More supported functions in toDataFrame DSL

Author: koperagen

core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/api/toDataFrame.kt

@@ -169,6 +169,10 @@ public interface TraversePropertiesDsl {
     public fun preserve(vararg properties: KCallable<*>)
 }
 
+/**
+ * Store values of given type [T] in ValueColumns without transformation into ColumnGroups or FrameColumns.
+ */
+@Interpretable("PreserveT")
 public inline fun <reified T> TraversePropertiesDsl.preserve(): Unit = preserve(T::class)
 
 public abstract class CreateDataFrameDsl<T> : TraversePropertiesDsl {
@@ -177,8 +181,10 @@ public abstract class CreateDataFrameDsl<T> : TraversePropertiesDsl {
 
     public abstract fun add(column: AnyBaseCol, path: ColumnPath? = null)
 
+    @Interpretable("ToDataFrameDslIntoString")
     public infix fun AnyBaseCol.into(name: String): Unit = add(this, pathOf(name))
 
+    @Interpretable("ToDataFrameDslIntoPath")
     public infix fun AnyBaseCol.into(path: ColumnPath): Unit = add(this, path)
 
     @Interpretable("Properties0")
@@ -191,6 +197,7 @@ public abstract class CreateDataFrameDsl<T> : TraversePropertiesDsl {
     public inline fun <reified R> expr(infer: Infer = Infer.Nulls, noinline expression: (T) -> R): DataColumn<R> =
         source.map { expression(it) }.toColumn(infer = infer)
 
+    @Interpretable("ToDataFrameDslAdd")
     public inline fun <reified R> add(name: String, noinline expression: (T) -> R): Unit =
         add(source.map { expression(it) }.toColumn(name, Infer.Nulls))
 
@@ -202,6 +209,7 @@ public abstract class CreateDataFrameDsl<T> : TraversePropertiesDsl {
     public inline infix fun <reified R> KProperty<R>.from(noinline expression: (T) -> R): Unit =
         add(columnName, expression)
 
+    @Interpretable("ToDataFrameDslFromInferType")
     public inline infix fun <reified R> String.from(inferType: InferType<T, R>): Unit =
         add(DataColumn.createByInference(this, source.map { inferType.expression(it) }))
 

core/src/test/kotlin/org/jetbrains/kotlinx/dataframe/api/toDataFrame.kt

@@ -167,6 +167,25 @@ class CreateDataFrameTests {
         df2.a.kind() shouldBe ColumnKind.Group
     }
 
+    class ExcludeTestData(val s: String, val data: NestedData)
+
+    class NestedData(val i: Int, val nestedStr: String)
+
+    @Test
+    fun `preserve T test`() {
+        val data = listOf(
+            ExcludeTestData("test", NestedData(42, "nested")),
+            ExcludeTestData("test2", NestedData(43, "nested2")),
+        )
+
+        val res = data.toDataFrame {
+            preserve<NestedData>()
+            properties(maxDepth = 2)
+        }
+
+        res.schema() shouldBe data.toDataFrame(maxDepth = 0).schema()
+    }
+
     enum class DummyEnum { A }
 
     @Test