util: use minimal object inspection with %s specifier

This improves `util.format()` by returning more meaningful results when using `%s` as specifier and any object as value. Besides that `BigInt` will also be represented with an `n` at the end to indicate that it's of type `BigInt`. PR-URL: #26927 Reviewed-By: Michaël Zasso <targos@protonmail.com> Reviewed-By: Yongsheng Zhang <zyszys98@gmail.com>
nodejs · Apr 4, 2019 · a9bf665 · a9bf665
1 parent adbcda1
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Showing 5 changed files with 42 additions and 13 deletions.
diff --git a/doc/api/util.md b/doc/api/util.md
@@ -220,15 +220,17 @@ as a `printf`-like format string which can contain zero or more format
 specifiers. Each specifier is replaced with the converted value from the
 corresponding argument. Supported specifiers are:
 
-* `%s` - `String`.
-* `%d` - `Number` (integer or floating point value) or `BigInt`.
-* `%i` - Integer or `BigInt`.
-* `%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
+* `%s` - `String` will be used to convert all values except `BigInt` and
+  `Object`. `BigInt` values will be represented with an `n` and Objects are
+  inspected using `util.inspect()` with options
+  `{ depth: 0, colors: false, compact: 3 }`.
+* `%d` - `Number` will be used to convert all values except `BigInt`.
+* `%i` - `parseInt(value, 10)` is used for all values except `BigInt`.
+* `%f` - `parseFloat(value)` is used for all values.
+* `%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, showProxy: true }`. This will show the full object
   including non-enumerable properties and proxies.
 * `%O` - `Object`. A string representation of an object with generic JavaScript

diff --git a/lib/internal/util/inspect.js b/lib/internal/util/inspect.js
@@ -1446,7 +1446,20 @@ function formatWithOptions(inspectOptions, ...args) {
         if (a + 1 !== args.length) {
           switch (nextChar) {
             case 115: // 's'
-              tempStr = String(args[++a]);
+              const tempArg = args[++a];
+              if (typeof tempArg === 'object' && tempArg !== null) {
+                tempStr = inspect(tempArg, {
+                  ...inspectOptions,
+                  compact: 3,
+                  colors: false,
+                  depth: 0
+                });
+              // eslint-disable-next-line valid-typeof
+              } else if (typeof tempArg === 'bigint') {
+                tempStr = `${tempArg}n`;
+              } else {
+                tempStr = String(tempArg);
+              }
               break;
             case 106: // 'j'
               tempStr = tryStringify(args[++a]);

diff --git a/test/parallel/test-http-response-statuscode.js b/test/parallel/test-http-response-statuscode.js
@@ -29,7 +29,7 @@ const server = http.Server(common.mustCall(function(req, res) {
       test(res, NaN, 'NaN');
       break;
     case 3:
-      test(res, {}, '[object Object]');
+      test(res, {}, '{}');
       break;
     case 4:
       test(res, 99, '99');
@@ -47,7 +47,7 @@ const server = http.Server(common.mustCall(function(req, res) {
       test(res, true, 'true');
       break;
     case 9:
-      test(res, [], '');
+      test(res, [], '[]');
       break;
     case 10:
       test(res, 'this is not valid', 'this is not valid');

diff --git a/test/parallel/test-stream-writable-change-default-encoding.js b/test/parallel/test-stream-writable-change-default-encoding.js
@@ -63,7 +63,7 @@ common.expectsError(function changeDefaultEncodingToInvalidValue() {
 }, {
   type: TypeError,
   code: 'ERR_UNKNOWN_ENCODING',
-  message: 'Unknown encoding: [object Object]'
+  message: 'Unknown encoding: {}'
 });
 
 (function checkVairableCaseEncoding() {

diff --git a/test/parallel/test-util-format.js b/test/parallel/test-util-format.js
@@ -123,11 +123,17 @@ assert.strictEqual(util.format('%f %f', 42), '42 %f');
 // String format specifier
 assert.strictEqual(util.format('%s'), '%s');
 assert.strictEqual(util.format('%s', undefined), 'undefined');
+assert.strictEqual(util.format('%s', null), 'null');
 assert.strictEqual(util.format('%s', 'foo'), 'foo');
 assert.strictEqual(util.format('%s', 42), '42');
 assert.strictEqual(util.format('%s', '42'), '42');
 assert.strictEqual(util.format('%s %s', 42, 43), '42 43');
 assert.strictEqual(util.format('%s %s', 42), '42 %s');
+assert.strictEqual(util.format('%s', 42n), '42n');
+assert.strictEqual(util.format('%s', Symbol('foo')), 'Symbol(foo)');
+assert.strictEqual(util.format('%s', true), 'true');
+assert.strictEqual(util.format('%s', { a: [1, 2, 3] }), '{ a: [Array] }');
+assert.strictEqual(util.format('%s', () => 5), '() => 5');
 
 // JSON format specifier
 assert.strictEqual(util.format('%j'), '%j');
@@ -346,3 +352,11 @@ assert.strictEqual(
   util.format(new SharedArrayBuffer(4)),
   'SharedArrayBuffer { [Uint8Contents]: <00 00 00 00>, byteLength: 4 }'
 );
+
+assert.strictEqual(
+  util.formatWithOptions(
+    { colors: true, compact: 3 },
+    '%s', [ 1, { a: true }]
+  ),
+  '[ 1, [Object] ]'
+);