From 2ec92d1dcfde988670a34b449639ac00e856393b Mon Sep 17 00:00:00 2001
From: Himura Kazuto <glagol15@gmail.com>
Date: Tue, 16 Jun 2020 18:25:45 +0300
Subject: [PATCH] Implement the desired brhavior

---
 lib/js-yaml/dumper.js | 65 ++++++++++++++++++++++++++-----------------
 1 file changed, 39 insertions(+), 26 deletions(-)

diff --git a/lib/js-yaml/dumper.js b/lib/js-yaml/dumper.js
index 995179f1..6686a920 100644
--- a/lib/js-yaml/dumper.js
+++ b/lib/js-yaml/dumper.js
@@ -194,32 +194,45 @@ function isPrintable(c) {
 // [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
-// [24] b-line-feed       ::=     #xA    /* LF */
-// [25] b-carriage-return ::=     #xD    /* CR */
-// [3]  c-byte-order-mark ::=     #xFEFF
-function isNsChar(c) {
-  return isPrintable(c) && !isWhitespace(c)
-      && c !== CHAR_BOM
-      // - b-char
+// Including s-white (for some reason, examples doesn't match specs in this aspect)
+// ns-char ::= c-printable - b-line-feed - b-carriage-return - c-byte-order-mark
+function isNsCharOrWhitespace(c) {
+  return isPrintable(c)
+    && c !== CHAR_BOM
+    // - b-char
     && c !== CHAR_CARRIAGE_RETURN
     && c !== CHAR_LINE_FEED;
 }
 
-// Simplified test for values allowed after the first character in plain style.
-function isPlainSafe(c, prev) {
-  // 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
-    // - ":" - "#"
-    // /* An ns-char preceding */ "#"
-    && c !== CHAR_COLON
-    && ((c !== CHAR_SHARP) || (prev && isNsChar(prev)));
+// [127]  ns-plain-safe(c) ::= c = flow-out  ⇒ ns-plain-safe-out
+//                             c = flow-in   ⇒ ns-plain-safe-in
+//                             c = block-key ⇒ ns-plain-safe-out
+//                             c = flow-key  ⇒ ns-plain-safe-in
+// [128] ns-plain-safe-out ::= ns-char
+// [129]  ns-plain-safe-in ::= ns-char - c-flow-indicator
+// [130]  ns-plain-char(c) ::=  ( ns-plain-safe(c) - “:” - “#” )
+//                            | ( /* An ns-char preceding */ “#” )
+//                            | ( “:” /* Followed by an ns-plain-safe(c) */ )
+function isPlainSafe(state, c, prev) {
+  var cIsNsCharOrWhitespace = isNsCharOrWhitespace(c);
+  var cIsNsChar = cIsNsCharOrWhitespace && !isWhitespace(c);
+  return (
+    // ns-plain-safe
+    state.flowLevel < 0 ? // c = flow-in
+      cIsNsCharOrWhitespace
+      : cIsNsCharOrWhitespace
+        // - 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
+  )
+    // ns-plain-char
+    && c !== CHAR_SHARP // false on '#'
+    && !(prev === CHAR_COLON && !cIsNsChar) // false on ': '
+    || (isNsCharOrWhitespace(prev) && !isWhitespace(prev) && c === CHAR_SHARP) // change to true on '[^ ]#'
+    || (prev === CHAR_COLON && cIsNsChar); // change to true on ':[^ ]'
 }
 
 // Simplified test for values allowed as the first character in plain style.
@@ -274,7 +287,7 @@ var STYLE_PLAIN   = 1,
 //    STYLE_PLAIN or STYLE_SINGLE => no \n are in the string.
 //    STYLE_LITERAL => no lines are suitable for folding (or lineWidth is -1).
 //    STYLE_FOLDED => a line > lineWidth and can be folded (and lineWidth != -1).
-function chooseScalarStyle(string, singleLineOnly, indentPerLevel, lineWidth, testAmbiguousType) {
+function chooseScalarStyle(state, string, singleLineOnly, indentPerLevel, lineWidth, testAmbiguousType) {
   var i;
   var char, prev_char;
   var hasLineBreak = false;
@@ -293,7 +306,7 @@ function chooseScalarStyle(string, singleLineOnly, indentPerLevel, lineWidth, te
         return STYLE_DOUBLE;
       }
       prev_char = i > 0 ? string.charCodeAt(i - 1) : null;
-      plain = plain && isPlainSafe(char, prev_char);
+      plain = plain && isPlainSafe(state, char, prev_char);
     }
   } else {
     // Case: block styles permitted.
@@ -313,7 +326,7 @@ function chooseScalarStyle(string, singleLineOnly, indentPerLevel, lineWidth, te
         return STYLE_DOUBLE;
       }
       prev_char = i > 0 ? string.charCodeAt(i - 1) : null;
-      plain = plain && isPlainSafe(char, prev_char);
+      plain = plain && isPlainSafe(state, char, prev_char);
     }
     // in case the end is missing a \n
     hasFoldableLine = hasFoldableLine || (shouldTrackWidth &&
@@ -373,7 +386,7 @@ function writeScalar(state, string, level, iskey) {
       return testImplicitResolving(state, string);
     }
 
-    switch (chooseScalarStyle(string, singleLineOnly, state.indent, lineWidth, testAmbiguity)) {
+    switch (chooseScalarStyle(state, string, singleLineOnly, state.indent, lineWidth, testAmbiguity)) {
       case STYLE_PLAIN:
         return string;
       case STYLE_SINGLE: