Fix the issue where decoding a nullable object or list could fail.

Fixes #6.
charleskorn · Aug 31, 2019 · 52fda15 · 52fda15
1 parent bb2b1cb
commit 52fda15
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Showing 2 changed files with 51 additions and 10 deletions.
diff --git a/src/main/kotlin/com/charleskorn/kaml/YamlInput.kt b/src/main/kotlin/com/charleskorn/kaml/YamlInput.kt
@@ -109,7 +109,14 @@ private class YamlListInput(val list: YamlList, context: SerialModule, configura
         return nextElementIndex++
     }
 
-    override fun decodeNotNullMark(): Boolean = checkTypeAndDecodeFromCurrentValue("a (possibly null) scalar value") { decodeNotNullMark() }
+    override fun decodeNotNullMark(): Boolean {
+        if (!haveStartedReadingElements) {
+            return true
+        }
+
+        return currentElementDecoder.decodeNotNullMark()
+    }
+
     override fun decodeString(): String = checkTypeAndDecodeFromCurrentValue("a string") { decodeString() }
     override fun decodeInt(): Int = checkTypeAndDecodeFromCurrentValue("an integer") { decodeInt() }
     override fun decodeLong(): Long = checkTypeAndDecodeFromCurrentValue("a long") { decodeLong() }
@@ -122,7 +129,7 @@ private class YamlListInput(val list: YamlList, context: SerialModule, configura
     override fun decodeEnum(enumDescription: EnumDescriptor): Int = checkTypeAndDecodeFromCurrentValue("an enumeration value") { decodeEnum(enumDescription) }
 
     private fun <T> checkTypeAndDecodeFromCurrentValue(expectedTypeDescription: String, action: YamlInput.() -> T): T {
-        if (!::currentElementDecoder.isInitialized) {
+        if (!haveStartedReadingElements) {
             throw IncorrectTypeException("Expected $expectedTypeDescription, but got a list", list.location)
         }
 
@@ -218,7 +225,14 @@ private class YamlMapInput(val map: YamlMap, context: SerialModule, configuratio
         throw UnknownPropertyException(name, knownPropertyNames, location)
     }
 
-    override fun decodeNotNullMark(): Boolean = checkTypeAndDecodeFromCurrentValue("a (possibly null) scalar value") { decodeNotNullMark() }
+    override fun decodeNotNullMark(): Boolean {
+        if (!haveStartedReadingEntries) {
+            return true
+        }
+
+        return fromCurrentValue { decodeNotNullMark() }
+    }
+
     override fun decodeString(): String = checkTypeAndDecodeFromCurrentValue("a string") { decodeString() }
     override fun decodeInt(): Int = checkTypeAndDecodeFromCurrentValue("an integer") { decodeInt() }
     override fun decodeLong(): Long = checkTypeAndDecodeFromCurrentValue("a long") { decodeLong() }
@@ -231,7 +245,7 @@ private class YamlMapInput(val map: YamlMap, context: SerialModule, configuratio
     override fun decodeEnum(enumDescription: EnumDescriptor): Int = checkTypeAndDecodeFromCurrentValue("an enumeration value") { decodeEnum(enumDescription) }
 
     private fun <T> checkTypeAndDecodeFromCurrentValue(expectedTypeDescription: String, action: YamlInput.() -> T): T {
-        if (!::currentValueDecoder.isInitialized) {
+        if (!haveStartedReadingEntries) {
             throw IncorrectTypeException("Expected $expectedTypeDescription, but got a map", map.location)
         }
 

diff --git a/src/test/kotlin/com/charleskorn/kaml/YamlReadingTest.kt b/src/test/kotlin/com/charleskorn/kaml/YamlReadingTest.kt
@@ -493,6 +493,14 @@ object YamlReadingTest : Spek({
                     }
                 }
 
+                context("parsing that input as a nullable list") {
+                    val result = Yaml.default.parse(makeNullable(String.serializer().list), input)
+
+                    it("deserializes it to the expected value") {
+                        assert(result).toBe(listOf("thing1", "thing2", "thing3"))
+                    }
+                }
+
                 context("parsing that input with a serializer that uses YAML location information when throwing exceptions") {
                     it("throws an exception with the correct location information") {
                         assert({ Yaml.default.parse(LocationThrowingSerializer.list, input) }).toThrow<LocationInformationException> {
@@ -1063,6 +1071,25 @@ object YamlReadingTest : Spek({
                     }
                 }
             }
+
+            context("given an object where the first property is nullable") {
+                val input = """
+                    mariaDb:
+                      host: "db.test.com"
+                """.trimIndent()
+
+                @Serializable
+                data class MariaDb(val host: String)
+
+                @Serializable
+                data class Server(val mariaDb: MariaDb? = null)
+
+                val result = Yaml.default.parse(Server.serializer(), input)
+
+                it("deserializes it to the expected object") {
+                    assert(result).toBe(Server(MariaDb("db.test.com")))
+                }
+            }
         }
 
         describe("parsing values with a dynamically installed serializer") {
@@ -1097,7 +1124,7 @@ object YamlReadingTest : Spek({
 
         describe("parsing values with mismatched types") {
             context("given a list") {
-                mapOf(
+                listOf(
                     "a string" to StringSerializer,
                     "an integer" to IntSerializer,
                     "a long" to LongSerializer,
@@ -1110,8 +1137,8 @@ object YamlReadingTest : Spek({
                     "an enumeration value" to EnumSerializer(TestEnum::class),
                     "a map" to (StringSerializer to StringSerializer).map,
                     "an object" to ComplexStructure.serializer(),
-                    "a (possibly null) scalar value" to makeNullable(StringSerializer)
-                ).forEach { description, serializer ->
+                    "a string" to makeNullable(StringSerializer)
+                ).forEach { (description, serializer) ->
                     val input = "- thing"
 
                     context("parsing that input as $description") {
@@ -1171,7 +1198,7 @@ object YamlReadingTest : Spek({
             }
 
             context("given a map") {
-                mapOf(
+                listOf(
                     "a string" to StringSerializer,
                     "an integer" to IntSerializer,
                     "a long" to LongSerializer,
@@ -1183,8 +1210,8 @@ object YamlReadingTest : Spek({
                     "a character" to CharSerializer,
                     "an enumeration value" to EnumSerializer(TestEnum::class),
                     "a list" to StringSerializer.list,
-                    "a (possibly null) scalar value" to makeNullable(StringSerializer)
-                ).forEach { description, serializer ->
+                    "a string" to makeNullable(StringSerializer)
+                ).forEach { (description, serializer) ->
                     val input = "key: value"
 
                     context("parsing that input as $description") {