readline: add option to stop duplicates in history

Adds `options.deDupeHistory` for `readline.createInterface(options)`. If `options.deDupeHistory` is `true`, when a new input line being added to the history list duplicates an older one, removes the older line from the list. Defaults to `false`. Many users would appreciate this option, as it is a common setting in shells. This option certainly should not be default behavior, as it would be problematic in applications such as the `repl`, which inherits from the readline `Interface`. Extends documentation to reflect this API addition. Adds tests for when `options.deDupeHistory` is truthy, and when `options.deDupeHistory` is falsey. PR-URL: #2982 Reviewed-By: Jeremiah Senkpiel <[email protected]>

Author: DannyNemer

doc/api/readline.md

@@ -370,6 +370,9 @@ changes:
 `crlfDelay` milliseconds, both `\r` and `\n` will be treated as separate
  end-of-line input. Default to `100` milliseconds.
 `crlfDelay` will be coerced to `[100, 2000]` range.
+*`deDupeHistory`{boolean} If `true`, when a new input line added to the
+ history list duplicates an older one, this removes the older line from the
+ list. Defaults to `false`.
 
 The `readline.createInterface()` method creates a new `readline.Interface`
 instance.

lib/readline.js

@@ -39,6 +39,7 @@ function Interface(input, output, completer, terminal){
 
 EventEmitter.call(this);
 varhistorySize;
+vardeDupeHistory=false;
 letcrlfDelay;
 letprompt='> ';
 
@@ -48,6 +49,7 @@ function Interface(input, output, completer, terminal){
 completer=input.completer;
 terminal=input.terminal;
 historySize=input.historySize;
+deDupeHistory=input.deDupeHistory;
 if(input.prompt!==undefined){
 prompt=input.prompt;
 }
@@ -80,6 +82,7 @@ function Interface(input, output, completer, terminal){
 this.output=output;
 this.input=input;
 this.historySize=historySize;
+this.deDupeHistory=!!deDupeHistory;
 this.crlfDelay=Math.max(kMincrlfDelay,
 Math.min(kMaxcrlfDelay,crlfDelay>>>0));
 
@@ -257,6 +260,12 @@ Interface.prototype._addHistory = function(){
 if(this.line.trim().length===0)returnthis.line;
 
 if(this.history.length===0||this.history[0]!==this.line){
+if(this.deDupeHistory){
+// Remove older history line if identical to new one
+constdupIndex=this.history.indexOf(this.line);
+if(dupIndex!==-1)this.history.splice(dupIndex,1);
+}
+
 this.history.unshift(this.line);
 
 // Only store so many

test/parallel/test-readline-interface.js

@@ -305,6 +305,67 @@ function isWarned(emitter){
 returnfalse;
 });
 
+// duplicate lines are removed from history when `options.deDupeHistory`
+// is `true`
+fi=newFakeInput();
+rli=newreadline.Interface({
+input: fi,
+output: fi,
+terminal: true,
+deDupeHistory: true
+});
+expectedLines=['foo','bar','baz','bar','bat','bat'];
+callCount=0;
+rli.on('line',function(line){
+assert.strictEqual(line,expectedLines[callCount]);
+callCount++;
+});
+fi.emit('data',expectedLines.join('\n')+'\n');
+assert.strictEqual(callCount,expectedLines.length);
+fi.emit('keypress','.',{name: 'up'});// 'bat'
+assert.strictEqual(rli.line,expectedLines[--callCount]);
+fi.emit('keypress','.',{name: 'up'});// 'bar'
+assert.notStrictEqual(rli.line,expectedLines[--callCount]);
+assert.strictEqual(rli.line,expectedLines[--callCount]);
+fi.emit('keypress','.',{name: 'up'});// 'baz'
+assert.strictEqual(rli.line,expectedLines[--callCount]);
+fi.emit('keypress','.',{name: 'up'});// 'foo'
+assert.notStrictEqual(rli.line,expectedLines[--callCount]);
+assert.strictEqual(rli.line,expectedLines[--callCount]);
+assert.strictEqual(callCount,0);
+rli.close();
+
+// duplicate lines are not removed from history when `options.deDupeHistory`
+// is `false`
+fi=newFakeInput();
+rli=newreadline.Interface({
+input: fi,
+output: fi,
+terminal: true,
+deDupeHistory: false
+});
+expectedLines=['foo','bar','baz','bar','bat','bat'];
+callCount=0;
+rli.on('line',function(line){
+assert.strictEqual(line,expectedLines[callCount]);
+callCount++;
+});
+fi.emit('data',expectedLines.join('\n')+'\n');
+assert.strictEqual(callCount,expectedLines.length);
+fi.emit('keypress','.',{name: 'up'});// 'bat'
+assert.strictEqual(rli.line,expectedLines[--callCount]);
+fi.emit('keypress','.',{name: 'up'});// 'bar'
+assert.notStrictEqual(rli.line,expectedLines[--callCount]);
+assert.strictEqual(rli.line,expectedLines[--callCount]);
+fi.emit('keypress','.',{name: 'up'});// 'baz'
+assert.strictEqual(rli.line,expectedLines[--callCount]);
+fi.emit('keypress','.',{name: 'up'});// 'bar'
+assert.strictEqual(rli.line,expectedLines[--callCount]);
+fi.emit('keypress','.',{name: 'up'});// 'foo'
+assert.strictEqual(rli.line,expectedLines[--callCount]);
+assert.strictEqual(callCount,0);
+rli.close();
+
 // sending a multi-byte utf8 char over multiple writes
 constbuf=Buffer.from('☮','utf8');
 fi=newFakeInput();