Add extensions API for DataSchemas

We cannot use gradle plugin to generate them because gradle plugin depends on the 'core', and gradle cannot resolve this dependency to a published versions and instead resolves to a local project, which leads to a cyclic dependency between tasks.

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

@@ -1,8 +1,10 @@
 package org.jetbrains.kotlinx.dataframe.api
 
+import org.jetbrains.kotlinx.dataframe.ColumnsContainer
 import org.jetbrains.kotlinx.dataframe.ColumnsSelector
 import org.jetbrains.kotlinx.dataframe.DataColumn
 import org.jetbrains.kotlinx.dataframe.DataFrame
+import org.jetbrains.kotlinx.dataframe.DataRow
 import org.jetbrains.kotlinx.dataframe.annotations.DataSchema
 import org.jetbrains.kotlinx.dataframe.columns.ColumnPath
 import org.jetbrains.kotlinx.dataframe.columns.ColumnReference
@@ -11,6 +13,7 @@ import org.jetbrains.kotlinx.dataframe.impl.columns.toColumns
 import kotlin.reflect.KProperty
 import kotlin.reflect.KType
 
+// region DataSchema
 @DataSchema
 public interface ColumnDescription {
     public val name: String
@@ -28,6 +31,35 @@ public interface ColumnDescription {
     public val max: Any
 }
 
+public val ColumnsContainer<ColumnDescription>.count: DataColumn<Int> @JvmName("ColumnDescription_count") get() = this["count"] as DataColumn<Int>
+public val DataRow<ColumnDescription>.count: Int @JvmName("ColumnDescription_count") get() = this["count"] as Int
+public val ColumnsContainer<ColumnDescription>.freq: DataColumn<Int> @JvmName("ColumnDescription_freq") get() = this["freq"] as DataColumn<Int>
+public val DataRow<ColumnDescription>.freq: Int @JvmName("ColumnDescription_freq") get() = this["freq"] as Int
+public val ColumnsContainer<ColumnDescription>.max: DataColumn<Any> @JvmName("ColumnDescription_max") get() = this["max"] as DataColumn<Any>
+public val DataRow<ColumnDescription>.max: Any @JvmName("ColumnDescription_max") get() = this["max"] as Any
+public val ColumnsContainer<ColumnDescription>.mean: DataColumn<Double> @JvmName("ColumnDescription_mean") get() = this["mean"] as DataColumn<Double>
+public val DataRow<ColumnDescription>.mean: Double @JvmName("ColumnDescription_mean") get() = this["mean"] as Double
+public val ColumnsContainer<ColumnDescription>.median: DataColumn<Any> @JvmName("ColumnDescription_median") get() = this["median"] as DataColumn<Any>
+public val DataRow<ColumnDescription>.median: Any @JvmName("ColumnDescription_median") get() = this["median"] as Any
+public val ColumnsContainer<ColumnDescription>.min: DataColumn<Any> @JvmName("ColumnDescription_min") get() = this["min"] as DataColumn<Any>
+public val DataRow<ColumnDescription>.min: Any @JvmName("ColumnDescription_min") get() = this["min"] as Any
+public val ColumnsContainer<ColumnDescription>.name: DataColumn<String> @JvmName("ColumnDescription_name") get() = this["name"] as DataColumn<String>
+public val DataRow<ColumnDescription>.name: String @JvmName("ColumnDescription_name") get() = this["name"] as String
+public val ColumnsContainer<ColumnDescription>.nulls: DataColumn<Int> @JvmName("ColumnDescription_nulls") get() = this["nulls"] as DataColumn<Int>
+public val DataRow<ColumnDescription>.nulls: Int @JvmName("ColumnDescription_nulls") get() = this["nulls"] as Int
+public val ColumnsContainer<ColumnDescription>.path: DataColumn<ColumnPath> @JvmName("ColumnDescription_path") get() = this["path"] as DataColumn<ColumnPath>
+public val DataRow<ColumnDescription>.path: ColumnPath @JvmName("ColumnDescription_path") get() = this["path"] as ColumnPath
+public val ColumnsContainer<ColumnDescription>.std: DataColumn<Double> @JvmName("ColumnDescription_std") get() = this["std"] as DataColumn<Double>
+public val DataRow<ColumnDescription>.std: Double @JvmName("ColumnDescription_std") get() = this["std"] as Double
+public val ColumnsContainer<ColumnDescription>.top: DataColumn<Any> @JvmName("ColumnDescription_top") get() = this["top"] as DataColumn<Any>
+public val DataRow<ColumnDescription>.top: Any @JvmName("ColumnDescription_top") get() = this["top"] as Any
+public val ColumnsContainer<ColumnDescription>.type: DataColumn<KType> @JvmName("ColumnDescription_type") get() = this["type"] as DataColumn<KType>
+public val DataRow<ColumnDescription>.type: KType @JvmName("ColumnDescription_type") get() = this["type"] as KType
+public val ColumnsContainer<ColumnDescription>.unique: DataColumn<Int> @JvmName("ColumnDescription_unique") get() = this["unique"] as DataColumn<Int>
+public val DataRow<ColumnDescription>.unique: Int @JvmName("ColumnDescription_unique") get() = this["unique"] as Int
+
+// endregion
+
 // region DataColumn
 
