[Port from snakeyaml-engine] Allow to avoid dumping anchors

Co-authored-by: Andrey Somov <[email protected]>

api/snakeyaml-engine-kmp.api

@@ -38,6 +38,7 @@ public final class it/krzeminski/snakeyaml/engine/kmp/api/DumpSettings {
 	public static final fun builder ()Lit/krzeminski/snakeyaml/engine/kmp/api/DumpSettingsBuilder;
 	public final fun getCustomProperty (Lit/krzeminski/snakeyaml/engine/kmp/api/SettingKey;)Ljava/lang/Object;
 	public final fun isCanonical ()Z
+	public final fun isDereferenceAliases ()Z
 	public final fun isExplicitEnd ()Z
 	public final fun isExplicitStart ()Z
 	public final fun isMultiLineFlow ()Z
@@ -57,6 +58,7 @@ public final class it/krzeminski/snakeyaml/engine/kmp/api/DumpSettingsBuilder {
 	public final fun setCustomProperty (Lit/krzeminski/snakeyaml/engine/kmp/api/SettingKey;Ljava/lang/Object;)Lit/krzeminski/snakeyaml/engine/kmp/api/DumpSettingsBuilder;
 	public final fun setDefaultFlowStyle (Lit/krzeminski/snakeyaml/engine/kmp/common/FlowStyle;)Lit/krzeminski/snakeyaml/engine/kmp/api/DumpSettingsBuilder;
 	public final fun setDefaultScalarStyle (Lit/krzeminski/snakeyaml/engine/kmp/common/ScalarStyle;)Lit/krzeminski/snakeyaml/engine/kmp/api/DumpSettingsBuilder;
+	public final fun setDereferenceAliases (Z)Lit/krzeminski/snakeyaml/engine/kmp/api/DumpSettingsBuilder;
 	public final fun setDumpComments (Z)Lit/krzeminski/snakeyaml/engine/kmp/api/DumpSettingsBuilder;
 	public final fun setExplicitEnd (Z)Lit/krzeminski/snakeyaml/engine/kmp/api/DumpSettingsBuilder;
 	public final fun setExplicitRootTag (Lit/krzeminski/snakeyaml/engine/kmp/nodes/Tag;)Lit/krzeminski/snakeyaml/engine/kmp/api/DumpSettingsBuilder;

src/commonMain/kotlin/it/krzeminski/snakeyaml/engine/kmp/api/DumpSettings.kt

@@ -52,6 +52,7 @@ class DumpSettings internal constructor(
     private val customProperties: Map<SettingKey, Any>,
     @JvmField val indentWithIndicator: Boolean,
     @JvmField val dumpComments: Boolean,
+    val isDereferenceAliases: Boolean,
 ) {
 
     fun getCustomProperty(key: SettingKey): Any? = customProperties[key]

src/commonMain/kotlin/it/krzeminski/snakeyaml/engine/kmp/api/DumpSettingsBuilder.kt

@@ -53,6 +53,7 @@ class DumpSettingsBuilder internal constructor() {
     private var maxSimpleKeyLength = 128
     private var indentWithIndicator = false
     private var dumpComments = false
+    private var isDereferenceAliases = false
     private var schema: Schema = JsonSchema()
 
     /**
@@ -328,6 +329,23 @@ class DumpSettingsBuilder internal constructor() {
         return this
     }
 
+    /**
+     *
+     * Disable usage of anchors and aliases while serialising an instance. Recursive objects will not
+     * work when they are disabled. (Forces Serializer to skip emitting anchors names, emit Node
+     * content instead of Alias, fail with SerializationException if serialized structure is
+     * recursive.)
+     *
+     * @param dereferenceAliases - true to use copies of objects instead of references to the same
+     * instance
+     * @return the builder with the provided value
+     */
+    fun setDereferenceAliases(dereferenceAliases: Boolean): DumpSettingsBuilder {
+        this.isDereferenceAliases = dereferenceAliases
+        return this
+    }
+
+
     /**
      * Create immutable DumpSettings
      *
@@ -358,6 +376,7 @@ class DumpSettingsBuilder internal constructor() {
             customProperties = customProperties,
             indentWithIndicator = indentWithIndicator,
             dumpComments = dumpComments,
+            isDereferenceAliases = isDereferenceAliases,
         )
     }
 }

src/commonMain/kotlin/it/krzeminski/snakeyaml/engine/kmp/serializer/IdentitySet.kt

