diff --git a/build.gradle b/build.gradle
index 61ab1cb58..94fba35ee 100644
--- a/build.gradle
+++ b/build.gradle
@@ -9,7 +9,7 @@ buildscript {
     }
 
     ext.versions = [
-            androidGradlePlugin         : '4.0.0-beta01',
+            androidGradlePlugin         : '3.6.1',
             kotlin                      : '1.3.70',
             dokkaGradlePlugin           : '0.10.0',
             ktlintGradle                : '9.1.1',
diff --git a/store/api/store.api b/store/api/store.api
index c141a8941..4c1fa5ea8 100644
--- a/store/api/store.api
+++ b/store/api/store.api
@@ -9,6 +9,30 @@ public abstract interface class com/dropbox/android/external/store4/DiskWrite {
 public abstract interface annotation class com/dropbox/android/external/store4/ExperimentalStoreApi : java/lang/annotation/Annotation {
 }
 
+public abstract interface class com/dropbox/android/external/store4/Fetcher {
+	public static final field Companion Lcom/dropbox/android/external/store4/Fetcher$Companion;
+	public abstract fun invoke (Ljava/lang/Object;Lkotlin/coroutines/Continuation;)Ljava/lang/Object;
+}
+
+public final class com/dropbox/android/external/store4/Fetcher$Companion {
+	public final fun fromNonFlowingFetcher (Lkotlin/jvm/functions/Function2;)Lcom/dropbox/android/external/store4/Fetcher;
+	public final fun fromNonFlowingValueFetcher (Lkotlin/jvm/functions/Function2;)Lcom/dropbox/android/external/store4/Fetcher;
+	public final fun fromValueFetcher (Lkotlin/jvm/functions/Function1;)Lcom/dropbox/android/external/store4/Fetcher;
+}
+
+public abstract class com/dropbox/android/external/store4/FetcherResponse {
+}
+
+public final class com/dropbox/android/external/store4/FetcherResponse$Error : com/dropbox/android/external/store4/FetcherResponse {
+	public fun <init> (Ljava/lang/Throwable;)V
+	public final fun getError ()Ljava/lang/Throwable;
+}
+
+public final class com/dropbox/android/external/store4/FetcherResponse$Value : com/dropbox/android/external/store4/FetcherResponse {
+	public fun <init> (Ljava/lang/Object;)V
+	public final fun getValue ()Ljava/lang/Object;
+}
+
 public final class com/dropbox/android/external/store4/MemoryPolicy {
 	public static final field Companion Lcom/dropbox/android/external/store4/MemoryPolicy$Companion;
 	public static final field DEFAULT_SIZE_POLICY J
@@ -65,6 +89,7 @@ public abstract interface class com/dropbox/android/external/store4/StoreBuilder
 }
 
