contextual: Make ContextSensitiveBinder work with requireExplicitBindings().

Same as regular toProvider() bindings, an explicit binding for the
provider is *not* required, unless to provider itself is injected
somewhere.  This is accomplished by generating a unique linked-key
binding for each ContextSensitiveProvider.

3 files changed, 42 insertions, 3 deletions

diff --git a/sangria-contextual/pom.xml b/sangria-contextual/pom.xml
index c939076..702616f 100644
--- a/sangria-contextual/pom.xml
+++ b/sangria-contextual/pom.xml
@@ -38,6 +38,12 @@
         </dependency>
 
         <dependency>
+            <groupId>com.tavianator.sangria</groupId>
+            <artifactId>sangria-test</artifactId>
+            <scope>test</scope>
+        </dependency>
+
+        <dependency>
             <groupId>junit</groupId>
             <artifactId>junit</artifactId>
             <scope>test</scope>
diff --git a/sangria-contextual/src/main/java/com/tavianator/sangria/contextual/ContextSensitiveBinder.java b/sangria-contextual/src/main/java/com/tavianator/sangria/contextual/ContextSensitiveBinder.java
index 6d5e502..fdc1ad0 100644
--- a/sangria-contextual/src/main/java/com/tavianator/sangria/contextual/ContextSensitiveBinder.java
+++ b/sangria-contextual/src/main/java/com/tavianator/sangria/contextual/ContextSensitiveBinder.java
@@ -40,6 +40,7 @@ import com.google.inject.spi.ProviderWithExtensionVisitor;
 import com.google.inject.spi.ProvisionListener;
 
 import com.tavianator.sangria.core.DelayedError;
+import com.tavianator.sangria.core.UniqueAnnotations;
 
 /**
  * A binder for {@link ContextSensitiveProvider}s.
@@ -139,10 +140,17 @@ public class ContextSensitiveBinder {
         public void toContextSensitiveProvider(Key<? extends ContextSensitiveProvider<? extends T>> key) {
             error.cancel();
 
-            binder.bind(bindingKey).toProvider(new ProviderKeyAdapter<>(key));
+            binder.bind(bindingKey).toProvider(new ProviderKeyAdapter<>(key, makeLinkedKey(key)));
             binder.bindListener(new BindingMatcher(bindingKey), new Trigger(bindingKey));
         }
 
+        private <U> Key<U> makeLinkedKey(Key<U> key) {
+            Key<U> linkedKey = Key.get(key.getTypeLiteral(), UniqueAnnotations.create());
+            binder.bind(linkedKey)
+                    .to(key);
+            return linkedKey;
+        }
+
         @Override
         public void toContextSensitiveProvider(ContextSensitiveProvider<? extends T> provider) {
             error.cancel();
@@ -190,15 +198,19 @@ public class ContextSensitiveBinder {
 
     private static class ProviderKeyAdapter<T> extends ProviderAdapter<T> implements ContextSensitiveProviderKeyBinding<T> {
         private final Key<? extends ContextSensitiveProvider<? extends T>> providerKey;
+        private final Key<? extends ContextSensitiveProvider<? extends T>> linkedKey;
         private Provider<? extends ContextSensitiveProvider<? extends T>> provider;
 
-        ProviderKeyAdapter(Key<? extends ContextSensitiveProvider<? extends T>> providerKey) {
+        ProviderKeyAdapter(
+                Key<? extends ContextSensitiveProvider<? extends T>> providerKey,
+                Key<? extends ContextSensitiveProvider<? extends T>> linkedKey) {
             this.providerKey = providerKey;
+            this.linkedKey = linkedKey;
         }
 
         @Inject
         void inject(Injector injector) {
-            provider = injector.getProvider(providerKey);
+            provider = injector.getProvider(linkedKey);
         }
 
         @Override
diff --git a/sangria-contextual/src/test/java/com/tavianator/sangria/contextual/ContextSensitiveBinderTest.java b/sangria-contextual/src/test/java/com/tavianator/sangria/contextual/ContextSensitiveBinderTest.java
index 1e2ab49..68250cb 100644
--- a/sangria-contextual/src/test/java/com/tavianator/sangria/contextual/ContextSensitiveBinderTest.java
+++ b/sangria-contextual/src/test/java/com/tavianator/sangria/contextual/ContextSensitiveBinderTest.java
@@ -28,6 +28,7 @@ import com.google.inject.Guice;
 import com.google.inject.Injector;
 import com.google.inject.Key;
 import com.google.inject.MembersInjector;
+import com.google.inject.Module;
 import com.google.inject.Provider;
 import com.google.inject.ProvisionException;
 import com.google.inject.TypeLiteral;
@@ -40,6 +41,7 @@ import org.junit.Rule;
 import org.junit.Test;
 import org.junit.rules.ExpectedException;
 
+import static com.tavianator.sangria.test.SangriaMatchers.*;
 import static org.hamcrest.Matchers.*;
 import static org.junit.Assert.*;
 
@@ -54,6 +56,10 @@ public class ContextSensitiveBinderTest {
     public @Rule ExpectedException thrown = ExpectedException.none();
 
     private static class SelfProvider implements ContextSensitiveProvider<String> {
+        @Inject
+        SelfProvider() {
+        }
+
         // For testing getInjectionPoints() in the SPI below
         @SuppressWarnings("unused")
         @Inject Injector injector;
@@ -191,6 +197,21 @@ public class ContextSensitiveBinderTest {
         assertThat(hasSelf.selfProvider.get(), equalTo("<unknown>"));
     }
 
+    @Test
+    public void testBestPractices() {
+        Module module = new AbstractModule() {
+            @Override
+            protected void configure() {
+                ContextSensitiveBinder.create(binder())
+                        .bind(String.class)
+                        .annotatedWith(Names.named("self"))
+                        .toContextSensitiveProvider(SelfProvider.class);
+            }
+        };
+        assertThat(module, is(atomic()));
+        assertThat(module, followsBestPractices());
+    }
+
     private static class RequiredContextProvider implements ContextSensitiveProvider<String> {
         @Override
         public String getInContext(InjectionPoint injectionPoint) {