From 60a89e424f6ad477ecc89760407d6999c5ee8d48 Mon Sep 17 00:00:00 2001
From: Michael Williamson <mike@zwobble.org>
Date: Sat, 20 Jun 2026 10:32:54 +0100
Subject: Handle subnamespaces when mapping namespaces to Java packages

---
 .../output/generators/java/JavaGenerator.java      | 22 +++++++++++++++-------
 .../hobgoblin/compiler/types/NamespaceName.java    |  8 ++++++++
 .../output/lang/java/JavaGeneratorTests.java       | 21 ++++++++++++++++++++-
 3 files changed, 43 insertions(+), 8 deletions(-)

(limited to 'src')

diff --git a/src/main/java/org/zwobble/hobgoblin/compiler/output/generators/java/JavaGenerator.java b/src/main/java/org/zwobble/hobgoblin/compiler/output/generators/java/JavaGenerator.java
index 617d438..e68acaa 100644
--- a/src/main/java/org/zwobble/hobgoblin/compiler/output/generators/java/JavaGenerator.java
+++ b/src/main/java/org/zwobble/hobgoblin/compiler/output/generators/java/JavaGenerator.java
@@ -34,14 +34,22 @@ public class JavaGenerator {
     }
 
     public List<String> namespaceToJavaPackageParts(NamespaceName namespaceName) {
-        // TODO: handle subpackages
-        return this.config.namespaceConfig(namespaceName)
-            .map(namespaceConfig -> namespaceConfig.packageName())
-            .orElseGet(() -> {
-                var packageParts = new ArrayList<>(this.config.packageName());
-                packageParts.addAll(namespaceName.parts());
+        var ancestorNamespaceName = namespaceName;
+        var remainingNamespaceNameParts = new ArrayList<String>();
+        while (!ancestorNamespaceName.isRoot()) {
+            var namespaceConfig = this.config.namespaceConfig(ancestorNamespaceName);
+            if (namespaceConfig.isPresent()) {
+                var packageParts = new ArrayList<>(namespaceConfig.get().packageName());
+                packageParts.addAll(remainingNamespaceNameParts.reversed());
                 return packageParts;
-            });
+            }
+            remainingNamespaceNameParts.add(ancestorNamespaceName.parts().getLast());
+            ancestorNamespaceName = ancestorNamespaceName.parent();
+        }
+
+        var packageParts = new ArrayList<>(this.config.packageName());
+        packageParts.addAll(namespaceName.parts());
+        return packageParts;
     }
 
     public JavaTypeRef generateTypeRef(Type type) {
diff --git a/src/main/java/org/zwobble/hobgoblin/compiler/types/NamespaceName.java b/src/main/java/org/zwobble/hobgoblin/compiler/types/NamespaceName.java
index e0fb2d3..2cb3497 100644
--- a/src/main/java/org/zwobble/hobgoblin/compiler/types/NamespaceName.java
+++ b/src/main/java/org/zwobble/hobgoblin/compiler/types/NamespaceName.java
@@ -8,6 +8,14 @@ public record NamespaceName(List<String> parts) {
         return new NamespaceName(Arrays.asList(parts));
     }
 
+    public NamespaceName parent() {
+        return new NamespaceName(parts.subList(0, parts.size() - 1));
+    }
+
+    public boolean isRoot() {
+        return parts.isEmpty();
+    }
+
     @Override
     public String toString() {
         return String.join("/", parts);
diff --git a/src/test/java/org/zwobble/hobgoblin/compiler/output/lang/java/JavaGeneratorTests.java b/src/test/java/org/zwobble/hobgoblin/compiler/output/lang/java/JavaGeneratorTests.java
index 9cbd5d9..d7c3eeb 100644
--- a/src/test/java/org/zwobble/hobgoblin/compiler/output/lang/java/JavaGeneratorTests.java
+++ b/src/test/java/org/zwobble/hobgoblin/compiler/output/lang/java/JavaGeneratorTests.java
@@ -28,7 +28,7 @@ public class JavaGeneratorTests {
     }
 
     @Test
-    public void explicitJavaPackageIsUsedForNamespaceWhenAvailable() {
+    public void explicitJavaPackageIsUsedForNamespaceWhenExactNamespaceHasMapping() {
         var config = new JavaGeneratorConfig(
             List.of("com", "example"),
             Map.ofEntries(
@@ -45,4 +45,23 @@ public class JavaGeneratorTests {
 
         assertThat(result, equalTo(List.of("com", "other")));
     }
+
+    @Test
+    public void explicitJavaPackageIsUsedForNamespaceWhenAncestorNamespaceHasMapping() {
+        var config = new JavaGeneratorConfig(
+            List.of("com", "example"),
+            Map.ofEntries(
+                Map.entry(
+                    NamespaceName.of("a", "b"),
+                    new JavaNamespaceConfig(List.of("com", "other"))
+                )
+            ),
+            Map.of()
+        );
+        var generator = new JavaGenerator(config);
+
+        var result = generator.namespaceToJavaPackageParts(NamespaceName.of("a", "b", "c", "d"));
+
+        assertThat(result, equalTo(List.of("com", "other", "c", "d")));
+    }
 }
-- 
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