Add API to read Config using PathAnchor resolutions (#212)

* use getConstructor for plugin instantiation

* add API for reading Config from Config.Resource

* fallback to getDeclaredConstructor after trying getConstructor

src/main/java/com/worksap/nlp/sudachi/Config.java

@@ -22,6 +22,7 @@
 import javax.json.Json;
 import javax.json.JsonArrayBuilder;
 import javax.json.JsonObject;
+import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.io.InputStream;
 import java.lang.reflect.Constructor;
@@ -221,6 +222,43 @@ public static Config fromClasspathMerged(String name) throws IOException {
         return fromClasspathMerged(Config.class.getClassLoader(), name);
     }
 
+    /**
+     * Create Config object from the passed resource. Resources are created by
+     * {@link PathAnchor}.
+     *
+     * @param resource
+     *            resource object capturing
+     * @param anchor
+     *            object that will be used for path resolution and class loading
+     * @return parsed Config object
+     * @param <T>
+     *            can be anything
+     * @throws IOException
+     *             when IO fails
+     * @throws FileNotFoundException
+     *             if resource can not be found
+     * @see PathAnchor#resource(String)
+     */
+    public static <T> Config fromResource(Resource<T> resource, PathAnchor anchor) throws IOException {
+        if (resource instanceof Resource.Classpath) {
+            return fromClasspath((URL) resource.repr(), anchor);
+        }
+        if (resource instanceof Resource.Filesystem) {
+            return fromFile((Path) resource.repr(), anchor);
+        }
+        if (resource instanceof Resource.Ready) {
+            Object ready = resource.repr();
+            if (ready instanceof Config) {
+                return (Config) ready;
+            }
+            throw new ClassCastException("expected Config, was " + ready.getClass());
+        }
+        if (resource instanceof Resource.NotFound) {
+            throw new FileNotFoundException(resource.toString());
+        }
+        throw new IllegalStateException("should not happen");
+    }
+
     /**
      * Parses all config files with the specified name in the classpath, merging
      * them. Files are loaded with the provided classloader.
@@ -694,7 +732,7 @@ public T instantiate(PathAnchor anchor) {
 
             T result;
             try {
-                Constructor<? extends T> constructor = clz.getDeclaredConstructor();
+                Constructor<? extends T> constructor = lookupConstructor(clz);
                 result = constructor.newInstance();
             } catch (InstantiationException | IllegalAccessException | NoSuchMethodException
                     | InvocationTargetException e) {
@@ -706,6 +744,19 @@ public T instantiate(PathAnchor anchor) {
             return result;
         }
 
+        private Constructor<? extends T> lookupConstructor(Class<? extends T> clz) throws NoSuchMethodException {
+            try {
+                return clz.getConstructor();
+            } catch (NoSuchMethodException ignored) {
+                try {
+                    return clz.getDeclaredConstructor();
+                } catch (NoSuchMethodException | SecurityException ignored2) {
+                    throw new NoSuchElementException("class " + clz
+                            + " did not have accessible no-arg constructor or security policy forbids access");
+                }
+            }
+        }
+
         /**
          * Add a string value to the plugin configuration
          *

src/test/java/com/worksap/nlp/sudachi/ConfigTest.kt

@@ -16,6 +16,9 @@
 
 package com.worksap.nlp.sudachi
 
+import com.worksap.nlp.sudachi.Config.Resource
+import com.worksap.nlp.sudachi.dictionary.build.res
+import java.io.FileNotFoundException
 import java.net.URL
 import java.nio.file.Path
 import java.nio.file.Paths
@@ -144,4 +147,40 @@ class ConfigTest {
     cfg.anchoredWith(PathAnchor.filesystem("test"))
     assertIs<PathAnchor.Chain>(cfg.anchor)
   }
+
+  @Test
+  fun fromResourceFile() {
+    val anchor = PathAnchor.filesystem("src/test/resources")
+    val cfgFile = anchor.resource<Any>("sudachi.json")
+    val cfg = Config.fromResource(cfgFile, anchor)
+    assertEquals(1, cfg.userDictionaries.size)
+  }
+
+  @Test
+  fun fromResourceClasspath() {
+    val anchor = PathAnchor.classpath(javaClass.classLoader)
+    val cfgFile = anchor.resource<Any>("sudachi.json")
+    val cfg = Config.fromResource(cfgFile, anchor)
+    assertEquals(1, cfg.userDictionaries.size)
+  }
+
+  @Test
+  fun fromReady() {
+    val configRes = Resource.ready(Config.defaultConfig())
+    val cfg = Config.fromResource(configRes, PathAnchor.none())
+    assertEquals(1, cfg.userDictionaries.size)
+  }
+
+  @Test
+  fun fromReadyInvalidClass() {
+    val res = Resource.ready(10)
+    assertFailsWith<ClassCastException> { Config.fromResource(res, PathAnchor.none()) }
+  }
+
+  @Test
+  fun fromReadyNotFound() {
+    val anchor = PathAnchor.none()
+    val res = anchor.resource<Any>("not_found.resource")
+    assertFailsWith<FileNotFoundException> { Config.fromResource(res, anchor) }
+  }
 }