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readline: add history event and option to set initial history
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Add a history event which is emitted when the history has
been changed. This enables persisting of the history in
some way but also to allows a listener to alter the
history. One use-case could be to prevent passwords from
ending up in the history.

A constructor option is also added to allow for setting
an initial history list when creating a Readline interface.

PR-URL: #33662
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
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mattiasrunge authored and targos committed Feb 2, 2021
1 parent 2cfe795 commit 7512429
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35 changes: 32 additions & 3 deletions doc/api/readline.md
Original file line number Diff line number Diff line change
Expand Up @@ -88,6 +88,28 @@ rl.on('line', (input) => {
});
```

### Event: `'history'`
<!-- YAML
added: REPLACEME
-->

The `'history'` event is emitted whenever the history array has changed.

The listener function is called with an array containing the history array.
It will reflect all changes, added lines and removed lines due to
`historySize` and `removeHistoryDuplicates`.

The primary purpose is to allow a listener to persist the history.
It is also possible for the listener to change the history object. This
could be useful to prevent certain lines to be added to the history, like
a password.

```js
rl.on('history', (history) => {
console.log(`Received: ${history}`);
});
```

### Event: `'pause'`
<!-- YAML
added: v0.7.5
Expand Down Expand Up @@ -522,6 +544,9 @@ the current position of the cursor down.
<!-- YAML
added: v0.1.98
changes:
- version: REPLACEME
pr-url: https://github.com/nodejs/node/pull/33662
description: The `history` option is supported now.
- version: v13.9.0
pr-url: https://github.com/nodejs/node/pull/31318
description: The `tabSize` option is supported now.
Expand Down Expand Up @@ -550,21 +575,25 @@ changes:
* `terminal` {boolean} `true` if the `input` and `output` streams should be
treated like a TTY, and have ANSI/VT100 escape codes written to it.
**Default:** checking `isTTY` on the `output` stream upon instantiation.
* `history` {string[]} Initial list of history lines. This option makes sense
only if `terminal` is set to `true` by the user or by an internal `output`
check, otherwise the history caching mechanism is not initialized at all.
**Default:** `[]`.
* `historySize` {number} Maximum number of history lines retained. To disable
the history set this value to `0`. This option makes sense only if
`terminal` is set to `true` by the user or by an internal `output` check,
otherwise the history caching mechanism is not initialized at all.
**Default:** `30`.
* `removeHistoryDuplicates` {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. **Default:** `false`.
* `prompt` {string} The prompt string to use. **Default:** `'> '`.
* `crlfDelay` {number} If the delay between `\r` and `\n` exceeds
`crlfDelay` milliseconds, both `\r` and `\n` will be treated as separate
end-of-line input. `crlfDelay` will be coerced to a number no less than
`100`. It can be set to `Infinity`, in which case `\r` followed by `\n`
will always be considered a single newline (which may be reasonable for
[reading files][] with `\r\n` line delimiter). **Default:** `100`.
* `removeHistoryDuplicates` {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. **Default:** `false`.
* `escapeCodeTimeout` {number} The duration `readline` will wait for a
character (when reading an ambiguous key sequence in milliseconds one that
can both form a complete key sequence using the input read so far and can
Expand Down
22 changes: 20 additions & 2 deletions lib/readline.js
Original file line number Diff line number Diff line change
Expand Up @@ -73,6 +73,7 @@ const {
ERR_INVALID_CURSOR_POS,
} = codes;
const {
validateArray,
validateCallback,
validateString,
validateUint32,
Expand Down Expand Up @@ -142,6 +143,7 @@ function Interface(input, output, completer, terminal) {
this.tabSize = 8;

FunctionPrototypeCall(EventEmitter, this,);
let history;
let historySize;
let removeHistoryDuplicates = false;
let crlfDelay;
Expand All @@ -152,6 +154,7 @@ function Interface(input, output, completer, terminal) {
output = input.output;
completer = input.completer;
terminal = input.terminal;
history = input.history;