 public final class com/dropbox/android/external/store4/StoreBuilder$Companion {
+	public final fun from (Lcom/dropbox/android/external/store4/Fetcher;)Lcom/dropbox/android/external/store4/StoreBuilder;
 	public final fun from (Lkotlin/jvm/functions/Function1;)Lcom/dropbox/android/external/store4/StoreBuilder;
 	public final fun fromNonFlow (Lkotlin/jvm/functions/Function2;)Lcom/dropbox/android/external/store4/StoreBuilder;
 }
diff --git a/store/src/main/java/com/dropbox/android/external/store4/Fetcher.kt b/store/src/main/java/com/dropbox/android/external/store4/Fetcher.kt
new file mode 100644
index 000000000..56d47a55a
--- /dev/null
+++ b/store/src/main/java/com/dropbox/android/external/store4/Fetcher.kt
@@ -0,0 +1,85 @@
+package com.dropbox.android.external.store4
+
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.catch
+import kotlinx.coroutines.flow.flow
+import kotlinx.coroutines.flow.map
+import java.util.concurrent.CancellationException
+
+/**
+ * The interface that defines a Fetcher, which is responsible to fetch data from a remote data
+ * source. (e.g. make API calls).
+ *
+ * To create a fetcher, use the convenience methods ([fromValueFetcher], [fromNonFlowingFetcher],
+ * [fromNonFlowingValueFetcher]).
+ */
+interface Fetcher<Key, Output> {
+    suspend operator fun invoke(key: Key): Flow<FetcherResponse<Output>>
+
+    companion object {
+        /**
+         * Creates a [Fetcher] from the given flow generating function. If the returned [Flow] emits
+         * an error, it will be wrapped in a [FetcherResponse.Error].
+         */
+        fun <Key, Output> fromValueFetcher(
+            doFetch: (key: Key) -> Flow<Output>
+        ): Fetcher<Key, Output> = FlowingValueFetcher(doFetch)
+
+        /**
+         * Creates a [Fetcher] from the given function. If it throws an error, the response will be
+         * wrapped in a [FetcherResponse.Error].
+         */
+        fun <Key, Output> fromNonFlowingValueFetcher(
+            doFetch: suspend (key: Key) -> Output
+        ): Fetcher<Key, Output> = NonFlowingValueFetcher(doFetch)
+
+        /**
+         * Creates a [Fetcher] that returns only 1 value (e.g. a single web request, not a stream).
+         * An exception thrown from this function will not be caught by Store.
+         */
+        fun <Key, Output> fromNonFlowingFetcher(
+            doFetch: suspend (key: Key) -> FetcherResponse<Output>
+        ): Fetcher<Key, Output> = NonFlowingFetcher(doFetch)
+    }
+}
+
+internal class NonFlowingFetcher<Key, Output>(
+    private val doFetch: suspend (key: Key) -> FetcherResponse<Output>
+) : Fetcher<Key, Output> {
+    override suspend fun invoke(key: Key): Flow<FetcherResponse<Output>> {
+        return flow {
+            emit(doFetch(key))
+        }
+    }
+}
+
+internal class NonFlowingValueFetcher<Key, Output>(
+    private val doFetch: suspend (key: Key) -> Output
+) : Fetcher<Key, Output> {
+    override suspend fun invoke(key: Key): Flow<FetcherResponse<Output>> {
+        return flow {
+            try {
+                emit(FetcherResponse.Value(doFetch(key)))
+            } catch (th: Throwable) {
+                if (th is CancellationException) {
+                    throw th
+                }
+                emit(
+                    FetcherResponse.Error(th)
+                )
+            }
+        }
+    }
+}
+
+internal class FlowingValueFetcher<Key, Output>(
+    private val doFetch: (key: Key) -> Flow<Output>
+) : Fetcher<Key, Output> {
+    override suspend fun invoke(key: Key): Flow<FetcherResponse<Output>> {
+        return doFetch(key).map {
+            FetcherResponse.Value(it) as FetcherResponse<Output>
+        }.catch {
+            emit(FetcherResponse.Error(it))
+        }
+    }
+}
\ No newline at end of file
diff --git a/store/src/main/java/com/dropbox/android/external/store4/FetcherResponse.kt b/store/src/main/java/com/dropbox/android/external/store4/FetcherResponse.kt
new file mode 100644
index 000000000..984d55212
--- /dev/null
+++ b/store/src/main/java/com/dropbox/android/external/store4/FetcherResponse.kt
@@ -0,0 +1,21 @@
+package com.dropbox.android.external.store4
+
+/**
+ * Value type emitted by the [Fetcher]'s `Flow`.
+ */
+sealed class FetcherResponse<T> {
+    /**
+     * Success result, should include a non-null value.
+     */
+    class Value<T>(
+        val value: T
+    ) : FetcherResponse<T>()
+
+    /**
+     * Error result, it should contain the error information
+     */
+    // TODO support non-throwable errors ?
+    class Error<T>(
+        val error: Throwable
+    ) : FetcherResponse<T>()
+}
\ No newline at end of file
diff --git a/store/src/main/java/com/dropbox/android/external/store4/StoreBuilder.kt b/store/src/main/java/com/dropbox/android/external/store4/StoreBuilder.kt
index 74fda0241..438aedc6f 100644
--- a/store/src/main/java/com/dropbox/android/external/store4/StoreBuilder.kt
+++ b/store/src/main/java/com/dropbox/android/external/store4/StoreBuilder.kt
@@ -118,13 +118,14 @@ interface StoreBuilder<Key : Any, Output : Any> {
          * @param fetcher a function for fetching network records.
          */
         @OptIn(ExperimentalTime::class)
+        @Deprecated(message = "Creating a flow from a function is deprecated, use Fetcher",
+            replaceWith = ReplaceWith(
+                expression = "StoreBuilder.from(Fetcher.fromNonFlowingValueFetcher(fetcher))",
+                imports = ["com.dropbox.android.external.store4.Fetcher"]
+            ))
         fun <Key : Any, Output : Any> fromNonFlow(
             fetcher: suspend (key: Key) -> Output
-        ): StoreBuilder<Key, Output> = BuilderImpl { key: Key ->
-            flow {
-                emit(fetcher(key))
-            }
-        }
+        ): StoreBuilder<Key, Output> = BuilderImpl(Fetcher.fromNonFlowingValueFetcher(fetcher))
 
         /**
          * Creates a new [StoreBuilder] from a [Flow] fetcher.
@@ -135,9 +136,18 @@ interface StoreBuilder<Key : Any, Output : Any> {
          * @param fetcher a function for fetching a flow of network records.
          */
         @OptIn(ExperimentalTime::class)
+        @Deprecated(message = "Creating a flow from a function is deprecated, use Fetcher",
+            replaceWith = ReplaceWith(
+                expression = "StoreBuilder.from(Fetcher.fromValueFetcher(fetcher))",
+                imports = ["com.dropbox.android.external.store4.Fetcher"]
+            ))
         fun <Key : Any, Output : Any> from(
             fetcher: (key: Key) -> Flow<Output>
-        ): StoreBuilder<Key, Output> = BuilderImpl(fetcher)
+        ): StoreBuilder<Key, Output> = BuilderImpl(Fetcher.fromValueFetcher(fetcher))
+
+        fun <Key : Any, Output : Any> from(
+            fetcher: Fetcher<Key, Output>
+        ) : StoreBuilder<Key, Output> = BuilderImpl(fetcher)
     }
 }
 
