Made ColumnsResolver sealed to prevent unexpected behavior. Also, asColumnSet is now more efficient and retains the original object if it already was a ColumnSet. (preventing bugs again)

Author: Jolanrensen

core/generated-sources/src/main/kotlin/org/jetbrains/kotlinx/dataframe/columns/ColumnSet.kt

@@ -17,11 +17,22 @@ import org.jetbrains.kotlinx.dataframe.api.asSingleColumn
 public interface ColumnSet<out C> : ColumnsResolver<C>
 
 internal fun <C> ColumnsResolver<C>.asColumnSet(): ColumnSet<C> =
-    object : ColumnSet<C>, ColumnsResolver<C> by this {}
+    when (this) {
+        is ColumnSet<C> -> this
+        else -> object : ColumnSet<C> {
+            override fun resolve(context: ColumnResolutionContext): List<ColumnWithPath<C>> =
+                this@asColumnSet.resolve(context)
+        }
+    }
 
+@Suppress("UNCHECKED_CAST")
 @PublishedApi
 internal fun <C> SingleColumn<C>.asColumnSet(): ColumnSet<C> =
-    object : ColumnSet<C>, SingleColumn<C> by this {}
+    when (this) {
+        is ColumnSet<*> -> this as ColumnSet<C>
+        else -> object : ColumnSet<C>, SingleColumn<C> by this {}
+    }
+
 
 internal fun <C> ColumnsSelectionDsl<C>.asColumnSet(): ColumnSet<DataRow<C>> =
     asSingleColumn().asColumnSet()

core/generated-sources/src/main/kotlin/org/jetbrains/kotlinx/dataframe/columns/ColumnsResolver.kt

@@ -19,7 +19,7 @@ import org.jetbrains.kotlinx.dataframe.impl.columns.*
  * @see [TransformableColumnSet]
  * @see [TransformableSingleColumn]
  */
-public interface ColumnsResolver<out C> {
+public sealed interface ColumnsResolver<out C> {
 
     /**
      * Resolves this [ColumnsResolver] as a [List]<[ColumnWithPath]<[C]>>.

core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/columns/ColumnSet.kt

@@ -17,11 +17,22 @@ import org.jetbrains.kotlinx.dataframe.api.asSingleColumn
 public interface ColumnSet<out C> : ColumnsResolver<C>
 
 internal fun <C> ColumnsResolver<C>.asColumnSet(): ColumnSet<C> =
-    object : ColumnSet<C>, ColumnsResolver<C> by this {}
+    when (this) {
+        is ColumnSet<C> -> this
+        else -> object : ColumnSet<C> {
+            override fun resolve(context: ColumnResolutionContext): List<ColumnWithPath<C>> =
+                this@asColumnSet.resolve(context)
+        }
+    }
 
+@Suppress("UNCHECKED_CAST")
 @PublishedApi
 internal fun <C> SingleColumn<C>.asColumnSet(): ColumnSet<C> =
-    object : ColumnSet<C>, SingleColumn<C> by this {}
+    when (this) {
+        is ColumnSet<*> -> this as ColumnSet<C>
+        else -> object : ColumnSet<C>, SingleColumn<C> by this {}
+    }
+
 
 internal fun <C> ColumnsSelectionDsl<C>.asColumnSet(): ColumnSet<DataRow<C>> =
     asSingleColumn().asColumnSet()

core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/columns/ColumnsResolver.kt

@@ -19,7 +19,7 @@ import org.jetbrains.kotlinx.dataframe.impl.columns.*
  * @see [TransformableColumnSet]
  * @see [TransformableSingleColumn]
  */
-public interface ColumnsResolver<out C> {
+public sealed interface ColumnsResolver<out C> {
 
     /**
      * Resolves this [ColumnsResolver] as a [List]<[ColumnWithPath]<[C]>>.