### New properties in an existing class

When adding a property to an existing class (task, extension, domain object, etc), the API should consist of managed lazy properties.  However, some exceptions need to be made to keep backwards compatibility with existing builds.

This is preferred when the implementation type is internal:

```groovy

        // Should not throw exception
    }

    // Test addFieldLog with existing field
    @Test
    public void test_addFieldLog_existingField() {
        Map<String, List<String>> fieldLogMap = new HashMap<>();
        List<String> existingList = new ArrayList<>();
        existingList.add("existing");
        fieldLogMap.put("field", existingList);

### Negative Consequences

* **Historical inconsistencies**: Existing code may contain British English spellings that cannot be changed due to backward compatibility

### Migration and Enforcement

* **New code**: All new contributions must use American English

    builder.addEscape(' ', "_");
    Escaper first = builder.build();
    // Modify one of the existing mappings before creating a new escaper.
    builder.addEscape(' ', "-");
    builder.addEscape('!', "$");
    Escaper second = builder.build();
    // This should have no effect on existing escapers.
    builder.addEscape(' ', "*");

    // Test both escapers after modifying the builder.

    // next map.get()
    when(backingMap.get(KEY)).thenReturn(existingZero);
    // since get returned zero, try a replace; that fails due to a simulated race
    when(backingMap.replace(eq(KEY), eq(existingZero), isA(AtomicInteger.class))).thenReturn(false);
    when(backingMap.putIfAbsent(eq(KEY), isA(AtomicInteger.class))).thenReturn(existing);

    // another map.get()

        Map<String, Object> dataMap = new HashMap<>();
        dataMap.put("url", "http://example.com/test");
        dataMap.put("doc_id", "existing-doc-id");

        indexUpdateCallback.store(paramMap, dataMap);

        // Should keep existing doc_id
        assertEquals("existing-doc-id", dataMap.get("doc_id"));
    }

    @Test
    public void test_concurrentStore() throws Exception {
        // Test thread safety

When sharing data with external tools, we use JSON.

## Consequences

* The configuration cache serialization infrastructure should be used for all serialization.
* Existing usages of Serializer outside of this infrastructure should be migrated to use it.
* Existing usages of Java serialization should be migrated to use it.
* It is ok for Serializer to be used as a replacement for Java serialization as a migration step.

    public void test_update() throws Exception {
        writeTestFile("a,b => c\nd,e => f\n");

        // Get existing item
        OptionalEntity<CharMappingItem> existing = charMappingFile.get(1L);
        assertTrue(existing.isPresent());

        // Update the item
        CharMappingItem updateItem = existing.get();
        updateItem.setNewInputs(new String[] { "m", "n" });
        updateItem.setNewOutput("o");

1.  Any significant changes should be accompanied by tests. The project already
    has good test coverage, so look at some existing tests if you're unsure how
    to go about it.
2.  All contributions must be licensed Apache 2.0 and all files must have a copy
    of the boilerplate license comment (can be copied from an existing file).
3.  Files should be formatted according to Google's [Java style guide][].

                return existingInfo;
            }

            @Override
            public void store(CrawlingInfo entity) {
                // Should not be called for existing info
                fail("Store should not be called for existing info");
            }

            @Override
            public void storeInfo(List<CrawlingInfoParam> crawlingInfoParamList) {