fix: guard possible changes in serialization (#182)

* fix: guard possible changes in serialization

Confidence/src/main/java/com/spotify/confidence/cache/FileDiskStorage.kt

@@ -10,7 +10,7 @@ import java.io.File
 internal const val FLAGS_FILE_NAME = "confidence_flags_cache.json"
 internal const val APPLY_FILE_NAME = "confidence_apply_cache.json"
 
-internal class FileDiskStorage private constructor(
+internal class FileDiskStorage internal constructor(
     private val flagsFile: File,
     private val applyFile: File
 ) : DiskStorage {
@@ -33,7 +33,12 @@ internal class FileDiskStorage private constructor(
         return if (fileText.isEmpty()) {
             mutableMapOf()
         } else {
-            Json.decodeFromString(fileText)
+            try {
+                Json.decodeFromString(fileText)
+            } catch (e: Throwable) {
+                applyFile.delete()
+                mutableMapOf()
+            }
         }
     }
 
@@ -47,7 +52,12 @@ internal class FileDiskStorage private constructor(
         return if (fileText.isEmpty()) {
             FlagResolution.EMPTY
         } else {
-            Json.decodeFromString(fileText)
+            try {
+                Json.decodeFromString(fileText)
+            } catch (e: Throwable) {
+                flagsFile.delete()
+                FlagResolution.EMPTY
+            }
         }
     }
 

Confidence/src/test/java/com/spotify/confidence/FileDiskStorageTest.kt

@@ -0,0 +1,67 @@
+package com.spotify.confidence
+
+import com.spotify.confidence.apply.ApplyInstance
+import com.spotify.confidence.apply.EventStatus
+import com.spotify.confidence.cache.FileDiskStorage
+import org.junit.Assert
+import org.junit.Before
+import org.junit.Test
+import java.io.File
+import java.nio.file.Files
+import java.util.Date
+
+class FileDiskStorageTest {
+    private lateinit var diskStorage: FileDiskStorage
+    private lateinit var flagsFile: File
+    private lateinit var applyFile: File
+
+    val badFile = "{\"context\":{\"name\":\"emu64a\",\"version\":\"1.0\",\"density\":2.625,\"height\":1857.0,\"width\":1080,\"namespace\":\"com.example.confidencedemoapp\",\"build\":\"1\",\"manufacturer\":\"Google\",\"model\":\"sdk_gphone64_arm64\",\"type\":\"android\",\"targeting_key\":\"a98a4291-53b0-49d9-bae8-73d3f5da2070\"},\"flags\":[{\"flag\":\"hatten\",\"variant\":\"\",\"reason\":\"RESOLVE_REASON_NO_SEGMENT_MATCH\"}],\"resolveToken\":\"meh\"}"
+    val badApply = "{\"apply\":{\"apply\":\"apply\"}"
+
+    @Before
+    fun setup() {
+        flagsFile = Files.createTempFile("flags", ".txt").toFile()
+        applyFile = Files.createTempFile("apply", ".txt").toFile()
+        diskStorage = FileDiskStorage(flagsFile, applyFile)
+    }
+
+    @Test
+    fun handleCrashingDeserializationForFlags() {
+        flagsFile.writeText(badFile)
+        val read = diskStorage.read()
+        Assert.assertEquals(FlagResolution.EMPTY, read)
+        Assert.assertFalse(flagsFile.exists())
+
+        diskStorage.store(FlagResolution(mapOf("name" to ConfidenceValue.String("emu64a")), listOf(), "abcd"))
+        Assert.assertTrue(flagsFile.exists())
+    }
+
+    @Test
+    fun handleCrashingDeserializationForApplyData() {
+        applyFile.writeText(badApply)
+        val read = diskStorage.readApplyData()
+        Assert.assertEquals(emptyMap<String, MutableMap<String, ApplyInstance>>(), read)
+
+        diskStorage.writeApplyData(mutableMapOf("apply" to mutableMapOf("apply" to ApplyInstance(Date(), EventStatus.CREATED))))
+        Assert.assertTrue(applyFile.exists())
+    }
+
+    @Test
+    fun readEmptyFlagsFile() {
+        val read = diskStorage.read()
+        Assert.assertEquals(FlagResolution.EMPTY, read)
+    }
+
+    @Test
+    fun readEmptyApplyFile() {
+        val read = diskStorage.readApplyData()
+        Assert.assertEquals(emptyMap<String, MutableMap<String, ApplyInstance>>(), read)
+    }
+
+    @Test
+    fun testStoreFlagResolution() {
+        diskStorage.store(FlagResolution.EMPTY)
+        val read = diskStorage.read()
+        Assert.assertEquals(FlagResolution.EMPTY, read)
+    }
+}