Fixed: default currency fraction limits now matches NumberFormatter for .currency style, and correctness is confirmed by unit tests.

Author: oscbyspro

Sources/DiffableTextStylesXNumeric/Helpers/Lexicon.swift

@@ -51,10 +51,12 @@ extension Lexicon {
     // MARK: Initializers
     //=------------------------------------------------------------------------=
 
+    /// Requires that formatter.numberStyle == .decimal.
     @inlinable static func standard(_ formatter: NumberFormatter) -> Lexicon {
         Lexicon(signs: .standard(formatter), digits: .standard(formatter), separators: .standard(formatter))
     }
 
+    /// Requires that formatter.numberStyle == .decimal.
     @inlinable static func currency(_ formatter: NumberFormatter) -> Lexicon {
         Lexicon(signs: .currency(formatter), digits: .currency(formatter), separators: .currency(formatter))
     }

Sources/DiffableTextStylesXNumeric/Models/Scheme+Currency.swift

@@ -39,10 +39,17 @@ import Foundation
         // MARK: Instantiate
         //=--------------------------------------=
         self.identifier = identifier
-        self.defaults = .init(formatter)
+        //=--------------------------------------=
+        // MARK: Instantiate: Style == Decimal
+        //=--------------------------------------=
         self.lexicon = .currency(formatter)
-        self.label = .currency(identifier.locale,
+        self.label   = .currency(identifier.locale,
         code: identifier.code, lexicon: lexicon)
+        //=--------------------------------------=
+        // MARK: Instantiate: Style == Currency
+        //=--------------------------------------=
+        formatter.numberStyle = .currency
+        self.defaults = Defaults(formatter)
     }
 
     //=------------------------------------------------------------------------=

Sources/DiffableTextStylesXNumeric/Models/Scheme+Standard.swift

@@ -36,6 +36,9 @@ import Foundation
         // MARK: Instantiate
         //=--------------------------------------=
         self.identifier = identifier
+        //=--------------------------------------=
+        // MARK: Instantiate: Style == Decimal
+        //=--------------------------------------=
         self.lexicon = .standard(formatter)
     }
 

Tests/DiffableTextStylesXNumericTests/Styles/StyleTests+Currency.swift

@@ -26,6 +26,39 @@ final class StyleTestsXCurrency: Tests, StyleTests {
     func XCTInterpretLocalesXCurrencies<T: Values.Currencyable>(_ value: T) {
          XCTInterpretLocalesXCurrencies(value, format: T.FormatStyle.Currency.init)
     }
+    
+    func XCTAssertDefaultFractionLimitsIsSameAs(_ formatter: NumberFormatter) {
+        let style = NumericTextStyle<Decimal>.Currency(code: formatter.currencyCode, locale: formatter.locale)
+        let lhs = style.precision.lower.fraction  ... style.precision.upper.fraction
+        let rhs = formatter.minimumFractionDigits ... formatter.minimumFractionDigits
+        XCTAssertEqual(lhs, rhs)
+    }
+}
+
+//=----------------------------------------------------------------------------=
+// MARK: + Defaults
+//=----------------------------------------------------------------------------=
+
+extension StyleTestsXCurrency {
+    
+    //=------------------------------------------------------------------------=
+    // MARK: Tests
+    //=------------------------------------------------------------------------=
+    
+    func testDefaultFractionLimitsIsSameAsCurrencyFormatter() {
+        let formatter = NumberFormatter()
+        formatter.numberStyle = .currency
+        //=--------------------------------------=
+        // MARK: Locales, Currencies
+        //=--------------------------------------=
+        for locale in locales {
+            formatter.locale = locale
+            for currencyCode in currencyCodes {
+                formatter.currencyCode = currencyCode
+                XCTAssertDefaultFractionLimitsIsSameAs(formatter)
+            }
+        }
+    }
 }
 
 //=----------------------------------------------------------------------------=

Tests/DiffableTextStylesXNumericTests/Styles/StyleTests.swift

@@ -32,9 +32,10 @@ extension StyleTests {
         XCTAssertEqual(format.precision(.fractionLength(0...)).format(value), result)
     }
 
+    /// Fraction limits is set to max because a style's default precision depends on context.
     func XCTInterpret<F: Format>(_ value: F.Value, format: F, info: @autoclosure () -> Any) {
-        let commit = _NumericTextStyle(format).interpret(value)
         let characters = format.precision(.fractionLength(0...)).format(value)
+        let commit = _NumericTextStyle(format).precision(Precision(fraction: 0...)).interpret(value)
         XCTAssertEqual(commit.value, value, String(describing: info()))
         XCTAssertEqual(commit.snapshot.characters, characters, String(describing: info()))
     }