Revert nodeca#470/nodeca#473 for dumper: too many situations where th…

…e rendered output is ambiguous and hence erroneous YAML.

lib/js-yaml/dumper.js

@@ -117,9 +117,9 @@ function State(options) {
   this.noCompatMode  = options['noCompatMode'] || false;
   this.condenseFlow  = options['condenseFlow'] || false;
   this.scalarQuoteStyle = options['scalarQuoteStyle'] || null;
-  this.forceSeqFlow = options['forceSeqFlow'] || false;
+  this.forceSeqFlow  = options['forceSeqFlow'] || false;
   // accept a `quoteKeys` option *explicitly* set to FALSE:
-  this.quoteKeys    = (options['quoteKeys'] != null ? options['quoteKeys'] : !!this.condenseFlow);
+  this.quoteKeys     = (options['quoteKeys'] != null ? options['quoteKeys'] : !!this.condenseFlow);
   if (this.quoteKeys) {
     if (this.quoteKeys === true) {
       this.quoteKeys = '"';
@@ -201,7 +201,18 @@ function isPrintable(c) {
 
 // Simplified test for values allowed after the first character in plain style.
 function isPlainSafe(c) {
-  return isPrintable(c) && c !== 0xFEFF;
+  // Uses a subset of nb-char - c-flow-indicator - ":" - "#"
+  // where nb-char ::= c-printable - b-char - c-byte-order-mark.
+  return isPrintable(c) && c !== 0xFEFF
+    // - c-flow-indicator
+    && c !== CHAR_COMMA
+    && c !== CHAR_LEFT_SQUARE_BRACKET
+    && c !== CHAR_RIGHT_SQUARE_BRACKET
+    && c !== CHAR_LEFT_CURLY_BRACKET
+    && c !== CHAR_RIGHT_CURLY_BRACKET
+    // - ":" - "#"
+    && c !== CHAR_COLON
+    && c !== CHAR_SHARP;
 }
 
 // Simplified test for values allowed as the first character in plain style.
@@ -265,9 +276,7 @@ function chooseScalarStyle(string, singleLineOnly, indentPerLevel, lineWidth, te
   var shouldTrackWidth = lineWidth !== -1;
   var previousLineBreak = -1; // count the first line correctly
   var plain = isPlainSafeFirst(string.charCodeAt(0))
-          && !isWhitespace(string.charCodeAt(string.length - 1))
-          && /\s#/.test(string) === false
-          && /:(?:\s|$)/.test(string) === false;
+          && !isWhitespace(string.charCodeAt(string.length - 1));
 
   if (singleLineOnly) {
     // Case: no block styles.
@@ -301,7 +310,7 @@ function chooseScalarStyle(string, singleLineOnly, indentPerLevel, lineWidth, te
     // in case the end is missing a \n
     hasFoldableLine = hasFoldableLine || (shouldTrackWidth &&
       (i - previousLineBreak - 1 > lineWidth &&
-      string[previousLineBreak + 1] !== ' '));
+       string[previousLineBreak + 1] !== ' '));
   }
   // Although every style can represent \n without escaping, prefer block styles
   // for multiline, since they're more readable and they don't add empty lines.