Add custom function support to predicates and sort descriptors

Sources/CoreDataModel/FunctionEvaluation.swift

@@ -0,0 +1,302 @@
+//
+//  FunctionEvaluation.swift
+//  CoreDataModel
+//
+//  Created by Alsey Coleman Miller on 7/16/26.
+//
+
+#if canImport(CoreData)
+import Foundation
+import CoreModel
+
+// MARK: - Function detection
+
+internal extension FetchRequest {
+
+    /// Whether this fetch request references any custom `.function` expression and
+    /// therefore requires in-memory evaluation — CoreData cannot execute a custom
+    /// function as part of a native fetch.
+    var requiresInMemoryEvaluation: Bool {
+        if predicate?.containsFunction == true {
+            return true
+        }
+        return sortDescriptors.contains { descriptor in
+            if case .function = descriptor.term { return true } else { return false }
+        }
+    }
+}
+
+internal extension FetchRequest.Predicate {
+
+    /// Whether this predicate references any `.function` expression.
+    var containsFunction: Bool {
+        switch self {
+        case .value:
+            return false
+        case let .comparison(comparison):
+            return comparison.left.containsFunction || comparison.right.containsFunction
+        case let .compound(compound):
+            return compound.subpredicates.contains { $0.containsFunction }
+        }
+    }
+
+    /// Replace every comparison that references a function with `.value(true)`, so the
+    /// remaining predicate can be evaluated natively by CoreData as a superset filter.
+    /// The full predicate is then re-applied in memory.
+    func strippingFunctionComparisons() -> FetchRequest.Predicate {
+        switch self {
+        case .value:
+            return self
+        case let .comparison(comparison):
+            let usesFunction = comparison.left.containsFunction || comparison.right.containsFunction
+            return usesFunction ? .value(true) : self
+        case let .compound(compound):
+            switch compound {
+            case let .and(subpredicates):
+                return .compound(.and(subpredicates.map { $0.strippingFunctionComparisons() }))
+            case let .or(subpredicates):
+                return .compound(.or(subpredicates.map { $0.strippingFunctionComparisons() }))
+            case let .not(subpredicate):
+                return .compound(.not(subpredicate.strippingFunctionComparisons()))
+            }
+        }
+    }
+}
+
+internal extension FetchRequest.Predicate.Expression {
+
+    var containsFunction: Bool {
+        switch self {
+        case .function:
+            return true
+        case .attribute, .relationship, .keyPath:
+            return false
+        }
+    }
+}
+
+// MARK: - In-memory evaluation
+
+internal extension FetchRequest.Predicate {
+
+    /// Evaluate this predicate against a fetched object in memory, calling registered
+    /// functions for any `.function` expression.
+    func evaluate(
+        with data: ModelData,
+        functions: [String: DatabaseFunction]
+    ) -> Bool {
+        switch self {
+        case let .value(value):
+            return value
+        case let .compound(compound):
+            switch compound {
+            case let .and(subpredicates):
+                return subpredicates.allSatisfy { $0.evaluate(with: data, functions: functions) }
+            case let .or(subpredicates):
+                return subpredicates.contains { $0.evaluate(with: data, functions: functions) }
+            case let .not(subpredicate):
+                return subpredicate.evaluate(with: data, functions: functions) == false
+            }
+        case let .comparison(comparison):
+            return comparison.evaluate(with: data, functions: functions)
+        }
+    }
+}
+
+internal extension FetchRequest.Predicate.Comparison {
+
+    func evaluate(
+        with data: ModelData,
+        functions: [String: DatabaseFunction]
+    ) -> Bool {
+        let lhs = left.evaluate(with: data, functions: functions)
+        let rhs = right.evaluate(with: data, functions: functions)
+        return type.evaluate(lhs, rhs, options: options)
+    }
+}
+
+internal extension FetchRequest.Predicate.Expression {
+
+    /// Resolve this expression to a value for a fetched object.
