Fix JSON sources to convert to Lists and other types

docs/json-argument-source.adoc

@@ -79,6 +79,13 @@ This parametrized test will generate the following tests:
 * [1] Luke
 * [2] Yoda
 
+The extension will automatically map JSON types to their corresponding Java types, including arrays:
+
+[source,java,indent=0]
+----
+include::{json-demo}/[tag=inline_source_with_list]
+----
+
 === Multiple Argument Methods
 
 If the method has multiple arguments, each JSON object argument will be deconstructed to each of the method arguments.

src/demo/java/org/junitpioneer/jupiter/json/JsonArgumentSourceExtensionDemo.java

@@ -10,6 +10,8 @@
 
 package org.junitpioneer.jupiter.json;
 
+import java.util.List;
+
 import org.junit.jupiter.api.Nested;
 import org.junit.jupiter.params.ParameterizedTest;
 
@@ -94,6 +96,20 @@ void singleJediProperty(
 		// end::inline_source_with_property[]
 		// @formatter:on
 
+		// @formatter:off
+		// tag::inline_source_with_list[]
+		@ParameterizedTest
+		@JsonSource({
+				"{ name: 'Yoda', padawans: ['Dooku', 'Luke']  }",
+				"{ name: 'Obi-Wan', padawans: ['Anakin', 'Luke'] }"
+		})
+		void multipleJedis(
+				@Property("padawans") List<String> padawanNames) {
+			// YOUR TEST CODE HERE
+		}
+		// end::inline_source_with_list[]
+		// @formatter:on
+
 		// @formatter:off
 		// tag::inline_source_deconstruct_from_array[]
 		@ParameterizedTest

src/main/java/org/junitpioneer/jupiter/json/AbstractJsonArgumentsProvider.java

@@ -55,15 +55,16 @@ private static Object createArgumentForCartesianProvider(Parameter parameter, No
 	}
 
 	private static Arguments createArguments(Method method, Node node) {
-		boolean singleParameter = method.getParameterCount() == 1;
-		if (singleParameter) {
+		if (method.getParameterCount() == 1) {
 			Parameter onlyParameter = method.getParameters()[0];
 			// When there is a single parameter, the user might want to extract a single value or an entire type.
 			// When the parameter has the `@Property` annotation, then a single value needs to be extracted.
 			Property property = onlyParameter.getAnnotation(Property.class);
 			if (property == null) {
 				// no property specified -> the node should be converted in the parameter type
-				return Arguments.arguments(node.toType(onlyParameter.getType()));
+				// We must explicitly wrap the return into an Object[] because otherwise the return
+				// value is mistakenly interpreted as an Object[] and throws a ClassCastException
+				return () -> new Object[] { node.toType(onlyParameter.getParameterizedType()) };
 			}
 
 			// otherwise, treat this as method arguments
@@ -82,7 +83,7 @@ private static Arguments createArgumentsForMethod(Method method, Node node) {
 							: property.value();
 					return node
 							.getNode(name)
-							.map(value -> value.value(parameter.getType()))
+							.map(value -> value.value(parameter.getParameterizedType()))
 							.orElse(null);
 				})
 				.toArray();

src/main/java/org/junitpioneer/jupiter/json/JacksonNode.java

@@ -11,6 +11,7 @@
 package org.junitpioneer.jupiter.json;
 
 import java.io.UncheckedIOException;
+import java.lang.reflect.Type;
 import java.util.Optional;
 import java.util.stream.Stream;
 import java.util.stream.StreamSupport;
@@ -43,9 +44,9 @@ public Stream<Node> elements() {
 	}
 
 	@Override
-	public <T> T toType(Class<T> type) {
+	public <T> T toType(Type type) {
 		try {
-			return objectMapper.treeToValue(node, type);
+			return objectMapper.treeToValue(node, objectMapper.constructType(type));
 		}
 		catch (JsonProcessingException e) {
 			throw new UncheckedIOException("Failed to convert to type " + type, e);
@@ -62,7 +63,7 @@ public Optional<Node> getNode(String name) {
 	}
 
 	@Override
-	public Object value(Class<?> typeHint) {
+	public Object value(Type typeHint) {
 		if (node.isTextual()) {
 			return node.textValue();
 		} else if (node.isInt()) {
@@ -81,7 +82,7 @@ public Object value(Class<?> typeHint) {
 			return node.decimalValue();
 		} else if (node.isBigInteger()) {
 			return node.bigIntegerValue();
-		} else if (node.isObject()) {
+		} else if (node.isObject() || node.isArray()) {
 			return toType(typeHint);
 		}
 		return node;

src/main/java/org/junitpioneer/jupiter/json/Node.java

@@ -10,6 +10,7 @@
 
 package org.junitpioneer.jupiter.json;
 