@@ -0,0 +1,29 @@
+package it.krzeminski.snakeyaml.engine.kmp.serializer
+
+import it.krzeminski.snakeyaml.engine.kmp.internal.IdentityHashCode
+import it.krzeminski.snakeyaml.engine.kmp.internal.identityHashCode
+
+/**
+ * A set that compares objects by their identities, not values.
+ * It's an attempt to reimplement `Collections.newSetFromMap(new IdentityHashMap<Node, Boolean>())`
+ * from the JVM.
+ */
+internal class IdentitySet<T> {
+    private val contents: MutableSet<IdentityHashCode> = mutableSetOf()
+
+    fun add(obj: T) {
+        contents.add(identityHashCode(obj))
+    }
+
+    fun contains(obj: T): Boolean {
+        return contents.contains(identityHashCode(obj))
+    }
+
+    fun clear() {
+        contents.clear()
+    }
+
+    fun remove(obj: T) {
+        contents.remove(identityHashCode(obj))
+    }
+}

src/commonMain/kotlin/it/krzeminski/snakeyaml/engine/kmp/serializer/Serializer.kt

@@ -18,6 +18,7 @@ import it.krzeminski.snakeyaml.engine.kmp.comments.CommentLine
 import it.krzeminski.snakeyaml.engine.kmp.common.Anchor
 import it.krzeminski.snakeyaml.engine.kmp.emitter.Emitable
 import it.krzeminski.snakeyaml.engine.kmp.events.*
+import it.krzeminski.snakeyaml.engine.kmp.exceptions.YamlEngineException
 import it.krzeminski.snakeyaml.engine.kmp.nodes.*
 
 /**
@@ -33,6 +34,8 @@ class Serializer(
 ) {
     private val serializedNodes: MutableSet<Node> = mutableSetOf()
     private val anchors: MutableMap<Node, Anchor?> = mutableMapOf()
+    private val isDereferenceAliases: Boolean = settings.isDereferenceAliases
+    private val recursive: IdentitySet<Node> = IdentitySet()
 
     /**
      * Serialize document
@@ -55,6 +58,7 @@ class Serializer(
         emitable.emit(DocumentEndEvent(settings.isExplicitEnd))
         serializedNodes.clear()
         anchors.clear()
+        recursive.clear()
     }
 
     /** Emit [StreamStartEvent] */
@@ -110,8 +114,18 @@ class Serializer(
     private fun serializeNode(node: Node) {
         val realNode = if (node is AnchorNode) node.realNode else node
 
-        val tAlias = (anchors[realNode])
-        if (serializedNodes.contains(realNode)) {
+
+        if (isDereferenceAliases && recursive.contains(node)) {
+            throw YamlEngineException("Cannot dereference aliases for recursive structures.")
+        }
+        recursive.add(node)
+        val tAlias = if (!isDereferenceAliases) {
+            anchors[realNode]
+        } else {
+            null
+        }
+
+        if (!isDereferenceAliases && serializedNodes.contains(realNode)) {
             emitable.emit(AliasEvent(tAlias))
         } else {
             serializedNodes.add(realNode)
@@ -184,6 +198,7 @@ class Serializer(
                 NodeType.ANCHOR   -> {}
             }
         }
+        recursive.remove(node)
     }
 
     private fun serializeComments(comments: List<CommentLine>?) {

src/commonTest/kotlin/it/krzeminski/snakeyaml/engine/kmp/serializer/IdentitySetTest.kt

@@ -0,0 +1,54 @@
+package it.krzeminski.snakeyaml.engine.kmp.serializer
+
+import io.kotest.core.spec.style.FunSpec
+import io.kotest.matchers.shouldBe
+
+data class TestClass(val value: String)
+
+class IdentitySetTest : FunSpec({
+    val objectFoo1 = TestClass(value = "foo")
+    val objectFoo2 = TestClass(value = "foo")
+    val objectBar = TestClass(value = "bar")
+
+    test("expecting existence of the same object wrt. identity") {
+        val identitySet = IdentitySet<TestClass>()
+        identitySet.add(objectFoo1)
+        identitySet.contains(objectFoo1) shouldBe true
+    }
+
+    test("comparing two objects that are equal according to 'equals'") {
+        val identitySet = IdentitySet<TestClass>()
+        identitySet.add(objectFoo1)
+        identitySet.contains(objectFoo2) shouldBe false
+    }
+
+    test("comparing two objects that are not equal according to 'equals'") {
+        val identitySet = IdentitySet<TestClass>()
+        identitySet.add(objectFoo1)
+        identitySet.contains(objectBar) shouldBe false
+    }
+
+    test("clearing the set") {
+        val identitySet = IdentitySet<TestClass>()
+        identitySet.add(objectFoo1)
+        identitySet.contains(objectFoo1) shouldBe true
+        identitySet.clear()
+        identitySet.contains(objectFoo1) shouldBe false
+    }
+
+    test("removing the same object") {
+        val identitySet = IdentitySet<TestClass>()
+        identitySet.add(objectFoo1)
+        identitySet.contains(objectFoo1) shouldBe true
+        identitySet.remove(objectFoo1)
+        identitySet.contains(objectFoo1) shouldBe false
+    }
+
+    test("removing object that is equal according to 'equals'") {
+        val identitySet = IdentitySet<TestClass>()
+        identitySet.add(objectFoo1)
+        identitySet.contains(objectFoo1) shouldBe true
+        identitySet.remove(objectFoo2)
+        identitySet.contains(objectFoo1) shouldBe true
+    }
+})

src/jvmTest/java/it/krzeminski/snakeyaml/engine/kmp/usecases/references/DereferenceAliasesTest.kt

