[New] add maxStringLength option

Added to `util.inspect` in nodejs/node#32392, in node v12.17, v13.13, v14+

Author: ljharb

.eslintrc

@@ -3,14 +3,15 @@
     "extends": "@ljharb",
     "rules": {
 		"complexity": 0,
-		"func-style": [2, 'declaration'],
+		"func-style": [2, "declaration"],
         "indent": [2, 4],
-        "max-lines-per-function": [2, 130],
+        "max-lines-per-function": 1,
         "max-params": [2, 4],
 		"max-statements": [2, 90],
         "max-statements-per-line": [2, { "max": 2 }],
         "no-magic-numbers": 0,
-		"no-param-reassign": 1,
+        "no-param-reassign": 1,
+        "operator-linebreak": [2, "before"],
         "strict": 0, // TODO
     },
     "globals": {

index.js

@@ -24,6 +24,14 @@ module.exports = function inspect_(obj, options, depth, seen) {
     if (has(opts, 'quoteStyle') && (opts.quoteStyle !== 'single' && opts.quoteStyle !== 'double')) {
         throw new TypeError('option "quoteStyle" must be "single" or "double"');
     }
+    if (
+        has(opts, 'maxStringLength') && (typeof opts.maxStringLength === 'number'
+            ? opts.maxStringLength < 0 && opts.maxStringLength !== Infinity
+            : opts.maxStringLength !== null
+        )
+    ) {
+        throw new TypeError('option "maxStringLength", if provided, must be a positive integer, Infinity, or `null`');
+    }
 
     if (typeof obj === 'undefined') {
         return 'undefined';
@@ -259,6 +267,11 @@ function isElement(x) {
 }
 
 function inspectString(str, opts) {
+    if (str.length > opts.maxStringLength) {
+        var remaining = str.length - opts.maxStringLength;
+        var trailer = '... ' + remaining + ' more character' + (remaining > 1 ? 's' : '');
+        return inspectString(str.slice(0, opts.maxStringLength), opts) + trailer;
+    }
     // eslint-disable-next-line no-control-regex
     var s = str.replace(/(['\\])/g, '\\$1').replace(/[\x00-\x1f]/g, lowbyte);
     return wrapQuotes(s, 'single', opts);

package.json

@@ -10,6 +10,7 @@
     "eslint": "^7.1.0",
     "nyc": "^10.3.2",
     "safe-publish-latest": "^1.1.4",
+    "string.prototype.repeat": "^1.0.0",
     "tape": "^5.0.1"
   },
   "scripts": {

readme.markdown

@@ -45,6 +45,7 @@ Return a string `s` with the string representation of `obj` up to a depth of `op
 
 Additional options:
   - `quoteStyle`: must be "single" or "double", if present
+  - `maxStringLength`: must be `0`, a positive integer, `Infinity`, or `null`, if present
 
 # install
 

test/inspect.js

@@ -1,6 +1,7 @@
 var test = require('tape');
 var hasSymbols = require('has-symbols')();
 var utilInspect = require('../util.inspect');
+var repeat = require('string.prototype.repeat');
 
 var inspect = require('..');
 
@@ -18,3 +19,13 @@ test('inspect custom symbol', { skip: !hasSymbols || !utilInspect }, function (t
 
     t.equal(inspect([obj, []]), '[ ' + (utilInspect.custom ? 'symbol' : 'string') + ', [] ]');
 });
+
+test('maxStringLength', function (t) {
+    t.equal(
+        inspect([repeat('a', 1e8)], { maxStringLength: 10 }),
+        '[ \'aaaaaaaaaa\'... 99999990 more characters ]',
+        'maxStringLength option limits output'
+    );
+
+    t.end();
+});