Fix #860: Nested Type name clashes within same package

src/main/java/com/squareup/javapoet/CodeWriter.java

@@ -401,8 +401,16 @@ String lookupName(ClassName className) {
 
     // If the class is in the same package, we're done.
     if (Objects.equals(packageName, className.packageName())) {
-      referencedNames.add(topLevelSimpleName);
-      return join(".", className.simpleNames());
+      String conflictClassName = packageName+"."+className.simpleName;//From same package (Nest)
+      //For nested conflict situation, the simpleName should be in QualifyList
+      //But its full name dont contains its super name
+      if(alwaysQualify.contains(className.simpleName)
+              &&Objects.equals(conflictClassName,className.canonicalName)){
+
+      }else{//If not, do regular trim
+        referencedNames.add(topLevelSimpleName);
+        return join(".", className.simpleNames());
+      }
     }
 
     // We'll have to use the fully-qualified name. Mark the type as importable for a future pass.

src/test/java/com/squareup/javapoet/FooInterface.java

@@ -0,0 +1,5 @@
+package com.squareup.javapoet;
+
+public interface FooInterface {
+    public class Nest{};
+}

src/test/java/com/squareup/javapoet/JavaFileTest.java

@@ -757,6 +757,50 @@ private TypeSpec importStaticTypeSpec(String name) {
         + "}\n");
   }
 
+  @Test public void avoidClashesWithNestedClasses_SamePackageTest() {
+    String source = JavaFile.builder("com.squareup.javapoet",
+            TypeSpec.classBuilder("Taco")
+                    // The external Name should be full
+                    .addField(ClassName.get(com.squareup.javapoet.Nest.class), "external_Nest")
+                    // The internal Name would be better with super name
+                    .addField(ClassName.get(com.squareup.javapoet.FooInterface.Nest.class), "interface_Nest")
+                    .addSuperinterface(com.squareup.javapoet.FooInterface.class)
+                    .build())
+            .build()
+            .toString();
+    assertThat(source).isEqualTo("package com.squareup.javapoet;\n" +
+            "\n" +
+            "class Taco implements FooInterface {\n" +
+            "  com.squareup.javapoet.Nest external_Nest;\n" +
+            "\n" +
+            "  FooInterface.Nest interface_Nest;\n" +
+            "}"+"\n");
+  }
+
+  @Test public void avoidClashesWithNestedClasses_InterExterPackageTest() {
+    String source = JavaFile.builder("com.squareup.javapoet",
+            TypeSpec.classBuilder("Taco")
+                    // The external Name should be full
+                    .addField(ClassName.get(com.squareup.javapoet.Nest.class), "external_Nest")
+                    // The internal Name would be better with super name
+                    .addField(ClassName.get(com.squareup.javapoet.FooInterface.Nest.class), "interface_Nest")
+                    // The external Name from external package
+                    .addField(ClassName.get("other","Nest"), "interface_Nest")
+                    .addSuperinterface(com.squareup.javapoet.FooInterface.class)
+                    .build())
+            .build()
+            .toString();
+    assertThat(source).isEqualTo("package com.squareup.javapoet;\n" +
+            "\n" +
+            "class Taco implements FooInterface {\n" +
+            "  com.squareup.javapoet.Nest external_Nest;\n" +
+            "\n" +
+            "  FooInterface.Nest interface_Nest;\n" +
+            "\n" +
+            "  other.Nest interface_Nest;\n" +
+            "}"+"\n");
+  }
+
   @Test public void avoidClashesWithNestedClasses_viaClass() {
     String source = JavaFile.builder("com.squareup.tacos",
         TypeSpec.classBuilder("Taco")
@@ -876,6 +920,10 @@ class NestedTypeB {
     }
   }
 
+  static class NestedTypeA{
+
+  }
+
   private TypeSpec.Builder childTypeBuilder() {
     return TypeSpec.classBuilder("Child")
         .addMethod(MethodSpec.methodBuilder("optionalString")

src/test/java/com/squareup/javapoet/Nest.java

@@ -0,0 +1,4 @@
+package com.squareup.javapoet;
+
+public class Nest {
+}