resolve oneof field name conflicts with imported packages (#1947)

Include oneof field names in conflict detection to properly generate
_root_ prefixes when oneof fields conflict with imported package names.

This fixes issue #1911 where ScalaPB would generate incorrect import
paths for oneof fields that conflict with imported package names.

The fix includes:
- Enhanced conflict detection in DescriptorImplicits.scala to include oneof field names
- Updated ProtobufGenerator.scala to properly handle conflicts when generating imports
- Added comprehensive tests to verify the fix works correctly
- Fixed test file to use correct generated class name (OneofImportConflictTest)

Closes #1911

Author: i-am-the-slime

compiler-plugin/src/main/scala/scalapb/compiler/DescriptorImplicits.scala

@@ -387,10 +387,13 @@ class DescriptorImplicits private[compiler] (
       case FieldDescriptor.JavaType.BYTE_STRING => "_root_.com.google.protobuf.ByteString"
       case FieldDescriptor.JavaType.STRING      => "_root_.scala.Predef.String"
       case FieldDescriptor.JavaType.MESSAGE =>
-        fd.getMessageType.scalaType
-          .fullNameWithMaybeRoot(fd.getContainingType.fields.map(_.scalaName))
+        val contextNames = fd.getContainingType.fields.map(_.scalaName) ++
+          fd.getContainingType.getRealOneofs.asScala.map(_.scalaName.nameSymbol)
+        fd.getMessageType.scalaType.fullNameWithMaybeRoot(contextNames)
       case FieldDescriptor.JavaType.ENUM =>
-        fd.getEnumType.scalaType.fullNameWithMaybeRoot(fd.getContainingType.fields.map(_.scalaName))
+        val contextNames = fd.getContainingType.fields.map(_.scalaName) ++
+          fd.getContainingType.getRealOneofs.asScala.map(_.scalaName.nameSymbol)
+        fd.getEnumType.scalaType.fullNameWithMaybeRoot(contextNames)
     }
 
     def singleScalaTypeName = customSingleScalaTypeName.getOrElse(baseSingleScalaTypeName)

compiler-plugin/src/main/scala/scalapb/compiler/ProtobufGenerator.scala

@@ -188,11 +188,15 @@ class ProtobufGenerator(
             .mkString("_root_.com.google.protobuf.ByteString.copyFrom(Array[Byte](", ", ", "))")
       case FieldDescriptor.JavaType.STRING => escapeScalaString(defaultValue.asInstanceOf[String])
       case FieldDescriptor.JavaType.MESSAGE =>
+        val contextNames = field.getContainingType.fields.map(_.scalaName) ++
+          field.getContainingType.getRealOneofs.asScala.map(_.scalaName.nameSymbol)
         field.getMessageType.scalaType
-          .fullNameWithMaybeRoot(field.getContainingType) + ".defaultInstance"
+          .fullNameWithMaybeRoot(contextNames) + ".defaultInstance"
       case FieldDescriptor.JavaType.ENUM =>
+        val contextNames = field.getContainingType.fields.map(_.scalaName) ++
+          field.getContainingType.getRealOneofs.asScala.map(_.scalaName.nameSymbol)
         field.getEnumType.scalaType
-          .fullNameWithMaybeRoot(field.getContainingType) + "." + defaultValue
+          .fullNameWithMaybeRoot(contextNames) + "." + defaultValue
           .asInstanceOf[EnumValueDescriptor]
           .scalaName
           .asSymbol
@@ -217,13 +221,22 @@ class ProtobufGenerator(
       case FieldDescriptor.JavaType.BYTE_STRING => Identity
       case FieldDescriptor.JavaType.STRING      => Identity
       case FieldDescriptor.JavaType.MESSAGE =>
-        FunctionApplication(field.getMessageType.scalaType.fullName + ".fromJavaProto")
+        val contextNames = field.getContainingType.fields.map(_.scalaName) ++
+          field.getContainingType.getRealOneofs.asScala.map(_.scalaName.nameSymbol)
+        FunctionApplication(
+          field.getMessageType.scalaType.fullNameWithMaybeRoot(contextNames) + ".fromJavaProto"
+        )
       case FieldDescriptor.JavaType.ENUM =>
+        val contextNames = field.getContainingType.fields.map(_.scalaName) ++
+          field.getContainingType.getRealOneofs.asScala.map(_.scalaName.nameSymbol)
         if (!field.legacyEnumFieldTreatedAsClosed())
           MethodApplication("intValue") andThen FunctionApplication(
-            field.getEnumType.scalaType.fullName + ".fromValue"
+            field.getEnumType.scalaType.fullNameWithMaybeRoot(contextNames) + ".fromValue"
+          )
+        else
+          FunctionApplication(
+            field.getEnumType.scalaType.fullNameWithMaybeRoot(contextNames) + ".fromJavaValue"
           )
-        else FunctionApplication(field.getEnumType.scalaType.fullName + ".fromJavaValue")
     }
     baseValueConversion andThen toCustomTypeExpr(field)
   }
@@ -289,12 +302,20 @@ class ProtobufGenerator(
       case FieldDescriptor.JavaType.BYTE_STRING => Identity
       case FieldDescriptor.JavaType.STRING      => Identity
       case FieldDescriptor.JavaType.MESSAGE =>
-        FunctionApplication(field.getMessageType.scalaType.fullName + ".toJavaProto")
+        val contextNames = field.getContainingType.fields.map(_.scalaName) ++
+          field.getContainingType.getRealOneofs.asScala.map(_.scalaName.nameSymbol)
+        FunctionApplication(
+          field.getMessageType.scalaType.fullNameWithMaybeRoot(contextNames) + ".toJavaProto"
+        )
       case FieldDescriptor.JavaType.ENUM =>
+        val contextNames = field.getContainingType.fields.map(_.scalaName) ++
+          field.getContainingType.getRealOneofs.asScala.map(_.scalaName.nameSymbol)
         if (!field.legacyEnumFieldTreatedAsClosed())
           (MethodApplication("value") andThen maybeBox("_root_.scala.Int.box"))
         else
-          FunctionApplication(field.getEnumType.scalaType.fullName + ".toJavaValue")
+          FunctionApplication(
+            field.getEnumType.scalaType.fullNameWithMaybeRoot(contextNames) + ".toJavaValue"
+          )
     }
   }
 

