Make preserved trailing commas apply to record types too. (#1751)

I missed this part of the language when I added support of preserving
trailing commas. They should have always been preserved here, so I
didn't language version this change. If someone has preserve trailing
commas on but isn't on 3.10 yet, I think they will still want this
change.

Fix #1721.

Author: munificent

CHANGELOG.md

@@ -3,6 +3,11 @@
 * Support dot shorthand syntax.
 * Enable language version 3.10.
 
+### Bug fixes
+
+* Preserved trailing commas (`trailing_commas: preserve`) applies to record
+  type annotations too (#1721).
+
 ### Style changes
 
 This change only applies to code whose language version is 3.10 or higher:

lib/src/front_end/ast_node_visitor.dart

@@ -1814,9 +1814,13 @@ final class AstNodeVisitor extends ThrowingAstVisitor<void> with PieceFactory {
     var namedFields = node.namedFields;
     var positionalFields = node.positionalFields;
 
-    // Single positional record types always have a trailing comma.
+    // Single positional record types always have a trailing comma and are not
+    // forced to split.
+    var isSinglePositional =
+        positionalFields.length == 1 && namedFields == null;
+
     var listStyle =
-        positionalFields.length == 1 && namedFields == null
+        isSinglePositional
             ? const ListStyle(commas: Commas.alwaysTrailing)
             : const ListStyle(commas: Commas.trailing);
     var builder = DelimitedListBuilder(this, listStyle);
@@ -1849,7 +1853,13 @@ final class AstNodeVisitor extends ThrowingAstVisitor<void> with PieceFactory {
     }
 
     builder.rightBracket(node.rightParenthesis, delimiter: rightDelimiter);
-    pieces.add(builder.build());
+    pieces.add(
+      builder.build(
+        forceSplit:
+            !isSinglePositional &&
+            hasPreservedTrailingComma(rightDelimiter ?? node.rightParenthesis),
+      ),
+    );
     pieces.token(node.question);
   }
 

test/tall/preserve_trailing_commas/record_type.unit

@@ -0,0 +1,49 @@
+40 columns                              |
+(trailing_commas preserve)
+>>> Forces split with multiple positional fields and trailing comma.
+typedef R = (int,int,);
+<<< 3.7
+typedef R =
+    (
+      int,
+      int,
+    );
+<<< 3.8
+typedef R = (
+  int,
+  int,
+);
+>>> Doesn't force split with one positional field.
+typedef R = (int,);
+<<<
+typedef R = (int,);
+>>> Doesn't force split without trailing comma.
+typedef R = (int,int,int);
+<<<
+typedef R = (int, int, int);
+>>> Forces split with named fields and trailing comma.
+typedef R = ({int name,});
+<<< 3.7
+typedef R =
+    ({
+      int name,
+    });
+<<< 3.8
+typedef R = ({
+  int name,
+});
+>>> May still split without trailing comma if doesn't fit.
+typedef R = (int element1, int element2, int element3);
+<<< 3.7
+typedef R =
+    (
+      int element1,
+      int element2,
+      int element3,
+    );
+<<< 3.8
+typedef R = (
+  int element1,
+  int element2,
+  int element3,
+);

test/tall/regression/1700/1721.unit

@@ -0,0 +1,9 @@
+(trailing_commas preserve)
+>>>
+typedef RawPhoto = ({DateTime addedAt, String name, String url,});
+<<< 3.8
+typedef RawPhoto = ({
+  DateTime addedAt,
+  String name,
+  String url,
+});