historySize = input.historySize;
if (input.tabSize !== undefined) {
validateUint32(input.tabSize, 'tabSize', true);
Expand Down Expand Up @@ -179,6 +182,12 @@ function Interface(input, output, completer, terminal) {
throw new ERR_INVALID_ARG_VALUE('completer', completer);
}

if (history === undefined) {
history = [];
} else {
validateArray(history, 'history');
}

if (historySize === undefined) {
historySize = kHistorySize;
}
Expand All @@ -201,6 +210,7 @@ function Interface(input, output, completer, terminal) {
this[kSubstringSearch] = null;
this.output = output;
this.input = input;
this.history = history;
this.historySize = historySize;
this.removeHistoryDuplicates = !!removeHistoryDuplicates;
this.crlfDelay = crlfDelay ?
Expand Down Expand Up @@ -292,7 +302,6 @@ function Interface(input, output, completer, terminal) {
// Cursor position on the line.
this.cursor = 0;

this.history = [];
this.historyIndex = -1;

if (output !== null && output !== undefined)
Expand Down Expand Up @@ -439,7 +448,16 @@ Interface.prototype._addHistory = function() {
}

this.historyIndex = -1;
return this.history[0];

// The listener could change the history object, possibly
// to remove the last added entry if it is sensitive and should
// not be persisted in the history, like a password
const line = this.history[0];

// Emit history event to notify listeners of update
this.emit('history', this.history);

return line;
};


Expand Down
81 changes: 54 additions & 27 deletions test/parallel/test-readline-interface.js
Original file line number Diff line number Diff line change
Expand Up @@ -116,35 +116,30 @@ function assertCursorRowsAndCols(rli, rows, cols) {
code: 'ERR_INVALID_ARG_VALUE'
});

// Constructor throws if historySize is not a positive number
assert.throws(() => {
readline.createInterface({
input,
historySize: 'not a number'
});
}, {
name: 'RangeError',
code: 'ERR_INVALID_ARG_VALUE'
});

assert.throws(() => {
readline.createInterface({
input,
historySize: -1
// Constructor throws if history is not an array
['not an array', 123, 123n, {}, true, Symbol(), null].forEach((history) => {
assert.throws(() => {
readline.createInterface({
input,
history,
});
}, {
name: 'TypeError',
code: 'ERR_INVALID_ARG_TYPE'
});
}, {
name: 'RangeError',
code: 'ERR_INVALID_ARG_VALUE'
});

assert.throws(() => {
readline.createInterface({
input,
historySize: NaN
// Constructor throws if historySize is not a positive number
['not a number', -1, NaN, {}, true, Symbol(), null].forEach((historySize) => {
assert.throws(() => {
readline.createInterface({
input,
historySize,
});
}, {
name: 'RangeError',
code: 'ERR_INVALID_ARG_VALUE'
});
}, {
name: 'RangeError',
code: 'ERR_INVALID_ARG_VALUE'
});

// Check for invalid tab sizes.
Expand Down Expand Up @@ -239,6 +234,38 @@ function assertCursorRowsAndCols(rli, rows, cols) {
rli.close();
}

// Adding history lines should emit the history event with
// the history array
{
const [rli, fi] = getInterface({ terminal: true });
const expectedLines = ['foo', 'bar', 'baz', 'bat'];
rli.on('history', common.mustCall((history) => {
const expectedHistory = expectedLines.slice(0, history.length).reverse();
assert.deepStrictEqual(history, expectedHistory);
}, expectedLines.length));
for (const line of expectedLines) {
fi.emit('data', `${line}\n`);
}
rli.close();
}

// Altering the history array in the listener should not alter
// the line being processed
{
const [rli, fi] = getInterface({ terminal: true });
const expectedLine = 'foo';
rli.on('history', common.mustCall((history) => {
assert.strictEqual(history[0], expectedLine);
history.shift();
}));
rli.on('line', common.mustCall((line) => {
assert.strictEqual(line, expectedLine);
assert.strictEqual(rli.history.length, 0);
}));
fi.emit('data', `${expectedLine}\n`);
rli.close();
}

// Duplicate lines are removed from history when
// `options.removeHistoryDuplicates` is `true`
{
Expand Down Expand Up @@ -774,7 +801,7 @@ for (let i = 0; i < 12; i++) {
assert.strictEqual(rli.historySize, 0);

fi.emit('data', 'asdf\n');
assert.deepStrictEqual(rli.history, terminal ? [] : undefined);
assert.deepStrictEqual(rli.history, []);
rli.close();
}

Expand All @@ -784,7 +811,7 @@ for (let i = 0; i < 12; i++) {
assert.strictEqual(rli.historySize, 30);

fi.emit('data', 'asdf\n');
assert.deepStrictEqual(rli.history, terminal ? ['asdf'] : undefined);
assert.deepStrictEqual(rli.history, terminal ? ['asdf'] : []);
rli.close();
}

Expand Down

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