@@ -146,7 +156,7 @@ interface StoreBuilder<Key : Any, Output : Any> {
 @ExperimentalStdlibApi
 @ExperimentalCoroutinesApi
 private class BuilderImpl<Key : Any, Output : Any>(
-    private val fetcher: (key: Key) -> Flow<Output>
+    private val fetcher: Fetcher<Key, Output>
 ) : StoreBuilder<Key, Output> {
     private var scope: CoroutineScope? = null
     private var cachePolicy: MemoryPolicy? = StoreDefaults.memoryPolicy
@@ -249,7 +259,7 @@ private class BuilderImpl<Key : Any, Output : Any>(
 @ExperimentalStdlibApi
 @ExperimentalCoroutinesApi
 private class BuilderWithSourceOfTruth<Key : Any, Input : Any, Output : Any>(
-    private val fetcher: (key: Key) -> Flow<Input>,
+    private val fetcher: Fetcher<Key, Input>,
     private val sourceOfTruth: SourceOfTruth<Key, Input, Output>? = null
 ) : StoreBuilder<Key, Output> {
     private var scope: CoroutineScope? = null
diff --git a/store/src/main/java/com/dropbox/android/external/store4/impl/FetcherController.kt b/store/src/main/java/com/dropbox/android/external/store4/impl/FetcherController.kt
index 39044b037..10cad90c1 100644
--- a/store/src/main/java/com/dropbox/android/external/store4/impl/FetcherController.kt
+++ b/store/src/main/java/com/dropbox/android/external/store4/impl/FetcherController.kt
@@ -15,6 +15,8 @@
  */
 package com.dropbox.android.external.store4.impl
 
+import com.dropbox.android.external.store4.Fetcher
+import com.dropbox.android.external.store4.FetcherResponse
 import com.dropbox.android.external.store4.ResponseOrigin
 import com.dropbox.android.external.store4.StoreResponse
 import com.dropbox.flow.multicast.Multicaster
@@ -22,7 +24,6 @@ import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.ExperimentalCoroutinesApi
 import kotlinx.coroutines.FlowPreview
 import kotlinx.coroutines.flow.Flow
-import kotlinx.coroutines.flow.catch
 import kotlinx.coroutines.flow.emitAll
 import kotlinx.coroutines.flow.flow
 import kotlinx.coroutines.flow.map
@@ -46,7 +47,7 @@ internal class FetcherController<Key, Input, Output>(
     /**
      * The function that provides the actualy fetcher flow when needed
      */
-    private val realFetcher: (Key) -> Flow<Input>,
+    private val realFetcher: Fetcher<Key, Input>,
     /**
      * [SourceOfTruth] to send the data each time fetcher dispatches a value. Can be `null` if
      * no [SourceOfTruth] is available.
@@ -65,12 +66,18 @@ internal class FetcherController<Key, Input, Output>(
                 scope = scope,
                 bufferSize = 0,
                 source = flow { emitAll(realFetcher(key)) }.map {
-                    StoreResponse.Data(
-                        it,
-                        origin = ResponseOrigin.Fetcher
-                    ) as StoreResponse<Input>
-                }.catch {
-                    emit(StoreResponse.Error(it, origin = ResponseOrigin.Fetcher))
+                    when (it) {
+                        is FetcherResponse.Value<Input> ->
+                            StoreResponse.Data(
+                                value = it.value,
+                                origin = ResponseOrigin.Fetcher
+                            ) as StoreResponse<Input>
+                        is FetcherResponse.Error<Input> ->
+                            StoreResponse.Error(
+                                error = it.error,
+                                origin = ResponseOrigin.Fetcher
+                            )
+                    }
                 },
                 piggybackingDownstream = enablePiggyback,
                 onEach = { response ->
diff --git a/store/src/main/java/com/dropbox/android/external/store4/impl/RealStore.kt b/store/src/main/java/com/dropbox/android/external/store4/impl/RealStore.kt
index ee07cc869..9b6b2370a 100644
--- a/store/src/main/java/com/dropbox/android/external/store4/impl/RealStore.kt
+++ b/store/src/main/java/com/dropbox/android/external/store4/impl/RealStore.kt
@@ -18,6 +18,7 @@ package com.dropbox.android.external.store4.impl
 import com.dropbox.android.external.cache4.Cache
 import com.dropbox.android.external.store4.CacheType
 import com.dropbox.android.external.store4.ExperimentalStoreApi
+import com.dropbox.android.external.store4.Fetcher
 import com.dropbox.android.external.store4.MemoryPolicy
 import com.dropbox.android.external.store4.ResponseOrigin
 import com.dropbox.android.external.store4.Store
@@ -44,7 +45,7 @@ import kotlin.time.ExperimentalTime
 @FlowPreview
 internal class RealStore<Key : Any, Input : Any, Output : Any>(
     scope: CoroutineScope,
-    fetcher: (Key) -> Flow<Input>,
+    fetcher: Fetcher<Key, Input>,
     sourceOfTruth: SourceOfTruth<Key, Input, Output>? = null,
     private val memoryPolicy: MemoryPolicy?
 ) : Store<Key, Output> {
diff --git a/store/src/test/java/com/dropbox/android/external/store3/StoreTest.kt b/store/src/test/java/com/dropbox/android/external/store3/StoreTest.kt
index f1b477651..584a1b595 100644
--- a/store/src/test/java/com/dropbox/android/external/store3/StoreTest.kt
+++ b/store/src/test/java/com/dropbox/android/external/store3/StoreTest.kt
@@ -1,7 +1,7 @@
 package com.dropbox.android.external.store3
 
