util: add maxArrayLength option to Set and Map

Author: cola119

doc/api/util.md

@@ -586,8 +586,9 @@ changes:
   * `showProxy` {boolean} If `true`, `Proxy` inspection includes
     the [`target` and `handler`][] objects. **Default:** `false`.
   * `maxArrayLength` {integer} Specifies the maximum number of `Array`,
-    [`TypedArray`][], [`WeakMap`][], and [`WeakSet`][] elements to include when
-    formatting. Set to `null` or `Infinity` to show all elements. Set to `0` or
+    [`TypedArray`][], [`Map`][], [`Set`][], [`WeakMap`][],
+    and [`WeakSet`][] elements to include when formatting.
+    Set to `null` or `Infinity` to show all elements. Set to `0` or
     negative to show no elements. **Default:** `100`.
   * `maxStringLength` {integer} Specifies the maximum number of characters to
     include when formatting. Set to `null` or `Infinity` to show all elements.

lib/internal/util/inspect.js

@@ -1487,6 +1487,8 @@ function addNumericSeparatorEnd(integerString) {
     `${result}${integerString.slice(i)}`;
 }
 
+const remainingText = (remaining) => `... ${remaining} more item${remaining > 1 ? 's' : ''}`;
+
 function formatNumber(fn, number, numericSeparator) {
   if (!numericSeparator) {
     // Format -0 as '-0'. Checking `number === -0` won't distinguish 0 from -0.
@@ -1613,7 +1615,7 @@ function formatSpecialArray(ctx, value, recurseTimes, maxLength, output, i) {
       output.push(ctx.stylize(message, 'undefined'));
     }
   } else if (remaining > 0) {
-    output.push(`... ${remaining} more item${remaining > 1 ? 's' : ''}`);
+    output.push(remainingText(remaining));
   }
   return output;
 }
@@ -1650,7 +1652,7 @@ function formatArray(ctx, value, recurseTimes) {
     output.push(formatProperty(ctx, value, recurseTimes, i, kArrayType));
   }
   if (remaining > 0)
-    output.push(`... ${remaining} more item${remaining > 1 ? 's' : ''}`);
+    output.push(remainingText(remaining));
   return output;
 }
 
@@ -1665,7 +1667,7 @@ function formatTypedArray(value, length, ctx, ignored, recurseTimes) {
     output[i] = elementFormatter(ctx.stylize, value[i], ctx.numericSeparator);
   }
   if (remaining > 0) {
-    output[maxLength] = `... ${remaining} more item${remaining > 1 ? 's' : ''}`;
+    output[maxLength] = remainingText(remaining);
   }
   if (ctx.showHidden) {
     // .buffer goes last, it's not a primitive like the others.
@@ -1687,22 +1689,40 @@ function formatTypedArray(value, length, ctx, ignored, recurseTimes) {
 }
 
 function formatSet(value, ctx, ignored, recurseTimes) {
+  const length = value.size;
+  const maxLength = MathMin(MathMax(0, ctx.maxArrayLength), length);
+  const remaining = length - maxLength;
   const output = [];
   ctx.indentationLvl += 2;
+  let i = 0;
   for (const v of value) {
+    if (i >= maxLength) break;
     ArrayPrototypePush(output, formatValue(ctx, v, recurseTimes));
+    i++;
+  }
+  if (remaining > 0) {
+    ArrayPrototypePush(output, remainingText(remaining));
   }
   ctx.indentationLvl -= 2;
   return output;
 }
 
 function formatMap(value, ctx, ignored, recurseTimes) {
+  const length = value.size;
+  const maxLength = MathMin(MathMax(0, ctx.maxArrayLength), length);
+  const remaining = length - maxLength;
   const output = [];
   ctx.indentationLvl += 2;
+  let i = 0;
   for (const { 0: k, 1: v } of value) {
+    if (i >= maxLength) break;
     output.push(
       `${formatValue(ctx, k, recurseTimes)} => ${formatValue(ctx, v, recurseTimes)}`
     );
+    i++;
+  }
+  if (remaining > 0) {
+    ArrayPrototypePush(output, remainingText(remaining));
   }
   ctx.indentationLvl -= 2;
   return output;
@@ -1725,8 +1745,7 @@ function formatSetIterInner(ctx, recurseTimes, entries, state) {
   }
   const remaining = entries.length - maxLength;
   if (remaining > 0) {
-    ArrayPrototypePush(output,
-                       `... ${remaining} more item${remaining > 1 ? 's' : ''}`);
+    ArrayPrototypePush(output, remainingText(remaining));
   }
   return output;
 }
@@ -1764,7 +1783,7 @@ function formatMapIterInner(ctx, recurseTimes, entries, state) {
   }
   ctx.indentationLvl -= 2;
   if (remaining > 0) {
-    output.push(`... ${remaining} more item${remaining > 1 ? 's' : ''}`);
+    output.push(remainingText(remaining));
   }
   return output;
 }

test/parallel/test-util-inspect.js

@@ -1171,6 +1171,7 @@ if (typeof Symbol !== 'undefined') {
 {
   assert.strictEqual(util.inspect(new Set()), 'Set(0) {}');
   assert.strictEqual(util.inspect(new Set([1, 2, 3])), 'Set(3) { 1, 2, 3 }');
+  assert.strictEqual(util.inspect(new Set([1, 2, 3]), { maxArrayLength: 1 }), 'Set(3) { 1, ... 2 more items }');
   const set = new Set(['foo']);
   set.bar = 42;
   assert.strictEqual(
@@ -1191,6 +1192,8 @@ if (typeof Symbol !== 'undefined') {
   assert.strictEqual(util.inspect(new Map()), 'Map(0) {}');
   assert.strictEqual(util.inspect(new Map([[1, 'a'], [2, 'b'], [3, 'c']])),
                      "Map(3) { 1 => 'a', 2 => 'b', 3 => 'c' }");
+  assert.strictEqual(util.inspect(new Map([[1, 'a'], [2, 'b'], [3, 'c']]), { maxArrayLength: 1 }),
+                     "Map(3) { 1 => 'a', ... 2 more items }");
   const map = new Map([['foo', null]]);
   map.bar = 42;
   assert.strictEqual(util.inspect(map, true),