Allow blockquoted tabs

lib/dumper.js

@@ -199,6 +199,12 @@ function isPrintable(c) {
       ||  (0x10000 <= c && c <= 0x10FFFF);
 }
 
+// Return true if the char is printable or a tab.
+// derived from nb-char - #x85 - #xA0 - #x2028 - #x2029.
+function isPrintableWithTabs(c) {
+  return isPrintable(c) || c === CHAR_TAB;
+}
+
 // [34] ns-char ::= nb-char - s-white
 // [27] nb-char ::= c-printable - b-char - c-byte-order-mark
 // [26] b-char  ::= b-line-feed | b-carriage-return
@@ -332,7 +338,7 @@ function chooseScalarStyle(string, singleLineOnly, indentPerLevel, lineWidth,
     // Check for disallowed characters to rule out plain and single.
     for (i = 0; i < string.length; char >= 0x10000 ? i += 2 : i++) {
       char = codePointAt(string, i);
-      if (!isPrintable(char)) {
+      if (!isPrintableWithTabs(char)) {
         return STYLE_DOUBLE;
       }
       plain = plain && isPlainSafe(char, prevChar, inblock);
@@ -352,7 +358,7 @@ function chooseScalarStyle(string, singleLineOnly, indentPerLevel, lineWidth,
              string[previousLineBreak + 1] !== ' ');
           previousLineBreak = i;
         }
-      } else if (!isPrintable(char)) {
+      } else if (!isPrintableWithTabs(char)) {
         return STYLE_DOUBLE;
       }
       plain = plain && isPlainSafe(char, prevChar, inblock);

test/issues/0682-1.yml

@@ -0,0 +1,3 @@
+value: |-
+  a
+  	b

test/issues/0682-2.yml

@@ -0,0 +1,7 @@
+value: |2
+
+  some text
+   less indented text
+other: |2
+      some text
+  less indented text

test/issues/0682.js

@@ -0,0 +1,33 @@
+'use strict';
+
+const assert = require('assert');
+const fs     = require('fs');
+const yaml   = require('../..');
+
+
+it('Should serialize strings with tabs as blocks', function () {
+  const expected = fs.readFileSync(require('path').join(__dirname, '/0682-1.yml'), 'utf8');
+  const result = yaml.dump({ value: 'a\n\tb' });
+  assert.strictEqual(expected, result);
+});
+
+it('Should serialize strings with tabs and carriage returns as blocks and deserialize them', function () {
+  const data = {
+    value: '\r\n    \tsome text\r\n  more text but less indented \r\neven less indentation'
+  };
+  const result = yaml.dump(data);
+  const loaded = yaml.load(result);
+  assert.deepEqual(data, loaded);
+});
+
+it('Should serialize strings where the initial whitespace is less than the following', function () {
+  const data = {
+    value: '    \nsome text\n less indented text\n',
+    other: '    some text\nless indented text\n'
+  };
+  const result = yaml.dump(data);
+  const loaded = yaml.load(result);
+  assert.deepEqual(data, loaded);
+  const expected = fs.readFileSync(require('path').join(__dirname, '/0682-2.yml'), 'utf8');
+  assert.strictEqual(expected, result);
+});

test/issues/0682.yml

@@ -0,0 +1,3 @@
+value: |-
+  a
+  	b