e2e/src/main/protobuf/location/v1/location.proto

@@ -0,0 +1,8 @@
+syntax = "proto3";
+
+package location.v1;
+
+message Coordinate {
+  double latitude = 1;
+  double longitude = 2;
+} 

e2e/src/main/protobuf/oneof_import_conflict.proto

@@ -0,0 +1,23 @@
+syntax = "proto3";
+
+package com.thesamet.proto.e2e;
+
+import "location/v1/location.proto";
+
+// Test case for oneof field name conflicting with imported package name.
+// This ensures ScalaPB correctly adds _root_ prefixes to avoid naming conflicts.
+message OneofImportConflictTest {
+  oneof location {  // This field name conflicts with the imported package "location"
+    location.v1.Coordinate location_coordinate = 2;
+  }
+}
+
+// Additional test with multiple conflicts
+message MultipleConflictTest {
+  oneof location {
+    location.v1.Coordinate coord = 1;
+  }
+
+  // Regular field with same type should also get _root_ prefix due to oneof conflict
+  location.v1.Coordinate regular_coord = 2;
+}

e2e/src/test/scala/OneofImportConflictSpec.scala

@@ -0,0 +1,45 @@
+import org.scalatest.flatspec.AnyFlatSpec
+import org.scalatest.matchers.should.Matchers
+import com.thesamet.proto.e2e.oneof_import_conflict.{OneofImportConflictTest, MultipleConflictTest}
+
+class OneofImportConflictSpec extends AnyFlatSpec with Matchers {
+
+  "oneof field conflicting with imported package name" should "generate correct code with _root_ prefixes" in {
+    // Test basic oneof conflict - the fact this compiles means _root_ prefixes work
+    val coord = _root_.location.v1.location.Coordinate(latitude = 1.0, longitude = 2.0)
+
+    val message = OneofImportConflictTest(
+      location = OneofImportConflictTest.Location.LocationCoordinate(coord)
+    )
+
+    // Test functionality works correctly
+    message.getLocationCoordinate shouldBe coord
+    message.location.isLocationCoordinate shouldBe true
+    message.location.locationCoordinate shouldBe Some(coord)
+
+    // Test serialization round-trip
+    val bytes  = message.toByteArray
+    val parsed = OneofImportConflictTest.parseFrom(bytes)
+    parsed shouldBe message
+  }
+
+  "multiple field types with import conflicts" should "all use _root_ prefixes consistently" in {
+    val coord1 = _root_.location.v1.location.Coordinate(latitude = 3.0, longitude = 4.0)
+    val coord2 = _root_.location.v1.location.Coordinate(latitude = 5.0, longitude = 6.0)
+
+    val message = MultipleConflictTest(
+      location = MultipleConflictTest.Location.Coord(coord1),
+      regularCoord = Some(coord2)
+    )
+
+    // Test both oneof and regular fields work correctly
+    message.location.isCoord shouldBe true
+    message.location.coord shouldBe Some(coord1)
+    message.regularCoord shouldBe Some(coord2)
+
+    // Test serialization round-trip
+    val bytes  = message.toByteArray
+    val parsed = MultipleConflictTest.parseFrom(bytes)
+    parsed shouldBe message
+  }
+}