zig fmt: array literals with no trailing comma all on one line

Author: andrewrk

std/zig/parser_test.zig

@@ -229,16 +229,14 @@ test "zig fmt: add trailing comma to array literal" {
         \\comptime {
         \\    return []u16{'m', 's', 'y', 's', '-' // hi
         \\   };
+        \\    return []u16{'m', 's', 'y', 's',
+        \\      '-'};
         \\}
     ,
         \\comptime {
-        \\    return []u16{
-        \\        'm',
-        \\        's',
-        \\        'y',
-        \\        's',
-        \\        '-', // hi
+        \\    return []u16{ 'm', 's', 'y', 's', '-' // hi
         \\    };
+        \\    return []u16{ 'm', 's', 'y', 's', '-'};
         \\}
         \\
     );

std/zig/render.zig

@@ -557,11 +557,11 @@ fn renderExpression(allocator: &mem.Allocator, stream: var, tree: &ast.Tree, ind
                     };
 
 
-                    const new_indent = indent + indent_delta;
-                    try renderToken(tree, stream, lbrace, new_indent, Space.Newline);
-                    try stream.writeByteNTimes(' ', new_indent);
-
                     if (maybe_row_size) |row_size| {
+                        const new_indent = indent + indent_delta;
+                        try renderToken(tree, stream, lbrace, new_indent, Space.Newline);
+                        try stream.writeByteNTimes(' ', new_indent);
+
                         var it = exprs.iterator(0);
                         var i: usize = 0;
                         while (it.next()) |expr| {
@@ -597,6 +597,30 @@ fn renderExpression(allocator: &mem.Allocator, stream: var, tree: &ast.Tree, ind
                         return;
                     }
 
+                    const src_has_trailing_comma = blk: {
+                        const maybe_comma = tree.prevToken(suffix_op.rtoken);
+                        break :blk tree.tokens.at(maybe_comma).id == Token.Id.Comma;
+                    };
+                    if (!src_has_trailing_comma) {
+                        try renderToken(tree, stream, lbrace, indent, Space.Space);
+                        var it = exprs.iterator(0);
+                        while (it.next()) |expr| {
+                            try renderExpression(allocator, stream, tree, indent, expr.*, Space.None);
+
+                            if (it.peek()) |next_expr| {
+                                const comma = tree.nextToken(expr.*.lastToken());
+                                try renderToken(tree, stream, comma, indent, Space.Space); // ,
+                            }
+                        }
+
+                        try renderToken(tree, stream, suffix_op.rtoken, indent, space);
+                        return;
+                    }
+
+                    const new_indent = indent + indent_delta;
+                    try renderToken(tree, stream, lbrace, new_indent, Space.Newline);
+                    try stream.writeByteNTimes(' ', new_indent);
+
                     var it = exprs.iterator(0);
                     while (it.next()) |expr| {