Make java library earlier on classpath

scala/private/phases/phase_compile.bzl

@@ -254,7 +254,7 @@ def _compile_or_empty(
             full_jars.append(java_jar.jar)
 
         if java_jar:
-            merged_provider = java_common.merge([scala_compilation_provider, java_jar.java_compilation_provider])
+            merged_provider = java_common.merge([java_jar.java_compilation_provider, scala_compilation_provider])
         else:
             merged_provider = scala_compilation_provider
 

test/src/main/scala/scalarules/test/java_classpath_order/BUILD

@@ -0,0 +1,28 @@
+load("//scala:scala.bzl", "scala_library", "scala_test")
+
+# Original library with the class to be shadowed
+scala_library(
+    name = "original",
+    srcs = ["Original.scala"],
+)
+
+# Library that shadows the Overridable class with a Java file
+# The Java file (Overridable.java) should take precedence over
+# the Overridable class from the :original dependency
+scala_library(
+    name = "with_java_override",
+    srcs = ["Overridable.java"],
+    deps = [":original"],
+)
+
+# Test that verifies the Java override works correctly
+# Note: This test is incompatible with strict deps checking because the checker
+# doesn't understand class shadowing - it sees Overridable as coming from :original
+# rather than the shadowed version from :with_java_override
+scala_test(
+    name = "verify_override_test",
+    srcs = ["VerifyOverride.scala"],
+    tags = ["no-strict-deps"],
+    unused_dependency_checker_mode = "off",
+    deps = [":with_java_override"],
+)

test/src/main/scala/scalarules/test/java_classpath_order/Original.scala

@@ -0,0 +1,6 @@
+package scalarules.test.java_classpath_order
+
+class Overridable {
+  def getValue(): String = "original"
+}
+

test/src/main/scala/scalarules/test/java_classpath_order/Overridable.java

@@ -0,0 +1,8 @@
+package scalarules.test.java_classpath_order;
+
+public class Overridable {
+  public String getValue() {
+    return "overridden";
+  }
+}
+

test/src/main/scala/scalarules/test/java_classpath_order/VerifyOverride.scala

@@ -0,0 +1,25 @@
+package scalarules.test.java_classpath_order
+
+import org.scalatest.flatspec.AnyFlatSpec
+import org.scalatest.matchers.should.Matchers
+
+/**
+ * This test verifies that the Java class (Overridable) shadows
+ * the Scala class from the dependency.
+ *
+ * The expected behavior is:
+ * - The Java file compiled in the scala_library with_java_override should
+ *   appear first on the classpath
+ * - When instantiating Overridable, we should get the Java version
+ *   which returns "overridden"
+ */
+class VerifyOverrideTest extends AnyFlatSpec with Matchers {
+
+  "Java class in scala_library" should "shadow the dependency's class" in {
+    val instance = new Overridable()
+    val value = instance.getValue()
+
+    value shouldBe "overridden"
+  }
+}
+

test_rules_scala.sh

@@ -19,10 +19,10 @@ $runner bazel build src/... test/...
 $runner bazel test "${test_output_flag}" src/... test/...
 $runner bazel test "${test_output_flag}" third_party/...
 $runner bazel build --extra_toolchains=//test/toolchains:high_level_transitive_deps_strict_deps_error -- test/...
-$runner bazel build --extra_toolchains=//scala:minimal_direct_source_deps -- test/...
+$runner bazel build --extra_toolchains=//scala:minimal_direct_source_deps --build_tag_filters=-no-strict-deps -- test/...
 #$runner bazel build --extra_toolchains=//test/toolchains:high_level_transitive_deps_strict_deps_error --all_incompatible_changes -- test/...
 $runner bazel test "${test_output_flag}" --extra_toolchains=//test/toolchains:high_level_transitive_deps_strict_deps_error -- test/...
-$runner bazel test "${test_output_flag}" --extra_toolchains=//scala:minimal_direct_source_deps -- test/...
+$runner bazel test "${test_output_flag}" --extra_toolchains=//scala:minimal_direct_source_deps --build_tag_filters=-no-strict-deps --test_tag_filters=-no-strict-deps -- test/...
 $runner bazel build test_expect_failure/missing_direct_deps/internal_deps/... --strict_java_deps=warn --extra_toolchains=//test/toolchains:high_level_transitive_deps_strict_deps_warn
 $runner bazel build //test_expect_failure/proto_source_root/... --strict_proto_deps=off
 $runner bazel test "$test_output_flag" //test/... --extra_toolchains="//test_expect_failure/plus_one_deps:plus_one_deps"