Don't fail on missing columns in remove.

Author: nikitinas

src/main/kotlin/org/jetbrains/kotlinx/dataframe/api/merge.kt

@@ -64,7 +64,7 @@ public fun <T, C, R> Merge<T, C, R>.into(path: ColumnPath): DataFrame<T> {
     if (mergePath != path) {
         // target path existed before merge, but
         // it may have already been removed
-        res = res.removeImpl(true) { path }.df.move(mergePath).into { path }
+        res = res.removeImpl(allowMissingColumns = true) { path }.df.move(mergePath).into { path }
     }
     return res
 }

src/main/kotlin/org/jetbrains/kotlinx/dataframe/api/remove.kt

@@ -10,7 +10,7 @@ import kotlin.reflect.KProperty
 
 // region DataFrame
 
-public fun <T> DataFrame<T>.remove(columns: ColumnsSelector<T, *>): DataFrame<T> = removeImpl(columns = columns).df
+public fun <T> DataFrame<T>.remove(columns: ColumnsSelector<T, *>): DataFrame<T> = removeImpl(allowMissingColumns = true, columns = columns).df
 public fun <T> DataFrame<T>.remove(vararg columns: KProperty<*>): DataFrame<T> = remove { columns.toColumns() }
 public fun <T> DataFrame<T>.remove(vararg columns: String): DataFrame<T> = remove { columns.toColumns() }
 public fun <T> DataFrame<T>.remove(vararg columns: Column): DataFrame<T> = remove { columns.toColumns() }

src/test/kotlin/org/jetbrains/kotlinx/dataframe/api/remove.kt

@@ -6,10 +6,30 @@ import org.junit.Test
 
 class RemoveTests {
 
+    val df = dataFrameOf("a", "b")(1, 2)
+    val b by column<Int>()
+    data class C(val b: Int)
+
+    @Test
+    fun `simple remove`() {
+        val e = df.select("a")
+        df.remove("b") shouldBe e
+        df.remove { b } shouldBe e
+        df.remove(C::b) shouldBe e
+    }
+
     @Test
     fun `remove renamed`() {
-        val df = dataFrameOf("a", "b")(1, 2)
         val (_, removed) = df.removeImpl { "a" named "c" }
         removed[0].data.column!!.name shouldBe "c"
     }
+
+    @Test
+    fun `remove missing column`(){
+        val d = df.remove { b }
+
+        d.remove("b") shouldBe d
+        d.remove { b } shouldBe d
+        d.remove(C::b) shouldBe d
+    }
 }