Start merging #611 piece by piece

src/main/java/com/fasterxml/jackson/core/TSFBuilder.java

@@ -276,16 +276,25 @@ public B outputDecorator(OutputDecorator dec) {
     // // // Support for subtypes
 
     protected void _legacyEnable(JsonParser.Feature f) {
-        _streamReadFeatures |= f.getMask();
+        if (f != null) {
+            _streamReadFeatures |= f.getMask();
+        }
     }
+
     protected void _legacyDisable(JsonParser.Feature f) {
-        _streamReadFeatures &= ~f.getMask();
+        if (f != null) {
+            _streamReadFeatures &= ~f.getMask();
+        }
     }
 
     protected void _legacyEnable(JsonGenerator.Feature f) {
-        _streamWriteFeatures |= f.getMask();
+        if (f != null) {
+            _streamWriteFeatures |= f.getMask();
+        }
     }
     protected void _legacyDisable(JsonGenerator.Feature f) {
-        _streamWriteFeatures &= ~f.getMask();
+        if (f != null) {
+            _streamWriteFeatures &= ~f.getMask();
+        }
     }
 }

src/main/java/com/fasterxml/jackson/core/json/JsonReadFeature.java

@@ -106,7 +106,20 @@ public enum JsonReadFeature
      */
     @SuppressWarnings("deprecation")
     ALLOW_LEADING_ZEROS_FOR_NUMBERS(false, JsonParser.Feature.ALLOW_NUMERIC_LEADING_ZEROS),
-
+
+    /**
+     * Feature that determines whether parser will allow
+     * JSON decimal numbers to start with a decimal point
+     * (like: .123). If enabled, no exception is thrown, and the number
+     * is parsed as though a leading 0 had been present.
+     *<p>
+     * Since JSON specification does not allow leading decimal,
+     * this is a non-standard feature, and as such disabled by default.
+     *
+     * @since 2.11
+     */
+    ALLOW_LEADING_DECIMAL_POINT_FOR_NUMBERS(false, null),
+
     /**
      * Feature that allows parser to recognize set of
      * "Not-a-Number" (NaN) tokens as legal floating number

src/test/java/com/fasterxml/jackson/failing/NonStandardNumbers611Test.java

@@ -0,0 +1,52 @@
+package com.fasterxml.jackson.failing;
+
+import com.fasterxml.jackson.core.*;
+import com.fasterxml.jackson.core.json.JsonReadFeature;
+
+public class NonStandardNumbers611Test
+    extends com.fasterxml.jackson.core.BaseTest
+{
+    /**
+     * The format ".NNN" (as opposed to "0.NNN") is not valid JSON, so this should fail
+     */
+    public void testLeadingDotInDecimal() throws Exception {
+        for (int mode : ALL_MODES) {
+            JsonParser p = createParser(mode, " .123 ");
+            try {
+                p.nextToken();
+                fail("Should not pass");
+            } catch (JsonParseException e) {
+                verifyException(e, "Unexpected character ('.'");
+            }
+            p.close();
+        }
+    }
+
+    public void testLeadingDotInDecimalAllowed() throws Exception {
+        final JsonFactory f = JsonFactory.builder()
+                .enable(JsonReadFeature.ALLOW_LEADING_DECIMAL_POINT_FOR_NUMBERS)
+                .build();
+
+// TODO:
+/*
+        for (int mode : ALL_MODES) {
+            _testLeadingDotInDecimalAllowed(f, mode);
+        }
+        */
+
+
+        _testLeadingDotInDecimalAllowed(f, MODE_INPUT_STREAM);
+        _testLeadingDotInDecimalAllowed(f, MODE_INPUT_STREAM_THROTTLED);
+        _testLeadingDotInDecimalAllowed(f, MODE_READER);
+        _testLeadingDotInDecimalAllowed(f, MODE_DATA_INPUT);
+    }
+
+    private void _testLeadingDotInDecimalAllowed(JsonFactory f, int mode) throws Exception
+    {
+        JsonParser p = createParser(f, mode, " .123 ");
+        assertEquals(JsonToken.VALUE_NUMBER_FLOAT, p.nextToken());
+        assertEquals(0.123, p.getValueAsDouble());
+        assertEquals("0.123", p.getDecimalValue().toString());
+        p.close();
+    }
+}