Quantity Decimal Places Limitation Conflicts with XRechnung Compliance (Needs Immediate Fix)

[fktrdui]

According to the XRechnung specification, as highlighted in the attached screenshot (section 8.8 "Quantity"), the quantity values should not have a limitation on decimal places. The specification explicitly mentions that the quantity field should allow a floating-point number without limitation on decimal places ("ohne Limitierung der Nachkommastellen").

However, the Mustang project appears to limit the number of decimal places for quantities in certain methods.
Specifically, in the ZUGFeRD2PullProvider class, the quantityFormat method restricts quantities to 4 decimal places:

protected String quantityFormat(BigDecimal value) {
    return XMLTools.nDigitFormat(value, 4);
}

This method is called by:

+ "<ram:BasisQuantity unitCode=\"" + XMLTools.encodeXML(currentItem.getProduct().getUnit())
+ "\">" + quantityFormat(currentItem.getBasisQuantity()) + "</ram:BasisQuantity>"

Additionally, in the IZUGFeRDExportableItem interface, the getBasisQuantity() method also uses BigDecimal.ONE.setScale(4), which imposes a restriction of 4 decimal places for the quantity.

default BigDecimal getBasisQuantity() {
    return BigDecimal.ONE.setScale(4);
}

Request for Immediate Action
This issue requires urgent attention as it directly impacts XRechnung compliance. Non-compliant e-invoices could lead to legal and financial risks, such as invoice rejections.

Proposed Fix:
Modify the following methods to allow arbitrary precision for quantity values:
quantityFormat in the ZUGFeRD2PullProvider class.
getBasisQuantity in the IZUGFeRDExportableItem interface.

[fktrdui]

Thank you for your immediate update.
Due to changes there are some test issues in the project:

Failed tests: testDXExport(org.mustangproject.ZUGFeRD.DXTest): expected:<400.0000> but was:<400.000000000000000000>
testOXEdgeExport(org.mustangproject.ZUGFeRD.OXTest): expected:<1.0000> but was:<1.000000000000000000>
testOXExport(org.mustangproject.ZUGFeRD.OXTest): expected:<400.0000> but was:<400.000000000000000000>
testExport(org.mustangproject.ZUGFeRD.ZF2Test): expected:<1.0000[00000000000000]> but was:<1.0000[]>
testInvoiceImport(org.mustangproject.ZUGFeRD.ZF2ZInvoiceImporterTest): expected:<400.0000[]> but was:<400.0000[00000000000000]>

[langfr]

PR #497 created to fix these issues.

[jstaerk]

@fktrdui can you provide one or two tests?

[fktrdui]

@jstaerk I would be happy to modify the previous tests to reflect the changes in the ZUGFeRD2PullProvider.
My suggestion for modified methods in ZUGFeRD2PullProvider is:

protected String priceFormat(BigDecimal value) {
                String digit = XMLTools.nDigitFormat(value, 18);
		BigDecimal digitDecimal = BigDecimal.valueOf(Double.parseDouble(digit));
		return digitDecimal.stripTrailingZeros().toPlainString();
	}

	protected String quantityFormat(BigDecimal value) {
                String digit = XMLTools.nDigitFormat(value, 18);
		BigDecimal digitDecimal = BigDecimal.valueOf(Double.parseDouble(digit));
                return digitDecimal.stripTrailingZeros().toPlainString();
	}

With these changes, unnecessary trailing zeros are eliminated, and the quantities are formatted as required by the specification.

[fktrdui]

Modified Test Cases:

1. org.mustangproject.ZUGFeRD.DXTest: testDXExport
   Line 301:
   assertEquals(new BigDecimal("400"), i.getZFItems()[1].getQuantity());

2. org.mustangproject.ZUGFeRD.OXTest: testOXExport
   Line 300:
   assertEquals(new BigDecimal("400"), i.getZFItems()[1].getQuantity());

3. org.mustangproject.ZUGFeRD.OXTest: testOXEdgeExport
   Line 354:
   assertEquals(new BigDecimal("1"), i.getZFItems()[1].getQuantity());

4. org.mustangproject.ZUGFeRD.ZF2Test: testExport
   Line 236:
   assertEquals(li.get(0).getQuantity().toString(), "1");

5. org.mustangproject.ZUGFeRD.ZF2ZInvoiceImporterTest: testInvoiceImport
   Line 60-63:

assertEquals("400", invoice.getZFItems()[1].getQuantity().toString());
assertEquals("AB321", invoice.getReferenceNumber());
assertEquals("160", invoice.getZFItems()[0].getPrice().toString());