url: add custom inspection for URLSearchParams and its iterators

lib/internal/url.js

@@ -8,6 +8,7 @@ function getPunycode() {
   }
 }
 const punycode = getPunycode();
+const util = require('util');
 const binding = process.binding('url');
 const context = Symbol('context');
 const cannotBeBase = Symbol('cannot-be-base');
@@ -859,6 +860,32 @@ class URLSearchParams {
 // https://heycam.github.io/webidl/#es-iterable-entries
 URLSearchParams.prototype[Symbol.iterator] = URLSearchParams.prototype.entries;
 
+URLSearchParams.prototype[util.inspect.custom] =
+  function inspect(recurseTimes, ctx) {
+    const innerOpts = Object.assign({}, ctx);
+    if (recurseTimes !== null) {
+      innerOpts.depth = recurseTimes - 1;
+    }
+    const innerInspect = (v) => util.inspect(v, innerOpts);
+
+    const list = this[searchParams];
+    const output = [];
+    for (var i = 0; i < list.length; i += 2)
+      output.push(`${innerInspect(list[i])} => ${innerInspect(list[i + 1])}`);
+
+    const colorRe = /\u001b\[\d\d?m/g;
+    const length = output.reduce((prev, cur) => {
+      return prev + cur.replace(colorRe, '').length + ', '.length;
+    }, -', '.length);
+    if (length > ctx.breakLength) {
+      return `${this.constructor.name} {\n  ${output.join(',\n  ')} }`;
+    } else if (output.length) {
+      return `${this.constructor.name} { ${output.join(', ')} }`;
+    } else {
+      return `${this.constructor.name} {}`;
+    }
+  };
+
 // https://heycam.github.io/webidl/#dfn-default-iterator-object
 function createSearchParamsIterator(target, kind) {
   const iterator = Object.create(URLSearchParamsIteratorPrototype);
@@ -909,6 +936,37 @@ const URLSearchParamsIteratorPrototype = Object.setPrototypeOf({
       value: result,
       done: false
     };
+  },
+  [util.inspect.custom]: function inspect(recurseTimes, ctx) {
+    const innerOpts = Object.assign({}, ctx);
+    if (recurseTimes !== null) {
+      innerOpts.depth = recurseTimes - 1;
+    }
+    const {
+      target,
+      kind,
+      index
+    } = this[context];
+    const output = target[searchParams].slice(index).reduce((prev, cur, i) => {
+      const key = i % 2 === 0;
+      if (kind === 'key' && key) {
+        prev.push(cur);
+      } else if (kind === 'value' && !key) {
+        prev.push(cur);
+      } else if (kind === 'key+value' && !key) {
+        prev.push([target[searchParams][index + i - 1], cur]);
+      }
+      return prev;
+    }, []);
+    const breakLn = util.inspect(output, innerOpts).includes('\n');
+    const outputStrs = output.map((p) => util.inspect(p, innerOpts));
+    let outputStr;
+    if (breakLn) {
+      outputStr = `\n  ${outputStrs.join(',\n  ')}`;
+    } else {
+      outputStr = ` ${outputStrs.join(', ')}`;
+    }
+    return `${this[Symbol.toStringTag]} {${outputStr} }`;
   }
 }, IteratorPrototype);
 

test/parallel/test-whatwg-url-searchparams-inspect.js

@@ -0,0 +1,30 @@
+'use strict';
+
+require('../common');
+const assert = require('assert');
+const util = require('util');
+const URL = require('url').URL;
+
+// Until we export URLSearchParams
+const m = new URL('http://example.org');
+const URLSearchParams = m.searchParams.constructor;
+
+const sp = new URLSearchParams('?a=a&b=b&b=c');
+assert.strictEqual(util.inspect(sp),
+                   "URLSearchParams { 'a' => 'a', 'b' => 'b', 'b' => 'c' }");
+assert.strictEqual(util.inspect(sp.keys()),
+                   "URLSearchParamsIterator { 'a', 'b', 'b' }");
+assert.strictEqual(util.inspect(sp.values()),
+                   "URLSearchParamsIterator { 'a', 'b', 'c' }");
+
+const iterator = sp.entries();
+assert.strictEqual(util.inspect(iterator),
+                   "URLSearchParamsIterator { [ 'a', 'a' ], [ 'b', 'b' ], " +
+                                             "[ 'b', 'c' ] }");
+iterator.next();
+assert.strictEqual(util.inspect(iterator),
+                   "URLSearchParamsIterator { [ 'b', 'b' ], [ 'b', 'c' ] }");
+iterator.next();
+iterator.next();
+assert.strictEqual(util.inspect(iterator),
+                   'URLSearchParamsIterator {  }');