fix(shorebird_cli): ignore Mach-O UUID when checking for iOS patchability (#1783)

packages/shorebird_cli/lib/src/archive_analysis/ios_archive_differ.dart

@@ -1,5 +1,6 @@
 import 'dart:io';
 import 'dart:isolate';
+import 'dart:typed_data';
 
 import 'package:archive/archive_io.dart';
 import 'package:collection/collection.dart';
@@ -7,6 +8,7 @@ import 'package:crypto/crypto.dart';
 import 'package:path/path.dart' as p;
 import 'package:shorebird_cli/src/archive_analysis/archive_differ.dart';
 import 'package:shorebird_cli/src/archive_analysis/file_set_diff.dart';
+import 'package:shorebird_cli/src/archive_analysis/macho.dart';
 
 /// Finds differences between two IPAs or zipped Xcframeworks.
 ///
@@ -112,7 +114,14 @@ class IosArchiveDiffer extends ArchiveDiffer {
     }
 
     final outFile = File(outPath);
-    return _hash(outFile.readAsBytesSync());
+    final Uint8List bytes;
+    if (MachO.isMachOFile(outFile)) {
+      bytes = MachO.bytesWithZeroedUUID(outFile);
+    } else {
+      bytes = outFile.readAsBytesSync();
+    }
+
+    return _hash(bytes);
   }
 
   /// Uses assetutil to write a json description of a .car file to disk and

packages/shorebird_cli/lib/src/archive_analysis/macho.dart

@@ -0,0 +1,60 @@
+import 'dart:io';
+import 'dart:typed_data';
+
+const machOHeaderSize = 32;
+const uuidLoadCommandType = 0x1b;
+
+/// Utilities for interacting with Mach-O files.
+/// See https://en.wikipedia.org/wiki/Mach-O.
+class MachO {
+  /// Reads a 32-bit integer as a little-endian value from the provided bytes.
+  static int _readInt32(Uint8List bytes, int offset) {
+    return bytes[offset + 3] << 24 |
+        bytes[offset + 2] << 16 |
+        bytes[offset + 1] << 8 |
+        bytes[offset];
+  }
+
+  /// Returns `true` if the provided file is a Mach-O file.
+  static bool isMachOFile(File file) {
+    final bytes = file.readAsBytesSync();
+    final magic = _readInt32(bytes, 0);
+
+    // These are the magic numbers for Mach-O files.
+    // See https://en.wikipedia.org/wiki/Mach-O#Mach-O_header
+    return magic == 0xfeedface || magic == 0xfeedfacf;
+  }
+
+  /// Returns a copy of the provided Mach-O file with the UUID load command
+  /// zeroed out. This is necessary because the same code built in different
+  /// locations will generate Mach-O files with different UUIDs as the only
+  /// difference.
+  static Uint8List bytesWithZeroedUUID(File file) {
+    final bytes = file.readAsBytesSync();
+
+    // The number of load commands is a 32-bit int at offset 16. We could
+    // probably write a more robust MachO header parser, but this is all we need
+    // for now.
+    final numberOfLoadCommands = _readInt32(bytes, 16);
+
+    // The load commands are immediately after the header.
+    var offset = machOHeaderSize;
+    for (var i = 0; i < numberOfLoadCommands; i++) {
+      final commandType = _readInt32(bytes, offset);
+      final commandLength = _readInt32(bytes, offset + 4);
+
+      if (commandType == uuidLoadCommandType) {
+        // Zero out the UUID bytes.
+        final loadCommandStart = offset + 8;
+        for (var j = loadCommandStart; j < offset + commandLength; j++) {
+          bytes[j] = 0;
+        }
+        break;
+      }
+
+      offset += commandLength;
+    }
+
+    return bytes;
+  }
+}

packages/shorebird_cli/test/src/archive_analysis/ios_archive_differ_test.dart

@@ -9,15 +9,19 @@ void main() {
     xcarchiveFixturesBasePath,
     'base.xcarchive.zip',
   );
-  final changedAssetIpaPath = p.join(
+  final baseChangedUuidPath = p.join(
+    xcarchiveFixturesBasePath,
+    'base_changed_uuid.xcarchive.zip',
+  );
+  final changedAssetXcarchivePath = p.join(
     xcarchiveFixturesBasePath,
     'changed_asset.xcarchive.zip',
   );
-  final changedDartIpaPath = p.join(
+  final changedDartXcarchivePath = p.join(
     xcarchiveFixturesBasePath,
     'changed_dart.xcarchive.zip',
   );
-  final changedSwiftIpaPath = p.join(
+  final changedSwiftXcarchivePath = p.join(
     xcarchiveFixturesBasePath,
     'changed_swift.xcarchive.zip',
   );
@@ -72,10 +76,21 @@ void main() {
             );
           });
 
