CLDR-18963 Allow numberSystem attribute for currency element (#5205)

Author: btangmu

common/dtd/ldml.dtd

@@ -2510,6 +2510,8 @@ CLDR data files are interpreted according to the LDML specification (http://unic
 <!ATTLIST currency validSubLocales CDATA #IMPLIED >
     <!--@VALUE-->
     <!--@DEPRECATED-->
+<!ATTLIST currency numberSystem CDATA #IMPLIED >
+    <!--@MATCH:bcp47/nu-->
 
 <!ELEMENT symbol ( #PCDATA ) >
 <!ATTLIST symbol choice (true | false) #IMPLIED >

tools/cldr-code/src/main/java/org/unicode/cldr/test/CheckNumbers.java

@@ -259,21 +259,19 @@ public CheckCLDR handleCheck(
         }
         XPathParts parts = XPathParts.getFrozenInstance(path);
 
-        // TODO: re-enable this commented-out check
-        // Reference: https://unicode-org.atlassian.net/browse/CLDR-18722
-        /*
-        // Check that number formats are for an explicit number system.
-        String numberSystem = parts.getAttributeValue(2, "numberSystem");
-        if (numberSystem == null) {
-            result.add(
-                    new CheckStatus()
-                            .setCause(this)
-                            .setMainType(CheckStatus.errorType)
-                            .setSubtype(Subtype.missingNumberingSystem)
-                            .setMessage(
-                                    "Number formats must have an explicit numberSystem attribute."));
+        // Check that number formats are for an explicit number system (but not for currency paths)
+        if (type != NumericType.CURRENCY) {
+            String numberSystem = parts.getAttributeValue(2, "numberSystem");
+            if (numberSystem == null) {
+                result.add(
+                        new CheckStatus()
+                                .setCause(this)
+                                .setMainType(CheckStatus.errorType)
+                                .setSubtype(Subtype.missingNumberingSystem)
+                                .setMessage(
+                                        "Number formats must have an explicit numberSystem attribute."));
+            }
         }
-         */
 
         // Do tests that need to split the values
 

tools/cldr-code/src/test/java/org/unicode/cldr/unittest/TestDtdData.java

@@ -949,6 +949,8 @@ public void testEmptyPcdata() {
                     // OPTIONAL
                     "//ldml…/symbols[@ references < numberSystem", // Status: metadata ≠
                     // distinguished Mode: OPTIONAL
+                    "//ldml…/currency[@ references < numberSystem", // Status: metadata ≠
+                    // distinguished	Mode: OPTIONAL
                     "//supplementalData…/languagePopulation[@ writingPercent < populationPercent", // Status: value    Mode: OPTIONAL ≠ REQUIRED
                     "//supplementalData…/metazoneId[@ longId < deprecated", // Status: value
                     // Mode: OPTIONAL ≠ NULL