`java.lang.StringBuffer` cannot be deserialized

[Lolf1010]

Describe the bug
I recently tried to update my jackson-version from 2.10.3 to 2.13.1 and it appears that the java.lang.StringBuffer can no longer be deserialized. java.lang.StringBuilder and java.lang.String both work as expected.

Is there a reason why the support for StringBuffer was removed somewhere between the versions or is it a bug?

Version information
2.13.1

To Reproduce

ObjectMapper mapper = new ObjectMapper();
StringBuffer a = new StringBuffer("test");
String json = mapper.writeValueAsString(a);                  // is the string "test"
StringBuffer b = mapper.readValue(json, StringBuffer.class); // throws Exception

com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot construct instance of `java.lang.StringBuffer` (although at least one Creator exists): no String-argument constructor/factory method to deserialize from String value ('test')

Expected behavior
java.lang.String, java.lang.StringBuilder, java.lang.StringBuffer can be serialized and deserialized.

EDIT (by @cowtowncoder )

Regression affects versions 2.12.x and 2.13.0 - 2.13.2; fixed in 2.13.3, did not affect versions up to 2.11.x.

[GedMarc]

Uhhhh, StringBuffer, is not recommended for use at all, why are you using it?

[Lolf1010]

I am not using it directly.
Groovy is using it.
https://docs.groovy-lang.org/latest/html/groovy-jdk/java/lang/String.html#leftShift(java.lang.Object)

In the project i am working at, where this issue occurred, is it possible for developers to define and execute groovy-scripts as part of BPMN-models that can be executed. Instead of using "+" to append strings, some where using "<<" which creates a StringBuffer instead of a String - for whatever reason. After the update, problems occurred in models with this operators since the deserialization failed.

Nevertheless, i expected all java.lang-String-Classes to be able to get serialized and deserialized.
Especially since StringBuffer is not marked deprecated - even in the newest version of java.
Maybe i miss the info in a changelog-file?

[cowtowncoder]

@Lolf1010 I can't remember any explicit change to cause this, so does sound like a bug.

At practical level, if there is no unit test to test certain functionality, it is not really supported feature -- if there was, we'd have had regression failure for whatever change occurred.
So I suspect only String and StringBuilder have test coverage.

I hope to have time to check this out, probably simple to fix.