Merge pull request #666 from square/joel.improve-binding-validation-e…

…rror-messages Improve the error message for failed binding validations when the parameter and return type do not match
square · Dec 16, 2022 · 84ba1e5 · 84ba1e5
2 parents a4a932c + 7f2cac3
commit 84ba1e5
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Showing 2 changed files with 65 additions and 4 deletions.
diff --git a/compiler/src/main/java/com/squareup/anvil/compiler/codegen/dagger/BindsMethodValidator.kt b/compiler/src/main/java/com/squareup/anvil/compiler/codegen/dagger/BindsMethodValidator.kt
@@ -7,6 +7,7 @@ import com.squareup.anvil.compiler.codegen.PrivateCodeGenerator
 import com.squareup.anvil.compiler.daggerBindsFqName
 import com.squareup.anvil.compiler.daggerModuleFqName
 import com.squareup.anvil.compiler.internal.reference.AnvilCompilationExceptionFunctionReference
+import com.squareup.anvil.compiler.internal.reference.ClassReference
 import com.squareup.anvil.compiler.internal.reference.FunctionReference
 import com.squareup.anvil.compiler.internal.reference.allSuperTypeClassReferences
 import com.squareup.anvil.compiler.internal.reference.classAndInnerClassReferences
@@ -75,28 +76,48 @@ internal class BindsMethodValidator : PrivateCodeGenerator() {
     )
 
     if (!function.parameterMatchesReturnType() && !function.receiverMatchesReturnType()) {
+      val returnType = function.returnType().asClassReference().shortName
+      val paramSuperTypes = (function.parameterSuperTypes() ?: function.receiverSuperTypes())!!
+        .map { it.shortName }
+        .toList()
+
+      val superTypesMessage = if (paramSuperTypes.size == 1) {
+        "has no supertypes."
+      } else {
+        "only has the following supertypes: ${paramSuperTypes.drop(1)}"
+      }
       throw AnvilCompilationExceptionFunctionReference(
-        message = "@Binds methods' parameter type must be assignable to the return type",
+        message = "@Binds methods' parameter type must be assignable to the return type. " +
+          "Expected binding of type $returnType but impl parameter of type " +
+          "${paramSuperTypes.first()} $superTypesMessage",
         functionReference = function
       )
     }
   }
 
   private fun FunctionReference.Psi.parameterMatchesReturnType(): Boolean {
+    return parameterSuperTypes()
+      ?.contains(returnType().asClassReference())
+      ?: false
+  }
+
+  private fun FunctionReference.Psi.parameterSuperTypes(): Sequence<ClassReference>? {
     return parameters.singleOrNull()
       ?.type()
       ?.asClassReference()
       ?.allSuperTypeClassReferences(includeSelf = true)
+  }
+
+  private fun FunctionReference.Psi.receiverMatchesReturnType(): Boolean {
+    return receiverSuperTypes()
       ?.contains(returnType().asClassReference())
       ?: false
   }
 
-  private fun FunctionReference.Psi.receiverMatchesReturnType(): Boolean {
+  private fun FunctionReference.Psi.receiverSuperTypes(): Sequence<ClassReference>? {
     return function.receiverTypeReference
       ?.toTypeReference(declaringClass)
       ?.asClassReference()
       ?.allSuperTypeClassReferences(includeSelf = true)
-      ?.contains(returnType().asClassReference())
-      ?: false
   }
 }
diff --git a/compiler/src/test/java/com/squareup/anvil/compiler/dagger/BindsMethodValidatorTest.kt b/compiler/src/test/java/com/squareup/anvil/compiler/dagger/BindsMethodValidatorTest.kt
@@ -29,6 +29,41 @@ class BindsMethodValidatorTest(
 
   @Test
   fun `a binding with an incompatible parameter type fails to compile`() {
+    compile(
+      """
+      package com.squareup.test
+ 
+      import dagger.Binds
+      import dagger.Module
+      import javax.inject.Inject
+
+      interface Lorem
+      open class Ipsum
+      class Foo @Inject constructor() : Ipsum(), Lorem
+      interface Bar
+
+      @Module
+      abstract class BarModule {
+        @Binds
+        abstract fun bindsBar(impl: Foo): Bar
+      }
+      """
+    ) {
+      assertThat(exitCode).isError()
+      assertThat(messages).contains(
+        "@Binds methods' parameter type must be assignable to the return type"
+      )
+      if (!useDagger) {
+        assertThat(messages).contains(
+          "Expected binding of type Bar but impl parameter of type Foo only has the following " +
+            "supertypes: [Ipsum, Lorem]"
+        )
+      }
+    }
+  }
+
+  @Test
+  fun `a binding with an incompatible parameter type with no supertypes fails to compile`() {
     compile(
       """
       package com.squareup.test
@@ -51,6 +86,11 @@ class BindsMethodValidatorTest(
       assertThat(messages).contains(
         "@Binds methods' parameter type must be assignable to the return type"
       )
+      if (!useDagger) {
+        assertThat(messages).contains(
+          "Expected binding of type Bar but impl parameter of type Foo has no supertypes."
+        )
+      }
     }
   }