+          test('finds no differences when only Mach-O UUID differs', () async {
+            final fileSetDiff = await differ.changedFiles(
+              baseIpaPath,
+              baseChangedUuidPath,
+            );
+            expect(
+              fileSetDiff,
+              isEmpty,
+            );
+          });
+
           test('finds differences between two different xcarchives', () async {
             final fileSetDiff = await differ.changedFiles(
               baseIpaPath,
-              changedAssetIpaPath,
+              changedAssetXcarchivePath,
             );
             if (platform.isMacOS) {
               expect(
@@ -102,8 +117,10 @@ void main() {
 
         group('changedFiles', () {
           test('detects asset changes', () async {
-            final fileSetDiff =
-                await differ.changedFiles(baseIpaPath, changedAssetIpaPath);
+            final fileSetDiff = await differ.changedFiles(
+              baseIpaPath,
+              changedAssetXcarchivePath,
+            );
             expect(differ.assetsFileSetDiff(fileSetDiff), isNotEmpty);
             expect(
               differ.dartFileSetDiff(fileSetDiff),
@@ -113,16 +130,20 @@ void main() {
           });
 
           test('detects dart changes', () async {
-            final fileSetDiff =
-                await differ.changedFiles(baseIpaPath, changedDartIpaPath);
+            final fileSetDiff = await differ.changedFiles(
+              baseIpaPath,
+              changedDartXcarchivePath,
+            );
             expect(differ.assetsFileSetDiff(fileSetDiff), isEmpty);
             expect(differ.dartFileSetDiff(fileSetDiff), isNotEmpty);
             expect(differ.nativeFileSetDiff(fileSetDiff), isEmpty);
           });
 
           test('detects swift changes', () async {
-            final fileSetDiff =
-                await differ.changedFiles(baseIpaPath, changedSwiftIpaPath);
+            final fileSetDiff = await differ.changedFiles(
+              baseIpaPath,
+              changedSwiftXcarchivePath,
+            );
             expect(differ.assetsFileSetDiff(fileSetDiff), isEmpty);
             expect(differ.dartFileSetDiff(fileSetDiff), isEmpty);
             expect(differ.nativeFileSetDiff(fileSetDiff), isNotEmpty);
@@ -134,7 +155,7 @@ void main() {
               () async {
             final fileSetDiff = await differ.changedFiles(
               baseIpaPath,
-              changedAssetIpaPath,
+              changedAssetXcarchivePath,
             );
             expect(
               differ.containsPotentiallyBreakingAssetDiffs(fileSetDiff),
@@ -146,7 +167,7 @@ void main() {
               () async {
             final fileSetDiff = await differ.changedFiles(
               baseIpaPath,
-              changedDartIpaPath,
+              changedDartXcarchivePath,
             );
             expect(
               differ.containsPotentiallyBreakingAssetDiffs(fileSetDiff),
@@ -159,7 +180,7 @@ void main() {
           test('returns true if Swift files have been changed', () async {
             final fileSetDiff = await differ.changedFiles(
               baseIpaPath,
-              changedSwiftIpaPath,
+              changedSwiftXcarchivePath,
             );
             expect(
               differ.containsPotentiallyBreakingNativeDiffs(fileSetDiff),
@@ -170,7 +191,7 @@ void main() {
           test('returns false if Swift files have not been changed', () async {
             final fileSetDiff = await differ.changedFiles(
               baseIpaPath,
-              changedAssetIpaPath,
+              changedAssetXcarchivePath,
             );
             expect(
               differ.containsPotentiallyBreakingNativeDiffs(fileSetDiff),