+    func evaluate(
+        with data: ModelData,
+        functions: [String: DatabaseFunction]
+    ) -> AttributeValue? {
+        switch self {
+        case let .attribute(value):
+            return value
+        case let .keyPath(keyPath):
+            return data.attributes[PropertyKey(rawValue: keyPath.rawValue)]
+        case let .function(function):
+            guard let registered = functions[function.name] else {
+                return nil
+            }
+            let arguments = function.arguments.map { $0.evaluate(with: data, functions: functions) }
+            return registered.evaluate(arguments)
+        case .relationship:
+            // relationships aren't compared by the in-memory function path
+            return nil
+        }
+    }
+}
+
+// MARK: - Operator evaluation
+
+private extension FetchRequest.Predicate.Comparison.Operator {
+
+    func evaluate(
+        _ lhs: AttributeValue?,
+        _ rhs: AttributeValue?,
+        options: Set<FetchRequest.Predicate.Comparison.Option>
+    ) -> Bool {
+        let caseInsensitive = options.contains(.caseInsensitive)
+        switch self {
+        case .equalTo:
+            return AttributeValue.areEqual(lhs, rhs, caseInsensitive: caseInsensitive)
+        case .notEqualTo:
+            return AttributeValue.areEqual(lhs, rhs, caseInsensitive: caseInsensitive) == false
+        case .lessThan:
+            return (AttributeValue.order(lhs, rhs)).map { $0 < 0 } ?? false
+        case .lessThanOrEqualTo:
+            return (AttributeValue.order(lhs, rhs)).map { $0 <= 0 } ?? false
+        case .greaterThan:
+            return (AttributeValue.order(lhs, rhs)).map { $0 > 0 } ?? false
+        case .greaterThanOrEqualTo:
+            return (AttributeValue.order(lhs, rhs)).map { $0 >= 0 } ?? false
+        case .beginsWith:
+            return AttributeValue.stringCompare(lhs, rhs, caseInsensitive: caseInsensitive) { $0.hasPrefix($1) }
+        case .endsWith:
+            return AttributeValue.stringCompare(lhs, rhs, caseInsensitive: caseInsensitive) { $0.hasSuffix($1) }
+        case .contains:
+            return AttributeValue.stringCompare(lhs, rhs, caseInsensitive: caseInsensitive) { $0.contains($1) }
+        case .like, .matches:
+            return AttributeValue.stringCompare(lhs, rhs, caseInsensitive: caseInsensitive) { subject, pattern in
+                subject.range(of: like(pattern: pattern, matches: self == .matches), options: .regularExpression) != nil
+            }
+        case .in, .between:
+            // right-hand collections aren't represented as a single AttributeValue
+            return false
+        }
+    }
+
+    /// Convert a Cocoa-style `LIKE` pattern (`*`, `?`) or a full regular expression into
+    /// an anchored regular expression string.
+    private func like(pattern: String, matches: Bool) -> String {
+        guard matches == false else {
+            return pattern // already a regular expression
+        }
+        let escaped = NSRegularExpression.escapedPattern(for: pattern)
+            .replacingOccurrences(of: "\\*", with: ".*")
+            .replacingOccurrences(of: "\\?", with: ".")
+        return "^" + escaped + "$"
+    }
+}
+
+private extension AttributeValue {
+
+    /// A numeric representation for comparable value types, for ordering comparisons.
+    var comparableDouble: Double? {
+        switch self {
+        case let .bool(value):      return value ? 1 : 0
+        case let .int16(value):     return Double(value)
+        case let .int32(value):     return Double(value)
+        case let .int64(value):     return Double(value)
+        case let .float(value):     return Double(value)
+        case let .double(value):    return value
+        case let .decimal(value):   return NSDecimalNumber(decimal: value).doubleValue
+        case let .date(value):      return value.timeIntervalSinceReferenceDate
+        default:                    return nil
+        }
+    }
+
+    var stringValue: String? {
+        if case let .string(value) = self { return value }
+        return nil
+    }
+
+    static func areEqual(_ lhs: AttributeValue?, _ rhs: AttributeValue?, caseInsensitive: Bool) -> Bool {
+        switch (lhs, rhs) {
+        case (.none, .none), (.some(.null), .none), (.none, .some(.null)), (.some(.null), .some(.null)):
+            return true
+        case let (.some(left), .some(right)):
+            if caseInsensitive, let l = left.stringValue, let r = right.stringValue {
+                return l.caseInsensitiveCompare(r) == .orderedSame
+            }
+            return left == right
+        default:
+            return false
+        }
+    }
+
+    /// Ordering of two values: negative if `lhs < rhs`, zero if equal, positive if greater;
+    /// `nil` if the values aren't order-comparable.
