feature: support to cast config to value

README.md

@@ -167,7 +167,7 @@ compile(group = "com.github.uchuhimo.konf", name = "konf", version = "master-SNA
 
     ```kotlin
     val config = Config { addSpec(ServerSpec) }
-            .from.yaml.file("/path/to/server.yml")
+            .from.yaml.file("server.yml")
             .from.json.resource("server.json")
             .from.env()
             .from.systemProperties()
@@ -177,27 +177,27 @@ compile(group = "com.github.uchuhimo.konf", name = "konf", version = "master-SNA
 
     ```kotlin
     val config = Config { addSpec(ServerSpec) }.withSource(
-        Source.from.yaml.file("/path/to/server.yml") +
+        Source.from.yaml.file("server.yml") +
         Source.from.json.resource("server.json") +
         Source.from.env() +
         Source.from.systemProperties()
     )
     ```
 
-    This config contains all items defined in `ServerSpec`, and load values from 4 different sources. Values in resource file `server.json` will override those in file `/path/to/server.yml`, values from system environment will override those in `server.json`, and values from system properties will override those from system environment.
+    This config contains all items defined in `ServerSpec`, and load values from 4 different sources. Values in resource file `server.json` will override those in file `server.yml`, values from system environment will override those in `server.json`, and values from system properties will override those from system environment.
 
-    If you want to watch file `/path/to/server.yml` and reload values when file content is changed, you can use `watchFile` instead of `file`:
+    If you want to watch file `server.yml` and reload values when file content is changed, you can use `watchFile` instead of `file`:
 
     ```kotlin
     val config = Config { addSpec(ServerSpec) }
-            .from.yaml.watchFile("/path/to/server.yml")
+            .from.yaml.watchFile("server.yml")
             .from.json.resource("server.json")
             .from.env()
             .from.systemProperties()
     ```
 
 3. Define values in source. You can define in any of these sources:
-    - in `/path/to/server.yml`:
+    - in `server.yml`:
         ```yaml
         server:
             host: 0.0.0.0
@@ -224,10 +224,27 @@ compile(group = "com.github.uchuhimo.konf", name = "konf", version = "master-SNA
 
 4. Retrieve values from config with type-safe APIs:
     ```kotlin
+    data class Server(val host: String, val port: Int) {
+        fun start() {}
+    }
+
     val server = Server(config[ServerSpec.host], config[ServerSpec.port])
     server.start()
     ```
 
+5. Retrieve values from multiple sources without using config spec:
+
+    ```kotlin
+    val server = Config()
+            .from.yaml.file("server.yml")
+            .from.json.resource("server.json")
+            .from.env()
+            .from.systemProperties()
+            .at("server")
+            .toValue<Server>()
+    server.start()
+    ```
+
 ## Define items
 
