Support collection.distinct() in Java shell

packages/java-shell/src/main/kotlin/com/mongodb/mongosh/service/JavaServiceProvider.kt

@@ -385,8 +385,16 @@ internal class JavaServiceProvider(private val client: MongoClient,
     }
 
     @HostAccess.Export
-    override fun distinct(database: String, collection: String, fieldName: String, filter: Value?, options: Value?): Value = promise<Any?> {
-        Left(NotImplementedError())
+    override fun distinct(database: String, collection: String, fieldName: String, filter: Value?, options: Value?): Value = promise {
+        val filter = toDocument(filter, "filter") ?: Document()
+        val options = toDocument(options, "options") ?: Document()
+        getDatabase(database, null).flatMap { db ->
+            convert(null, distinctConverters, distinctDefaultConverter, options).map { _ ->
+                val fieldClass = db.getCollection(collection).find(filter).asSequence().take(1_000_000).firstNotNullOfOrNull { it[fieldName] }?.javaClass
+                    ?: throw Exception("Cannot determine type of field $fieldName")
+                converter.toJs(db.getCollection(collection).distinct(fieldName, filter, fieldClass))
+            }
+        }
     }
 
     @HostAccess.Export

packages/java-shell/src/main/kotlin/com/mongodb/mongosh/service/optionConverters.kt

@@ -583,6 +583,10 @@ internal val insertManyConverters: Map<String, (InsertManyOptions, Any?) -> Eith
 
 internal val insertManyDefaultConverter = unrecognizedField<InsertManyOptions>("insert many options")
 
+internal val distinctConverters: Map<String, (Any?, Any?) -> Either<Any?>> = mapOf()
+
+internal val distinctDefaultConverter = unrecognizedField<Any?>("distinct options")
+
 internal val renameCollectionConverters: Map<String, (RenameCollectionOptions, Any?) -> Either<RenameCollectionOptions>> = mapOf(
     typed("dropTarget", Boolean::class.java) { opt, value ->
         opt.dropTarget(value)

packages/java-shell/src/test/resources/collection/distinct.expected.txt

@@ -1 +1,7 @@
-kotlin.NotImplementedError: An operation is not implemented.
+[ 1, 2, 3 ]
+[ "hello", "world" ]
+org.bson.BsonInvalidOperationException: Invalid numeric type, found: STRING
+[ 1 ]
+[ { }, { "a": 1 } ]
+[ "hello" ]
+com.mongodb.mongosh.result.CommandException: unrecognized distinct options field: collation

packages/java-shell/src/test/resources/collection/distinct.js

@@ -1,9 +1,21 @@
 // before
 db.coll.deleteMany({});
-db.coll.insertOne({a: 1});
-db.coll.insertOne({a: 2});
-db.coll.insertOne({a: 3});
+db.coll.insertOne({num: 1, str: "hello", mixedType: 1,       doc: {},     category: "café"});
+db.coll.insertOne({num: 2, str: "world", mixedType: "hello", doc: {},     category: "cafe"});
+db.coll.insertOne({num: 3, str: "hello", mixedType: 2,       doc: {a: 1}, category: "cafE", onlyInOneDoc: 1});
 // command
-db.coll.distinct("a");
+db.coll.distinct("num");
+// command
+db.coll.distinct("str");
+// command
+db.coll.distinct("mixedType");
+// command
+db.coll.distinct("onlyInOneDoc");
+// command
+db.coll.distinct("doc");
+// command
+db.coll.distinct("str", {num: 1});
+// command
+db.coll.distinct("category", {}, {collation: {locale: "fr", strength: 1}});
 // clear
 db.coll.drop();