From 84e165e8a934f60a92ba6159ba7e9cf772aece9e Mon Sep 17 00:00:00 2001
From: Kamil Podsiadlo <kpodsiadlo@virtuslab.com>
Date: Tue, 16 Nov 2021 15:53:11 +0100
Subject: [PATCH] Implement alias lookup & add tests

---
 .../yaml/internal/load/compose/Composer.scala |   6 +-
 .../virtuslab/yaml/decoder/DecoderSuite.scala | 103 ++++++++++++++++++
 2 files changed, 107 insertions(+), 2 deletions(-)

diff --git a/yaml/shared/src/main/scala/org/virtuslab/yaml/internal/load/compose/Composer.scala b/yaml/shared/src/main/scala/org/virtuslab/yaml/internal/load/compose/Composer.scala
index 62e550d08..b036eadb3 100644
--- a/yaml/shared/src/main/scala/org/virtuslab/yaml/internal/load/compose/Composer.scala
+++ b/yaml/shared/src/main/scala/org/virtuslab/yaml/internal/load/compose/Composer.scala
@@ -51,8 +51,10 @@ object ComposerImpl extends Composer:
           s.metadata.anchor.foreach(anchor => aliases.put(anchor, node))
           Right(Result(node, tail))
         // todo #88
-        case _: EventKind.Alias =>
-          Left(ComposerError(s"Aliases aren't currently supported"))
+        case EventKind.Alias(alias) =>
+          aliases.get(alias) match
+            case Some(node) => Right(Result(node, tail))
+            case None       => Left(ComposerError(s"There is no anchor for $alias alias"))
         case event => Left(ComposerError(s"Expected YAML node, but found: $event"))
     case Nil =>
       Left(ComposerError("No events available"))
diff --git a/yaml/shared/src/test/scala/org/virtuslab/yaml/decoder/DecoderSuite.scala b/yaml/shared/src/test/scala/org/virtuslab/yaml/decoder/DecoderSuite.scala
index 8a0139290..2e85cccd3 100644
--- a/yaml/shared/src/test/scala/org/virtuslab/yaml/decoder/DecoderSuite.scala
+++ b/yaml/shared/src/test/scala/org/virtuslab/yaml/decoder/DecoderSuite.scala
@@ -186,6 +186,109 @@ class DecoderSuite extends munit.FunSuite:
     assertEquals(yaml.as[Spec], Right(expectedSpec))
   }
 
+  test("alias for scalar node") {
+    val yaml =
+      s"""|- &a 5
+          |- *a
+          |""".stripMargin
+
+    assertEquals(yaml.as[Any], Right(List(5, 5)))
+  }
+
+  test("alias for sequence node") {
+    val yaml =
+      s"""|seq1: &a 
+          | - 1
+          | - 2
+          |seq2: *a
+          |""".stripMargin
+
+    assertEquals(
+      yaml.as[Any],
+      Right(
+        Map(
+          "seq1" -> List(1, 2),
+          "seq2" -> List(1, 2)
+        )
+      )
+    )
+  }
+
+  test("alias for value in sequence") {
+    val yaml =
+      s"""|- &b
+          |  name: Mark McGwire
+          |  hr:   65
+          |- *b
+          |""".stripMargin
+
+    assertEquals(
+      yaml.as[Any],
+      Right(
+        List(
+          Map("name" -> "Mark McGwire", "hr" -> 65),
+          Map("name" -> "Mark McGwire", "hr" -> 65)
+        )
+      )
+    )
+  }
+
+  test("alias for flow sequence node") {
+    val yaml =
+      s"""|seq1: &a [1, 2]
+          |seq2: *a
+          |""".stripMargin
+
+    assertEquals(
+      yaml.as[Any],
+      Right(
+        Map(
+          "seq1" -> List(1, 2),
+          "seq2" -> List(1, 2)
+        )
+      )
+    )
+  }
+
+  test("alias for mapping node") {
+    val yaml =
+      s"""|map1: &a 
+          |  1: 2  
+          |  k1: v1
+          |map2: *a
+          |""".stripMargin
+
+    assertEquals(
+      yaml.as[Any],
+      Right(
+        Map(
+          "map1" -> Map(1 -> 2, "k1" -> "v1"),
+          "map2" -> Map(1 -> 2, "k1" -> "v1")
+        )
+      )
+    )
+  }
+
+  test("alias for flow mapping node") {
+    val yaml =
+      s"""|map1: &a {
+          |  1: 2,  
+          |  k1: v1
+          |}
+          |map2: *a
+          |""".stripMargin
+
+    assertEquals(
+      yaml.as[Any],
+      Right(
+        Map(
+          "map1" -> Map(1 -> 2, "k1" -> "v1"),
+          "map2" -> Map(1 -> 2, "k1" -> "v1")
+        )
+      )
+    )
+  }
+
   test("decode into Map[Any, Any]") {
 
     val yaml =