 Config items is declared in config spec, added to config by `Config#addSpec`. All items in same config spec have same prefix. Define a config spec with prefix `local.server`:
@@ -358,6 +375,14 @@ or:
 val host = config<String>("server.host")
 ```
 
+### Cast config to value
+
+Cast config to a value with the target type:
+
+```kotlin
+val server = config.toValue<Server>()
+```
+
 ### Check whether an item exists in config or not
 
 Check whether an item exists in config or not:

konf-all/build.gradle.kts

@@ -31,4 +31,6 @@ dependencies {
 
     val main by sourceSets
     snippetImplementation(main.output)
+    val snippet by sourceSets
+    testImplementation(snippet.output)
 }

konf-all/src/snippet/kotlin/com/uchuhimo/konf/snippet/QuickStart.kt

@@ -20,33 +20,52 @@ import com.uchuhimo.konf.Config
 import com.uchuhimo.konf.ConfigSpec
 import com.uchuhimo.konf.source.Source
 import com.uchuhimo.konf.source.yaml
+import com.uchuhimo.konf.toValue
+import java.io.File
 
 object ServerSpec : ConfigSpec() {
     val host by optional("0.0.0.0")
     val port by required<Int>()
 }
 
 fun main(args: Array<String>) {
+    val file = File("server.yml")
+    file.writeText("""
+        server:
+            host: 127.0.0.1
+            port: 8080
+    """.trimIndent())
+    file.deleteOnExit()
     val config = Config { addSpec(ServerSpec) }
-        .from.yaml.file("/path/to/server.yml")
+        .from.yaml.file("server.yml")
         .from.json.resource("server.json")
         .from.env()
         .from.systemProperties()
     run {
         val config = Config { addSpec(ServerSpec) }.withSource(
-            Source.from.yaml.file("/path/to/server.yml") +
+            Source.from.yaml.file("server.yml") +
                 Source.from.json.resource("server.json") +
                 Source.from.env() +
                 Source.from.systemProperties()
         )
     }
     run {
         val config = Config { addSpec(ServerSpec) }
-            .from.yaml.watchFile("/path/to/server.yml")
+            .from.yaml.watchFile("server.yml")
             .from.json.resource("server.json")
             .from.env()
             .from.systemProperties()
     }
     val server = Server(config[ServerSpec.host], config[ServerSpec.port])
     server.start()
+    run {
+        val server = Config()
+            .from.yaml.file("server.yml")
+            .from.json.resource("server.json")
+            .from.env()
+            .from.systemProperties()
+            .at("server")
+            .toValue<Server>()
+        server.start()
+    }
 }

konf-all/src/snippet/resources/server.json

@@ -0,0 +1,6 @@
+{
+  "server": {
+    "host": "127.0.0.1",
+    "port": 8080
+  }
+}

konf-all/src/test/kotlin/com/uchuhimo/konf/source/QuickStartSpec.kt

@@ -0,0 +1,99 @@
+/*
+ * Copyright 2017-2019 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.uchuhimo.konf.source
+
+import com.natpryce.hamkrest.assertion.assertThat
+import com.natpryce.hamkrest.equalTo
+import com.uchuhimo.konf.Config
+import com.uchuhimo.konf.snippet.Server
+import com.uchuhimo.konf.snippet.ServerSpec
+import com.uchuhimo.konf.toValue
+import org.jetbrains.spek.api.Spek
+import org.jetbrains.spek.api.dsl.it
+import org.jetbrains.spek.api.dsl.on
+import java.io.File
+
+object QuickStartSpec : Spek({
+    on("use default loaders") {
+        val config = useFile {
+            Config { addSpec(ServerSpec) }
+                .from.yaml.file("server.yml")
+                .from.json.resource("server.json")
+                .from.env()
+                .from.systemProperties()
+        }
+        it("should load all values") {
+            assertThat(config.toMap(),
+                equalTo(mapOf("server.host" to "127.0.0.1", "server.port" to 8080)))
+        }
+    }
+    on("use default providers") {
+        val config = useFile {
+            Config { addSpec(ServerSpec) }.withSource(
+                Source.from.yaml.file("server.yml") +
+                    Source.from.json.resource("server.json") +
+                    Source.from.env() +
+                    Source.from.systemProperties()
+            )
+        }
+        it("should load all values") {
+            assertThat(config.toMap(),
+                equalTo(mapOf("server.host" to "127.0.0.1", "server.port" to 8080)))
+        }
+    }
+    on("watch file") {
+        val config = useFile {
+            Config { addSpec(ServerSpec) }
+                .from.yaml.watchFile("server.yml")
+                .from.json.resource("server.json")
+                .from.env()
+                .from.systemProperties()
+        }
+        it("should load all values") {
+            assertThat(config.toMap(),
+                equalTo(mapOf("server.host" to "127.0.0.1", "server.port" to 8080)))
+        }
+    }
+    on("cast to value") {
+        val config = useFile {
+            Config()
+                .from.yaml.file("server.yml")
+                .from.json.resource("server.json")
+                .from.env()
+                .from.systemProperties()
+                .at("server")
+        }
+        val server = config.toValue<Server>()
+        it("should load all values") {
