dataconnect: FirebaseDataConnect.logLevel changed to MutableStateFlow

firebase-dataconnect/CHANGELOG.md

@@ -1,5 +1,8 @@
 # Unreleased
-
+* [changed] `FirebaseDataConnect.logLevel` type changed from `LogLevel` to
+  `MutableStateFlow<LogLevel>`. This enables apps to "collect" the flow to,
+  for example, update a UI component when the log level changes.
+  ([#6586](https://github.com/firebase/firebase-android-sdk/pull/6586))
 
 # 16.0.0-beta03
 * [changed] Requires Data Connect emulator version 1.6.1 or later for code generation.

firebase-dataconnect/api.txt

@@ -112,8 +112,7 @@ package com.google.firebase.dataconnect {
   public final class FirebaseDataConnectKt {
     method @NonNull public static com.google.firebase.dataconnect.FirebaseDataConnect getInstance(@NonNull com.google.firebase.dataconnect.FirebaseDataConnect.Companion, @NonNull com.google.firebase.FirebaseApp app, @NonNull com.google.firebase.dataconnect.ConnectorConfig config, @NonNull com.google.firebase.dataconnect.DataConnectSettings settings = com.google.firebase.dataconnect.DataConnectSettings());
     method @NonNull public static com.google.firebase.dataconnect.FirebaseDataConnect getInstance(@NonNull com.google.firebase.dataconnect.FirebaseDataConnect.Companion, @NonNull com.google.firebase.dataconnect.ConnectorConfig config, @NonNull com.google.firebase.dataconnect.DataConnectSettings settings = com.google.firebase.dataconnect.DataConnectSettings());
-    method @NonNull public static com.google.firebase.dataconnect.LogLevel getLogLevel(@NonNull com.google.firebase.dataconnect.FirebaseDataConnect.Companion);
-    method public static void setLogLevel(@NonNull com.google.firebase.dataconnect.FirebaseDataConnect.Companion, @NonNull com.google.firebase.dataconnect.LogLevel);
+    method @NonNull public static kotlinx.coroutines.flow.MutableStateFlow<com.google.firebase.dataconnect.LogLevel> getLogLevel(@NonNull com.google.firebase.dataconnect.FirebaseDataConnect.Companion);
   }
 
   @kotlinx.serialization.Serializable(with=LocalDateSerializer::class) public final class LocalDate {

firebase-dataconnect/src/main/kotlin/com/google/firebase/dataconnect/FirebaseDataConnect.kt

@@ -23,6 +23,7 @@ import com.google.firebase.app
 import com.google.firebase.dataconnect.core.FirebaseDataConnectFactory
 import com.google.firebase.dataconnect.core.LoggerGlobals
 import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.serialization.DeserializationStrategy
 import kotlinx.serialization.SerializationStrategy
 import kotlinx.serialization.modules.SerializersModule
@@ -381,8 +382,14 @@ public fun FirebaseDataConnect.Companion.getInstance(
 /**
  * The log level used by all [FirebaseDataConnect] instances.
  *
+ * As a [MutableStateFlow], the log level can be changed by assigning [MutableStateFlow.value].
+ * Also, the flow can be "collected" as a means of observing the log level, which may be useful in
+ * the case that a user interface shows a UI element, such as a checkbox, to represent whether debug
+ * logging is enabled.
+ *
  * The default log level is [LogLevel.WARN]. Setting this to [LogLevel.DEBUG] will enable debug
  * logging, which is especially useful when reporting issues to Google or investigating problems
  * yourself. Setting it to [LogLevel.NONE] will disable all logging.
  */
-public var FirebaseDataConnect.Companion.logLevel: LogLevel by LoggerGlobals::logLevel
+public val FirebaseDataConnect.Companion.logLevel: MutableStateFlow<LogLevel>
+  get() = LoggerGlobals.logLevel

