dataforge-data/src/commonMain/kotlin/space/kscience/dataforge/actions/AbstractAction.kt

@@ -37,21 +37,23 @@ public abstract class AbstractAction<T : Any, R : Any>(
      * Update part of the data set using provided data
      *
      * @param source the source data tree in case we need several data items to update
+     * @param meta the metadata used for the whole data tree
+     * @param updatedData an updated item
      */
     protected open fun DataSink<R>.update(
         source: DataTree<T>,
         meta: Meta,
-        namedData: NamedData<T>,
-    ){
+        updatedData: NamedData<T>,
+    ) {
         //by default regenerate the whole data set
-        generate(source,meta)
+        generate(source, meta)
     }
 
     @OptIn(DFInternal::class)
     override fun execute(
         dataSet: DataTree<T>,
         meta: Meta,
-    ): DataTree<R> = if(dataSet.isObservable()) {
+    ): DataTree<R> = if (dataSet.isObservable()) {
         MutableDataTree<R>(outputType, dataSet.updatesScope).apply {
             generate(dataSet, meta)
             dataSet.updates().onEach {
@@ -64,8 +66,8 @@ public abstract class AbstractAction<T : Any, R : Any>(
                 close()
             }
         }
-    } else{
-        DataTree(outputType){
+    } else {
+        DataTree(outputType) {
             generate(dataSet, meta)
         }
     }

dataforge-data/src/commonMain/kotlin/space/kscience/dataforge/actions/MapAction.kt

@@ -86,8 +86,8 @@ internal class MapAction<T : Any, R : Any>(
         data.forEach { mapOne(it.name, it.data, meta) }
     }
 
-    override fun DataSink<R>.update(source: DataTree<T>, meta: Meta, namedData: NamedData<T>) {
-        mapOne(namedData.name, namedData.data, namedData.meta)
+    override fun DataSink<R>.update(source: DataTree<T>, meta: Meta, updatedData: NamedData<T>) {
+        mapOne(updatedData.name, updatedData.data, updatedData.meta)
     }
 }
 

dataforge-data/src/commonMain/kotlin/space/kscience/dataforge/actions/SplitAction.kt

@@ -77,8 +77,8 @@ internal class SplitAction<T : Any, R : Any>(
         data.forEach { splitOne(it.name, it.data, meta) }
     }
 
-    override fun DataSink<R>.update(source: DataTree<T>, meta: Meta, namedData: NamedData<T>) {
-        splitOne(namedData.name, namedData.data, namedData.meta)
+    override fun DataSink<R>.update(source: DataTree<T>, meta: Meta, updatedData: NamedData<T>) {
+        splitOne(updatedData.name, updatedData.data, updatedData.meta)
     }
 }
 

dataforge-data/src/commonMain/kotlin/space/kscience/dataforge/data/NamedData.kt

@@ -10,7 +10,7 @@ public interface NamedData<out T> : Named, Data<T> {
 }
 
 public operator fun NamedData<*>.component1(): Name = name
-public operator fun <T: Any> NamedData<T>.component2(): Data<T> = data
+public operator fun <T> NamedData<T>.component2(): Data<T> = data
 
 private class NamedDataImpl<T>(
     override val name: Name,

dataforge-meta/src/commonMain/kotlin/space/kscience/dataforge/meta/MutableMeta.kt

@@ -19,6 +19,10 @@ public annotation class MetaBuilderMarker
 public interface MutableMetaProvider : MetaProvider, MutableValueProvider {
     override fun get(name: Name): MutableMeta?
     public operator fun set(name: Name, node: Meta?)
+
+    /**
+     * Set value with the given name. Does nothing if value is not changed.
+     */
     override fun setValue(name: Name, value: Value?)
 }
 
@@ -48,11 +52,13 @@ public interface MutableMeta : Meta, MutableMetaProvider {
     }
 
     override fun setValue(name: Name, value: Value?) {
-        getOrCreate(name).value = value
+        if (value != getValue(name)) {
+            getOrCreate(name).value = value
+        }
     }
 
