Readline proposal and bugfixes. Related: #2737 #2756

- Removed extra newline from .question(); Users can input a
  newline if it they require it.
- Removed .close() due to it only emulating closing, causing a bug where
  readline is left open to trigger events such as .on('line', ...').
- Removed ._attemptClose()
- .pause() now triggers event .on('pause', ...)
- .resume() now triggers event .on('resume', ...)
- CTRL-C (SIGINT) in readline will now default to .pause() if no SIGINT event
  is present.
- CTRL-D (delete right) will also default to .pause() if there is nothing to
  delete (signaling the end of the file).
- Added new event `SIGTSTP`
- Added new event `SIGCONT`
- Added `resume` to `write` to resume the stream if paused.
- Docs updated.
- Updated repl.js

doc/api/readline.markdown

@@ -4,8 +4,8 @@ To use this module, do `require('readline')`. Readline allows reading of a
 stream (such as STDIN) on a line-by-line basis.
 
 Note that once you've invoked this module, your node program will not
-terminate until you've closed the interface, and the STDIN stream. Here's how
-to allow your program to gracefully terminate:
+terminate until you've paused the interface. Here's how to allow your
+program to gracefully pause:
 
     var rl = require('readline');
 
@@ -14,10 +14,7 @@ to allow your program to gracefully terminate:
       // TODO: Log the answer in a database
       console.log("Thank you for your valuable feedback.");
 
-      // These two lines together allow the program to terminate. Without
-      // them, it would run forever.
-      i.close();
-      process.stdin.destroy();
+      i.pause();
     });
 
 ### rl.createInterface(input, output, completer)
@@ -48,6 +45,9 @@ Sets the prompt, for example when you run `node` on the command line, you see
 Readies readline for input from the user, putting the current `setPrompt`
 options on a new line, giving the user a new spot to write.
 
+This will also resume the `in` stream used with `createInterface` if it has
+been paused.
+
 <!-- ### rl.getColumns() Not available? -->
 
 ### rl.question(query, callback)
@@ -56,27 +56,29 @@ Prepends the prompt with `query` and invokes `callback` with the user's
 response. Displays the query to the user, and then invokes `callback` with the
 user's response after it has been typed.
 
+This will also resume the `in` stream used with `createInterface` if it has
+been paused.
+
 Example usage:
 
     interface.question('What is your favorite food?', function(answer) {
       console.log('Oh, so your favorite food is ' + answer);
     });
 
-### rl.close()
-
-  Closes tty.
-
 ### rl.pause()
 
-  Pauses tty.
+Pauses the readline `in` stream, allowing it to be resumed later if needed.
 
 ### rl.resume()
 
-  Resumes tty.
+Resumes the readline `in` stream.
 
 ### rl.write()
 
-  Writes to tty.
+Writes to tty.
+
+This will also resume the `in` stream used with `createInterface` if it has
+been paused.
 
 ### Event: 'line'
 
@@ -91,27 +93,98 @@ Example of listening for `line`:
       console.log('You just typed: '+cmd);
     });
 
-### Event: 'close'
+### Event: 'pause'
 
 `function () {}`
 
-Emitted whenever the `in` stream receives a `^C` or `^D`, respectively known
-as `SIGINT` and `EOT`. This is a good way to know the user is finished using
-your program.
+Emitted whenever the `in` stream is paused or receives `^D`, respectively known
+as `EOT`. This event is also called if there is no `SIGINT` event listener
+present when the `in` stream receives a `^C`, respectively known as `SIGINT`.
 