 import com.dropbox.android.external.cache4.Cache
-import com.dropbox.android.external.store4.Fetcher
+import com.dropbox.android.external.store4.Store3Fetcher
 import com.dropbox.android.external.store4.Persister
 import com.dropbox.android.external.store4.fresh
 import com.dropbox.android.external.store4.get
@@ -38,7 +38,7 @@ class StoreTest(
 ) {
     private val testScope = TestCoroutineScope()
     private val counter = AtomicInteger(0)
-    private val fetcher: Fetcher<String, BarCode> = mock()
+    private val fetcher: Store3Fetcher<String, BarCode> = mock()
     private var persister: Persister<String, BarCode> = mock()
     private val barCode = BarCode("key", "value")
 
diff --git a/store/src/test/java/com/dropbox/android/external/store3/StoreThrowOnNoItems.kt b/store/src/test/java/com/dropbox/android/external/store3/StoreThrowOnNoItems.kt
index 66dc5c0cd..88951950d 100644
--- a/store/src/test/java/com/dropbox/android/external/store3/StoreThrowOnNoItems.kt
+++ b/store/src/test/java/com/dropbox/android/external/store3/StoreThrowOnNoItems.kt
@@ -1,6 +1,6 @@
 package com.dropbox.android.external.store3
 
-import com.dropbox.android.external.store4.Fetcher
+import com.dropbox.android.external.store4.Store3Fetcher
 import com.dropbox.android.external.store4.Persister
 import com.dropbox.android.external.store4.get
 import com.dropbox.android.external.store4.legacy.BarCode
@@ -26,7 +26,7 @@ class StoreThrowOnNoItems(
 ) {
     private val testScope = TestCoroutineScope()
     private val counter = AtomicInteger(0)
-    private val fetcher: Fetcher<String, BarCode> = mock()
+    private val fetcher: Store3Fetcher<String, BarCode> = mock()
     private var persister: Persister<String, BarCode> = mock()
     private val barCode = BarCode("key", "value")
 
diff --git a/store/src/test/java/com/dropbox/android/external/store3/StreamOneKeyTest.kt b/store/src/test/java/com/dropbox/android/external/store3/StreamOneKeyTest.kt
index e44af2234..15b34f664 100644
--- a/store/src/test/java/com/dropbox/android/external/store3/StreamOneKeyTest.kt
+++ b/store/src/test/java/com/dropbox/android/external/store3/StreamOneKeyTest.kt
@@ -1,6 +1,6 @@
 package com.dropbox.android.external.store3
 
-import com.dropbox.android.external.store4.Fetcher
+import com.dropbox.android.external.store4.Store3Fetcher
 import com.dropbox.android.external.store4.Persister
 import com.dropbox.android.external.store4.StoreRequest
 import com.dropbox.android.external.store4.fresh
@@ -32,7 +32,7 @@ class StreamOneKeyTest(
     private val storeType: TestStoreType
 ) {
 
-    val fetcher: Fetcher<String, BarCode> = mock()
+    val fetcher: Store3Fetcher<String, BarCode> = mock()
     val persister: Persister<String, BarCode> = mock()
     private val barCode = BarCode("key", "value")
     private val barCode2 = BarCode("key2", "value2")
diff --git a/store/src/test/java/com/dropbox/android/external/store3/TestStoreBuilder.kt b/store/src/test/java/com/dropbox/android/external/store3/TestStoreBuilder.kt
index 93e5fee17..2fb0f5d67 100644
--- a/store/src/test/java/com/dropbox/android/external/store3/TestStoreBuilder.kt
+++ b/store/src/test/java/com/dropbox/android/external/store3/TestStoreBuilder.kt
@@ -17,6 +17,7 @@ package com.dropbox.android.external.store3
 
 import com.dropbox.android.external.store3.util.KeyParser
 import com.dropbox.android.external.store4.Fetcher
+import com.dropbox.android.external.store4.Store3Fetcher
 import com.dropbox.android.external.store4.MemoryPolicy
 import com.dropbox.android.external.store4.Persister
 import com.dropbox.android.external.store4.Store
@@ -44,7 +45,7 @@ data class TestStoreBuilder<Key : Any, Output : Any>(
 
