From a74e0785a083bc529977b44731cd16b413f10f9b Mon Sep 17 00:00:00 2001
From: Eduardo Ruiz Alonso <eduardo.ruiz@hablapps.com>
Date: Tue, 29 Mar 2022 09:51:10 +0200
Subject: [PATCH] fix: [~] str interpolator now prints empty if null column
 (issue #191) (#199)

---
 .../main/scala/doric/syntax/Interpolators.scala |  6 +++---
 .../scala/doric/syntax/InterpolatorsSpec.scala  | 17 +++++++++++++++--
 2 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/core/src/main/scala/doric/syntax/Interpolators.scala b/core/src/main/scala/doric/syntax/Interpolators.scala
index efeab86a9..191951387 100644
--- a/core/src/main/scala/doric/syntax/Interpolators.scala
+++ b/core/src/main/scala/doric/syntax/Interpolators.scala
@@ -4,15 +4,15 @@ package syntax
 trait Interpolators {
   implicit class doricStringInterpolator(val sc: StringContext) {
     def ds(columns: StringColumn*): StringColumn = {
-      val literals: Seq[DoricColumn[String]] = sc.parts.map(_.lit)
+      val literals: Seq[StringColumn] = sc.parts.map(_.lit)
 
-      val cols: Seq[DoricColumn[String]] = literals
+      val cols: Seq[StringColumn] = literals
         .zipAll(columns, "".lit, "".lit)
         .flatMap { case (a, b) =>
           List(a, b)
         }
 
-      concat(cols: _*)
+      concatWs("".lit, cols: _*)
     }
   }
 }
diff --git a/core/src/test/scala/doric/syntax/InterpolatorsSpec.scala b/core/src/test/scala/doric/syntax/InterpolatorsSpec.scala
index e3562569f..0396f8e6a 100644
--- a/core/src/test/scala/doric/syntax/InterpolatorsSpec.scala
+++ b/core/src/test/scala/doric/syntax/InterpolatorsSpec.scala
@@ -1,11 +1,10 @@
 package doric
 package syntax
 
+import org.apache.spark.sql.{functions => f}
 import org.scalatest.EitherValues
 import org.scalatest.matchers.should.Matchers
 
-import org.apache.spark.sql.{functions => f}
-
 class InterpolatorsSpec
     extends DoricTestElements
     with EitherValues
@@ -34,6 +33,20 @@ class InterpolatorsSpec
         )
       )
     }
+
+    it("should work if null columns") {
+      val dfNull = List("value 1", null)
+        .toDF(colName)
+      dfNull.testColumns2(colName, "Column has value:")(
+        (c, str) => ds"${str.lit} -->${colString(c)}",
+        (c, str) =>
+          f.concat(f.lit(str), f.lit(" -->"), f.coalesce(f.col(c), f.lit(""))),
+        List(
+          Some("Column has value: -->value 1"),
+          Some("Column has value: -->")
+        )
+      )
+    }
   }
 
 }