Make tab width configurable

README.md

@@ -23,7 +23,7 @@ When a domain-specific language that compiles to JavaScript uses JSON as a forma
 
 #### Editing forms/JSON
 
-When a form also allows to edit JSON representation of data on the same screen, this module can be used to sinchronise navigation in JSON and in the form.
+When a form also allows to edit JSON representation of data on the same screen, this module can be used to synchronise navigation in JSON and in the form.
 
 
 ## Usage
@@ -107,11 +107,12 @@ Location object has properties (zero-based numbers):
 
 Options:
 - _bigint_: parse large integers as [BigInt](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/BigInt).
+- _tabWidth_: tab width for column calculation
 
 Whitespace:
 - the only character that increases line number in mappings is line feed ('\n'), so if your JSON string has '\r\n' sequence, it will still be counted as one line,
 - both '\r' and '\n' are counted as a character when determining `pos` (it is possible to slice sections of JSON string using `pos` property), but `column` counter is reset when `r` or `n` is encountered,
-- tabs ('\t') are counted as four spaces when determining `column` but as a single character for `pos`.
+- tabs ('\t') are by default counted as four spaces (configurable through the `tabWidth` option) when determining `column` but as a single character for `pos`.
 
 Comparison with the standard `JSON.parse`:
 - when it is not possible to parse JSON, a SyntaxError exception with exactly the same message is thrown,
@@ -132,6 +133,7 @@ Comparison with the standard `JSON.stringify`:
 Options:
 - _space_: same as `space` parameter.
 - _es6_: stringify ES6 Maps, Sets and Typed arrays (as JSON arrays).
+- _tabWidth_: need to be the same as for `parse` to get identical result
 
 
 ## License

index.js

@@ -20,6 +20,7 @@ exports.parse = function (source, _, options) {
   var column = 0;
   var pos = 0;
   var bigint = options && options.bigint && typeof BigInt != 'undefined';
+  var tabWidth = (options && options.tabWidth && typeof options.tabWidth === 'number')  ? options.tabWidth : 4;
   return {
     data: _parse('', true),
     pointers: pointers
@@ -55,7 +56,7 @@ exports.parse = function (source, _, options) {
       while (pos < source.length) {
         switch (source[pos]) {
           case ' ': column++; break;
-          case '\t': column += 4; break;
+          case '\t': column += tabWidth; break;
           case '\r': column = 0; break;
           case '\n': column = 0; line++; break;
           default: break loop;
@@ -243,6 +244,10 @@ exports.stringify = function (data, _, options) {
   var whitespace = typeof options == 'object'
                     ? options.space
                     : options;
+  var tabWidth = (typeof options == 'object' &&
+                    typeof options.tabWidth === 'number')
+                    ? options.tabWidth
+                    : 4;
   switch (typeof whitespace) {
     case 'number':
       var len = whitespace > 10
@@ -262,7 +267,7 @@ exports.stringify = function (data, _, options) {
         var char = whitespace[j];
         switch (char) {
           case ' ': wsColumn++; break;
-          case '\t': wsColumn += 4; break;
+          case '\t': wsColumn += tabWidth; break;
           case '\r': wsColumn = 0; break;
           case '\n': wsColumn = 0; wsLine++; break;
           default: throw new Error('whitespace characters not allowed in JSON');

spec/index.js

@@ -95,6 +95,40 @@ describe('parse', function() {
       });
     });
 
+    it.only('should support whitespace with tabs and custom tabWidth', function () {
+      var json = '{\n\
+\t"foo": [\n\
+\t\t{\n\
+\t\t\t"bar": true\n\
+\t\t}\n\
+\t]\n\
+}';
+
+      var pointers = testParse(json, JSON.parse(json), null, '\t', {tabWidth: 1});
+      assert.deepStrictEqual(pointers, {
+        '': {
+          value: { line: 0, column: 0, pos: 0 },
+          valueEnd: { line: 6, column: 1, pos: 39 }
+        },
+        '/foo': {
+          key: { line: 1, column: 1, pos: 3 },
+          keyEnd: { line: 1, column: 6, pos: 8 },
+          value: { line: 1, column: 8, pos: 10 },
+          valueEnd: { line: 5, column: 2, pos: 37 }
+        },
+        '/foo/0': {
+          value: { line: 2, column: 2, pos: 14 },
+          valueEnd: { line: 4, column: 3, pos: 34 }
+        },
+        '/foo/0/bar': {
+          key: { line: 3, column: 3, pos: 19 },
+          keyEnd: { line: 3, column: 8, pos: 24 },
+          value: { line: 3, column: 10, pos: 26 },
+          valueEnd: { line: 3, column: 14, pos: 30 }
+        }
+      });
+    });
+
     it('should support whitespace with CRs', function () {
       var json = '{\r\n\
   "foo": [\r\n\
@@ -293,15 +327,17 @@ describe('parse', function() {
   });
 
 
-  function testParse(json, expectedData, skipReverseCheck, whitespace) {
-    var result = jsonMap.parse(json);
+  function testParse(json, expectedData, skipReverseCheck, whitespace, options) {
+    var result = jsonMap.parse(json, null, options);
     var data = result.data;
     var pointers = result.pointers;
     assert.deepStrictEqual(data, expectedData);
     testResult(json, pointers, data);
 
     if (!skipReverseCheck) {
-      var reverseResult = jsonMap.stringify(expectedData, null, whitespace);
+      var reverseResult = jsonMap.stringify(expectedData, null, {
+        space: whitespace, tabWidth: options && options.tabWidth
+      });
       assert.strictEqual(json, reverseResult.json);
       assert.deepStrictEqual(pointers, reverseResult.pointers);
     }