         fun <Key : Any, Output : Any> from(
             scope: CoroutineScope,
-            fetcher: Fetcher<Output, Key>,
+            fetcher: Store3Fetcher<Output, Key>,
             persister: Persister<Output, Key>? = null,
             inflight: Boolean = true
         ): TestStoreBuilder<Key, Output> = from(
@@ -68,7 +69,7 @@ data class TestStoreBuilder<Key : Any, Output : Any>(
             cached = cached,
             cacheMemoryPolicy = cacheMemoryPolicy,
             persister = persister,
-            fetcher = object : Fetcher<Output, Key> {
+            fetcher = object : Store3Fetcher<Output, Key> {
                 override suspend fun invoke(key: Key): Output = fetcher(key)
             }
         )
@@ -84,21 +85,15 @@ data class TestStoreBuilder<Key : Any, Output : Any>(
             fetchParser: KeyParser<Key, Output, Output>? = null,
             // parser that runs after get from db
             postParser: KeyParser<Key, Output, Output>? = null,
-            fetcher: Fetcher<Output, Key>
+            fetcher: Store3Fetcher<Output, Key>
         ): TestStoreBuilder<Key, Output> {
             return TestStoreBuilder(
                 buildStore = {
-                    StoreBuilder
-                        .from { key: Key ->
-                            flow {
-                                val value = fetcher.invoke(key = key)
-                                if (fetchParser != null) {
-                                    emit(fetchParser.apply(key, value))
-                                } else {
-                                    emit(value)
-                                }
-                            }
-                        }
+                    StoreBuilder.from(
+                        Fetcher.fromNonFlowingValueFetcher {key : Key ->
+                            val value = fetcher.invoke(key = key)
+                            fetchParser?.apply(key, value) ?: value
+                        })
                         .scope(scope)
                         .let {
                             if (cached) {
diff --git a/store/src/test/java/com/dropbox/android/external/store4/FetcherControllerTest.kt b/store/src/test/java/com/dropbox/android/external/store4/FetcherControllerTest.kt
index 818400c4f..b4f90cdc6 100644
--- a/store/src/test/java/com/dropbox/android/external/store4/FetcherControllerTest.kt
+++ b/store/src/test/java/com/dropbox/android/external/store4/FetcherControllerTest.kt
@@ -15,7 +15,6 @@
  */
 package com.dropbox.android.external.store4
 
-import com.dropbox.android.external.store4.ResponseOrigin.Fetcher
 import com.dropbox.android.external.store4.StoreResponse.Data
 import com.dropbox.android.external.store4.impl.FetcherController
 import com.google.common.truth.Truth.assertThat
@@ -42,7 +41,7 @@ class FetcherControllerTest {
     fun simple() = testScope.runBlockingTest {
         val fetcherController = FetcherController<Int, Int, Int>(
                 scope = testScope,
-                realFetcher = { key: Int ->
+                realFetcher = Fetcher.fromValueFetcher{ key: Int ->
                     flow {
                         emit(key * key)
                     }
@@ -57,7 +56,7 @@ class FetcherControllerTest {
         assertThat(received).isEqualTo(
                 Data(
                         value = 9,
-                        origin = Fetcher
+                        origin = ResponseOrigin.Fetcher
                 )
         )
         assertThat(fetcherController.fetcherSize()).isEqualTo(0)
@@ -68,7 +67,7 @@ class FetcherControllerTest {
         var createdCnt = 0
         val fetcherController = FetcherController<Int, Int, Int>(
                 scope = testScope,
-                realFetcher = { key: Int ->
+                realFetcher = Fetcher.fromValueFetcher{ key: Int ->
                     createdCnt++
                     flow {
                         // make sure it takes time, otherwise, we may not share
@@ -93,7 +92,7 @@ class FetcherControllerTest {
             assertThat(it.await()).isEqualTo(
                     Data(
                             value = 9,
-                            origin = Fetcher
+                            origin = ResponseOrigin.Fetcher
                     )
             )
         }
diff --git a/store/src/test/java/com/dropbox/android/external/store4/Fetcher.kt b/store/src/test/java/com/dropbox/android/external/store4/Store3Fetcher.kt
similarity index 87%
rename from store/src/test/java/com/dropbox/android/external/store4/Fetcher.kt
rename to store/src/test/java/com/dropbox/android/external/store4/Store3Fetcher.kt
index a21a6b28d..14db3b412 100644
--- a/store/src/test/java/com/dropbox/android/external/store4/Fetcher.kt
+++ b/store/src/test/java/com/dropbox/android/external/store4/Store3Fetcher.kt
@@ -6,7 +6,8 @@ package com.dropbox.android.external.store4
  * @param <Raw> data type before parsing
 </Raw> */
 @Deprecated("used in tests")
-interface Fetcher<Raw, Key> {
+// TODO cleanup
+interface Store3Fetcher<Raw, Key> {
 
