[BuildOperation] Change the summary about the cache hit/miss metrics to combine all hits/misses

Separating by compiler is not that useful, this is intended for a high-level overview.
A couple of changes
* Report the combined cache hits/misses
* Report the summary as a diagnostic note to make it more visible

Author: akyrtzi

Sources/SWBBuildSystem/BuildOperation.swift

@@ -666,22 +666,24 @@ package final class BuildOperation: BuildSystemOperation {
         let aggregatedCounters = await adaptor.getAggregatedCounters()
         let aggregatedTaskCounters = await adaptor.getAggregatedTaskCounters()
         do {
-            let swiftCacheHits = aggregatedCounters[.swiftCacheHits, default: 0]
-            let swiftCacheMisses = aggregatedCounters[.swiftCacheMisses, default: 0]
-            let clangCacheHits = aggregatedCounters[.clangCacheHits, default: 0]
-            let clangCacheMisses = aggregatedCounters[.clangCacheMisses, default: 0]
-            if swiftCacheHits + swiftCacheMisses > 0 || clangCacheHits + clangCacheMisses > 0 {
-                adaptor.withActivity(ruleInfo: "CompilationCacheMetrics", executionDescription: "Report compilation cache metrics", signature: "compilation_cache_metrics", target: nil, parentActivity: nil) { activity in
+            let cacheHits: Int
+            let cacheMisses: Int
+            do {
+                let swiftCacheHits = aggregatedCounters[.swiftCacheHits, default: 0]
+                let swiftCacheMisses = aggregatedCounters[.swiftCacheMisses, default: 0]
+                let clangCacheHits = aggregatedCounters[.clangCacheHits, default: 0]
+                let clangCacheMisses = aggregatedCounters[.clangCacheMisses, default: 0]
+                cacheHits = swiftCacheHits + clangCacheHits
+                cacheMisses = swiftCacheMisses + clangCacheMisses
+            }
+            if cacheHits + cacheMisses > 0 {
+                let signature = ByteString(encodingAsUTF8: "compilation_cache_metrics")
+                adaptor.withActivity(ruleInfo: "CompilationCacheMetrics", executionDescription: "Report compilation cache metrics", signature: signature, target: nil, parentActivity: nil) { activity in
                     func getSummary(hits: Int, misses: Int) -> String {
                         let hitPercent = Int((Double(hits) / Double(hits + misses) * 100).rounded())
                         return "\(hits) hit\(hits == 1 ? "" : "s") (\(hitPercent)%), \(misses) miss\(misses == 1 ? "" : "es")"
                     }
-                    if swiftCacheHits + swiftCacheMisses > 0 {
-                        delegate.emit(data: ByteString(encodingAsUTF8: "Swift compiler: \(getSummary(hits: swiftCacheHits, misses: swiftCacheMisses))").bytes, for: activity, signature: "compilation_cache_metrics")
-                    }
-                    if clangCacheHits + clangCacheMisses > 0 {
-                        delegate.emit(data: ByteString(encodingAsUTF8: "Clang compiler: \(getSummary(hits: clangCacheHits, misses: clangCacheMisses))").bytes, for: activity, signature: "compilation_cache_metrics")
-                    }
+                    delegate.emit(diagnostic: Diagnostic(behavior: .note, location: .unknown, data: DiagnosticData(getSummary(hits: cacheHits, misses: cacheMisses))), for: activity, signature: signature)
                     return .succeeded
                 }
 

Tests/SWBBuildSystemTests/ClangCompilationCachingTests.swift

@@ -234,7 +234,7 @@ fileprivate struct ClangCompilationCachingTests: CoreBasedTests {
                 // Make sure scanning happens before compilation...
                 results.check(event: .taskHadEvent(scanTask, event: .completed), precedes: .taskHadEvent(compileTask, event: .started))
 
-                results.check(contains: .activityEmittedData(ruleInfo: "CompilationCacheMetrics", ByteString(encodingAsUTF8: "Clang compiler: 0 hits (0%), 1 miss").bytes))
+                results.checkNote("0 hits (0%), 1 miss")
                 results.checkCompileCacheMiss(compileTask)
                 results.checkNoDiagnostics()
             }
@@ -262,7 +262,7 @@ fileprivate struct ClangCompilationCachingTests: CoreBasedTests {
                     // Make sure scanning happens before compilation.
                     results.check(event: .taskHadEvent(scanTask, event: .completed), precedes: .taskHadEvent(compileTask, event: .started))
 
-                    results.check(contains: .activityEmittedData(ruleInfo: "CompilationCacheMetrics", ByteString(encodingAsUTF8: "Clang compiler: 1 hit (100%), 0 misses").bytes))
+                    results.checkNote("1 hit (100%), 0 misses")
                     results.checkCompileCacheHit(compileTask)
                 }
                 results.checkNoDiagnostics()

Tests/SWBBuildSystemTests/SwiftCompilationCachingTests.swift

@@ -109,7 +109,7 @@ fileprivate struct SwiftCompilationCachingTests: CoreBasedTests {
                     numCompile += tasks.count
                 }
 
-                results.check(contains: .activityEmittedData(ruleInfo: "CompilationCacheMetrics", ByteString(encodingAsUTF8: "Swift compiler: 0 hits (0%), 4 misses").bytes))
+                results.checkNote("0 hits (0%), 4 misses")
 
                 results.checkNoTask()
             }
@@ -121,7 +121,7 @@ fileprivate struct SwiftCompilationCachingTests: CoreBasedTests {
 
             tester.userInfo = rawUserInfo.withAdditionalEnvironment(environment: metricsEnv("two"))
             try await tester.checkBuild(runDestination: .anyiOSDevice, persistent: true) { results in
-                results.check(contains: .activityEmittedData(ruleInfo: "CompilationCacheMetrics", ByteString(encodingAsUTF8: "Swift compiler: 4 hits (100%), 0 misses").bytes))
+                results.checkNote("4 hits (100%), 0 misses")
             }
             #expect(try readMetrics("two").contains("\"swiftCacheHits\":\(numCompile),\"swiftCacheMisses\":0"))
         }