readline: keypress trigger for escape character

Fixes: #7379
PR-URL: #7382
Reviewed-By: jasnell - James M Snell <jasnell@gmail.com>
Reviewed-By: Roman Reiss <me@silverwind.io>

Author: princejwesley

lib/internal/readline.js

@@ -376,11 +376,15 @@ function* emitKeys(stream) {
       key.name = ch.toLowerCase();
       key.shift = /^[A-Z]$/.test(ch);
       key.meta = escaped;
+    } else if (escaped) {
+      // Escape sequence timeout
+      key.name = ch.length ? undefined : 'escape';
+      key.meta = true;
     }
 
     key.sequence = s;
 
-    if (key.name !== undefined) {
+    if (s.length !== 0 && (key.name !== undefined || escaped)) {
       /* Named character or sequence */
       stream.emit('keypress', escaped ? undefined : s, key);
     } else if (s.length === 1) {

lib/readline.js

@@ -926,6 +926,9 @@ exports.Interface = Interface;
 const KEYPRESS_DECODER = Symbol('keypress-decoder');
 const ESCAPE_DECODER = Symbol('escape-decoder');
 
+// GNU readline library - keyseq-timeout is 500ms (default)
+const ESCAPE_CODE_TIMEOUT = 500;
+
 function emitKeypressEvents(stream, iface) {
   if (stream[KEYPRESS_DECODER]) return;
   var StringDecoder = require('string_decoder').StringDecoder; // lazy load
@@ -934,17 +937,26 @@ function emitKeypressEvents(stream, iface) {
   stream[ESCAPE_DECODER] = emitKeys(stream);
   stream[ESCAPE_DECODER].next();
 
+  const escapeCodeTimeout = () => stream[ESCAPE_DECODER].next('');
+  let timeoutId;
+
   function onData(b) {
     if (stream.listenerCount('keypress') > 0) {
       var r = stream[KEYPRESS_DECODER].write(b);
       if (r) {
+        clearTimeout(timeoutId);
+
         for (var i = 0; i < r.length; i++) {
           if (r[i] === '\t' && typeof r[i + 1] === 'string' && iface) {
             iface.isCompletionEnabled = false;
           }
 
           try {
             stream[ESCAPE_DECODER].next(r[i]);
+            // Escape letter at the tail position
+            if (r[i] === '\x1b' && i + 1 === r.length) {
+              timeoutId = setTimeout(escapeCodeTimeout, ESCAPE_CODE_TIMEOUT);
+            }
           } catch (err) {
             // if the generator throws (it could happen in the `keypress`
             // event), we need to restart it.

test/parallel/test-readline-keys.js

@@ -44,6 +44,49 @@ function addTest(sequences, expectedKeys) {
   assert.deepStrictEqual(keys, expectedKeys);
 }
 
+// Simulate key interval test cases
+// Returns a function that takes `next` test case and returns a thunk
+// that can be called to run tests in sequence
+// e.g.
+// addKeyIntervalTest(..)
+//   (addKeyIntervalTest(..)
+//      (addKeyIntervalTest(..)(noop)))()
+// where noop is a terminal function(() => {}).
+
+const addKeyIntervalTest = (sequences, expectedKeys, interval = 550,
+                            assertDelay = 550) => {
+  return (next) => () => {
+
+    if (!Array.isArray(sequences)) {
+      sequences = [ sequences ];
+    }
+
+    if (!Array.isArray(expectedKeys)) {
+      expectedKeys = [ expectedKeys ];
+    }
+
+    expectedKeys = expectedKeys.map(function(k) {
+      return k ? extend({ ctrl: false, meta: false, shift: false }, k) : k;
+    });
+
+    const keys = [];
+    fi.on('keypress', (s, k) => keys.push(k));
+
+    const emitKeys = ([head, ...tail]) => {
+      if (head) {
+        fi.write(head);
+        setTimeout(() => emitKeys(tail), interval);
+      } else {
+        setTimeout(() => {
+          next();
+          assert.deepStrictEqual(keys, expectedKeys);
+        }, assertDelay);
+      }
+    };
+    emitKeys(sequences);
+  };
+};
+
 // regular alphanumerics
 addTest('io.JS', [
   { name: 'i', sequence: 'i' },
@@ -149,3 +192,22 @@ addTest('\x1b[31ma\x1b[39ma', [
   { name: 'undefined', sequence: '\x1b[39m', code: '[39m' },
   { name: 'a', sequence: 'a' },
 ]);
+
+// Reduce array of addKeyIntervalTest(..) right to left
+// with () => {} as initial function
+const runKeyIntervalTests = [
+  // escape character
+  addKeyIntervalTest('\x1b', [
+    { name: 'escape', sequence: '\x1b', meta: true }
+  ]),
+  // chain of escape characters
+  addKeyIntervalTest('\x1b\x1b\x1b\x1b'.split(''), [
+    { name: 'escape', sequence: '\x1b', meta: true },
+    { name: 'escape', sequence: '\x1b', meta: true },
+    { name: 'escape', sequence: '\x1b', meta: true },
+    { name: 'escape', sequence: '\x1b', meta: true }
+  ])
+].reverse().reduce((acc, fn) => fn(acc), () => {});
+
+// run key interval tests one after another
+runKeyIntervalTests();