Fix FasterXML#68

Author: cowtowncoder

release-notes/CREDITS-2.x

@@ -32,3 +32,8 @@ Yegor Borovikov (yborovikov@gitub)
 * Reported #81 (yaml): Jackson 2.9.5, 2.9.6 incompatible with snakeyaml 1.20, 1.21
  (2.9.7)
 
+Gowtam Lal (baconmania@github)
+
+* Reported #68: (yaml) When field names are reserved words, they should be
+  written out with quotes
+ (2.9.9)

release-notes/VERSION-2.x

@@ -12,6 +12,8 @@ Modules:
 
 #63: (yaml) `null` Object Id serialized as anchor for YAML
  (reported by jflefebvre06@github)
+#68: (yaml) When field names are reserved words, they should be written out with quotes
+ (reported by Gowtam L)
 #90: (yaml) Exception when decoding Jackson-encoded `Base64` binary value in YAML
  (reported by Tanguy L)
 #122: (csv) `readValues(null)` causes infinite loop

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

@@ -5,7 +5,9 @@
 import java.math.BigInteger;
 import java.util.Arrays;
 import java.util.Collections;
+import java.util.HashSet;
 import java.util.Map;
+import java.util.Set;
 import java.util.regex.Pattern;
 
 import org.yaml.snakeyaml.DumperOptions;
@@ -169,6 +171,16 @@ private Feature(boolean defaultState) {
     protected final static Pattern PLAIN_NUMBER_P = Pattern.compile("[0-9]*(\\.[0-9]*)?");
     protected final static String TAG_BINARY = Tag.BINARY.toString();
 
+    /* As per <a href="https://yaml.org/type/bool.html">YAML Spec</a> there are a few
+     * aliases for booleans, and we better quote such values as keys; although Jackson
+     * itself has no problems dealing with them, some other tools do have.
+     */
+    private final static Set<String> RESERVED_NAMES = new HashSet<>(Arrays.asList(
+            "y", "Y", "yes", "Yes", "YES", "n", "N", "no", "No", "NO",
+            "true", "True", "TRUE", "false", "False", "FALSE",
+            "on", "On", "ON", "off", "Off", "OFF"
+    ));
+
     /*
     /**********************************************************
     /* Configuration
@@ -188,9 +200,13 @@ private Feature(boolean defaultState) {
 
     protected DumperOptions _outputOptions;
 
-    // for field names, leave out quotes
-    private final static Character STYLE_NAME = null;
-
+    /**
+     * Names are written unquoted, by default.
+     *
+     * @since 2.10
+     */
+    private Character _styleName = null;
+    
     // numbers, booleans, should use implicit
     private final static Character STYLE_SCALAR = null;
     // Strings quoted for fun
@@ -429,7 +445,13 @@ public final void writeStringField(String fieldName, String value)
     private final void _writeFieldName(String name)
         throws IOException
     {
-        _writeScalar(name, "string", STYLE_NAME);
+        Character style = _styleName;
+        if (style == null) {
+            if (RESERVED_NAMES.contains(name)) {
+                style = STYLE_QUOTED;
+            }
+        }
+        _writeScalar(name, "string", style);
     }
 
     /*

yaml/src/test/java/com/fasterxml/jackson/dataformat/yaml/ModuleTestBase.java

@@ -168,8 +168,8 @@ protected void verifyException(Throwable e, String... matches)
     protected static String trimDocMarker(String doc)
     {
         if (doc.startsWith("---")) {
-            doc = doc.substring(3).trim();
+            doc = doc.substring(3);
         }
-        return doc;
+        return doc.trim();
     }
 }

yaml/src/test/java/com/fasterxml/jackson/dataformat/yaml/misc/ObjectIdTest.java

@@ -7,7 +7,6 @@
 import com.fasterxml.jackson.dataformat.yaml.ModuleTestBase;
 import com.fasterxml.jackson.dataformat.yaml.YAMLGenerator;
 import com.fasterxml.jackson.dataformat.yaml.YAMLMapper;
-import com.fasterxml.jackson.dataformat.yaml.YAMLGenerator.Feature;
 
 public class ObjectIdTest extends ModuleTestBase
 {

yaml/src/test/java/com/fasterxml/jackson/dataformat/yaml/misc/ReservedNamesTest.java

@@ -0,0 +1,34 @@
+package com.fasterxml.jackson.dataformat.yaml.misc;
+
+import java.util.*;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.dataformat.yaml.ModuleTestBase;
+
+// [dataformats-text#68]: should quote reserved names
+public class ReservedNamesTest extends ModuleTestBase
+{
+    private final ObjectMapper MAPPER = newObjectMapper();
+
+    public void testQuotingOfBooleanKeys() throws Exception
+    {
+        for (String value : new String[] {
+                "true", "True",
+                "false", "False",
+                "yes", "y", "Y",
+                "no", "n", "N",
+                "on",
+                "off",
+        }) {
+            _testQuotingOfBooleanKeys(value);
+        }
+    }
+
+    private void _testQuotingOfBooleanKeys(String key) throws Exception
+    {
+        final Map<String, Integer> input = Collections.singletonMap(key, 123);
+        final String doc = trimDocMarker(MAPPER.writeValueAsString(input).trim());
+
+        assertEquals("\""+key+"\": 123", doc);
+    }
+}