+import java.lang.reflect.Type;
 import java.util.Optional;
 import java.util.stream.Stream;
 
@@ -36,7 +37,7 @@ interface Node {
 	 * @param <T> the type
 	 * @return the converted type
 	 */
-	<T> T toType(Class<T> type);
+	<T> T toType(Type type);
 
 	/**
 	 * Get the node value with the given name.
@@ -52,6 +53,6 @@ interface Node {
 	 * @param typeHint the potential type of the value
 	 * @return the node value
 	 */
-	Object value(Class<?> typeHint);
+	Object value(Type typeHint);
 
 }

src/test/java/org/junitpioneer/jupiter/json/ArrayNodeToListTests.java

@@ -0,0 +1,169 @@
+/*
+ * Copyright 2016-2022 the original author or authors.
+ *
+ * All rights reserved. This program and the accompanying materials are
+ * made available under the terms of the Eclipse Public License v2.0 which
+ * accompanies this distribution and is available at
+ *
+ * http://www.eclipse.org/legal/epl-v20.html
+ */
+
+package org.junitpioneer.jupiter.json;
+
+import static org.junitpioneer.testkit.assertion.PioneerAssert.assertThat;
+
+import java.io.UncheckedIOException;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.function.Predicate;
+
+import org.assertj.core.api.Assertions;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junitpioneer.jupiter.ReportEntry;
+import org.junitpioneer.testkit.ExecutionResults;
+import org.junitpioneer.testkit.PioneerTestKit;
+
+@DisplayName("Converting JSON to lists")
+public class ArrayNodeToListTests {
+
+	private static final String COMPOSERS = "org/junitpioneer/jupiter/json/composers.json";
+	private static final String POETS = "org/junitpioneer/jupiter/json/poets.json";
+	private static final String BAD_POEMS = "org/junitpioneer/jupiter/json/bad_poems.json";
+
+	@Test
+	@DisplayName("can convert classpath source arrays to List")
+	void classpathTest() {
+		ExecutionResults results = PioneerTestKit
+				.executeTestMethodWithParameterTypes(ArrayNodeToListTests.class, "convertFromClasspath", String.class,
+					List.class);
+
+		assertThat(results).hasNumberOfSucceededTests(2);
+		assertThat(results)
+				.hasNumberOfReportEntries(2)
+				.withValues("[Spartacus, Piano Concerto in D-flat major]",
+					"[The Isle of the Dead, Morceaux de fantaisie]");
+	}
+
+	@Test
+	@DisplayName("can convert annotation source arrays to list")
+	void annotationTest() {
+		ExecutionResults results = PioneerTestKit
+				.executeTestMethodWithParameterTypes(ArrayNodeToListTests.class, "convertFromAnnotation", List.class);
+
+		assertThat(results).hasNumberOfSucceededTests(2);
+		assertThat(results).hasNumberOfReportEntries(2).withValues("[1, 4, 7]", "[2, 4, 9]");
+	}
+
+	@Test
+	@DisplayName("can convert using a specific List implementation")
+	void specificImplementation() {
+		ExecutionResults results = PioneerTestKit
+				.executeTestMethodWithParameterTypes(ArrayNodeToListTests.class, "convertWithExplicitListType",
+					LinkedList.class);
+
+		assertThat(results).hasNumberOfSucceededTests(2);
+		assertThat(results).hasNumberOfReportEntries(2).withValues("[false, true, false]", "[true, false, true]");
+	}
+
+	@Test
+	@DisplayName("can convert classpath source arrays to List with more complex objects")
+	void classpathTestWithComplexObject() {
+		ExecutionResults results = PioneerTestKit
+				.executeTestMethodWithParameterTypes(ArrayNodeToListTests.class, "convertToComplexObject", String.class,
+					List.class);
+
+		assertThat(results).hasNumberOfSucceededTests(2);
+		assertThat(results)
+				.hasNumberOfReportEntries(2)
+				.withValues(
+					"Edgar Allan Poe: [The Black Cat (1843), The Cask of Amontillado (1846), The Pit and the Pendulum (1842)]",
+					"T. S. Eliot: [The Hollow Men (1925), Ash Wednesday (1930)]");
+	}
+
+	@Test
+	@DisplayName("throws a ParameterResolutionException if it can not convert complex objects")
+	void throwsForMalformedComplexObjects() {
+		ExecutionResults results = PioneerTestKit
+				.executeTestMethodWithParameterTypes(ArrayNodeToListTests.BadConfigurationTestCase.class,
+					"conversionException", List.class);
+
+		assertThat(results)
+				.hasSingleFailedContainer()
+				.withExceptionInstanceOf(UncheckedIOException.class)
+				.hasMessageContaining("Failed to convert to type");
+	}
+
+	@ParameterizedTest
+	@JsonClasspathSource(COMPOSERS)
+	@ReportEntry("{1}")
+	void convertFromClasspath(@Property("name") String name, @Property("music") List<String> works) {
+		Assertions.assertThat(name).isNotEmpty();
+		Assertions.assertThat(works).hasSize(2);
+	}
+
+	@ParameterizedTest
+	@JsonSource({ "{ 'single': [1, 4, 7] }", "{ 'single': [2, 4, 9] }" })
+	@ReportEntry("{0}")
+	void convertFromAnnotation(@Property("single") List<Integer> numbers) {
+		Assertions.assertThat(numbers).hasSize(3);
+	}
+
+	@ParameterizedTest
+	@JsonSource({ "{ 'statements': [true, false, true] }", "{ 'statements': [false, true, false] }" })
+	@ReportEntry("{0}")
+	void convertWithExplicitListType(@Property("statements") LinkedList<Boolean> numbers) {
+		Assertions.assertThat(numbers).hasSize(3);
+	}
+
+	@ParameterizedTest
+	@JsonClasspathSource(POETS)
+	@ReportEntry("{0}: {1}")
+	void convertToComplexObject(@Property("name") String name, @Property("works") List<Poem> poems) {
+		Predicate<Integer> predicate = name.equals("T. S. Eliot") ? release -> release < 1900
+				: release -> release > 1900;
+		Assertions.assertThat(poems).extracting(Poem::getRelease).noneMatch(predicate);
+	}
+
+	static class BadConfigurationTestCase {
+
+		@ParameterizedTest
+		@JsonClasspathSource(BAD_POEMS)
+		void conversionException(@Property("poems") List<Poem> poems) {
+		}
+
+	}
+
+	public static class Poem {
+
+		private String title;
+		private int release;
+
+		public Poem() {
+		}
+
+		public int getRelease() {
+			return release;
+		}
+
+		public void setRelease(int release) {
+			this.release = release;
+		}
+
+		public String getTitle() {
+			return title;
+		}
+
+		public void setTitle(String title) {
+			this.title = title;
+		}
+
+		@Override
+		public String toString() {
+			return title + " (" + release + ")";
+		}
+
+	}
+
+}

