fixup example

docs/changelog.md

@@ -11,6 +11,26 @@ These alpha releases mark the start of the work on LeakCanary 3. It's not stable
 
 New APIs, not stable yet: the `shark-heap-growth` artifact contains APIs for writing test scenarios that detect repeated heap growth.
 
+Here's how it's used with an Espresso test:
+
+```kotlin
+class MyEspressoTest {
+
+  @Test
+  fun greeter_says_hello_does_not_leak() {
+    // Runs in a loop until the heap stops growing or we reach max heap dumps.
+    val heapTraversal = HeapGrowthDetector.detectRepeatedHeapGrowth {
+      // Runs repeatedly until the heap stops growing or we reach maxHeapDumps.
+      onView(withId(R.id.name_field)).perform(typeText("Steve"))
+      onView(withId(R.id.greet_button)).perform(click())
+      onView(withText("Hello Steve!")).check(matches(isDisplayed()))
+    }
+
+    assertThat(heapTraversal.growingNodes).isEmpty()
+  }
+}
+```
+
 Here's an example set up, this is all very manual for now.
 
 Add the new dependency:
@@ -25,21 +45,22 @@ dependencies {
 Create an implementation setup for Espresso in process UI tests:
 
 ```kotlin
-
 import leakcanary.AndroidDebugHeapDumper
 import shark.AndroidReferenceMatchers
 import shark.AndroidReferenceReaderFactory
+import shark.CloseableHeapGraph
 import shark.DiffingHeapGrowthDetector
 import shark.HeapGraphProvider
 import shark.HeapTraversal
 import shark.HprofHeapGraph.Companion.openHeapGraph
+import shark.IgnoredReferenceMatcher
 import shark.LiveHeapGrowthDetector
 import shark.LoopingHeapGrowthDetector
 import shark.MatchingGcRootProvider
+import shark.ReferencePattern.InstanceFieldPattern
 import java.io.File
 import java.text.SimpleDateFormat
 import java.util.Date
-import java.util.EnumSet
 import java.util.Locale
 
 /**
@@ -49,10 +70,12 @@ import java.util.Locale
  * then assert that the resulting [shark.HeapTraversalWithDiff.growingNodes] is empty.
  */
 val HeapGrowthDetector by lazy {
-  val referenceMatchers = AndroidReferenceMatchers.appDefaults + HeapTraversal.ignoredReferences
+  val referenceMatchers = AndroidReferenceMatchers.appDefaults +
+    HeapTraversal.ignoredReferences +
+    // https://cs.android.com/android/_/android/platform/frameworks/base/+/6985fb39f07294fb979b14ba0ebabfd2fea06d34
+    IgnoredReferenceMatcher(InstanceFieldPattern("android.os.StrictMode", "sLastVmViolationTime"))
 
   val dateFormat = SimpleDateFormat("yyyy-MM-dd_HH-mm-ss_SSS'-heap-growth.hprof'", Locale.US)
-  // Magical path that we automatically upload as artifacts of failed builds in CI.
   val uploadedTracesDirectory = File("/sdcard/traces/")
   uploadedTracesDirectory.mkdirs()
   check(uploadedTracesDirectory.exists()) {
@@ -66,7 +89,13 @@ val HeapGrowthDetector by lazy {
     check(heapDumpFile.exists()) {
       "Expected file to exist after heap dump: ${heapDumpFile.absolutePath}"
     }
-    heapDumpFile.openHeapGraph()
+    val realGraph = heapDumpFile.openHeapGraph()
+    object : CloseableHeapGraph by realGraph {
+      override fun close() {
+        realGraph.close()
+        heapDumpFile.delete()
+      }
+    }
   }
 
   LiveHeapGrowthDetector(
@@ -81,6 +110,7 @@ val HeapGrowthDetector by lazy {
     )
   )
 }
+
 ```
 
 Ensure your UI tests have enough heap by updating `src/androidTest/AndroidManifest.xml`:
@@ -96,26 +126,6 @@ Ensure your UI tests have enough heap by updating `src/androidTest/AndroidManife
 </manifest>
 ```
 
-Use it:
-
-```kotlin
-class MyEspressoTest {
-
-  @Test
-  fun greeter_says_hello_does_not_leak() {
-    // Runs in a loop until the heap stops growing or we reach max heap dumps.
-    val heapTraversal = HeapGrowthDetector.detectRepeatedHeapGrowth {
-      // Runs repeatedly until the heap stops growing or we reach maxHeapDumps.
-      onView(withId(R.id.name_field)).perform(typeText("Steve"))
-      onView(withId(R.id.greet_button)).perform(click())
-      onView(withText("Hello Steve!")).check(matches(isDisplayed()))
-    }
-
-    assertThat(heapTraversal.growingNodes).isEmpty()
-  }
-}
-```
-
 ### Reference readers
 
  New APIs, not stable yet: `ReferenceReader` implementations aka expanders, are now public APIs. The names might change. These class define how LeakCanary traverses the graph, and allow for the creating of virtual references, as [introduced here](#improved-support-for-data-structure-internals). These new APIs make it possible to add support for more custom data structures, and they're also useful when working directly with the `shark` APIs (for example, these APIs were necessary to build the heap growth detection tooling mentioned above).