util: implement %o and %O as formatting specifiers

Implementing the %o and %O formatting specifiers for util.format.
Based on discussion in issue, this specifier should just call
util.inspect to format the value.

PR-URL: https://github.com/nodejs/node/pull/14558
Fixes: https://github.com/nodejs/node/issues/14545
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Roman Reiss <me@silverwind.io>
Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Evan Lucas <evanlucas@me.com>
Reviewed-By: Timothy Gu <timothygu99@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Yuta Hiroto <hello@about-hiroppy.com>

doc/api/util.md

@@ -167,6 +167,14 @@ corresponding argument. Supported placeholders are:
 * `%f` - Floating point value.
 * `%j` - JSON.  Replaced with the string `'[Circular]'` if the argument
 contains circular references.
+* `%o` - Object. A string representation of an object
+  with generic JavaScript object formatting.
+  Similar to `util.inspect()` with options `{ showHidden: true, depth: 4, showProxy: true }`.
+  This will show the full object including non-enumerable symbols and properties.
+* `%O` - Object. A string representation of an object
+  with generic JavaScript object formatting.
+  Similar to `util.inspect()` without options.
+  This will show the full object not including non-enumerable symbols and properties.
 * `%%` - single percent sign (`'%'`). This does not consume an argument.
 
 If the placeholder does not have a corresponding argument, the placeholder is

lib/util.js

@@ -137,6 +137,17 @@ function format(f) {
             str += f.slice(lastPos, i);
           str += String(arguments[a++]);
           break;
+        case 79: // 'O'
+          if (lastPos < i)
+            str += f.slice(lastPos, i);
+          str += inspect(arguments[a++]);
+          break;
+        case 111: // 'o'
+          if (lastPos < i)
+            str += f.slice(lastPos, i);
+          str += inspect(arguments[a++],
+                         { showHidden: true, depth: 4, showProxy: true });
+          break;
         case 37: // '%'
           if (lastPos < i)
             str += f.slice(lastPos, i);

test/parallel/test-util-format.js

@@ -101,6 +101,84 @@ assert.strictEqual(util.format('%j', '42'), '"42"');
 assert.strictEqual(util.format('%j %j', 42, 43), '42 43');
 assert.strictEqual(util.format('%j %j', 42), '42 %j');
 
+// Object format specifier
+const obj = {
+  foo: 'bar',
+  foobar: 1,
+  func: function() {}
+};
+const nestedObj = {
+  foo: 'bar',
+  foobar: {
+    foo: 'bar',
+    func: function() {}
+  }
+};
+assert.strictEqual(util.format('%o'), '%o');
+assert.strictEqual(util.format('%o', 42), '42');
+assert.strictEqual(util.format('%o', 'foo'), '\'foo\'');
+assert.strictEqual(
+  util.format('%o', obj),
+  '{ foo: \'bar\',\n' +
+  '  foobar: 1,\n' +
+  '  func: \n' +
+  '   { [Function: func]\n' +
+  '     [length]: 0,\n' +
+  '     [name]: \'func\',\n' +
+  '     [prototype]: func { [constructor]: [Circular] } } }');
+assert.strictEqual(
+  util.format('%o', nestedObj),
+  '{ foo: \'bar\',\n' +
+  '  foobar: \n' +
+  '   { foo: \'bar\',\n' +
+  '     func: \n' +
+  '      { [Function: func]\n' +
+  '        [length]: 0,\n' +
+  '        [name]: \'func\',\n' +
+  '        [prototype]: func { [constructor]: [Circular] } } } }');
+assert.strictEqual(
+  util.format('%o %o', obj, obj),
+  '{ foo: \'bar\',\n' +
+  '  foobar: 1,\n' +
+  '  func: \n' +
+  '   { [Function: func]\n' +
+  '     [length]: 0,\n' +
+  '     [name]: \'func\',\n' +
+  '     [prototype]: func { [constructor]: [Circular] } } }' +
+  ' { foo: \'bar\',\n' +
+  '  foobar: 1,\n' +
+  '  func: \n' +
+  '   { [Function: func]\n' +
+  '     [length]: 0,\n' +
+  '     [name]: \'func\',\n' +
+  '     [prototype]: func { [constructor]: [Circular] } } }');
+assert.strictEqual(
+  util.format('%o %o', obj),
+  '{ foo: \'bar\',\n' +
+  '  foobar: 1,\n' +
+  '  func: \n' +
+  '   { [Function: func]\n' +
+  '     [length]: 0,\n' +
+  '     [name]: \'func\',\n' +
+  '     [prototype]: func { [constructor]: [Circular] } } } %o');
+
+assert.strictEqual(util.format('%O'), '%O');
+assert.strictEqual(util.format('%O', 42), '42');
+assert.strictEqual(util.format('%O', 'foo'), '\'foo\'');
+assert.strictEqual(
+  util.format('%O', obj),
+  '{ foo: \'bar\', foobar: 1, func: [Function: func] }');
+assert.strictEqual(
+  util.format('%O', nestedObj),
+  '{ foo: \'bar\', foobar: { foo: \'bar\', func: [Function: func] } }');
+assert.strictEqual(
+  util.format('%O %O', obj, obj),
+  '{ foo: \'bar\', foobar: 1, func: [Function: func] } ' +
+  '{ foo: \'bar\', foobar: 1, func: [Function: func] }');
+assert.strictEqual(
+  util.format('%O %O', obj),
+  '{ foo: \'bar\', foobar: 1, func: [Function: func] } %O');
+
 // Various format specifiers
 assert.strictEqual(util.format('%%s%s', 'foo'), '%sfoo');
 assert.strictEqual(util.format('%s:%s'), '%s:%s');
@@ -125,6 +203,10 @@ assert.strictEqual(util.format('%f:%f'), '%f:%f');
 assert.strictEqual(util.format('o: %j, a: %j', {}, []), 'o: {}, a: []');
 assert.strictEqual(util.format('o: %j, a: %j', {}), 'o: {}, a: %j');
 assert.strictEqual(util.format('o: %j, a: %j'), 'o: %j, a: %j');
+assert.strictEqual(util.format('o: %o, a: %O', {}, []), 'o: {}, a: []');
+assert.strictEqual(util.format('o: %o, a: %o', {}), 'o: {}, a: %o');
+assert.strictEqual(util.format('o: %O, a: %O'), 'o: %O, a: %O');
+
 
 // Invalid format specifiers
 assert.strictEqual(util.format('a% b', 'x'), 'a% b x');