-Example of listening for `close`, and exiting the program afterward:
+Also emitted whenever the `in` stream is not paused and receives the `SIGCONT`
+event. (See events `SIGTSTP` and `SIGCONT`)
 
-    rl.on('close', function() {
-      console.log('goodbye!');
-      process.exit(0);
+Example of listening for `pause`:
+
+    rl.on('pause', function() {
+      console.log('Readline paused.');
+    });
+
+### Event: 'resume'
+
+`function () {}`
+
+Emitted whenever the `in` stream is resumed.
+
+Example of listening for `resume`:
+
+    rl.on('resume', function() {
+      console.log('Readline resumed.');
     });
 
+### Event: 'SIGINT'
+
+`function () {}`
+
+Emitted whenever the `in` stream receives a `^C`, respectively known as
+`SIGINT`. If there is no `SIGINT` event listener present when the `in` stream
+receives a `SIGINT`, `pause` will be triggered.
+
+Example of listening for `SIGINT`:
+
+    rl.on('SIGINT', function() {
+      rl.question('Are you sure you want to exit?', function(answer) {
+        if (answer.match(/^y(es)?$/i)) rl.pause();
+      });
+    });
+
+### Event: 'SIGTSTP'
+
+`function () {}`
+
+Emitted whenever the `in` stream receives a `^Z`, respectively known as
+`SIGTSTP`. If there is no `SIGTSTP` event listener present when the `in` stream
+receives a `SIGTSTP`, the program will be sent to the background.
+
+When the program is resumed with `fg`, the `pause` and `SIGCONT` events will be
+emitted. You can use either to resume the stream.
+
+The `pause` and `SIGCONT` events will not be triggered if the stream was paused
+before the program was sent to the background.
+
+Example of listening for `SIGTSTP`:
+
+    rl.on('SIGTSTP', function() {
+      // This will override SIGTSTP and prevent the program from going to the
+      // background.
+      console.log('Caught SIGTSTP.');
+    });
+
+### Event: 'SIGCONT'
+
+`function () {}`
+
+Emitted whenever the `in` stream is sent to the background with `^Z`,
+respectively known as `SIGTSTP`, and then continued with `fg`. This event only
+emits if the stream was not paused before sending the program to the
+background.
+
+Example of listening for `SIGCONT`:
+
+    rl.on('SIGCONT', function() {
+      // `prompt` will automatically resume the stream
+      rl.prompt();
+    });
+
+
 Here's an example of how to use all these together to craft a tiny command
 line interface:
 
     var readline = require('readline'),
-      rl = readline.createInterface(process.stdin, process.stdout),
-      prefix = 'OHAI> ';
+        rl = readline.createInterface(process.stdin, process.stdout);
+
+    rl.setPrompt('OHAI> ');
+    rl.prompt();
 
     rl.on('line', function(line) {
       switch(line.trim()) {
@@ -122,18 +195,9 @@ line interface:
           console.log('Say what? I might have heard `' + line.trim() + '`');
           break;
       }
-      rl.setPrompt(prefix, prefix.length);
       rl.prompt();
-    }).on('close', function() {
+    }).on('pause', function() {
       console.log('Have a great day!');
       process.exit(0);
     });
-    console.log(prefix + 'Good to see you. Try typing stuff.');
-    rl.setPrompt(prefix, prefix.length);
-    rl.prompt();
-
 
-Take a look at this slightly more complicated
-[example](https://gist.github.com/901104), and
-[http-console](https://github.com/cloudhead/http-console) for a real-life use
-case.

lib/readline.js

@@ -126,6 +126,7 @@ Interface.prototype.setPrompt = function(prompt, length) {
 
 
 Interface.prototype.prompt = function(preserveCursor) {
+  if (this.paused) this.resume();
   if (this.enabled) {
     if (!preserveCursor) this.cursor = 0;
     this._refreshLine();
@@ -136,16 +137,13 @@ Interface.prototype.prompt = function(preserveCursor) {
 
 
 Interface.prototype.question = function(query, cb) {
-  if (cb) {
-    this.resume();
+  if (typeof cb === 'function') {
     if (this._questionCallback) {
-      this.output.write('\n');
       this.prompt();
     } else {
       this._oldPrompt = this._prompt;
       this.setPrompt(query);
       this._questionCallback = cb;
-      this.output.write('\n');
       this.prompt();
     }
   }
@@ -181,8 +179,6 @@ Interface.prototype._addHistory = function() {
 