     /**
      * @param key Container with Key and Type used as a request param
diff --git a/store/src/test/java/com/dropbox/android/external/store4/impl/FetcherResponseTest.kt b/store/src/test/java/com/dropbox/android/external/store4/impl/FetcherResponseTest.kt
new file mode 100644
index 000000000..d5e06a512
--- /dev/null
+++ b/store/src/test/java/com/dropbox/android/external/store4/impl/FetcherResponseTest.kt
@@ -0,0 +1,83 @@
+/*
+ * Copyright 2020 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
+ *
+ *     https://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.dropbox.android.external.store4.impl
+
+import com.dropbox.android.external.store4.Fetcher
+import com.dropbox.android.external.store4.FetcherResponse
+import com.dropbox.android.external.store4.ResponseOrigin
+import com.dropbox.android.external.store4.StoreBuilder
+import com.dropbox.android.external.store4.StoreRequest
+import com.dropbox.android.external.store4.StoreResponse
+import com.dropbox.android.external.store4.testutil.assertThat
+import com.google.common.truth.Truth
+
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.flowOf
+import kotlinx.coroutines.flow.toList
+import kotlinx.coroutines.test.TestCoroutineScope
+import kotlinx.coroutines.test.runBlockingTest
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.junit.runners.JUnit4
+
+@RunWith(JUnit4::class)
+@OptIn(ExperimentalStdlibApi::class)
+class FetcherResponseTest {
+    private val testScope = TestCoroutineScope()
+    @Test
+    fun `given a Fetcher that returns FetcherResponse, its exceptions should not be caught`() {
+        val store = StoreBuilder.from<Int, Int>(
+            Fetcher.fromNonFlowingFetcher {
+                throw RuntimeException("don't catch me")
+            }
+        ).scope(testScope).build()
+
+        val result = kotlin.runCatching {
+            testScope.runBlockingTest {
+
+                val result = store.stream(StoreRequest.fresh(1)).toList()
+                Truth.assertThat(result).isEmpty()
+            }
+        }
+        Truth.assertThat(result.isFailure).isTrue()
+        Truth.assertThat(result.exceptionOrNull()).hasMessageThat().contains(
+            "don't catch me"
+        )
+    }
+
+    @Test
+    fun `given a Fetcher that emits FetcherResponse, it can emit value after an error`() {
+        val exception = RuntimeException("first error")
+        testScope.runBlockingTest {
+            val store = StoreBuilder.from(
+                object : Fetcher<Int, String> {
+                    override suspend fun invoke(key: Int): Flow<FetcherResponse<String>> {
+                        return flowOf(
+                            FetcherResponse.Error(exception),
+                            FetcherResponse.Value("$key")
+                        )
+                    }
+                }
+            ).scope(testScope).build()
+            assertThat(store.stream(StoreRequest.fresh(1)))
+                .emitsExactly(
+                    StoreResponse.Loading(ResponseOrigin.Fetcher),
+                    StoreResponse.Error(exception, ResponseOrigin.Fetcher),
+                    StoreResponse.Data("1", ResponseOrigin.Fetcher)
+                )
+        }
+    }
+}
\ No newline at end of file
diff --git a/store/src/test/java/com/dropbox/android/external/store4/impl/FlowStoreTest.kt b/store/src/test/java/com/dropbox/android/external/store4/impl/FlowStoreTest.kt
index b3db3847d..9da4eedd9 100644
--- a/store/src/test/java/com/dropbox/android/external/store4/impl/FlowStoreTest.kt
+++ b/store/src/test/java/com/dropbox/android/external/store4/impl/FlowStoreTest.kt
@@ -15,8 +15,9 @@
  */
 package com.dropbox.android.external.store4.impl
 
+import com.dropbox.android.external.store4.Fetcher
+import com.dropbox.android.external.store4.ResponseOrigin
 import com.dropbox.android.external.store4.ResponseOrigin.Cache
-import com.dropbox.android.external.store4.ResponseOrigin.Fetcher
 import com.dropbox.android.external.store4.ResponseOrigin.Persister
 import com.dropbox.android.external.store4.Store
 import com.dropbox.android.external.store4.StoreBuilder
@@ -67,10 +68,10 @@ class FlowStoreTest {
         assertThat(pipeline.stream(StoreRequest.cached(3, refresh = false)))
             .emitsExactly(
                 Loading(
-                    origin = Fetcher
+                    origin = ResponseOrigin.Fetcher
                 ), Data(
                     value = "three-1",
-                    origin = Fetcher
+                    origin = ResponseOrigin.Fetcher
                 )
             )
         assertThat(
@@ -84,11 +85,11 @@ class FlowStoreTest {
         assertThat(pipeline.stream(StoreRequest.fresh(3)))
             .emitsExactly(
                 Loading(
-                    origin = Fetcher
+                    origin = ResponseOrigin.Fetcher
                 ),
                 Data(
                     value = "three-2",
-                    origin = Fetcher
+                    origin = ResponseOrigin.Fetcher
                 )
             )
         assertThat(
@@ -118,11 +119,11 @@ class FlowStoreTest {
         assertThat(pipeline.stream(StoreRequest.cached(3, refresh = false)))
             .emitsExactly(
                 Loading(
-                    origin = Fetcher
+                    origin = ResponseOrigin.Fetcher
                 ),
                 Data(
                     value = "three-1",
-                    origin = Fetcher
+                    origin = ResponseOrigin.Fetcher
                 )
             )
         assertThat(pipeline.stream(StoreRequest.cached(3, refresh = false)))
@@ -142,11 +143,11 @@ class FlowStoreTest {
         assertThat(pipeline.stream(StoreRequest.fresh(3)))
             .emitsExactly(
                 Loading(
-                    origin = Fetcher
+                    origin = ResponseOrigin.Fetcher
                 ),
                 Data(
                     value = "three-2",
-                    origin = Fetcher
+                    origin = ResponseOrigin.Fetcher
                 )
             )
         assertThat(pipeline.stream(StoreRequest.cached(3, refresh = false)))
@@ -180,11 +181,11 @@ class FlowStoreTest {
         assertThat(pipeline.stream(StoreRequest.cached(3, refresh = true)))
             .emitsExactly(
                 Loading(
-                    origin = Fetcher
+                    origin = ResponseOrigin.Fetcher
                 ),
                 Data(
                     value = "three-1",
-                    origin = Fetcher
+                    origin = ResponseOrigin.Fetcher
                 )
             )
 
