayLength + 1);
+  // Entries exist as [key1, val1, key2, val2, ...]
+  const remainder = entries.length / 2 > maxArrayLength;
+  const len = entries.length / 2 - (remainder ? 1 : 0);
+  const maxLength = Math.min(maxArrayLength, len);
+  let output = new Array(maxLength);
+  for (var i = 0; i < len; i++) {
+    const pos = i * 2;
+    output[i] = `${formatValue(ctx, entries[pos], recurseTimes)} => ` +
+      formatValue(ctx, entries[pos + 1], recurseTimes);
+  }
+  // Sort all entries to have a halfway reliable output (if more entries than
+  // retrieved ones exist, we can not reliably return the same output).
+  output = output.sort();
+  if (remainder > 0)
+    output.push('... more items');
+  for (i = 0; i < keys.length; i++)
+    output.push(formatProperty(ctx, value, recurseTimes, keys[i], 0));
+  return output;
+}
+
 function formatCollectionIterator(preview, ctx, value, recurseTimes, keys) {
   const output = [];
   for (const entry of preview(value)) {