process: improve --redirect-warnings handling

1) Acquiring the file descriptor is not observable anymore when using
   the `--redirect-warnings` flag.
2) If `fs.appendFile` fails, the warning is now redirected to the
   default output.
3) The code is smaller and simpler.

PR-URL: #24965
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>

lib/internal/process/warning.js

@@ -5,84 +5,50 @@ const { ERR_INVALID_ARG_TYPE } = require('internal/errors').codes;
 
 exports.setup = setupProcessWarnings;
 
-let options;
-function lazyOption(name) {
- if (!options) {
- options = require('internal/options');
+// Lazily loaded
+let fs;
+let fd;
+let warningFile;
+
+function lazyOption() {
+ // This will load `warningFile` only once. If the flag is not set,
+ // `warningFile` will be set to an empty string.
+ if (warningFile === undefined) {
+ warningFile = require('internal/options')
+ .getOptionValue('--redirect-warnings');
  }
- return options.getOptionValue(name);
+ return warningFile;
 }
 
-var cachedFd;
-var acquiringFd = false;
-function nop() {}
-
-// Lazily loaded
-var fs = null;
-
 function writeOut(message) {
  if (console && typeof console.error === 'function')
  return console.error(message);
  process._rawDebug(message);
 }
 
-function onClose(fd) {
- return () => {
- if (fs === null) fs = require('fs');
+function writeToFile(message) {
+ if (fd === undefined) {
+ fs = require('fs');
  try {
- fs.closeSync(fd);
- } catch {}
- };
-}
-
-function onOpen(cb) {
- return (err, fd) => {
- acquiringFd = false;
- if (fd !== undefined) {
- cachedFd = fd;
- process.on('exit', onClose(fd));
- }
- cb(err, fd);
- process.emit('_node_warning_fd_acquired', err, fd);
- };
-}
-
-function onAcquired(message) {
- // make a best effort attempt at writing the message
- // to the fd. Errors are ignored at this point.
- return (err, fd) => {
- if (err)
+ fd = fs.openSync(warningFile, 'a');
+ } catch {
  return writeOut(message);
- if (fs === null) fs = require('fs');
- fs.appendFile(fd, `${message}\n`, nop);
- };
-}
-
-function acquireFd(warningFile, cb) {
- if (cachedFd === undefined && !acquiringFd) {
- acquiringFd = true;
- if (fs === null) fs = require('fs');
- fs.open(warningFile, 'a', onOpen(cb));
- } else if (cachedFd !== undefined && !acquiringFd) {
- cb(null, cachedFd);
- } else {
- process.once('_node_warning_fd_acquired', cb);
- }
-}
-
-function output(message) {
- const warningFile = lazyOption('--redirect-warnings');
- if (warningFile) {
- acquireFd(warningFile, onAcquired(message));
- return;
+ }
+ process.on('exit', () => {
+ try {
+ fs.closeSync(fd);
+ } catch {}
+ });
  }
- writeOut(message);
+ fs.appendFile(fd, `${message}\n`, (err) => {
+ if (err) {
+ writeOut(message);
+ }
+ });
 }
 
 function doEmitWarning(warning) {
- return () => {
- process.emit('warning', warning);
- };
+ return () => process.emit('warning', warning);
 }
 
 function setupProcessWarnings() {
@@ -107,7 +73,11 @@ function setupProcessWarnings() {
  if (typeof warning.detail === 'string') {
  msg += `\n${warning.detail}`;
  }
- output(msg);
+ const warningFile = lazyOption();
+ if (warningFile) {
+ return writeToFile(msg);
+ }
+ writeOut(msg);
  });
  }