errors: add missing ERR_ prefix on util.callbackify error

The `FALSY_VALUE_REJECTION` error code added by
nodejs#12712 did not have the `ERR_` prefix,
nor was it added to the errors.md documentation. Add the prefix in for
consistency.

PR-URL: nodejs#13604
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Timothy Gu <timothygu99@gmail.com>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>

doc/api/errors.md

@@ -570,6 +570,12 @@ The `'ERR_ARG_NOT_ITERABLE'` error code is used generically to identify that an
 iterable argument (i.e. a value that works with `for...of` loops) is required,
 but not provided to a Node.js API.
 
+<a id="ERR_FALSY_VALUE_REJECTION"></a>
+### ERR_FALSY_VALUE_REJECTION
+
+The `ERR_FALSY_VALUE_REJECTION` error code is used by the `util.callbackify()`
+API when a callbackified `Promise` is rejected with a falsy value (e.g. `null`).
+
 <a id="ERR_INVALID_ARG_TYPE"></a>
 ### ERR_INVALID_ARG_TYPE
 

lib/internal/errors.js

@@ -112,6 +112,7 @@ module.exports = exports = {
 // Note: Please try to keep these in alphabetical order
 E('ERR_ARG_NOT_ITERABLE', '%s must be iterable');
 E('ERR_ASSERTION', (msg) => msg);
+E('ERR_FALSY_VALUE_REJECTION', 'Promise was rejected with falsy value');
 E('ERR_INVALID_ARG_TYPE', invalidArgType);
 E('ERR_INVALID_CALLBACK', 'callback must be a function');
 E('ERR_INVALID_FD', (fd) => `"fd" must be a positive integer: ${fd}`);
@@ -149,7 +150,6 @@ E('ERR_SOCKET_BAD_TYPE',
 E('ERR_SOCKET_CANNOT_SEND', 'Unable to send data');
 E('ERR_SOCKET_BAD_PORT', 'Port should be > 0 and < 65536');
 E('ERR_SOCKET_DGRAM_NOT_RUNNING', 'Not running');
-E('FALSY_VALUE_REJECTION', 'Promise was rejected with falsy value');
 // Add new errors from here...
 
 function invalidArgType(name, expected, actual) {

lib/util.js

@@ -1062,7 +1062,7 @@ function callbackifyOnRejected(reason, cb) {
   // occurred", we error-wrap so the callback consumer can distinguish between
   // "the promise rejected with null" or "the promise fulfilled with undefined".
   if (!reason) {
-    const newReason = new errors.Error('FALSY_VALUE_REJECTION');
+    const newReason = new errors.Error('ERR_FALSY_VALUE_REJECTION');
     newReason.reason = reason;
     reason = newReason;
     Error.captureStackTrace(reason, callbackifyOnRejected);

test/parallel/test-util-callbackify.js

@@ -79,7 +79,7 @@ const values = [
       if (err instanceof Error) {
         if ('reason' in err) {
           assert(!value);
-          assert.strictEqual(err.code, 'FALSY_VALUE_REJECTION');
+          assert.strictEqual(err.code, 'ERR_FALSY_VALUE_REJECTION');
           assert.strictEqual(err.reason, value);
         } else {
           assert.strictEqual(String(value).endsWith(err.message), true);
@@ -100,7 +100,7 @@ const values = [
       if (err instanceof Error) {
         if ('reason' in err) {
           assert(!value);
-          assert.strictEqual(err.code, 'FALSY_VALUE_REJECTION');
+          assert.strictEqual(err.code, 'ERR_FALSY_VALUE_REJECTION');
           assert.strictEqual(err.reason, value);
         } else {
           assert.strictEqual(String(value).endsWith(err.message), true);
@@ -125,7 +125,7 @@ const values = [
       if (err instanceof Error) {
         if ('reason' in err) {
           assert(!value);
-          assert.strictEqual(err.code, 'FALSY_VALUE_REJECTION');
+          assert.strictEqual(err.code, 'ERR_FALSY_VALUE_REJECTION');
           assert.strictEqual(err.reason, value);
         } else {
           assert.strictEqual(String(value).endsWith(err.message), true);