     /**
-     * Get existing node or create a new one
+     * Get an existing node or create a new one
      */
     public fun getOrCreate(name: Name): MutableMeta
 
@@ -198,10 +204,8 @@ public operator fun MutableMetaProvider.set(key: String, metas: Iterable<Meta>):
 
 
 /**
- * Update existing mutable node with another node. The rules are following:
- *  * value replaces anything
- *  * node updates node and replaces anything but node
- *  * node list updates node list if number of nodes in the list is the same and replaces anything otherwise
+ * Update the existing mutable node with another node.
+ * Values that are present in the current provider and are missing in [meta] are kept.
  */
 public fun MutableMetaProvider.update(meta: Meta) {
     meta.valueSequence().forEach { (name, value) ->
@@ -222,7 +226,7 @@ public fun <M : MutableTypedMeta<M>> MutableTypedMeta<M>.edit(name: Name, builde
     getOrCreate(name).apply(builder)
 
 /**
- * Set a value at a given [name]. If node does not exist, create it.
+ * Set a value at a given [name]. If a node does not exist, create it.
  */
 public operator fun <M : MutableTypedMeta<M>> MutableTypedMeta<M>.set(name: Name, value: Value?) {
     edit(name) {
@@ -367,6 +371,21 @@ public fun MutableMeta.append(name: Name, value: Value): Unit = append(name, Met
 
 public fun MutableMeta.append(key: String, value: Value): Unit = append(Name.parse(key), value)
 
+/**
+ * Update all items that exist in the [newMeta] and remove existing items that are missing in [newMeta].
+ * This produces the same result as clearing all items and updating blank meta with a [newMeta], but does not
+ * produce unnecessary invalidation events (if they are supported).
+ */
+public fun MutableMeta.reset(newMeta: Meta) {
+    //remove old items
+    (items.keys - newMeta.items.keys).forEach {
+        remove(it.asName())
+    }
+    newMeta.items.forEach { (token, item)->
+        set(token, item)
+    }
+}
+
 /**
  * Create a mutable copy of this meta. The copy is created even if the Meta is already mutable
  */

dataforge-meta/src/commonMain/kotlin/space/kscience/dataforge/meta/SealedMeta.kt

@@ -76,6 +76,8 @@ internal class MetaBuilder(
 
 
     override fun set(name: Name, node: Meta?) {
+        //skip setting if value has not changed
+        if(node == get(name)) return
         when (name.length) {
             0 -> error("Can't set a meta with empty name")
             1 -> {
@@ -89,7 +91,7 @@ internal class MetaBuilder(
             }
 
             else -> {
-                getOrCreate(name.first().asName()).set(name.cutFirst(), node)
+                getOrCreate(name.first().asName())[name.cutFirst()] = node
             }
         }
     }

dataforge-meta/src/commonTest/kotlin/space/kscience/dataforge/meta/MetaTest.kt

@@ -61,4 +61,33 @@ class MetaTest {
         assertEquals(null, indexed["8"])
         assertEquals(12, indexed["12"].int)
     }
+
+    @Test
+    fun reset() {
+        val oldMeta = MutableMeta {
+            "a" put {
+                "value" put "aValue"
+            }
+            "b" put {
+                "value" put "bValue"
+            }
+            "c" put {
+                "value" put "cValue"
+            }
+        }
+        val newMeta = Meta {
+            "a" put {
+                "value" put "aValue"
+            }
+            "b" put {
+                "value" put "bValue"
+            }
+            "d" put {
+                "value" put "dValue"
+            }
+        }
+        oldMeta.reset(newMeta)
+        println(oldMeta)
+        assertEquals(setOf("a", "b", "d"), oldMeta.items.keys.map { it.toString() }.toSet())
+    }
 }

gradle/wrapper/gradle-wrapper.properties

@@ -1,5 +1,5 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-8.4-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.6-bin.zip
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists