Merge "Add Utilities to trace flow values" into main

2 files changed, 39 insertions, 1 deletions

diff --git a/tracinglib/src/com/android/app/tracing/FlowTracing.kt b/tracinglib/src/com/android/app/tracing/FlowTracing.kt
new file mode 100644
index 0000000..d6fe63e
--- /dev/null
+++ b/tracinglib/src/com/android/app/tracing/FlowTracing.kt
@@ -0,0 +1,33 @@
+/*
+ * Copyright (C) 2023 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.android.app.tracing
+
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.onEach
+
+/** Utilities to trace Flows */
+object FlowTracing {
+
+    /** Logs each flow element to a trace. */
+    inline fun <T> Flow<T>.traceEach(
+            flowName: String,
+            logcat: Boolean = false,
+            crossinline valueToString: (T) -> String = { it.toString() }
+    ): Flow<T> {
+        val stateLogger = TraceStateLogger(flowName, logcat = logcat)
+        return onEach { stateLogger.log(valueToString(it)) }
+    }
+}
diff --git a/tracinglib/src/com/android/app/tracing/TraceStateLogger.kt b/tracinglib/src/com/android/app/tracing/TraceStateLogger.kt
index cca22e9..02c8737 100644
--- a/tracinglib/src/com/android/app/tracing/TraceStateLogger.kt
+++ b/tracinglib/src/com/android/app/tracing/TraceStateLogger.kt
@@ -17,6 +17,7 @@
 package com.android.app.tracing
 
 import android.os.Trace
+import android.util.Log
 
 /**
  * Utility class used to log state changes easily in a track with a custom name.
@@ -37,7 +38,8 @@ import android.os.Trace
 class TraceStateLogger(
     private val trackName: String,
     private val logOnlyIfDifferent: Boolean = true,
-    private val instantEvent: Boolean = true
+    private val instantEvent: Boolean = true,
+    private val logcat: Boolean = false,
 ) {
 
     private var previousValue: String? = null
@@ -50,6 +52,9 @@ class TraceStateLogger(
         if (logOnlyIfDifferent && previousValue == newValue) return
         Trace.asyncTraceForTrackEnd(Trace.TRACE_TAG_APP, trackName, 0)
         Trace.asyncTraceForTrackBegin(Trace.TRACE_TAG_APP, trackName, newValue, 0)
+        if (logcat) {
+            Log.d(trackName, "newValue: $newValue")
+        }
         previousValue = newValue
     }
 }