Allow custom ProblemDetail in ErrorResponse.Builder

Closes gh-30568

Author: rstoyanchev

spring-web/src/main/java/org/springframework/web/DefaultErrorResponseBuilder.java

@@ -53,13 +53,11 @@ final class DefaultErrorResponseBuilder implements ErrorResponse.Builder {
 	private Object[] detailMessageArguments;
 
 
-	DefaultErrorResponseBuilder(Throwable ex, HttpStatusCode statusCode, String detail) {
+	DefaultErrorResponseBuilder(Throwable ex, ProblemDetail problemDetail) {
 		Assert.notNull(ex, "Throwable is required");
-		Assert.notNull(statusCode, "HttpStatusCode is required");
-		Assert.notNull(detail, "`detail` is required");
 		this.exception = ex;
-		this.statusCode = statusCode;
-		this.problemDetail = ProblemDetail.forStatusAndDetail(statusCode, detail);
+		this.statusCode = HttpStatusCode.valueOf(problemDetail.getStatus());
+		this.problemDetail = problemDetail;
 		this.typeMessageCode = ErrorResponse.getDefaultTypeMessageCode(ex.getClass());
 		this.titleMessageCode = ErrorResponse.getDefaultTitleMessageCode(ex.getClass());
 		this.detailMessageCode = ErrorResponse.getDefaultDetailMessageCode(ex.getClass(), null);

spring-web/src/main/java/org/springframework/web/ErrorResponse.java

@@ -205,7 +205,16 @@ static ErrorResponse create(Throwable ex, HttpStatusCode statusCode, String deta
 	 * by a {@link MessageSource} lookup with {@link #getDetailMessageCode()}
 	 */
 	static Builder builder(Throwable ex, HttpStatusCode statusCode, String detail) {
-		return new DefaultErrorResponseBuilder(ex, statusCode, detail);
+		return builder(ex, ProblemDetail.forStatusAndDetail(statusCode, detail));
+	}
+
+	/**
+	 * Variant of {@link #builder(Throwable, HttpStatusCode, String)} for use
+	 * with a custom {@link ProblemDetail} instance.
+	 * @since 6.1
+	 */
+	static Builder builder(Throwable ex, ProblemDetail problemDetail) {
+		return new DefaultErrorResponseBuilder(ex, problemDetail);
 	}