feat: improve error displayed for malformed plist (#3487)

packages/shorebird_cli/lib/src/platform/apple/plist.dart

@@ -1,18 +1,39 @@
-// cspell:words propertylistserialization xcarchives
+// cspell:words propertylistserialization xcarchives plutil
 
 import 'dart:io';
 
 import 'package:propertylistserialization/propertylistserialization.dart';
 
+/// Exception thrown when a plist file cannot be parsed.
+class PlistParseException implements Exception {
+  /// Creates a new [PlistParseException].
+  const PlistParseException({required this.filePath, required this.cause});
+
+  /// The path to the plist file that failed to parse.
+  final String filePath;
+
+  /// The underlying exception that caused the parse failure.
+  final Exception cause;
+
+  @override
+  String toString() =>
+      'Failed to parse $filePath: $cause\n'
+      'Verify the plist is valid by running: plutil -lint $filePath';
+}
+
 /// A representation of an Info.plist file.
 class Plist {
   /// Creates a new [Plist] from the contents of the provided [file].
   Plist({required File file}) {
-    properties =
-        PropertyListSerialization.propertyListWithString(
-              file.readAsStringSync(),
-            )
-            as Map<String, Object>;
+    try {
+      properties =
+          PropertyListSerialization.propertyListWithString(
+                file.readAsStringSync(),
+              )
+              as Map<String, Object>;
+    } on PropertyListReadStreamException catch (e) {
+      throw PlistParseException(filePath: file.path, cause: e);
+    }
   }
 
   /// This key is a user-visible string for the version of the bundle. The

packages/shorebird_cli/test/src/platform/apple/plist_test.dart

@@ -0,0 +1,108 @@
+// cspell:words plutil
+import 'dart:io';
+
+import 'package:path/path.dart' as p;
+import 'package:shorebird_cli/src/platform/apple/plist.dart';
+import 'package:test/test.dart';
+
+void main() {
+  group('Plist', () {
+    late Directory tempDir;
+
+    setUp(() {
+      tempDir = Directory.systemTemp.createTempSync('plist_test_');
+    });
+
+    tearDown(() {
+      tempDir.deleteSync(recursive: true);
+    });
+
+    group('constructor', () {
+      test('throws PlistParseException when plist is malformed', () {
+        final file = File(p.join(tempDir.path, 'Info.plist'))
+          ..writeAsStringSync('not valid plist xml');
+
+        expect(
+          () => Plist(file: file),
+          throwsA(
+            isA<PlistParseException>()
+                .having(
+                  (e) => e.filePath,
+                  'filePath',
+                  file.path,
+                )
+                .having(
+                  (e) => e.toString(),
+                  'toString',
+                  allOf(
+                    contains('Failed to parse'),
+                    contains('plutil -lint'),
+                  ),
+                ),
+          ),
+        );
+      });
+    });
+
+    group('versionNumber', () {
+      test('returns version from standard plist', () {
+        final file = File(p.join(tempDir.path, 'Info.plist'))
+          ..writeAsStringSync('''
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>CFBundleShortVersionString</key>
+	<string>1.2.3</string>
+	<key>CFBundleVersion</key>
+	<string>4</string>
+</dict>
+</plist>
+''');
+
+        expect(Plist(file: file).versionNumber, equals('1.2.3+4'));
+      });
+
+      test('returns version without build number when not present', () {
+        final file = File(p.join(tempDir.path, 'Info.plist'))
+          ..writeAsStringSync('''
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>CFBundleShortVersionString</key>
+	<string>1.0.0</string>
+</dict>
+</plist>
+''');
+
+        expect(Plist(file: file).versionNumber, equals('1.0.0'));
+      });
+
+      test('throws when release version is missing', () {
+        final file = File(p.join(tempDir.path, 'Info.plist'))
+          ..writeAsStringSync('''
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>CFBundleVersion</key>
+	<string>1</string>
+</dict>
+</plist>
+''');
+
+        expect(
+          () => Plist(file: file).versionNumber,
+          throwsA(
+            isA<Exception>().having(
+              (e) => e.toString(),
+              'message',
+              contains('Could not determine release version'),
+            ),
+          ),
+        );
+      });
+    });
+  });
+}