Add helpers to create errors in ObjC/Swift

extension/apple/ExecuTorch/Exported/ExecuTorchError.h

@@ -12,4 +12,57 @@ NS_ASSUME_NONNULL_BEGIN
 
 FOUNDATION_EXPORT NSErrorDomain const ExecuTorchErrorDomain NS_SWIFT_NAME(ErrorDomain);
 
+/**
+ * Enum to define the error codes.
+ * Values can be a subset, but must numerically match exactly those defined in
+ * runtime/core/error.h
+ */
+typedef NS_ERROR_ENUM(ExecuTorchErrorDomain, ExecuTorchErrorCode) {
+  // System errors.
+  ExecuTorchErrorCodeOk                             = 0,
+  ExecuTorchErrorCodeInternal                       = 1,
+  ExecuTorchErrorCodeInvalidState                   = 2,
+  ExecuTorchErrorCodeEndOfMethod                    = 3,
+
+  // Logical errors.
+  ExecuTorchErrorCodeNotSupported                   = 16,
+  ExecuTorchErrorCodeNotImplemented                 = 17,
+  ExecuTorchErrorCodeInvalidArgument                = 18,
+  ExecuTorchErrorCodeInvalidType                    = 19,
+  ExecuTorchErrorCodeOperatorMissing                = 20,
+
+  // Resource errors.
+  ExecuTorchErrorCodeNotFound                       = 32,
+  ExecuTorchErrorCodeMemoryAllocationFailed         = 33,
+  ExecuTorchErrorCodeAccessFailed                   = 34,
+  ExecuTorchErrorCodeInvalidProgram                 = 35,
+  ExecuTorchErrorCodeInvalidExternalData            = 36,
+  ExecuTorchErrorCodeOutOfResources                 = 37,
+
+  // Delegate errors.
+  ExecuTorchErrorCodeDelegateInvalidCompatibility   = 48,
+  ExecuTorchErrorCodeDelegateMemoryAllocationFailed = 49,
+  ExecuTorchErrorCodeDelegateInvalidHandle          = 50,
+} NS_SWIFT_NAME(ErrorCode);
+
+/**
+ * Returns a brief error description for the given error code.
+ *
+ * @param code An ExecuTorchErrorCode value representing the error code.
+ * @return An NSString containing the error description.
+ */
+FOUNDATION_EXPORT
+__attribute__((deprecated("This API is experimental.")))
+NSString *ExecuTorchErrorDescription(ExecuTorchErrorCode code)
+    NS_SWIFT_NAME(ErrorDescription(_:));
+
+/**
+ * Create an NSError in the ExecuTorch domain for the given code.
+ *
+ * @param code The ExecuTorchErrorCode to wrap.
+ * @return An NSError with ExecuTorchErrorDomain, the specified code, and a localized description.
+ */
+FOUNDATION_EXPORT NSError *ExecuTorchErrorWithCode(ExecuTorchErrorCode code)
+    NS_SWIFT_NAME(Error(code:));
+
 NS_ASSUME_NONNULL_END

extension/apple/ExecuTorch/Exported/ExecuTorchError.m

@@ -9,3 +9,54 @@
 #import "ExecuTorchError.h"
 
