LibJS: Populate roundingPriority in Intl.PluralRules.resolvedOptions

This is inherited from Intl.NumberFormat.

Userland/Libraries/LibJS/Runtime/Intl/PluralRulesPrototype.cpp

@@ -76,6 +76,7 @@ JS_DEFINE_NATIVE_FUNCTION(PluralRulesPrototype::select_range)
 }
 
 // 16.3.4 Intl.PluralRules.prototype.resolvedOptions ( ), https://tc39.es/ecma402/#sec-intl.pluralrules.prototype.resolvedoptions
+// 1.4.5 Intl.PluralRules.prototype.resolvedOptions ( ), https://tc39.es/proposal-intl-numberformat-v3/out/pluralrules/proposed.html#sec-intl.pluralrules.prototype.resolvedoptions
 JS_DEFINE_NATIVE_FUNCTION(PluralRulesPrototype::resolved_options)
 {
     // 1. Let pr be the this value.
@@ -112,7 +113,25 @@ JS_DEFINE_NATIVE_FUNCTION(PluralRulesPrototype::resolved_options)
     // 6. Perform ! CreateDataProperty(options, "pluralCategories", CreateArrayFromList(pluralCategories)).
     MUST(options->create_data_property_or_throw(vm.names.pluralCategories, plural_categories));
 
-    // 7. Return options.
+    switch (plural_rules->rounding_type()) {
+    // 7. If pr.[[RoundingType]] is morePrecision, then
+    case NumberFormatBase::RoundingType::MorePrecision:
+        // a. Perform ! CreateDataPropertyOrThrow(options, "roundingPriority", "morePrecision").
+        MUST(options->create_data_property_or_throw(vm.names.roundingPriority, js_string(vm, "morePrecision"sv)));
+        break;
+    // 8. Else if pr.[[RoundingType]] is lessPrecision, then
+    case NumberFormatBase::RoundingType::LessPrecision:
+        // a. Perform ! CreateDataPropertyOrThrow(options, "roundingPriority", "lessPrecision").
+        MUST(options->create_data_property_or_throw(vm.names.roundingPriority, js_string(vm, "lessPrecision"sv)));
+        break;
+    // 9. Else,
+    default:
+        // a. Perform ! CreateDataPropertyOrThrow(options, "roundingPriority", "auto").
+        MUST(options->create_data_property_or_throw(vm.names.roundingPriority, js_string(vm, "auto"sv)));
+        break;
+    }
+
+    // 10. Return options.
     return options;
 }
 

Userland/Libraries/LibJS/Tests/builtins/Intl/PluralRules/PluralRules.js

@@ -116,6 +116,15 @@ describe("errors", () => {
             new Intl.PluralRules("en", { maximumSignificantDigits: 22 });
         }).toThrowWithMessage(RangeError, "Value 22 is NaN or is not between 1 and 21");
     });
+
+    test("roundingPriority option is invalid", () => {
+        expect(() => {
+            new Intl.PluralRules("en", { roundingPriority: "hello!" });
+        }).toThrowWithMessage(
+            RangeError,
+            "hello! is not a valid value for option roundingPriority"
+        );
+    });
 });
 
 describe("normal behavior", () => {
@@ -178,4 +187,12 @@ describe("normal behavior", () => {
             }).not.toThrow();
         }
     });
+
+    test("all valid roundingPriority options", () => {
+        ["auto", "morePrecision", "lessPrecision"].forEach(roundingPriority => {
+            expect(() => {
+                new Intl.PluralRules("en", { roundingPriority: roundingPriority });
+            }).not.toThrow();
+        });
+    });
 });

Userland/Libraries/LibJS/Tests/builtins/Intl/PluralRules/PluralRules.prototype.resolvedOptions.js

@@ -104,4 +104,14 @@ describe("correct behavior", () => {
         expect(gaOrdinal.pluralCategories).toBeDefined();
         expect(contains(gaOrdinal.pluralCategories, ["other", "one"])).toBeTrue();
     });
+
+    test("rounding priority", () => {
+        const en1 = new Intl.PluralRules("en");
+        expect(en1.resolvedOptions().roundingPriority).toBe("auto");
+
+        ["auto", "morePrecision", "lessPrecision"].forEach(roundingPriority => {
+            const en2 = new Intl.PluralRules("en", { roundingPriority: roundingPriority });
+            expect(en2.resolvedOptions().roundingPriority).toBe(roundingPriority);
+        });
+    });
 });