firebase-dataconnect/src/main/kotlin/com/google/firebase/dataconnect/LogLevel.kt

@@ -30,5 +30,26 @@ public enum class LogLevel {
   WARN,
 
   /** Do not log anything. */
-  NONE,
+  NONE;
+
+  internal companion object {
+
+    /**
+     * Returns one of the two given log levels, the one that is "noisier" (i.e. that logs more).
+     *
+     * It can be useful to figure out which of two log levels are noisier on log level change, to
+     * emit a message about the log level change at the noisiest level.
+     */
+    fun noisiestOf(logLevel1: LogLevel, logLevel2: LogLevel): LogLevel =
+      when (logLevel1) {
+        DEBUG -> DEBUG
+        NONE -> logLevel2
+        WARN ->
+          when (logLevel2) {
+            DEBUG -> DEBUG
+            WARN -> WARN
+            NONE -> WARN
+          }
+      }
+  }
 }

firebase-dataconnect/src/main/kotlin/com/google/firebase/dataconnect/core/Logger.kt

@@ -20,8 +20,17 @@ import android.util.Log
 import com.google.firebase.dataconnect.BuildConfig
 import com.google.firebase.dataconnect.LogLevel
 import com.google.firebase.dataconnect.core.LoggerGlobals.LOG_TAG
+import com.google.firebase.dataconnect.core.LoggerGlobals.Logger
 import com.google.firebase.util.nextAlphanumericString
 import kotlin.random.Random
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.DelicateCoroutinesApi
+import kotlinx.coroutines.GlobalScope
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.getAndUpdate
+import kotlinx.coroutines.flow.launchIn
+import kotlinx.coroutines.flow.onEach
 
 internal interface Logger {
   val name: String
@@ -58,31 +67,58 @@ private class LoggerImpl(override val name: String) : Logger {
 internal object LoggerGlobals {
   const val LOG_TAG = "FirebaseDataConnect"
 
-  @Volatile var logLevel: LogLevel = LogLevel.WARN
+  val logLevel =
+    MutableStateFlow(LogLevel.WARN).also { logLevelFlow ->
+      val logger = Logger("LogLevelChange")
+      @OptIn(DelicateCoroutinesApi::class)
+      logger.logChanges(logLevelFlow.value, logLevelFlow, GlobalScope)
+    }
 
   inline fun Logger.debug(message: () -> Any?) {
-    if (logLevel <= LogLevel.DEBUG) debug("${message()}")
+    if (logLevel.value <= LogLevel.DEBUG) debug("${message()}")
   }
 
   fun Logger.debug(message: String) {
-    if (logLevel <= LogLevel.DEBUG) log(null, LogLevel.DEBUG, message)
+    if (logLevel.value <= LogLevel.DEBUG) log(null, LogLevel.DEBUG, message)
   }
 
   inline fun Logger.warn(message: () -> Any?) {
-    if (logLevel <= LogLevel.WARN) warn("${message()}")
+    if (logLevel.value <= LogLevel.WARN) warn("${message()}")
   }
 
   inline fun Logger.warn(exception: Throwable?, message: () -> Any?) {
-    if (logLevel <= LogLevel.WARN) warn(exception, "${message()}")
+    if (logLevel.value <= LogLevel.WARN) warn(exception, "${message()}")
   }
 
   fun Logger.warn(message: String) {
     warn(null, message)
   }
 
   fun Logger.warn(exception: Throwable?, message: String) {
-    if (logLevel <= LogLevel.WARN) log(exception, LogLevel.WARN, message)
+    if (logLevel.value <= LogLevel.WARN) log(exception, LogLevel.WARN, message)
   }
 
