Fix fn:round, fn:round-hallf-to-even edge cases

1. Give back same answer on INF and NaN inputs
2. Use only as much precision as the value being rounded, to avoid overflows when a very big precision is input.

Author: alanpaxton

exist-core/src/main/java/org/exist/xquery/functions/fn/FunRoundBase.java

@@ -86,8 +86,15 @@ public Sequence eval(final Sequence[] args, final Sequence contextSequence) thro
      * @throws XPathException if a conversion goes wrong (it shouldn't)
      */
     private static Sequence convertValue(final IntegerValue precision, final NumericValue value, final RoundingMode roundingMode) throws XPathException {
+
+        if (value.isInfinite() || value.isNaN()) {
+            return value;
+        }
+
         final DecimalValue decimal = (DecimalValue)value.convertTo(Type.DECIMAL);
-        final DecimalValue rounded = (DecimalValue) Objects.requireNonNull(decimal).round(precision, roundingMode);
+        // (AP) This is as much precision as we can need, and prevents overflows scaling BigInteger
+        final IntegerValue usePrecision = truncatePrecision(decimal, precision);
+        final DecimalValue rounded = (DecimalValue) Objects.requireNonNull(decimal).round(usePrecision, roundingMode);
 
         if (value.isNegative() && rounded.isZero()) {
             //Extreme care!! (AP) -0 as DecimalValue will not be negative, -0.0f and -0.0d will be negative.
@@ -106,4 +113,12 @@ private static Sequence convertValue(final IntegerValue precision, final Numeric
         return rounded.convertTo(value.getType());
     }
 
+    private static IntegerValue truncatePrecision(final DecimalValue decimal, final IntegerValue precision) throws XPathException {
+
+        final IntegerValue decimalPrecision = new IntegerValue(decimal.getValue().precision());
+        if (decimalPrecision.compareTo(precision) < 0) {
+            return decimalPrecision;
+        }
+        return precision;
+    }
 }

exist-core/src/test/xquery/numbers/fn-round.xqm

@@ -114,6 +114,20 @@ function fr:round-half-to-even($number as xs:double) {
     fn:round-half-to-even($number)
 };
 
+declare
+    %test:args("3.567812E+3", 4294967296)
+    %test:assertEquals("3567.812")
+function fr:round-half-to-even-high-precision($number as xs:double, $precision as xs:integer) {
+    fn:round-half-to-even($number, $precision)
+};
+
+declare
+    %test:args("-0.05", 1)
+    %test:assertEquals("-0.1")
+function fr:round-half-to-even-inexact-halfway-float($number as xs:float, $precision as xs:integer) {
+    fn:round-half-to-even($number, $precision)
+};
+
 declare
     %test:args("-0.41",1)
     %test:assertEquals("-0.4")
@@ -143,4 +157,22 @@ declare
     %test:assertEquals("-0")
 function fr:round-negative-zero-float($number as xs:float, $precision as xs:integer) {
     fn:round($number, $precision)
+};
+
+declare
+    %test:args("INF")
+    %test:assertEquals("INF")
+    %test:args("-INF")
+    %test:assertEquals("-INF")
+function fr:round-inf-float($number as xs:float) {
+    fn:round($number)
+};
+
+declare
+    %test:args("INF")
+    %test:assertEquals("INF")
+    %test:args("-INF")
+    %test:assertEquals("-INF")
+function fr:round-inf-double($number as xs:double) {
+    fn:round($number)
 };