+    static func order(_ lhs: AttributeValue?, _ rhs: AttributeValue?) -> Int? {
+        guard let lhs, let rhs else { return nil }
+        if let l = lhs.comparableDouble, let r = rhs.comparableDouble {
+            if l < r { return -1 }
+            if l > r { return 1 }
+            return 0
+        }
+        if let l = lhs.stringValue, let r = rhs.stringValue {
+            switch l.compare(r) {
+            case .orderedAscending:  return -1
+            case .orderedSame:       return 0
+            case .orderedDescending: return 1
+            }
+        }
+        return nil
+    }
+
+    static func stringCompare(
+        _ lhs: AttributeValue?,
+        _ rhs: AttributeValue?,
+        caseInsensitive: Bool,
+        _ compare: (String, String) -> Bool
+    ) -> Bool {
+        guard var subject = lhs?.stringValue, var pattern = rhs?.stringValue else {
+            return false
+        }
+        if caseInsensitive {
+            subject = subject.lowercased()
+            pattern = pattern.lowercased()
+        }
+        return compare(subject, pattern)
+    }
+}
+
+// MARK: - In-memory sorting
+
+internal extension Array where Element == ModelData {
+
+    /// Sort in memory by the given descriptors, resolving function terms with the
+    /// registered functions. Property terms fall back to attribute ordering.
+    func sortedInMemory(
+        by sortDescriptors: [FetchRequest.SortDescriptor],
+        functions: [String: DatabaseFunction]
+    ) -> [ModelData] {
+        guard sortDescriptors.isEmpty == false else { return self }
+        return sorted { first, second in
+            for descriptor in sortDescriptors {
+                let lhs: AttributeValue?
+                let rhs: AttributeValue?
+                switch descriptor.term {
+                case let .property(property):
+                    lhs = first.attributes[property]
+                    rhs = second.attributes[property]
+                case let .function(function):
+                    let expression = FetchRequest.Predicate.Expression.function(function)
+                    lhs = expression.evaluate(with: first, functions: functions)
+                    rhs = expression.evaluate(with: second, functions: functions)
+                }
+                guard let comparison = AttributeValue.order(lhs, rhs), comparison != 0 else {
+                    continue
+                }
+                return descriptor.ascending ? comparison < 0 : comparison > 0
+            }
+            // stable tiebreaker on id, matching the native fetch's trailing id sort
+            return first.id.rawValue < second.id.rawValue
+        }
+    }
+}
+
+#endif

Sources/CoreDataModel/NSFetchRequest.swift

@@ -22,8 +22,13 @@ public extension FetchRequest {
         let fetchRequest = NSFetchRequest<ResultType>(entityName: entity.rawValue)
         fetchRequest.predicate = predicate?.toFoundation()
         fetchRequest.fetchLimit = fetchLimit
-        var sortDescriptors = sortDescriptors.map {
-            NSSortDescriptor(key: $0.property.rawValue, ascending: $0.ascending)
+        var sortDescriptors = sortDescriptors.compactMap { sort -> NSSortDescriptor? in
+            guard let property = sort.property else {
+                // Function-based sort terms are not supported by NSFetchRequest;
+                // they require in-memory evaluation, not yet implemented.
+                return nil
+            }
+            return NSSortDescriptor(key: property.rawValue, ascending: sort.ascending)
         }
         sortDescriptors.append(NSSortDescriptor(key: NSManagedObject.BuiltInProperty.id.rawValue, ascending: true))
         fetchRequest.sortDescriptors = sortDescriptors