From 48cda86e0705ea50df97149822305b3c8a0e8000 Mon Sep 17 00:00:00 2001
From: Johannes Link <business@johanneslink.net>
Date: Thu, 28 Nov 2024 14:11:56 +0100
Subject: [PATCH] Made Arbitrary provider method matching looser. Tackling bug
 https://github.com/jqwik-team/jqwik/issues/599

---
 .../InstanceBasedSubtypeProvider.java         |  7 +--
 .../PropertyMethodArbitraryResolverTests.java | 47 ++++++++++++++++++-
 2 files changed, 47 insertions(+), 7 deletions(-)

diff --git a/engine/src/main/java/net/jqwik/engine/properties/InstanceBasedSubtypeProvider.java b/engine/src/main/java/net/jqwik/engine/properties/InstanceBasedSubtypeProvider.java
index c24b80370..326de32e8 100644
--- a/engine/src/main/java/net/jqwik/engine/properties/InstanceBasedSubtypeProvider.java
+++ b/engine/src/main/java/net/jqwik/engine/properties/InstanceBasedSubtypeProvider.java
@@ -125,12 +125,7 @@ private Optional<Method> findProviderMethodByName(String generatorToFind, TypeUs
 			return provideAnnotation.map(Provide::value).orElse("");
 		};
 
-		TypeUsage effectiveTargetType = targetType.isTypeVariableOrWildcard() ? targetType : TypeUsage.wildcard(targetType);
-		TypeUsage expectedReturnType = TypeUsage.of(
-			Arbitrary.class,
-			effectiveTargetType
-		);
-
+		TypeUsage expectedReturnType = TypeUsage.of(Arbitrary.class);
 		return findGeneratorMethod(generatorToFind, contextInstance().getClass(), Provide.class, generatorNameSupplier, expectedReturnType);
 	}
 
diff --git a/engine/src/test/java/net/jqwik/engine/properties/PropertyMethodArbitraryResolverTests.java b/engine/src/test/java/net/jqwik/engine/properties/PropertyMethodArbitraryResolverTests.java
index 5ce1d6075..b1efff55a 100644
--- a/engine/src/test/java/net/jqwik/engine/properties/PropertyMethodArbitraryResolverTests.java
+++ b/engine/src/test/java/net/jqwik/engine/properties/PropertyMethodArbitraryResolverTests.java
@@ -28,6 +28,16 @@ public String toString() {
 		}
 	}
 
+	private class ThingArbitrary extends ArbitraryDecorator<Thing> {
+
+		@Override
+		protected Arbitrary<Thing> arbitrary() {
+			return  Arbitraries.just(new Thing());
+		}
+	}
+
+
+
 	@Target({ElementType.METHOD})
 	@Retention(RetentionPolicy.RUNTIME)
 	@Provide
@@ -208,6 +218,14 @@ void providerMethodCanHaveWildcardArbitrary() {
 			assertThingArbitrary(arbitraries.iterator().next());
 		}
 
+		@Example
+		void providerMethodCanReturnArbitrarySubtype() {
+			PropertyMethodArbitraryResolver provider = getResolver(WithNamedProviders.class);
+			MethodParameter parameter = getParameter(WithNamedProviders.class, "thingFromArbitrarySubtype");
+			Set<Arbitrary<?>> arbitraries = provider.forParameter(parameter);
+			assertThingArbitrary(arbitraries.iterator().next());
+		}
+
 		@Example
 		void providerMethodCanHaveTypeUsageParameter() {
 			PropertyMethodArbitraryResolver provider = getResolver(WithNamedProviders.class);
@@ -240,6 +258,13 @@ void findGeneratorByName() {
 			assertThingArbitrary(arbitraries.iterator().next());
 		}
 
+		@Example
+		void failWhenProviderMethodDoesNotReturnArbitrary() {
+			PropertyMethodArbitraryResolver provider = getResolver(WithNamedProviders.class);
+			MethodParameter parameter = getParameter(WithNamedProviders.class, "providerDoesNotReturnArbitrary");
+			assertThat(provider.forParameter(parameter)).isEmpty();
+		}
+
 		@Example
 		void findGeneratorBySupplier() {
 			PropertyMethodArbitraryResolver provider = getResolver(WithNamedProviders.class);
@@ -402,7 +427,7 @@ Arbitrary<Thing> aThingy() {
 			}
 
 			@Property
-			boolean thingFromWildcard(@ForAll("aThingFromWildcard") Object aThing) {
+			boolean thingFromWildcard(@ForAll("aThingFromWildcard") Thing aThing) {
 				return true;
 			}
 
@@ -411,6 +436,16 @@ Arbitrary<?> aThingFromWildcard() {
 				return Arbitraries.just(new Thing());
 			}
 
+			@Property
+			boolean thingFromArbitrarySubtype(@ForAll("aThingFromArbitrarySubtype") Thing aThing) {
+				return true;
+			}
+
+			@Provide
+			ThingArbitrary aThingFromArbitrarySubtype() {
+				return new ThingArbitrary();
+			}
+
 			@Property
 			boolean thingBySupplier(@ForAll(supplier = ThingSupplier.class) Thing aThing) {
 				return true;
@@ -514,6 +549,16 @@ Arbitrary<Thing> aThing() {
 				return Arbitraries.just(new Thing());
 			}
 
+			@Property
+			boolean providerDoesNotReturnArbitrary(@ForAll("notAnArbitrary") Thing aThing) {
+				return true;
+			}
+
+			@Provide
+			Thing notAnArbitrary() {
+				return new Thing();
+			}
+
 			@Group
 			class NestedWithNamedProviders {
 				@Property