fix: make BuildOperationMetrics fields tolerant of missing keys

Xcode projects using `betaFeature_enableExplicitModules` produce
xcactivitylog files where BuildOperationMetrics may not contain all
expected keys (e.g. clangCacheHits). This causes a DecodingError
when parsing these logs.

Add a custom Decodable initializer that uses decodeIfPresent with
a default of 0 for each field, so parsing succeeds even when keys
are absent.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Signed-off-by: fortmarek <marekfort@me.com>

Author: fortmarek

Sources/XCLogParser/activityparser/IDEActivityModel.swift

@@ -780,15 +780,23 @@ public class IDEActivityLogSectionAttachment: Encodable {
         public let swiftCacheMisses: Int
 
         public init(
-            clangCacheHits: Int,
-            clangCacheMisses: Int,
-            swiftCacheHits: Int,
-            swiftCacheMisses: Int
+            clangCacheHits: Int = 0,
+            clangCacheMisses: Int = 0,
+            swiftCacheHits: Int = 0,
+            swiftCacheMisses: Int = 0
         ) {
             self.clangCacheHits = clangCacheHits
             self.clangCacheMisses = clangCacheMisses
             self.swiftCacheHits = swiftCacheHits
             self.swiftCacheMisses = swiftCacheMisses
         }
+
+        public init(from decoder: Decoder) throws {
+            let container = try decoder.container(keyedBy: CodingKeys.self)
+            clangCacheHits = try container.decodeIfPresent(Int.self, forKey: .clangCacheHits) ?? 0
+            clangCacheMisses = try container.decodeIfPresent(Int.self, forKey: .clangCacheMisses) ?? 0
+            swiftCacheHits = try container.decodeIfPresent(Int.self, forKey: .swiftCacheHits) ?? 0
+            swiftCacheMisses = try container.decodeIfPresent(Int.self, forKey: .swiftCacheMisses) ?? 0
+        }
     }
 }

Tests/XCLogParserTests/ActivityParserTests.swift

@@ -562,4 +562,30 @@ class ActivityParserTests: XCTestCase {
         XCTAssertEqual(expectedDVTMemberDocumentLocation, documentMemberLocation)
     }
 
+    func testBuildOperationMetricsWithMissingKeys() throws {
+        let json = #"{}"#
+        let data = json.data(using: .utf8)!
+        let metrics = try JSONDecoder().decode(
+            IDEActivityLogSectionAttachment.BuildOperationMetrics.self,
+            from: data
+        )
+        XCTAssertEqual(metrics.clangCacheHits, 0)
+        XCTAssertEqual(metrics.clangCacheMisses, 0)
+        XCTAssertEqual(metrics.swiftCacheHits, 0)
+        XCTAssertEqual(metrics.swiftCacheMisses, 0)
+    }
+
+    func testBuildOperationMetricsWithPartialKeys() throws {
+        let json = #"{"swiftCacheHits":5,"swiftCacheMisses":3}"#
+        let data = json.data(using: .utf8)!
+        let metrics = try JSONDecoder().decode(
+            IDEActivityLogSectionAttachment.BuildOperationMetrics.self,
+            from: data
+        )
+        XCTAssertEqual(metrics.clangCacheHits, 0)
+        XCTAssertEqual(metrics.clangCacheMisses, 0)
+        XCTAssertEqual(metrics.swiftCacheHits, 5)
+        XCTAssertEqual(metrics.swiftCacheMisses, 3)
+    }
+
 }