`StdDeserializer` rejects blank (all-whitespace) strings for ints

[pburka]

Describe the bug
In Jackson 2.10.2 the standard deserializer converts empty strings and all-whitespace strings to zero when deserializing to ints. In 2.12 the default behavior changed: it accepts blank strings but not strings consisting only of whitespace (e.g. " "). Instead of deserializing to zero, it throws InvalidFormatException. I imagine this is related to the changes to leniency handling in 2.12. While it's great to be able to configure leniency, for backwards compatibility the library should maintain the old default behavior.

Version information
2.12.4

To Reproduce

import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.annotation.JsonDeserialize;

@JsonDeserialize
public class Jack {
    private final int j;

    @JsonCreator
    public Jack(@JsonProperty("J") int j) {
        this.j = j;
    }

    private static void test(String s) {
        final String json = "{ \"J\" : \"" + s + "\" }";
        try {
            final Jack jack = new ObjectMapper().readValue(json, Jack.class);
            System.out.println("j=" + jack.j);
        } catch (Throwable t) {
            t.printStackTrace();
        }
    }

    public static void main(String[] args) {
        // With Jackson 2.10.2 these all print j=0
        test("0");
        test("0 ");
        test(" 0");
        test(" 0 ");
        test("");
        // With Jackson 2.12.4 these throw InvalidFormatException
        test(" ");
        test("    ");
        test("\\n");
    }
}

Expected behavior

Expected behavior: the default deserializer should behave consistently in 2.10 and 2.12.

Actual behavior: the 2.12 deserializer is less lenient and rejects non-empty strings that contain only whitespace.

[cowtowncoder]

Hmmmh. It is worth noting that for this case to work, coercion from String to number is also needed.
I guess default settings should allow this case, in theory, but the combination of delegating creator makes it bit tricky.

But I agree that 2.12 behavior with default settings should be the same as with 2.10 here.