 public fun <T> DataColumn<T>.describe(): DataFrame<ColumnDescription> = describeImpl(listOf(this))

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

@@ -1,23 +1,32 @@
 package org.jetbrains.kotlinx.dataframe.api
 
 import org.jetbrains.kotlinx.dataframe.Column
+import org.jetbrains.kotlinx.dataframe.ColumnsContainer
 import org.jetbrains.kotlinx.dataframe.ColumnsSelector
 import org.jetbrains.kotlinx.dataframe.DataColumn
 import org.jetbrains.kotlinx.dataframe.DataFrame
+import org.jetbrains.kotlinx.dataframe.DataRow
 import org.jetbrains.kotlinx.dataframe.annotations.DataSchema
 import org.jetbrains.kotlinx.dataframe.impl.columns.toColumns
 import org.jetbrains.kotlinx.dataframe.impl.nameGenerator
 import kotlin.reflect.KProperty
 import kotlin.reflect.full.withNullability
 import kotlin.reflect.typeOf
 
-// region DataColumn
+// region DataSchema
 
 @DataSchema
 public interface ValueCount {
     public val count: Int
 }
 
+public val ColumnsContainer<ValueCount>.count: DataColumn<Int> @JvmName("ValueCount_count") get() = this["count"] as DataColumn<Int>
+public val DataRow<ValueCount>.count: Int @JvmName("ValueCount_count") get() = this["count"] as Int
+
+// endregion
+
+// region DataColumn
+
 internal val defaultCountColumnName: String = ValueCount::count.name
 
 public fun <T> DataColumn<T>.valueCounts(

core/src/test/kotlin/org/jetbrains/kotlinx/dataframe/codeGen/CodeGenerationTests.kt

@@ -6,6 +6,8 @@ import org.jetbrains.kotlinx.dataframe.AnyRow
 import org.jetbrains.kotlinx.dataframe.ColumnsContainer
 import org.jetbrains.kotlinx.dataframe.DataColumn
 import org.jetbrains.kotlinx.dataframe.DataRow
+import org.jetbrains.kotlinx.dataframe.api.ColumnDescription
+import org.jetbrains.kotlinx.dataframe.api.ValueCount
 import org.jetbrains.kotlinx.dataframe.api.dataFrameOf
 import org.jetbrains.kotlinx.dataframe.api.dropNulls
 import org.jetbrains.kotlinx.dataframe.api.move
@@ -252,6 +254,16 @@ class CodeGenerationTests : BaseTest() {
         }
     }
 
+    @Test
+    fun generateApi() {
+        val generator = CodeGenerator.create()
+        val valueCount = generator.generate<ValueCount>(InterfaceGenerationMode.None, extensionProperties = true)
+        println(valueCount.declarations)
+        println()
+        val describe = generator.generate<ColumnDescription>(InterfaceGenerationMode.None, extensionProperties = true)
+        println(describe.declarations)
+    }
+
     @Test
     fun patterns() {
         """^[\d]""".toRegex().matches("3fds")