`TokenBuffer` serialization fails when buffer contains integer encoded as String

[kirmerzlikin]

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Describe the bug

TokenBuffer serialization does not consider the case when buffer contains integer value encoded as String. After it is determined that the value is not Integer, BigInteger, Long or Short, serialization logic tries to cast it to Number and fails with ClassCastException.

I first encountered this issue when trying to serialize a TokenBuffer that was previously copied from JsonParser which pointed at a big integer value. Copying was done using copyCurrentStructure() which called _copyBufferValue() which in turn wrote a big integer using a "deferred" value which at that point turned out to be a String because it hasn't been decoded yet.

After examining TokenBuffer serialization logic I realized that this behaviour was not specific to big integers and it would lead to the same serialization error for any integer encoded as String.

Version Information

First encountered in 2.19.4 but it still exists in 3.x

Reproduction

Reproducing test case:

jackson-databind/src/test/java/tools/jackson/databind/util/TokenBufferTest.java

Lines 313 to 319 in 53baad9

	@Test
	void testNumberIntAsStringSerialization() throws IOException {
	try (TokenBuffer buf = new TokenBuffer(null, false)) {
	buf.writeNumber("42", true);
	assertEquals("42", MAPPER.writeValueAsString(buf));
	}
	}

Expected behavior

No response

Additional context

Suggested fix: dd1c910

jackson-databind/src/main/java/tools/jackson/databind/util/TokenBuffer.java

Lines 501 to 505 in dd1c910

	} else if (n instanceof String s) {
	gen.writeNumber(s);
	} else {
	gen.writeNumber(((Number) n).intValue());
	}

[cowtowncoder]

Thank you for reporting this -- reproduction and fix both make sense.

Just one request: you mention original use case for deferred number(s) (for BigInteger, but could happen for floating-point numbers too I think). Would it be possible to have test for that case? This because reproduction here is for bit different usage.

[cowtowncoder]

Fixed in 3.1(.0), 2.21(.1).