readline: make tab size configurable

This adds the `tabSize` option to readline to allow different tab
sizes.

PR-URL: #31318
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Denys Otrishko <shishugi@gmail.com>
Reviewed-By: Anto Aravinth <anto.aravinth.cse@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>

doc/api/readline.md

@@ -456,6 +456,9 @@ the current position of the cursor down.
 <!-- YAML
 added: v0.1.98
 changes:
+ - version: REPLACEME
+ pr-url: https://github.com/nodejs/node/pull/31318
+ description: The `tabSize` option is supported now.
  - version: v8.3.0, 6.11.4
  pr-url: https://github.com/nodejs/node/pull/13497
  description: Remove max limit of `crlfDelay` option.
@@ -499,6 +502,8 @@ changes:
  can both form a complete key sequence using the input read so far and can
  take additional input to complete a longer key sequence).
  **Default:** `500`.
+ * `tabSize` {integer} The number of spaces a tab is equal to (minimum 1).
+ **Default:** `8`.
 
 The `readline.createInterface()` method creates a new `readline.Interface`
 instance.

lib/readline.js

@@ -45,7 +45,10 @@ const {
  ERR_INVALID_CURSOR_POS,
  ERR_INVALID_OPT_VALUE
 } = require('internal/errors').codes;
-const { validateString } = require('internal/validators');
+const {
+ validateString,
+ validateUint32,
+} = require('internal/validators');
 const {
  inspect,
  getStringWidth,
@@ -105,6 +108,7 @@ function Interface(input, output, completer, terminal) {
  this._sawKeyPress = false;
  this._previousKey = null;
  this.escapeCodeTimeout = ESCAPE_CODE_TIMEOUT;
+ this.tabSize = 8;
 
  EventEmitter.call(this);
  let historySize;
@@ -118,6 +122,11 @@ function Interface(input, output, completer, terminal) {
  completer = input.completer;
  terminal = input.terminal;
  historySize = input.historySize;
+ if (input.tabSize !== undefined) {
+ const positive = true;
+ validateUint32(input.tabSize, 'tabSize', positive);
+ this.tabSize = input.tabSize;
+ }
  removeHistoryDuplicates = input.removeHistoryDuplicates;
  if (input.prompt !== undefined) {
  prompt = input.prompt;
@@ -718,10 +727,9 @@ Interface.prototype._getDisplayPos = function(str) {
  offset = 0;
  continue;
  }
- // Tabs must be aligned by an offset of 8.
- // TODO(BridgeAR): Make the tab size configurable.
+ // Tabs must be aligned by an offset of the tab size.
  if (char === '\t') {
- offset += 8 - (offset % 8);
+ offset += this.tabSize - (offset % this.tabSize);
  continue;
  }
  const width = getStringWidth(char);

test/parallel/test-readline-interface.js

@@ -138,6 +138,39 @@ function assertCursorRowsAndCols(rli, rows, cols) {
  name: 'RangeError',
  code: 'ERR_INVALID_OPT_VALUE'
  });
+
+ // Check for invalid tab sizes.
+ assert.throws(
+ () => new readline.Interface({
+ input,
+ tabSize: 0
+ }),
+ {
+ message: 'The value of "tabSize" is out of range. ' +
+ 'It must be >= 1 && < 4294967296. Received 0',
+ code: 'ERR_OUT_OF_RANGE'
+ }
+ );
+
+ assert.throws(
+ () => new readline.Interface({
+ input,
+ tabSize: '4'
+ }),
+ { code: 'ERR_INVALID_ARG_TYPE' }
+ );
+
+ assert.throws(
+ () => new readline.Interface({
+ input,
+ tabSize: 4.5
+ }),
+ {
+ code: 'ERR_OUT_OF_RANGE',
+ message: 'The value of "tabSize" is out of range. ' +
+ 'It must be an integer. Received 4.5'
+ }
+ );
 }
 
 // Sending a single character with no newline
@@ -632,6 +665,25 @@ function assertCursorRowsAndCols(rli, rows, cols) {
  rli.close();
 }
 
+// Multi-line input cursor position and long tabs
+{
+ const [rli, fi] = getInterface({ tabSize: 16, terminal: true, prompt: '' });
+ fi.columns = 10;
+ fi.emit('data', 'multi-line\ttext \t');
+ assert.strictEqual(rli.cursor, 17);
+ assertCursorRowsAndCols(rli, 3, 2);
+ rli.close();
+}
+
+// Check for the default tab size.
+{
+ const [rli, fi] = getInterface({ terminal: true, prompt: '' });
+ fi.emit('data', 'the quick\tbrown\tfox');
+ assert.strictEqual(rli.cursor, 19);
+ // The first tab is 7 spaces long, the second one 3 spaces.
+ assertCursorRowsAndCols(rli, 0, 27);
+}
+
 // Multi-line prompt cursor position
 {
  const [rli, fi] = getInterface({