+            assertThat(server, equalTo(Server(host = "127.0.0.1", port = 8080)))
+        }
+    }
+})
+
+private fun <T> useFile(block: () -> T): T {
+    val file = File("server.yml")
+    file.writeText("""
+        server:
+            host: 127.0.0.1
+            port: 8080
+    """.trimIndent())
+    try {
+        return block()
+    } finally {
+        file.delete()
+    }
+}

konf-core/src/main/kotlin/com/uchuhimo/konf/BaseConfig.kt

@@ -54,7 +54,7 @@ open class BaseConfig(
     private val specsInLayer: MutableList<Spec> = mutableListOf(),
     private val featuresInLayer: MutableMap<Feature, Boolean> = mutableMapOf(),
     private val nodeByItem: MutableMap<Item<*>, ItemNode> = mutableMapOf(),
-    private val tree: TreeNode = ContainerNode.empty(),
+    private val tree: TreeNode = ContainerNode.placeHolder(),
     private val hasChildren: Value<Boolean> = Value(false),
     private val lock: ReentrantReadWriteLock = ReentrantReadWriteLock()
 ) : Config {
@@ -68,25 +68,26 @@ open class BaseConfig(
         if (path.isEmpty()) {
             return this
         } else {
+            val originalConfig = this
             return object : BaseConfig(
                 name = name,
                 parent = parent?.at(path) as BaseConfig?,
                 mapper = mapper,
                 specsInLayer = specsInLayer,
                 featuresInLayer = featuresInLayer,
                 nodeByItem = nodeByItem,
-                tree = tree.getOrNull(path) ?: ContainerNode.empty().also {
+                tree = tree.getOrNull(path) ?: ContainerNode.placeHolder().also {
                     lock.write { tree[path] = it }
                 },
                 hasChildren = hasChildren,
                 lock = lock
             ) {
                 override val source: Source
                     get() {
-                        if (path !in this@BaseConfig.source) {
-                            this@BaseConfig.source.tree[path] = ContainerNode.empty()
+                        if (path !in originalConfig.source) {
+                            originalConfig.source.tree[path] = ContainerNode.placeHolder()
                         }
-                        return this@BaseConfig.source[path]
+                        return originalConfig.source[path]
                     }
             }
         }
@@ -96,6 +97,7 @@ open class BaseConfig(
         if (prefix.isEmpty()) {
             return this
         } else {
+            val originalConfig = this
             return object : BaseConfig(
                 name = name,
                 parent = parent?.withPrefix(prefix) as BaseConfig?,
@@ -104,11 +106,13 @@ open class BaseConfig(
                 featuresInLayer = featuresInLayer,
                 nodeByItem = nodeByItem,
                 tree = if (prefix.isEmpty()) tree
-                else ContainerNode.empty().apply { set(prefix, tree) },
+                else ContainerNode.empty().apply {
+                    set(prefix, tree)
+                },
                 hasChildren = hasChildren,
                 lock = lock
             ) {
-                override val source: Source get() = this@BaseConfig.source.withPrefix(prefix)
+                override val source: Source get() = originalConfig.source.withPrefix(prefix)
             }
         }
     }
@@ -303,7 +307,7 @@ open class BaseConfig(
         return if (this is LeafNode) {
             true
         } else if (path.isEmpty()) {
-            children.isNotEmpty()
+            !isEmpty()
         } else {
             val key = path.first()
             val rest = path.drop(1)
@@ -424,6 +428,9 @@ open class BaseConfig(
         lock.write {
             nodeByItem.clear()
             tree.children.clear()
+            if (tree is MapNode) {
+                tree.isPlaceHolder = true
+            }
         }
     }
 

konf-core/src/main/kotlin/com/uchuhimo/konf/Config.kt

@@ -355,7 +355,17 @@ interface Config : ItemContainer {
  * @return a property that can read/set associated value casted from config
  */
 inline fun <reified T> Config.cast() =
-    object : RequiredConfigProperty<T>(this.withPrefix("root"), name = "root") {}
+    object : RequiredConfigProperty<T>(this.withPrefix("root").withLayer(), name = "root") {}
+
+/**
+ * Returns a value casted from config.
+ *
+ * @return a value casted from config
+ */
+inline fun <reified T> Config.toValue(): T {
+    val value by cast<T>()
+    return value
+}
 
 /**
  * Returns a property that can read/set associated value for specified required item.
@@ -383,8 +393,7 @@ open class RequiredConfigProperty<T>(
     private val type: JavaType = TypeFactory.defaultInstance().constructType(this::class.java)
         .findSuperType(RequiredConfigProperty::class.java).bindings.typeParameters[0]
 
-    operator fun provideDelegate(thisRef: Any?, property: KProperty<*>):
-        ReadWriteProperty<Any?, T> {
+    operator fun provideDelegate(thisRef: Any?, property: KProperty<*>): ReadWriteProperty<Any?, T> {
         val item = object : RequiredItem<T>(Spec.dummy, name
             ?: property.name, description, type, nullable) {}
         config.addItem(item, prefix)