@@ -199,11 +200,11 @@ class FlowStoreTest {
                     origin = Persister
                 ),
                 Loading(
-                    origin = Fetcher
+                    origin = ResponseOrigin.Fetcher
                 ),
                 Data(
                     value = "three-2",
-                    origin = Fetcher
+                    origin = ResponseOrigin.Fetcher
                 )
             )
     }
@@ -222,11 +223,11 @@ class FlowStoreTest {
         assertThat(pipeline.stream(StoreRequest.cached(3, refresh = true)))
             .emitsExactly(
                 Loading(
-                    origin = Fetcher
+                    origin = ResponseOrigin.Fetcher
                 ),
                 Data(
                     value = "three-1",
-                    origin = Fetcher
+                    origin = ResponseOrigin.Fetcher
                 )
             )
 
@@ -237,11 +238,11 @@ class FlowStoreTest {
                     origin = Cache
                 ),
                 Loading(
-                    origin = Fetcher
+                    origin = ResponseOrigin.Fetcher
                 ),
                 Data(
                     value = "three-2",
-                    origin = Fetcher
+                    origin = ResponseOrigin.Fetcher
                 )
             )
     }
@@ -260,22 +261,22 @@ class FlowStoreTest {
         assertThat(pipeline.stream(StoreRequest.skipMemory(3, refresh = false)))
             .emitsExactly(
                 Loading(
-                    origin = Fetcher
+                    origin = ResponseOrigin.Fetcher
                 ),
                 Data(
                     value = "three-1",
-                    origin = Fetcher
+                    origin = ResponseOrigin.Fetcher
                 )
             )
 
