Fix modelSupport where prefix overlaps with different hardware chips (#326)

Before this change, the code was matching first prefix which could lead to selecting incorrect configuration.
For example, iPad 13,1 (A14) is prefix for iPad13,10, iPad13,11, iPad13,16, and iPad13,17 (M2).

Fixing this issue by using longest prefix match.

Tested with a unit test that covers all iPad / iPhone devices.

Author: a2they

Sources/WhisperKit/Core/Models.swift

@@ -254,12 +254,25 @@ public struct ModelSupportConfig: Codable {
 
     @available(macOS 13, iOS 16, watchOS 10, visionOS 1, *)
     public func modelSupport(for deviceIdentifier: String = WhisperKit.deviceName()) -> ModelSupport {
+        // Find the support with the longest matching identifier prefix
+        // i.e. `iPad13,16` should match exact `iPad13,16` instead of first prefix like `iPad13,1`
+        var bestMatch: (support: DeviceSupport, prefixLength: Int)? = nil
         for support in deviceSupports {
-            if support.identifiers.contains(where: { deviceIdentifier.hasPrefix($0) }) {
-                return support.models
+            for identifier in support.identifiers {
+                if deviceIdentifier.hasPrefix(identifier) {
+                    let matchLength = identifier.count
+                    if bestMatch == nil || matchLength > bestMatch!.prefixLength {
+                        bestMatch = (support, matchLength)
+                    }
+                }
             }
         }
 
+        if let match = bestMatch {
+            Logging.debug("Matched \(deviceIdentifier) to devices: \(match.support.identifiers)")
+            return match.support.models
+        }
+
         Logging.info("No device support found for \(deviceIdentifier), using default")
         return defaultSupport.models
     }

Tests/WhisperKitTests/UnitTests.swift

@@ -218,6 +218,78 @@ final class UnitTests: XCTestCase {
         }
     }
 
+    func testModelSupportForiOSDevices() throws {
+        let defaultDevicesList = [
+            // --- iPads ---
+            "iPad2,1", "iPad2,2", "iPad2,3", "iPad2,4", "iPad2,5", "iPad2,6", "iPad2,7",
+            "iPad3,1", "iPad3,2", "iPad3,3", "iPad3,4", "iPad3,5", "iPad3,6",
+            "iPad4,1", "iPad4,2", "iPad4,3", "iPad4,4", "iPad4,5", "iPad4,6", "iPad4,7", "iPad4,8", "iPad4,9",
+            "iPad5,1", "iPad5,2", "iPad5,3", "iPad5,4", "iPad6,11", "iPad6,12", "iPad6,3", "iPad6,4", "iPad6,7", "iPad6,8",
+            "iPad7,1", "iPad7,2", "iPad7,3", "iPad7,4", "iPad7,5", "iPad7,6", "iPad7,11", "iPad7,12",
+            "iPad8,1", "iPad8,2", "iPad8,3", "iPad8,4", "iPad8,5", "iPad8,6", "iPad8,7", "iPad8,8", "iPad8,9", "iPad8,10", "iPad8,11", "iPad8,12",
+            "iPad11,1", "iPad11,2", "iPad11,3", "iPad11,4", "iPad11,6", "iPad11,7",
+            "iPad12,1", "iPad12,2", // (should be A13 config, need new config)
+
+            // -- iPhones ---
+            "iPhone10,1", "iPhone10,2", "iPhone10,3", "iPhone10,4", "iPhone10,5", "iPhone10,6",
+            "iPhone4,1",
+            "iPhone5,1", "iPhone5,2", "iPhone5,3", "iPhone5,4",
+            "iPhone6,1", "iPhone6,2",
+            "iPhone7,1", "iPhone7,2",
+            "iPhone8,1", "iPhone8,2", "iPhone8,4",
+            "iPhone9,1", "iPhone9,2", "iPhone9,3", "iPhone9,4"
+        ]
+
+        let deviceMap = [
+            "A12": ["iPhone11,2", "iPhone11,4", "iPhone11,6", "iPhone11,8"],
+            "A13": ["iPhone12,1", "iPhone12,3", "iPhone12,5", "iPhone12,8"],
+            "A14": ["iPad13,1", "iPad13,18", "iPad13,19", "iPad13,2", "iPhone13,1", "iPhone13,2", "iPhone13,3", "iPhone13,4"],
+            "A15": ["iPad14,1", "iPad14,2", "iPhone14,2", "iPhone14,3", "iPhone14,4", "iPhone14,5", "iPhone14,6", "iPhone14,7", "iPhone14,8"],
+            "A16": ["iPhone15,2", "iPhone15,3", "iPhone15,4", "iPhone15,5"],
+            "A17": ["iPhone16,1", "iPhone16,2"],
+            "A18": ["iPhone17,1", "iPhone17,2", "iPhone17,3", "iPhone17,4"],
+            "M1": ["iPad13,10", "iPad13,11", "iPad13,16", "iPad13,17", "iPad13,4", "iPad13,5", "iPad13,6", "iPad13,7", "iPad13,8", "iPad13,9"],
+            "M2": ["iPad14,3", "iPad14,4", "iPad14,5", "iPad14,6", "iPad14,10", "iPad14,11", "iPad14,8", "iPad14,9"],
+            "A17 Pro": ["iPad16,1", "iPad16,2"],
+            "M4": ["iPad16,3", "iPad16,4", "iPad16,5", "iPad16,6"]
+        ]
+
+        let configFilePath = try XCTUnwrap(
+            Bundle.current(for: self).path(forResource: "config-v03", ofType: "json"),
+            "Config file not found"
+        )
+
+        let jsonData = try Data(contentsOf: URL(fileURLWithPath: configFilePath))
+        let decoder = JSONDecoder()
+        let loadedConfig = try decoder.decode(ModelSupportConfig.self, from: jsonData)
+
+        func supportedModels(chip: String) -> ModelSupport {
+            var supportedModels = loadedConfig.defaultSupport.models
+            for deviceSupport in loadedConfig.deviceSupports {
+                if let chips = deviceSupport.chips, chips.contains(chip) {
+                    supportedModels = deviceSupport.models
+                    break
+                }
+            }
+            return supportedModels
+        }
+
+        for device in deviceMap {
+            let supportedModelsForChip = supportedModels(chip: device.key)
+            for deviceIdentifier in device.value {
+                let modelSupport = modelSupport(for: deviceIdentifier, from: loadedConfig)
+                XCTAssertEqual(modelSupport, supportedModelsForChip, "Device: \(deviceIdentifier) (\(device.key))")
+            }
+        }
+
+        // Test devices that should use default configuration
+        let defaultModelSupport = loadedConfig.defaultSupport.models
+        for deviceIdentifier in defaultDevicesList {
+            let modelSupport = modelSupport(for: deviceIdentifier, from: loadedConfig)
+            XCTAssertEqual(modelSupport, defaultModelSupport, "Device: \(deviceIdentifier)")
+        }
+    }
+
     func testModelSupportConfigFetch() async throws {
         // Make sure remote repo config loads successfully from HF
         let modelRepoConfig = await WhisperKit.fetchModelSupportConfig()