src/test/resources/org/junitpioneer/jupiter/json/bad_poems.json

@@ -0,0 +1,15 @@
+[
+  {
+    "name": "Robert Frost",
+    "poems": [
+      {
+        "title": "The Road Not Taken",
+        "release": 1915
+      },
+      {
+        "title": "A Witness Tree",
+        "release": "abcd"
+      }
+    ]
+  }
+]

src/test/resources/org/junitpioneer/jupiter/json/composers.json

@@ -0,0 +1,16 @@
+[
+  {
+    "name": "Aram Khachaturian",
+    "music": [
+      "Spartacus",
+      "Piano Concerto in D-flat major"
+    ]
+  },
+  {
+    "name": "Sergei Rachmaninoff",
+    "music": [
+      "The Isle of the Dead",
+      "Morceaux de fantaisie"
+    ]
+  }
+]

src/test/resources/org/junitpioneer/jupiter/json/poets.json

@@ -0,0 +1,32 @@
+[
+  {
+    "name": "Edgar Allan Poe",
+    "works": [
+      {
+        "title": "The Black Cat",
+        "release": 1843
+      },
+      {
+        "title": "The Cask of Amontillado",
+        "release": 1846
+      },
+      {
+        "title": "The Pit and the Pendulum",
+        "release": 1842
+      }
+    ]
+  },
+  {
+    "name": "T. S. Eliot",
+    "works": [
+      {
+        "title": "The Hollow Men",
+        "release": 1925
+      },
+      {
+        "title": "Ash Wednesday",
+        "release": 1930
+      }
+    ]
+  }
+]