FIX FasterXML#180: YAML Generator now quotes strings containing speci…

…al chars

When using the YAMLGenerator in the MINIMIZE_QUOTES mode, the generator serializes strings in plain style, i.e. without quoting them. However, as stated in the YAML Spec [1] such plain style strings cannot contain some special characters such as ':', ',', and others.

[1] https://yaml.org/spec/1.2/spec.html#id2788859

As with the serialization of boolean-like strings, the YAMLGenerator should be adjusted to always quote strings containing those special characters.

I will shortly try to provide a pull request to fix this issue.

yaml/src/main/java/com/fasterxml/jackson/dataformat/yaml/YAMLGenerator.java

@@ -196,6 +196,14 @@ private Feature(boolean defaultState) {
             "on", "On", "ON", "off", "Off", "OFF",
             "null", "Null", "NULL"
     ));
+
+    /**
+     * As per YAML <a href="https://yaml.org/spec/1.2/spec.html#id2788859">Plain Style</a>unquoted strings are
+     * restriced to a reduced charset and must be quoted in case they contain one of the following characters.
+     */
+    private final static Set<String> SPECIAL_CHARS = new HashSet<>(Arrays.asList(
+            ":", "#", "[", "]", "{", "}", ","
+    ));
 
     /*
     /**********************************************************
@@ -480,7 +488,7 @@ public void close() throws IOException
         if (!isClosed()) {
             // 11-Dec-2019, tatu: Should perhaps check if content is to be auto-closed...
             //   but need END_DOCUMENT regardless
-            
+
             _emitEndDocument();
             _emit(new StreamEndEvent(null, null));
             super.close();
@@ -981,6 +989,16 @@ private boolean _valueNeedsQuoting(String name) {
         case 'Y': // Y/Yes/YES
             return MUST_QUOTE_VALUES.contains(name);
         }
+        return stringContainsItemFromList(name, SPECIAL_CHARS.toArray(new String[]{}));
+    }
+
+    private static boolean stringContainsItemFromList(String inputStr, String[] items) {
+        for(int i =0; i < items.length; i++) {
+            if (inputStr.contains( items[i] )) {
+                return true;
+            }
+        }
+
         return false;
     }
 

yaml/src/test/java/com/fasterxml/jackson/dataformat/yaml/ser/GeneratorWithMinimizeTest.java

@@ -91,6 +91,50 @@ public void testMinimizeQuotesWithNulls() throws Exception
                 "key: nuLL", yaml);
     }
 
+    public void testMinimizeQuotesWithStringsContainingSpecialChars() throws Exception {
+        Map<String, Object> content = new HashMap<String, Object>();
+        content.put("key", "a:b");
+        String yaml = MINIM_MAPPER.writeValueAsString(content).trim();
+        assertEquals("---\n" +
+                "key: \"a:b\"", yaml);
+
+        content.clear();
+        content.put("key", "a#b");
+        yaml = MINIM_MAPPER.writeValueAsString(content).trim();
+        assertEquals("---\n" +
+                "key: \"a#b\"", yaml);
+
+        content.clear();
+        content.put("key", "a[b");
+        yaml = MINIM_MAPPER.writeValueAsString(content).trim();
+        assertEquals("---\n" +
+                "key: \"a[b\"", yaml);
+
+        content.clear();
+        content.put("key", "a]b");
+        yaml = MINIM_MAPPER.writeValueAsString(content).trim();
+        assertEquals("---\n" +
+                "key: \"a]b\"", yaml);
+
+        content.clear();
+        content.put("key", "a{b");
+        yaml = MINIM_MAPPER.writeValueAsString(content).trim();
+        assertEquals("---\n" +
+                "key: \"a{b\"", yaml);
+
+        content.clear();
+        content.put("key", "a}b");
+        yaml = MINIM_MAPPER.writeValueAsString(content).trim();
+        assertEquals("---\n" +
+                "key: \"a}b\"", yaml);
+
+        content.clear();
+        content.put("key", "a,b");
+        yaml = MINIM_MAPPER.writeValueAsString(content).trim();
+        assertEquals("---\n" +
+                "key: \"a,b\"", yaml);
+    }
+
     public void testLiteralStringsMultiLine() throws Exception
     {
         Map<String, Object> content = new HashMap<String, Object>();