[BUG] `PointReaderWriter.wktToPolygon` crashes on malformed WKT instead of returning null

[SuperCorleone]

Describe the Bug

wktToPolygon explicitly returns null for null/empty input and for "no parseable points", establishing a "null = invalid" contract. But for other malformed WKT it throws instead of returning null:

• missing ((/)) → substring(indexOf("((")+2, lastIndexOf("))")) becomes substring(start, -1) → StringIndexOutOfBoundsException
• non-numeric coordinates → Double.parseDouble(...) → NumberFormatException

In practice the WKT is read from the PostGIS polygon column (always well-formed), so the trigger is low (DB corruption / manual edits), but it is an inconsistent contract.

Root Cause

public List<GeoPoint> wktToPolygon(String wkt) {
    if (wkt == null || wkt.trim().isEmpty()) return null;
    String coordinates = wkt.substring(wkt.indexOf("((") + 2, wkt.lastIndexOf("))"));  // -1 → StringIndexOOB
    String[] points = coordinates.split(",");
    List<GeoPoint> polygon = new ArrayList<>();
    for (String point : points) {
        String[] coords = point.trim().split("\\s+");
        if (coords.length >= 2) {
            double longitude = Double.parseDouble(coords[0]);  // non-numeric → NumberFormatException
            double latitude = Double.parseDouble(coords[1]);
            polygon.add(GeoPoint.from(latitude, longitude));
        }
    }
    return polygon.isEmpty() ? null : polygon;
}

Expected vs Observed

Expected: malformed WKT → null (consistent with the existing null/empty handling). Observed: StringIndexOutOfBoundsException / NumberFormatException.

Suggested Fix

Validate ((/)) presence and wrap parsing in try/catch returning null (or Optional.empty()), matching the sibling read() method which already catches NumberFormatException.

Corresponding Test (generated)

@Test
public void testWktToPolygon_ValidFormatButInvalidDoubleParsing_ReturnsNull() {
    String wkt = "POLYGON((abc def, ghi jkl))";
    List<GeoPoint> result = pointReaderWriter.wktToPolygon(wkt);
    assertNull(result);
}

@Test
public void testWktToPolygon_InvalidFormat_NoClosingParentheses_ReturnsNull() {
    String wkt = "POLYGON((lon1 lat1, lon2 lat2";
    List<GeoPoint> result = pointReaderWriter.wktToPolygon(wkt);
    assertNull(result);
}

@Test
public void testWktToPolygon_InvalidFormat_NoOpeningParentheses_ReturnsNull() {
    String wkt = "POLYGON lon1 lat1, lon2 lat2))";
    List<GeoPoint> result = pointReaderWriter.wktToPolygon(wkt);
    assertNull(result);
}

@Test
public void testWktToPolygon_InvalidFormat_NoDoubleParentheses_ReturnsNull() {
    String wkt = "POLYGON(lon1 lat1, lon2 lat2)";
    List<GeoPoint> result = pointReaderWriter.wktToPolygon(wkt);
    assertNull(result);
}

This input was generated by the test case generator TestFusion developed in our STAR lab.

[dgraf-gh]

We have the producing side in our code. Rather than trying to prevent a non existing problem I would rather let that fail fast, so we can fix the underlying problem.