@@ -0,0 +1,47 @@
+package it.krzeminski.snakeyaml.engine.kmp.usecases.references
+
+import it.krzeminski.snakeyaml.engine.kmp.api.Dump
+import it.krzeminski.snakeyaml.engine.kmp.api.DumpSettings
+import it.krzeminski.snakeyaml.engine.kmp.api.Load
+import it.krzeminski.snakeyaml.engine.kmp.api.LoadSettings
+import it.krzeminski.snakeyaml.engine.kmp.common.FlowStyle
+import it.krzeminski.snakeyaml.engine.kmp.exceptions.YamlEngineException
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Assertions.fail
+import org.junit.jupiter.api.Tag
+import org.junit.jupiter.api.Test
+import org.snakeyaml.engine.v2.utils.TestUtils
+import java.io.StringWriter
+
+@Tag("fast")
+class DereferenceAliasesTest {
+    @Test
+    fun testNoAliases() {
+        val settings = LoadSettings.builder().build()
+        val load = Load(settings)
+        val map = load.loadFromString(TestUtils.getResource("/issues/issue1086-1-input.yaml")) as Map<*, *>?
+        val setting = DumpSettings.builder().setDefaultFlowStyle(FlowStyle.BLOCK)
+            .setDereferenceAliases(true).build()
+        val dump = Dump(setting)
+        val node = dump.dumpToString(map)
+        val out = StringWriter()
+        val expected = TestUtils.getResource("/issues/issue1086-1-expected.yaml")
+        assertEquals(expected, node)
+    }
+
+    @Test
+    fun testNoAliasesRecursive() {
+        val settings = LoadSettings.builder().build()
+        val load = Load(settings)
+        val map = load.loadFromString(TestUtils.getResource("/issues/issue1086-2-input.yaml")) as Map<*, *>?
+        val setting = DumpSettings.builder().setDefaultFlowStyle(FlowStyle.BLOCK)
+            .setDereferenceAliases(true).build()
+        val dump = Dump(setting)
+        try {
+            dump.dumpToString(map)
+            fail()
+        } catch (e: YamlEngineException) {
+            assertEquals("Cannot dereference aliases for recursive structures.", e.message)
+        }
+    }
+}

src/jvmTest/resources/issues/issue1086-1-expected.yaml

@@ -0,0 +1,21 @@
+defines:
+  serverPattern1:
+    type: t3
+    strage: 500
+  serverPattern2:
+    type: t2
+    strage: 250
+  lbPattern1:
+    name: lbForPublic
+    vpc: vpc1
+  lbPattern2:
+    name: lbForInternal
+    vpc: vpc1
+current:
+  assenbled1:
+    server:
+      type: t3
+      strage: 500
+    lb:
+      name: lbForPublic
+      vpc: vpc1

src/jvmTest/resources/issues/issue1086-1-input.yaml

@@ -0,0 +1,17 @@
+defines:
+  serverPattern1: &server_HighPerformance
+    type: t3
+    strage: 500
+  serverPattern2: &server_LowPerformance
+    type: t2
+    strage: 250
+  lbPattern1: &lb_Public
+    name: lbForPublic
+    vpc: vpc1
+  lbPattern2: &lb_Internal
+    name: lbForInternal
+    vpc: vpc1
+current:
+  assenbled1:
+    server: *server_HighPerformance
+    lb: *lb_Public

src/jvmTest/resources/issues/issue1086-2-input.yaml

@@ -0,0 +1,34 @@
+&id002
+bankAccountOwner: &id001
+  bankAccountOwner: *id001
+  birthPlace: Leningrad
+  birthday: 1970-01-12T13:46:40Z
+  children: &id003
+    - *id002
+    - bankAccountOwner: *id001
+      birthPlace: New York
+      birthday: 1983-04-24T02:40:00Z
+      children: []
+      father: *id001
+      mother: &id004
+        bankAccountOwner: *id001
+        birthPlace: Saint-Petersburg
+        birthday: 1973-03-03T09:46:40Z
+        children: *id003
+        father: null
+        mother: null
+        name: Mother
+        partner: *id001
+      name: Daughter
+      partner: null
+  father: null
+  mother: null
+  name: Father
+  partner: *id004
+birthPlace: Munich
+birthday: 1979-10-28T23:06:40Z
+children: []
+father: *id001
+mother: *id004
+name: Son
+partner: null

upstream-commit.txt

@@ -1 +1 @@
-3d97ee77ff70ab1093a63e4d3dadda9e885fe857
+1af7dcd2c9c64a9d7cd9de3cd5f64bb2fc2aab6a