From 0303a2552e21bac4a8952ba5e1f17a2692f2f544 Mon Sep 17 00:00:00 2001
From: surya panikkal <surya.com@gmail.com>
Date: Fri, 22 Apr 2016 18:58:40 -0400
Subject: [PATCH] readline: allow history to be disabled

1.  The `historySize` to default to `30` only if `undefined`.
2.  If `historySize` is set to 0, then disable caching the line.
3.  Added unit tests.
4.  Updated documentation.

Fixes: https://github.com/nodejs/node/issues/6336
PR-URL: https://github.com/nodejs/node/pull/6352
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
---
 doc/api/readline.md                      |  3 ++-
 lib/readline.js                          |  8 +++++++-
 test/parallel/test-readline-interface.js | 19 +++++++++++++++++++
 3 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/doc/api/readline.md b/doc/api/readline.md
index db543d2306..f939368122 100644
--- a/doc/api/readline.md
+++ b/doc/api/readline.md
@@ -300,7 +300,8 @@ the following values:
    treated like a TTY, and have ANSI/VT100 escape codes written to it.
    Defaults to checking `isTTY` on the `output` stream upon instantiation.
 
- - `historySize` - maximum number of history lines retained. Defaults to `30`.
+ - `historySize` - maximum number of history lines retained. To disable the
+   history set this value to `0`. Defaults to `30`.
 
 The `completer` function is given the current line entered by the user, and
 is supposed to return an Array with 2 entries:
diff --git a/lib/readline.js b/lib/readline.js
index 3948d99053..680ffbf2cd 100644
--- a/lib/readline.js
+++ b/lib/readline.js
@@ -53,12 +53,15 @@ function Interface(input, output, completer, terminal) {
     historySize = input.historySize;
     input = input.input;
   }
-  historySize = historySize || kHistorySize;
 
   if (completer && typeof completer !== 'function') {
     throw new TypeError('Argument "completer" must be a function');
   }
 
+  if (historySize === undefined) {
+    historySize = kHistorySize;
+  }
+
   if (typeof historySize !== 'number' ||
       isNaN(historySize) ||
       historySize < 0) {
@@ -228,6 +231,9 @@ Interface.prototype._writeToOutput = function _writeToOutput(stringToWrite) {
 Interface.prototype._addHistory = function() {
   if (this.line.length === 0) return '';
 
+  // if the history is disabled then return the line
+  if (this.historySize === 0) return this.line;
+
   if (this.history.length === 0 || this.history[0] !== this.line) {
     this.history.unshift(this.line);
 
diff --git a/test/parallel/test-readline-interface.js b/test/parallel/test-readline-interface.js
index 02f6dc980a..ab0c6d8824 100644
--- a/test/parallel/test-readline-interface.js
+++ b/test/parallel/test-readline-interface.js
@@ -27,6 +27,25 @@ function isWarned(emitter) {
   var rli;
   var called;
 
+  // disable history
+  fi = new FakeInput();
+  rli = new readline.Interface({ input: fi, output: fi, terminal: terminal,
+                              historySize: 0 });
+  assert.strictEqual(rli.historySize, 0);
+
+  fi.emit('data', 'asdf\n');
+  assert.deepStrictEqual(rli.history, terminal ? [] : undefined);
+  rli.close();
+
+  // default history size 30
+  fi = new FakeInput();
+  rli = new readline.Interface({ input: fi, output: fi, terminal: terminal});
+  assert.strictEqual(rli.historySize, 30);
+
+  fi.emit('data', 'asdf\n');
+  assert.deepStrictEqual(rli.history, terminal ? ['asdf'] : undefined);
+  rli.close();
+
   // sending a full line
   fi = new FakeInput();
   rli = new readline.Interface({ input: fi, output: fi, terminal: terminal });