Use consistent return types

Author: codeboost

CLAUDE.md

@@ -0,0 +1,45 @@
+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Development Commands
+
+### Running Tests
+```bash
+clj -M:test
+```
+
+### Running a Single Test File
+```bash
+clj -M:test -n xitdb.database-test
+```
+
+### REPL Development
+```bash
+clj
+```
+
+## Architecture Overview
+
+This is a Clojure wrapper around the xitdb-java immutable database, providing atom-like semantics for persistent data structures.
+
+### Core Components
+
+- **xitdb.db**: Main database interface implementing IAtom protocol. The `XITDBDatabase` type wraps Java database instances and provides thread-safe operations via ReentrantLock.
+
+- **xitdb.xitdb-types**: Type dispatch system that handles reading/writing different data structures (HashMap, ArrayList, LinkedList, HashSet) to/from database cursors.
+
+- **Data Structure Implementations**: Each data type (hash-map, array-list, linked-list, hash-set) has its own namespace implementing Clojure collection protocols over persistent storage.
+
+- **Conversion Layer**: `util/conversion.clj` handles serialization between Clojure values and database slots.
+
+### Key Protocols
+
+- `ISlot`: For types that can provide their own database slot representation
+- `IReadFromCursor`: For reading values from database cursors  
+- `IMaterialize`: For converting lazy database structures to in-memory Clojure data
+- `IUnwrap`: For extracting wrapped values
+
+### Database Operations
+
+The database acts like a Clojure atom with `reset!` and `swap!` operations, but persists all changes to disk. History is maintained as an append-only log accessible via `db-history`.

src/xitdb/util/operations.clj

@@ -60,23 +60,23 @@
   [^WriteLinkedArrayList wlal v]
   (let [cursor (.appendCursor wlal)]
     (.write cursor (conversion/v->slot! cursor v))
-    nil))
+    wlal))
 
 (defn linked-array-list-insert-value!
   "Inserts a value at position pos in a WriteLinkedArrayList.
   Converts the value to an appropriate XitDB representation using v->slot!."
   [^WriteLinkedArrayList wlal pos v]
   (let [cursor (-> wlal .cursor)]
     (.insert wlal pos (conversion/v->slot! cursor v)))
-  nil)
+  wlal)
 
 (defn linked-array-list-pop!
   "Removes the first element from a WriteLinkedArrayList.
   This is a stack-like operation (LIFO) for linked lists.
-  Returns nil."
+  Returns the modified WriteLinkedArrayList."
   [^WriteLinkedArrayList wlal]
   (.remove wlal 0)
-  nil)
+  wlal)
 
 ;; ============================================================================
 ;; Map Operations
@@ -99,7 +99,8 @@
         key-cursor (.putKeyCursor whm key-hash)
         cursor     (.putCursor whm key-hash)]
     (.writeIfEmpty key-cursor (conversion/v->slot! key-cursor k))
-    (.write cursor (conversion/v->slot! cursor v))))
+    (.write cursor (conversion/v->slot! cursor v))
+    whm))
 
 (defn map-dissoc-key!
   "Removes a key-value pair from a WriteHashMap.