 NSErrorDomain const ExecuTorchErrorDomain = @"org.pytorch.executorch.error";
+
+NSString *ExecuTorchErrorDescription(ExecuTorchErrorCode code) {
+  switch (code) {
+    case ExecuTorchErrorCodeOk:
+      return @"";
+    case ExecuTorchErrorCodeInternal:
+      return @"Internal error";
+    case ExecuTorchErrorCodeInvalidState:
+      return @"Invalid executor state";
+    case ExecuTorchErrorCodeEndOfMethod:
+      return @"No more execution steps";
+    case ExecuTorchErrorCodeNotSupported:
+      return @"Operation not supported";
+    case ExecuTorchErrorCodeNotImplemented:
+      return @"Operation not implemented";
+    case ExecuTorchErrorCodeInvalidArgument:
+      return @"Invalid argument";
+    case ExecuTorchErrorCodeInvalidType:
+      return @"Invalid type";
+    case ExecuTorchErrorCodeOperatorMissing:
+      return @"Operator missing";
+    case ExecuTorchErrorCodeNotFound:
+      return @"Resource not found";
+    case ExecuTorchErrorCodeMemoryAllocationFailed:
+      return @"Memory allocation failed";
+    case ExecuTorchErrorCodeAccessFailed:
+      return @"Access failed";
+    case ExecuTorchErrorCodeInvalidProgram:
+      return @"Invalid program contents";
+    case ExecuTorchErrorCodeInvalidExternalData:
+      return @"Invalid external data";
+    case ExecuTorchErrorCodeOutOfResources:
+      return @"Out of resources";
+    case ExecuTorchErrorCodeDelegateInvalidCompatibility:
+      return @"Delegate version incompatible";
+    case ExecuTorchErrorCodeDelegateMemoryAllocationFailed:
+      return @"Delegate memory allocation failed";
+    case ExecuTorchErrorCodeDelegateInvalidHandle:
+      return @"Delegate handle invalid";
+    default:
+      return @"Unknown error";
+  }
+}
+
+NSError *ExecuTorchErrorWithCode(ExecuTorchErrorCode code) {
+  return [NSError errorWithDomain:ExecuTorchErrorDomain
+                             code:code
+                         userInfo:@{
+                           NSLocalizedDescriptionKey : ExecuTorchErrorDescription(code)
+                         }];
+}

extension/apple/ExecuTorch/Exported/ExecuTorchModule.mm

@@ -87,9 +87,7 @@ - (BOOL)loadWithVerification:(ExecuTorchVerification)verification
   const auto errorCode = _module->load(static_cast<Program::Verification>(verification));
   if (errorCode != Error::Ok) {
     if (error) {
-      *error = [NSError errorWithDomain:ExecuTorchErrorDomain
-                                   code:(NSInteger)errorCode
-                               userInfo:nil];
+      *error = ExecuTorchErrorWithCode((ExecuTorchErrorCode)errorCode);
     }
     return NO;
   }
@@ -110,9 +108,7 @@ - (BOOL)loadMethod:(NSString *)methodName
   const auto errorCode = _module->load_method(methodName.UTF8String);
   if (errorCode != Error::Ok) {
     if (error) {
-      *error = [NSError errorWithDomain:ExecuTorchErrorDomain
-                                   code:(NSInteger)errorCode
-                               userInfo:nil];
+      *error = ExecuTorchErrorWithCode((ExecuTorchErrorCode)errorCode);
     }
     return NO;
   }
@@ -127,9 +123,7 @@ - (BOOL)isMethodLoaded:(NSString *)methodName {
   const auto result = _module->method_names();
   if (!result.ok()) {
     if (error) {
-      *error = [NSError errorWithDomain:ExecuTorchErrorDomain
-                                   code:(NSInteger)result.error()
-                               userInfo:nil];
+      *error = ExecuTorchErrorWithCode((ExecuTorchErrorCode)result.error());
     }
     return nil;
   }
@@ -151,9 +145,7 @@ - (BOOL)isMethodLoaded:(NSString *)methodName {
   const auto result = _module->execute(methodName.UTF8String, inputs);
   if (!result.ok()) {
     if (error) {
-      *error = [NSError errorWithDomain:ExecuTorchErrorDomain
-                                   code:(NSInteger)result.error()
-                               userInfo:nil];
+      *error = ExecuTorchErrorWithCode((ExecuTorchErrorCode)result.error());
     }
     return nil;
   }

extension/apple/ExecuTorch/Exported/ExecuTorchTensor.mm

@@ -112,14 +112,10 @@ - (void)mutableBytesWithHandler:(void (^)(void *pointer, NSInteger count, ExecuT
 
 - (BOOL)resizeToShape:(NSArray<NSNumber *> *)shape
                 error:(NSError **)error {
-  const auto resizeError = resize_tensor_ptr(
-    _tensor, utils::toVector<SizesType>(shape)
-  );
-  if (resizeError != Error::Ok) {
+  const auto errorCode = resize_tensor_ptr(_tensor, utils::toVector<SizesType>(shape));
+  if (errorCode != Error::Ok) {
     if (error) {
-      *error = [NSError errorWithDomain:ExecuTorchErrorDomain
-                                   code:(NSInteger)resizeError
-                               userInfo:nil];
+      *error = ExecuTorchErrorWithCode((ExecuTorchErrorCode)errorCode);
     }
     return NO;
   }