Deserializing `BigDecimal` with large number of decimals result in incorrect value

[lnthai2002]

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Describe the bug

I have a string represents a number with 652 decimal places (-11000.00000...). When reading this string to BigDecimal i end up with a wrong number -1.1000E-648. The simple example is found at https://github.com/lnthai2002/jackson-databind-test/blob/db3e060ac38c555b001d91c549e004a19f9a17c7/src/main/java/App.java

Version Information

2.17.1

Reproduction

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import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.node.JsonNodeFactory;

import java.math.BigDecimal;

public class App {
  public static void main (String [] args) {
    JsonNodeFactory f = JsonNodeFactory.withExactBigDecimals(true);
    ObjectMapper mapper = new ObjectMapper();
    mapper.findAndRegisterModules()
        .setNodeFactory(f)
        .configure(JsonGenerator.Feature.WRITE_BIGDECIMAL_AS_PLAIN, true)
        .configure(DeserializationFeature.USE_BIG_DECIMAL_FOR_FLOATS, true);
    String str = "-11000.0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000";
    try {
      BigDecimal num = mapper.readValue(str, BigDecimal.class);
      System.out.println(num);
    } catch (Exception e) {
      throw new RuntimeException(e);
    }
  }
}

Expected behavior

should print "-11000.0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"

Additional context

If i switch back to 2.14.1 then i got the correct result

[pjfanning]

@cowtowncoder the issue is in FastDoubleParser JavaBigDecimalParser.parseBigDecimal(arr, 0, arr.length).

JavaBigDecimalParser.parseBigDecimal(str) handles the number fine but the char array method has a bug.

In Jackson 2.17, the BigDecimalParser uses the FastDoubleParser for BigDecimal when there are more than 500 chars.

I can report the issue to FastDoubleParser and also look at changing BigDecimalParser to work around the issue.

[cowtowncoder]

Ok. Let's first see if we could get a fix for FDP... Ideally would not want to add temporary work-arounds, esp. given we are shading the dependency so can relatively freely upgrade.

I think I can add a failing test here, for 2.17, and we can see what to do (workaround vs upgrade) in couple of days.