         assertThat(pipeline.stream(StoreRequest.skipMemory(3, refresh = false)))
             .emitsExactly(
                 Loading(
-                    origin = Fetcher
+                    origin = ResponseOrigin.Fetcher
                 ),
                 Data(
                     value = "three-2",
-                    origin = Fetcher
+                    origin = ResponseOrigin.Fetcher
                 )
             )
     }
@@ -298,15 +299,15 @@ class FlowStoreTest {
         assertThat(pipeline.stream(StoreRequest.fresh(3)))
             .emitsExactly(
                 Loading(
-                    origin = Fetcher
+                    origin = ResponseOrigin.Fetcher
                 ),
                 Data(
                     value = "three-1",
-                    origin = Fetcher
+                    origin = ResponseOrigin.Fetcher
                 ),
                 Data(
                     value = "three-2",
-                    origin = Fetcher
+                    origin = ResponseOrigin.Fetcher
                 )
             )
         assertThat(pipeline.stream(StoreRequest.cached(3, refresh = true)))
@@ -316,15 +317,15 @@ class FlowStoreTest {
                     origin = Persister
                 ),
                 Loading(
-                    origin = Fetcher
+                    origin = ResponseOrigin.Fetcher
                 ),
                 Data(
                     value = "three-1",
-                    origin = Fetcher
+                    origin = ResponseOrigin.Fetcher
                 ),
                 Data(
                     value = "three-2",
-                    origin = Fetcher
+                    origin = ResponseOrigin.Fetcher
                 )
             )
     }
@@ -349,7 +350,7 @@ class FlowStoreTest {
         assertThat(pipeline.stream(StoreRequest.cached(3, refresh = true)))
             .emitsExactly(
                 Loading(
-                    origin = Fetcher
+                    origin = ResponseOrigin.Fetcher
                 ),
                 Data(
                     value = "local-1",
@@ -383,7 +384,7 @@ class FlowStoreTest {
         assertThat(pipeline.stream(StoreRequest.cached(3, refresh = true)))
             .emitsExactly(
                 Loading(
-                    origin = Fetcher
+                    origin = ResponseOrigin.Fetcher
                 ),
                 Data(
                     value = "local-1",
@@ -391,7 +392,7 @@ class FlowStoreTest {
                 ),
                 Data(
                     value = "three-1",
-                    origin = Fetcher
+                    origin = ResponseOrigin.Fetcher
                 ),
                 Data(
                     value = "local-2",
@@ -399,7 +400,7 @@ class FlowStoreTest {
                 ),
                 Data(
                     value = "three-2",
-                    origin = Fetcher
+                    origin = ResponseOrigin.Fetcher
                 )
             )
     }
@@ -423,11 +424,11 @@ class FlowStoreTest {
         assertThat(pipeline.stream(StoreRequest.cached(key = 3, refresh = true)))
             .emitsExactly(
                 Loading(
-                    origin = Fetcher
+                    origin = ResponseOrigin.Fetcher
                 ),
                 StoreResponse.Error(
                     error = exception,
-                    origin = Fetcher
+                    origin = ResponseOrigin.Fetcher
                 ),
                 Data(
                     value = "local-1",
@@ -441,11 +442,11 @@ class FlowStoreTest {
                     origin = Persister
                 ),
                 Loading(
-                    origin = Fetcher
+                    origin = ResponseOrigin.Fetcher
                 ),
                 StoreResponse.Error(
                     error = exception,
-                    origin = Fetcher
+                    origin = ResponseOrigin.Fetcher
                 )
             )
     }
@@ -488,7 +489,7 @@ class FlowStoreTest {
                 ),
                 Data(
                     value = "three-2",
-                    origin = Fetcher
+                    origin = ResponseOrigin.Fetcher
                 )
             )
             collection.cancelAndJoin()
@@ -543,7 +544,7 @@ class FlowStoreTest {
                 ),
                 Data(
                     value = "three-2",
-                    origin = Fetcher
+                    origin = ResponseOrigin.Fetcher
                 )
             )
             collection.cancelAndJoin()
@@ -571,29 +572,29 @@ class FlowStoreTest {
             testScope.advanceUntilIdle()
             assertThat(fetcher1Collected).isEqualTo(
                 listOf(
-                    Loading<String>(origin = Fetcher),
-                    Data(origin = Fetcher, value = "three-1")
+                    Loading<String>(origin = ResponseOrigin.Fetcher),
+                    Data(origin = ResponseOrigin.Fetcher, value = "three-1")
                 )
             )
             assertThat(pipeline.stream(StoreRequest.cached(3, refresh = true)))
                 .emitsExactly(
                     Data(origin = Cache, value = "three-1"),
-                    Loading(origin = Fetcher),
-                    Data(origin = Fetcher, value = "three-2")
+                    Loading(origin = ResponseOrigin.Fetcher),
+                    Data(origin = ResponseOrigin.Fetcher, value = "three-2")
                 )
             assertThat(pipeline.stream(StoreRequest.cached(3, refresh = true)))
                 .emitsExactly(
                     Data(origin = Cache, value = "three-2"),
-                    Loading(origin = Fetcher),
-                    Data(origin = Fetcher, value = "three-3")
+                    Loading(origin = ResponseOrigin.Fetcher),
+                    Data(origin = ResponseOrigin.Fetcher, value = "three-3")
                 )
             testScope.advanceUntilIdle()
             assertThat(fetcher1Collected).isEqualTo(
                 listOf(
-                    Loading<String>(origin = Fetcher),
-                    Data(origin = Fetcher, value = "three-1"),
-                    Data(origin = Fetcher, value = "three-2"),
-                    Data(origin = Fetcher, value = "three-3")
+                    Loading<String>(origin = ResponseOrigin.Fetcher),
+                    Data(origin = ResponseOrigin.Fetcher, value = "three-1"),
+                    Data(origin = ResponseOrigin.Fetcher, value = "three-2"),
+                    Data(origin = ResponseOrigin.Fetcher, value = "three-3")
                 )
             )
             fetcher1Job.cancelAndJoin()
@@ -619,22 +620,22 @@ class FlowStoreTest {
             testScope.runCurrent()
             assertThat(fetcher1Collected).isEqualTo(
                 listOf(
-                    Loading<String>(origin = Fetcher),
-                    Data(origin = Fetcher, value = "three-1")
+                    Loading<String>(origin = ResponseOrigin.Fetcher),
+                    Data(origin = ResponseOrigin.Fetcher, value = "three-1")
                 )
             )
             assertThat(pipeline.stream(StoreRequest.cached(3, refresh = true)))
                 .emitsExactly(
                     Data(origin = Cache, value = "three-1"),
-                    Loading(origin = Fetcher),
-                    Data(origin = Fetcher, value = "three-2")
+                    Loading(origin = ResponseOrigin.Fetcher),
+                    Data(origin = ResponseOrigin.Fetcher, value = "three-2")
                 )
             testScope.runCurrent()
             assertThat(fetcher1Collected).isEqualTo(
                 listOf(
-                    Loading<String>(origin = Fetcher),
-                    Data(origin = Fetcher, value = "three-1"),
-                    Data(origin = Fetcher, value = "three-2")
+                    Loading<String>(origin = ResponseOrigin.Fetcher),
+                    Data(origin = ResponseOrigin.Fetcher, value = "three-1"),
+                    Data(origin = ResponseOrigin.Fetcher, value = "three-2")
                 )
             )
             fetcher1Job.cancelAndJoin()
@@ -686,12 +687,16 @@ class FlowStoreTest {
         }
 
         return if (nonFlowingFetcher != null) {
-            StoreBuilder.fromNonFlow(
-                nonFlowingFetcher
+            StoreBuilder.from(
+                Fetcher.fromNonFlowingValueFetcher(
+                    nonFlowingFetcher
+                )
             )
         } else {
             StoreBuilder.from(
-                flowingFetcher!!
+                Fetcher.fromValueFetcher(
+                    flowingFetcher!!
+                )
             )
         }.scope(testScope)
             .let {