Add DataRow.getValueOrNull(columnRef) and ColumnReference.getValueOrNull(row)

Author: nikitinas

src/main/kotlin/org/jetbrains/kotlinx/dataframe/DataRow.kt

@@ -33,6 +33,7 @@ public interface DataRow<out T> {
     public operator fun get(name: String): Any?
     public fun getColumnGroup(columnName: String): AnyRow = get(columnName) as AnyRow
     public fun getOrNull(name: String): Any?
+    public fun <R> getValueOrNull(column: ColumnReference<R>): R?
     public fun containsKey(name: String): Boolean
 
     // endregion

src/main/kotlin/org/jetbrains/kotlinx/dataframe/columns/ColumnPath.kt

@@ -43,6 +43,8 @@ public data class ColumnPath(val path: List<String>) : List<String> by path, Col
 
     override fun getValue(row: AnyRow): Any? = row.owner[this][row.index()]
 
+    override fun getValueOrNull(row: AnyRow): Any? = row.owner.getColumnOrNull(this)?.get(row.index())
+
     override fun toString(): String = path.toString()
 
     override fun <C> get(column: ColumnReference<C>): ColumnAccessor<C> = ColumnAccessorImpl(this + column.path())

src/main/kotlin/org/jetbrains/kotlinx/dataframe/columns/ColumnReference.kt

@@ -29,7 +29,9 @@ public interface ColumnReference<out C> : SingleColumn<C> {
 
     public fun path(): ColumnPath = ColumnPath(name)
 
-    public fun getValue(row: AnyRow): C = resolveFor(row)
+    public fun getValue(row: AnyRow): C = resolveFor(row.df())!![row.index()]
+
+    public fun getValueOrNull(row: AnyRow): C? = resolveFor(row.df())?.get(row.index())
 
     override fun resolveSingle(context: ColumnResolutionContext): ColumnWithPath<C>? {
         return context.df.getColumn<C>(path(), context.unresolvedColumnsPolicy)?.addPath(path(), context.df)
@@ -40,6 +42,4 @@ internal fun <C> ColumnReference<C>.renamedReference(newName: String): ColumnRef
 
 internal fun ColumnReference<*>.shortPath() = ColumnPath(name)
 
-internal fun <C> ColumnReference<C>.resolveFor(df: AnyFrame): ColumnWithPath<C> = resolveSingle(ColumnResolutionContext(df, UnresolvedColumnsPolicy.Fail))!!
-
-internal fun <C> ColumnReference<C>.resolveFor(row: AnyRow): C = resolveFor(row.df())[row.index()]
+internal fun <C> ColumnReference<C>.resolveFor(df: AnyFrame): ColumnWithPath<C>? = resolveSingle(ColumnResolutionContext(df, UnresolvedColumnsPolicy.Skip))

src/main/kotlin/org/jetbrains/kotlinx/dataframe/impl/DataRowImpl.kt

@@ -24,6 +24,11 @@ internal open class DataRowImpl<T>(private val index: Int, private val df: DataF
         return column.getValue(this)
     }
 
+    override fun <R> getValueOrNull(column: ColumnReference<R>): R? {
+        ColumnAccessTracker.registerColumnAccess(column.name())
+        return column.getValueOrNull(this)
+    }
+
     override fun index() = index
 
     private val values by lazy { df.columns().map { it[index] } }

src/main/kotlin/org/jetbrains/kotlinx/dataframe/impl/columns/ColumnAccessorImpl.kt

@@ -36,5 +36,7 @@ internal class ColumnAccessorImpl<T>(val path: ColumnPath) : ColumnAccessor<T> {
 
     override fun <C> get(column: ColumnReference<C>) = ColumnAccessorImpl<C>(path + column.path())
 
-    override fun getValue(row: AnyRow) = row[path] as T
+    override fun getValue(row: AnyRow) = path.getValue(row) as T
+
+    override fun getValueOrNull(row: AnyRow) = path.getValueOrNull(row) as T
 }

src/main/kotlin/org/jetbrains/kotlinx/dataframe/impl/columns/ColumnGroupImpl.kt

@@ -94,5 +94,7 @@ internal class ResolvingColumnGroup<T>(
 
     override fun getValue(row: AnyRow) = super<DataColumnGroup>.getValue(row)
 
+    override fun getValueOrNull(row: AnyRow) = super<DataColumnGroup>.getValueOrNull(row)
+
     override fun rename(newName: String) = ResolvingColumnGroup(source.rename(newName))
 }

src/main/kotlin/org/jetbrains/kotlinx/dataframe/impl/columns/ComputedColumnReference.kt

@@ -25,6 +25,8 @@ internal class ComputedColumnReference<R>(
     override fun rename(newName: String) = ComputedColumnReference(newName, type, infer, compute)
 
     override fun getValue(row: AnyRow) = compute(row, row)
+
+    override fun getValueOrNull(row: AnyRow) = compute(row, row)
 }
 
 @PublishedApi

src/main/kotlin/org/jetbrains/kotlinx/dataframe/impl/columns/FrameColumnImpl.kt

@@ -60,5 +60,7 @@ internal class ResolvingFrameColumn<T>(
 
     override fun getValue(row: AnyRow) = super<FrameColumn>.getValue(row)
 
+    override fun getValueOrNull(row: AnyRow) = super<FrameColumn>.getValueOrNull(row)
+
     override fun rename(newName: String) = ResolvingFrameColumn(source.rename(newName))
 }

src/main/kotlin/org/jetbrains/kotlinx/dataframe/impl/columns/RenamedColumnReference.kt

@@ -16,4 +16,6 @@ internal class RenamedColumnReference<C>(val source: ColumnReference<C>, val nam
     override fun rename(newName: String) = RenamedColumnReference(source, newName)
 
     override fun getValue(row: AnyRow) = source.getValue(row)
+
+    override fun getValueOrNull(row: AnyRow) = source.getValueOrNull(row)
 }

src/main/kotlin/org/jetbrains/kotlinx/dataframe/impl/columns/ValueColumnImpl.kt

@@ -59,5 +59,7 @@ internal class ResolvingValueColumn<T>(
 
     override fun getValue(row: AnyRow) = super<ValueColumn>.getValue(row)
 
+    override fun getValueOrNull(row: AnyRow) = super<ValueColumn>.getValueOrNull(row)
+
     override fun rename(newName: String) = ResolvingValueColumn(source.rename(newName))
 }