readline: support TERM=dumb

When TERM=dumb and .isTTY=true don't use ANSI escape codes
and ignore all keys, except 'escape', 'return' and 'ctrl-c'.

Fixes: nodejs#26187

lib/readline.js

@@ -181,7 +181,11 @@ function Interface(input, output, completer, terminal) {
   }
 
   function onkeypress(s, key) {
-    self._ttyWrite(s, key);
+    if (process.env.TERM === 'dumb') {
+      self._ttyWriteDumb(s, key);
+    } else {
+      self._ttyWrite(s, key);
+    }
     if (key && key.sequence) {
       // If the key.sequence is half of a surrogate pair
       // (>= 0xd800 and <= 0xdfff), refresh the line so
@@ -276,7 +280,7 @@ Interface.prototype._setRawMode = function(mode) {
 
 Interface.prototype.prompt = function(preserveCursor) {
   if (this.paused) this.resume();
-  if (this.terminal) {
+  if (this.terminal && process.env.TERM !== 'dumb') {
     if (!preserveCursor) this.cursor = 0;
     this._refreshLine();
   } else {
@@ -417,7 +421,15 @@ Interface.prototype.resume = function() {
 
 Interface.prototype.write = function(d, key) {
   if (this.paused) this.resume();
-  this.terminal ? this._ttyWrite(d, key) : this._normalWrite(d);
+  if (this.terminal) {
+    if (process.env.TERM === 'dumb') {
+      this._ttyWriteDumb(d, key);
+    } else {
+      this._ttyWrite(d, key);
+    }
+  } else {
+    this._normalWrite(d);
+  }
 };
 
 Interface.prototype._normalWrite = function(b) {
@@ -789,6 +801,49 @@ Interface.prototype._moveCursor = function(dx) {
   }
 };
 
+Interface.prototype._ttyWriteDumb = function(s, key) {
+  key = key || {};
+
+  if (key.name === 'escape') return;
+
+  if (this._sawReturnAt && key.name !== 'enter')
+    this._sawReturnAt = 0;
+
+  if (key.ctrl && key.name === 'c') {
+    if (this.listenerCount('SIGINT') > 0) {
+      this.emit('SIGINT');
+    } else {
+      // This readline instance is finished
+      this.close();
+    }
+  }
+
+  switch (key.name) {
+    case 'return':  // carriage return, i.e. \r
+      this._sawReturnAt = Date.now();
+      this._line();
+      break;
+
+    case 'enter':
+      // When key interval > crlfDelay
+      if (this._sawReturnAt === 0 ||
+          Date.now() - this._sawReturnAt > this.crlfDelay) {
+        this._line();
+      }
+      this._sawReturnAt = 0;
+      break;
+
+    default:
+      if (s instanceof Buffer)
+        s = s.toString('utf-8');
+
+      if (s) {
+        this.line += s;
+        this.cursor += s.length;
+        this._writeToOutput(s);
+      }
+  }
+};
 
 // handle a write from the tty
 Interface.prototype._ttyWrite = function(s, key) {

test/pseudo-tty/readline-dumb-tty.js

@@ -0,0 +1,21 @@
+'use strict';
+require('../common');
+
+process.env.TERM = 'dumb';
+
+const readline = require('readline');
+
+const rl = readline.createInterface({
+  input: process.stdin,
+  output: process.stdout
+});
+
+rl.write('text');
+rl.write(null, { ctrl: true, name: 'u' });
+rl.write(null, { name: 'return' });
+rl.write('text');
+rl.write(null, { name: 'backspace' });
+rl.write(null, { name: 'escape' });
+rl.write(null, { name: 'enter' });
+rl.write('text');
+rl.write(null, { ctrl: true, name: 'c' });

test/pseudo-tty/readline-dumb-tty.out

@@ -0,0 +1,3 @@
+text
+text
+text