   fun Logger(name: String): Logger = LoggerImpl(name)
+
+  // Log a message each time the log level changes. This is intended to provide context when debug
+  // logging is enabled and no logs are produced, to at least confirm that debug logging has been
+  // enabled. Also, it will leave a "mark" in the logs when debug logging is _disabled_ to explain
+  // why the debug logs stop.
+  private fun Logger.logChanges(
+    initialLogLevel: LogLevel,
+    flow: Flow<LogLevel>,
+    coroutineScope: CoroutineScope
+  ) {
+    val state = MutableStateFlow(initialLogLevel)
+    log(null, initialLogLevel, "Log level set to $initialLogLevel")
+    flow
+      .onEach { newLogLevel: LogLevel ->
+        val oldLogLevel = state.getAndUpdate { newLogLevel }
+        if (newLogLevel != oldLogLevel) {
+          val emitLogLevel = LogLevel.noisiestOf(newLogLevel, oldLogLevel)
+          log(null, emitLogLevel, "Log level changed to $newLogLevel (was $oldLogLevel)")
+        }
+      }
+      .launchIn(coroutineScope)
+  }
 }

firebase-dataconnect/src/test/kotlin/com/google/firebase/dataconnect/LogLevelUnitTest.kt

@@ -0,0 +1,50 @@
+/*
+ * Copyright 2024 Google LLC
+ *
+ * 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.google.firebase.dataconnect
+
+import io.kotest.assertions.assertSoftly
+import io.kotest.assertions.withClue
+import io.kotest.matchers.shouldBe
+import kotlinx.coroutines.test.runTest
+import org.junit.Test
+
+class LoggerUnitTest {
+
+  @Test
+  fun `noisiestOf()`() = runTest {
+    assertSoftly {
+      verifyNoisiestOf(LogLevel.NONE, LogLevel.NONE, LogLevel.NONE)
+      verifyNoisiestOf(LogLevel.NONE, LogLevel.WARN, LogLevel.WARN)
+      verifyNoisiestOf(LogLevel.NONE, LogLevel.DEBUG, LogLevel.DEBUG)
+      verifyNoisiestOf(LogLevel.WARN, LogLevel.NONE, LogLevel.WARN)
+      verifyNoisiestOf(LogLevel.WARN, LogLevel.WARN, LogLevel.WARN)
+      verifyNoisiestOf(LogLevel.WARN, LogLevel.DEBUG, LogLevel.DEBUG)
+      verifyNoisiestOf(LogLevel.DEBUG, LogLevel.NONE, LogLevel.DEBUG)
+      verifyNoisiestOf(LogLevel.DEBUG, LogLevel.WARN, LogLevel.DEBUG)
+      verifyNoisiestOf(LogLevel.DEBUG, LogLevel.DEBUG, LogLevel.DEBUG)
+    }
+  }
+
+  private companion object {
+
+    fun verifyNoisiestOf(logLevel1: LogLevel, logLevel2: LogLevel, expected: LogLevel) {
+      withClue("noisiestOf($logLevel1, $logLevel2)") {
+        LogLevel.noisiestOf(logLevel1, logLevel2) shouldBe expected
+      }
+    }
+  }
+}

firebase-dataconnect/testutil/src/main/kotlin/com/google/firebase/dataconnect/testutil/DataConnectLogLevelRule.kt

@@ -24,17 +24,17 @@ import org.junit.rules.ExternalResource
  * A JUnit test rule that sets the Firebase Data Connect log level to the desired level, then
  * restores it upon completion of the test.
  */
-class DataConnectLogLevelRule(val logLevelDuringTest: LogLevel? = LogLevel.DEBUG) :
+class DataConnectLogLevelRule(val logLevelDuringTest: LogLevel = LogLevel.DEBUG) :
   ExternalResource() {
 
   private lateinit var logLevelBefore: LogLevel
 
   override fun before() {
-    logLevelBefore = FirebaseDataConnect.logLevel
-    logLevelDuringTest?.also { FirebaseDataConnect.logLevel = it }
+    logLevelBefore = FirebaseDataConnect.logLevel.value
+    logLevelDuringTest.also { FirebaseDataConnect.logLevel.value = it }
   }
 
   override fun after() {
-    FirebaseDataConnect.logLevel = logLevelBefore
+    FirebaseDataConnect.logLevel.value = logLevelBefore
   }
 }