From 13c1f844566f587e0b7261f730862b8e4a3fb4be Mon Sep 17 00:00:00 2001
From: marc <marc@coursera.org>
Date: Fri, 31 Mar 2017 08:43:50 -0700
Subject: [PATCH] make record unapply compatible with exhaustiveness checking

---
 .../courier/generator/RecordGeneratorTest.scala    | 14 ++++++++++++++
 .../courier/templates/RecordClass.scala.txt        |  9 ++-------
 2 files changed, 16 insertions(+), 7 deletions(-)

diff --git a/scala/generator-test/src/test/scala/org/coursera/courier/generator/RecordGeneratorTest.scala b/scala/generator-test/src/test/scala/org/coursera/courier/generator/RecordGeneratorTest.scala
index 1901b43a..6bd0492b 100644
--- a/scala/generator-test/src/test/scala/org/coursera/courier/generator/RecordGeneratorTest.scala
+++ b/scala/generator-test/src/test/scala/org/coursera/courier/generator/RecordGeneratorTest.scala
@@ -26,6 +26,7 @@ import org.coursera.records.test.Empty
 import org.coursera.records.test.Empty2
 import org.coursera.records.test.InlineOptionalRecord
 import org.coursera.records.test.InlineRecord
+import org.coursera.records.test.Message
 import org.coursera.records.test.Simple
 import org.coursera.records.test.SimpleMap
 import org.coursera.records.test.WithComplexTypeDefaults
@@ -470,4 +471,17 @@ class RecordGeneratorTest extends GeneratorTest with SchemaFixtures {
     // Fortunately, nothing should depend solely on hashCode() for determining whether two
     // records match.
   }
+
+  @Test
+  def testUnapplyReturnsSomeType(): Unit = {
+    // If the unapply method returns Option[X] instead of Some[X], then the scala compiler turns
+    // off match exhaustivity checking for match statements that use the unapply method. This test
+    // This test asserts that the unapply method returns Some[X], so that we get better
+    // exhaustivity checking for match statements involving courier records.
+    assertCompiles("""
+      val record = Message("hello", "hello world")
+      Message.unapply(record): Some[(String, String)]
+    """)
+  }
+
 }
diff --git a/scala/generator/src/main/twirl/org/coursera/courier/templates/RecordClass.scala.txt b/scala/generator/src/main/twirl/org/coursera/courier/templates/RecordClass.scala.txt
index 4cc3a8bd..5490d3cd 100644
--- a/scala/generator/src/main/twirl/org/coursera/courier/templates/RecordClass.scala.txt
+++ b/scala/generator/src/main/twirl/org/coursera/courier/templates/RecordClass.scala.txt
@@ -203,13 +203,8 @@ object @(record.scalaType) extends RecordCompanion[@(record.scalaType)] {
       def unapply(record: @(record.scalaType)): Boolean = true
     }
     case i if i <= 22 => { @* Scala tuples only exist up to Tuple22. *@
-      def unapply(record: @(record.scalaType)): Option[(@(record.fieldsAsTypeParams))] = {
-        try {
-          Some((@(record.prefixedFieldParams("record."))))
-        } catch {
-          case cast: TemplateOutputCastException => None
-          case notPresent: RequiredFieldNotPresentException => None
-        }
+      def unapply(record: @(record.scalaType)): Some[(@(record.fieldsAsTypeParams))] = {
+        Some((@(record.prefixedFieldParams("record."))))
       }
     }
     case _ => {