 
 Interface.prototype._refreshLine = function() {
-  if (this._closed) return;
-
   // Cursor to left edge.
   this.output.cursorTo(0);
 
@@ -198,33 +194,29 @@ Interface.prototype._refreshLine = function() {
 };
 
 
-Interface.prototype.close = function(d) {
-  if (this._closing) return;
-  this._closing = true;
-  if (this.enabled) {
-    tty.setRawMode(false);
-  }
-  this.emit('close');
-  this._closed = true;
-};
-
-
 Interface.prototype.pause = function() {
+  if (this.paused) return;
   if (this.enabled) {
     tty.setRawMode(false);
   }
+  this.input.pause();
+  this.paused = true;
+  this.emit('pause');
 };
 
 
 Interface.prototype.resume = function() {
+  this.input.resume();
   if (this.enabled) {
     tty.setRawMode(true);
   }
+  this.paused = false;
+  this.emit('resume');
 };
 
 
 Interface.prototype.write = function(d, key) {
-  if (this._closed) return;
+  if (this.paused) this.resume();
   this.enabled ? this._ttyWrite(d, key) : this._normalWrite(d, key);
 };
 
@@ -454,16 +446,6 @@ Interface.prototype._historyPrev = function() {
 };
 
 
-Interface.prototype._attemptClose = function() {
-  if (this.listeners('attemptClose').length) {
-    // User is to call interface.close() manually.
-    this.emit('attemptClose');
-  } else {
-    this.close();
-  }
-};
-
-
 // handle a write from the tty
 Interface.prototype._ttyWrite = function(s, key) {
   var next_word, next_non_word, previous_word, previous_non_word;
@@ -489,8 +471,8 @@ Interface.prototype._ttyWrite = function(s, key) {
         if (this.listeners('SIGINT').length) {
           this.emit('SIGINT');
         } else {
-          // default behavior, end the readline
-          this._attemptClose();
+          // Pause the stream
+          this.pause();
         }
         break;
 
@@ -500,7 +482,7 @@ Interface.prototype._ttyWrite = function(s, key) {
 
       case 'd': // delete right or EOF
         if (this.cursor === 0 && this.line.length === 0) {
-          this._attemptClose();
+          this.pause();
         } else if (this.cursor < this.line.length) {
           this._deleteRight();
         }
@@ -549,7 +531,22 @@ Interface.prototype._ttyWrite = function(s, key) {
         break;
 
       case 'z':
-        process.kill(process.pid, 'SIGTSTP');
+        if (this.listeners('SIGTSTP').length) {
+          this.emit('SIGTSTP');
+        } else {
+          process.once('SIGCONT', (function(self) {
+            return function() {
+              // Don't raise events if stream has already been abandoned.
+              if (!self.paused) {
+                // Stream must be paused and resumed after SIGCONT to catch
+                // SIGINT, SIGTSTP, and EOF.
+                self.pause();
+                self.emit('SIGCONT');
+              }
+            };
+          })(this));
+          process.kill(process.pid, 'SIGTSTP');
+        }
         return;
 
       case 'w': // delete backwards to a word boundary

lib/repl.js

@@ -130,7 +130,7 @@ function REPLServer(prompt, stream, eval, useGlobal, ignoreUndefined) {
   var sawSIGINT = false;
   rli.on('SIGINT', function() {
     if (sawSIGINT) {
-      rli.close();
+      rli.pause();
       process.exit();
     }
 
@@ -733,7 +733,7 @@ function defineDefaultCommands(repl) {
   repl.defineCommand('exit', {
     help: 'Exit the repl',
     action: function() {
-      this.rli.close();
+      this.rli.pause();
     }
   });