Optionally use ext-readline to enable raw input mode if available

Author: clue

README.md

@@ -567,6 +567,13 @@ If this extension is missing, then this library will use a slighty slower Regex
 work-around that should otherwise work equally well.
 Installing `ext-mbstring` is highly recommended.
 
+Internally, it will use the `ext-readline` to enable raw terminal input mode.
+If this extension is missing, then this library will manually set the required
+TTY settings on start and will try to restore previous settings on exit.
+Input line editing is handled entirely within this library and does not rely on
+`ext-readline`.
+Installing `ext-readline` is entirely optional.
+
 Note that *Microsoft Windows is not supported*.
 Due to platform inconsistencies, PHP does not provide support for reading from
 standard console input without blocking.

src/Stdin.php

@@ -10,6 +10,10 @@ class Stdin extends Stream
 {
     private $oldMode = null;
 
+    /**
+     * @param LoopInterface $loop
+     * @codeCoverageIgnore this is covered by functional tests with/without ext-readline
+     */
     public function __construct(LoopInterface $loop)
     {
         // STDIN not defined ("php -a") or already closed (`fclose(STDIN)`)
@@ -26,6 +30,14 @@ public function __construct(LoopInterface $loop)
             return $this->close();
         }
 
+        if (function_exists('readline_callback_handler_install')) {
+            // Prefer `ext-readline` to install dummy handler to turn on raw input mode.
+            // We will nevery actually feed the readline handler and instead
+            // handle all input in our `Readline` implementation.
+            readline_callback_handler_install('', function () { });
+            return;
+        }
+
         if ($this->isTty()) {
             $this->oldMode = shell_exec('stty -g');
 
@@ -49,9 +61,15 @@ public function __destruct()
         $this->restore();
     }
 
+    /**
+     * @codeCoverageIgnore this is covered by functional tests with/without ext-readline
+     */
     private function restore()
     {
-        if ($this->oldMode !== null && $this->isTty()) {
+        if (function_exists('readline_callback_handler_remove')) {
+            // remove dummy readline handler to turn to default input mode
+            readline_callback_handler_remove();
+        } elseif ($this->oldMode !== null && $this->isTty()) {
             // Reset stty so it behaves normally again
             shell_exec(sprintf('stty %s', $this->oldMode));
             $this->oldMode = null;