Add option for ExportCSVConfig to target txn outputs (#262)

* Add transaction output name to the ExportCSVConfig action

* Add transaction_output_name alternative to export_csv_config_v2

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* Fix Call.target_type() for variadic builtin.tuple

builtin.tuple is registered as variadic (arity -1), so make_builtin
gives it an empty param list and the generic type-variable matching
can't resolve the return type T. Add a special case that infers
TupleType directly from the argument types, matching what _infer_type
already does in the parser.

Without this, IfElse nodes wrapping tuple constructs were typed as
interface{} in Go, causing a compile error when the function's declared
return type is []interface{}.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* Regenerate parsers, printers, and test snapshots

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* Add ExportCSVColumns/Source equality and transaction_output_name to ExportCSVConfig

ExportCSVColumns had no custom == so structural comparison fell back to identity,
breaking ExportCSVSource comparisons. Add equality for ExportCSVColumns first,
then ExportCSVSource, then wire csv_source, csv_config, and the new
transaction_output_name field into ExportCSVConfig ==, hash, and isequal.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* Regenerate parsers and printers

---------

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: davidwzhao

meta/src/meta/grammar.y

@@ -123,6 +123,7 @@
 %nonterm export_csv_column transactions.ExportCSVColumn
 %nonterm export_csv_columns_list Sequence[transactions.ExportCSVColumn]
 %nonterm export_csv_config transactions.ExportCSVConfig
+%nonterm export_csv_output_location Tuple[String, String]
 %nonterm export_csv_path String
 %nonterm export_csv_source transactions.ExportCSVSource
 %nonterm export_iceberg_config transactions.ExportIcebergConfig
@@ -1384,10 +1385,10 @@ export
         $3: transactions.ExportIcebergConfig = $$.iceberg_config
 
 export_csv_config
-    : "(" "export_csv_config_v2" export_csv_path export_csv_source csv_config ")"
-      construct: $$ = construct_export_csv_config_with_source($3, $4, $5)
+    : "(" "export_csv_config_v2" export_csv_output_location export_csv_source csv_config ")"
+      construct: $$ = construct_export_csv_config_with_location($3, $4, $5)
       deconstruct if builtin.length($$.data_columns) == 0:
-        $3: String = $$.path
+        $3: Tuple[String, String] = deconstruct_export_csv_output_location($$)
         $4: transactions.ExportCSVSource = $$.csv_source
         $5: logic.CSVConfig = $$.csv_config
     | "(" "export_csv_config" export_csv_path export_csv_columns_list config_dict ")"
@@ -1397,6 +1398,16 @@ export_csv_config
         $4: Sequence[transactions.ExportCSVColumn] = $$.data_columns
         $5: Sequence[Tuple[String, logic.Value]] = deconstruct_export_csv_config($$)
 
+export_csv_output_location
+    : "(" "path" STRING ")"
+      construct: $$ = builtin.tuple($3, "")
+      deconstruct if $$[0] != "":
+        $3: String = $$[0]
+    | "(" "transaction_output_name" name ")"
+      construct: $$ = builtin.tuple("", $3)
+      deconstruct if $$[1] != "":
+        $3: String = $$[1]
+
 export_csv_path
     : "(" "path" STRING ")"
 
@@ -1719,13 +1730,17 @@ def construct_export_csv_config(
         syntax_escapechar=builtin.some(syntax_escapechar),
     )
 
-def construct_export_csv_config_with_source(
-    path: String,
+def deconstruct_export_csv_output_location(msg: transactions.ExportCSVConfig) -> Tuple[String, String]:
+    return (msg.path, msg.transaction_output_name)
+
+def construct_export_csv_config_with_location(
+    location: Tuple[String, String],
     csv_source: transactions.ExportCSVSource,
     csv_config: logic.CSVConfig,
 ) -> transactions.ExportCSVConfig:
     return transactions.ExportCSVConfig(
-        path=path,
+        path=location[0],
+        transaction_output_name=location[1],
         csv_source=csv_source,
         csv_config=csv_config,
     )

meta/src/meta/target.py

@@ -345,6 +345,9 @@ def __post_init__(self):
     def target_type(self) -> "TargetType":
         if isinstance(self.func, (ParseNonterminal, PrintNonterminal)):
             return self.func.target_type()
+        # builtin.tuple is variadic; infer TupleType from the argument types directly.
+        if isinstance(self.func, Builtin) and self.func.name == "tuple":
+            return TupleType(tuple(a.target_type() for a in self.args))
         func_type = self.func.target_type()
         if isinstance(func_type, FunctionType):
             # Match parameter types against argument types to build type variable mapping

proto/relationalai/lqp/v1/transactions.proto

@@ -85,7 +85,13 @@ message Snapshot {
 //
 
 message ExportCSVConfig {
+  // The following two fields should be in a `oneof`, but compatibility makes that tricky.
+  // The `path` option should be used if the client needs to output a CSV file to a
+  // specific location.
+  // The `transaction_output_name` should be used if the client wants the CSV file to be
+  // returned as part of the transaction results.
   string path = 1;
+  string transaction_output_name = 12;
 
   ExportCSVSource csv_source = 10;
   CSVConfig csv_config = 11;