Added extra test for cross file substitions

hoplite-core/src/main/kotlin/com/sksamuel/hoplite/ConfigLoader.kt

@@ -335,10 +335,13 @@ class ConfigLoader constructor(
     }
   }
 
+  /**
+   * Loads all property sources and combines them into a single node.
+   */
   private fun loadNode(configs: List<ConfigSource>): ConfigResult<Node> {
     val srcs = propertySources + configs.map { ConfigFilePropertySource(it, parserRegistry) }
     return srcs.map { it.node() }.sequence()
-      .map { it.reduce { acc, b -> acc.fallback(b) } }
+      .map { it.reduce { acc, b -> acc.merge(b) } }
       .mapInvalid {
         val multipleFailures = ConfigFailure.MultipleFailures(it)
         multipleFailures

hoplite-core/src/main/kotlin/com/sksamuel/hoplite/fallback.kt

@@ -2,19 +2,19 @@ package com.sksamuel.hoplite
 
 /**
  * Returns a new [Node] which is the result of merging this node, with keys from the given node,
- * such as keys in this node take precedence.
+ * with keys in this node taking precedence.
  */
-fun Node.fallback(other: Node): Node {
-  return when (val self = this) {
+internal fun Node.merge(other: Node): Node {
+  return when (this) {
     is Undefined -> other
     is MapNode -> when (other) {
       is MapNode -> {
-        val keys = self.map.keys + other.map.keys
-        val map = keys.associateWith { self.atKey(it).fallback(other.atKey(it)) }
-        MapNode(map, self.pos, self.value.fallback(other.value))
+        val keys = this.map.keys + other.map.keys
+        val map = keys.associateWith { this.atKey(it).merge(other.atKey(it)) }
+        MapNode(map, this.pos, this.value.merge(other.value))
       }
-      else -> self
+      else -> this
     }
-    else -> self
+    else -> this
   }
 }

hoplite-core/src/test/kotlin/com/sksamuel/hoplite/FallbackTest.kt

@@ -23,12 +23,12 @@ class FallbackTest : FunSpec({
       Pos.NoPos
     )
 
-    val f = node1.fallback(node2)
+    val f = node1.merge(node2)
     f["a"] shouldBe StringNode("foo", Pos.NoPos)
     f["b"] shouldBe StringNode("bar", Pos.NoPos)
     f["c"] shouldBe StringNode("baz", Pos.NoPos)
 
-    val g = node2.fallback(node1)
+    val g = node2.merge(node1)
     g["a"] shouldBe StringNode("faz", Pos.NoPos)
     g["b"] shouldBe StringNode("bar", Pos.NoPos)
     g["c"] shouldBe StringNode("baz", Pos.NoPos)
@@ -63,13 +63,13 @@ class FallbackTest : FunSpec({
       Pos.NoPos
     )
 
-    val f = node1.fallback(node2)
+    val f = node1.merge(node2)
     f["a"] shouldBe StringNode("foo", Pos.NoPos)
     f["b"]["j"] shouldBe StringNode("jen", Pos.NoPos)
     f["b"]["k"] shouldBe StringNode("ken", Pos.NoPos)
     f["c"] shouldBe StringNode("baz", Pos.NoPos)
 
-    val g = node2.fallback(node1)
+    val g = node2.merge(node1)
     g["a"] shouldBe StringNode("foo", Pos.NoPos)
     g["b"]["j"] shouldBe StringNode("jen", Pos.NoPos)
     g["b"]["k"] shouldBe StringNode("kez", Pos.NoPos)

hoplite-yaml/src/test/kotlin/com/sksamuel/hoplite/yaml/LookupPreprocessorTest.kt

@@ -6,12 +6,18 @@ import io.kotest.matchers.shouldBe
 
 class LookupPreprocessorTest : FunSpec() {
 
-  data class Test(val a: String,
-                  val b: String,
-                  val c: String,
-                  val d: String,
-                  val e: String,
-                  val f: String
+  data class Test(
+    val a: String,
+    val b: String,
+    val c: String,
+    val d: String,
+    val e: String,
+    val f: String
+  )
+
+  data class Test2(
+    val env: String,
+    val hostname: String
   )
 
   init {
@@ -39,5 +45,13 @@ class LookupPreprocessorTest : FunSpec() {
           f = "f{{unknown}}"
         )
     }
+
+    test("lookup preprocessor across multiple files") {
+      ConfigLoader().loadConfigOrThrow<Test2>("/test_lookup1.yml", "/test_lookup2.yml") shouldBe
+        Test2(
+          env = "PROD",
+          hostname = "wibble.PROD"
+        )
+    }
   }
 }

hoplite-yaml/src/test/resources/test_lookup1.yml

@@ -0,0 +1 @@
+env: PROD

hoplite-yaml/src/test/resources/test_lookup2.yml

@@ -0,0 +1 @@
+hostname: wibble.{{env}}