fmt: improve conditions for single line if

vlib/v/fmt/fmt.v

@@ -1446,8 +1446,8 @@ pub fn (mut f Fmt) infix_expr(node ast.InfixExpr) {
 
 pub fn (mut f Fmt) if_expr(it ast.IfExpr) {
 	dollar := if it.is_comptime { '$' } else { '' }
-	single_line := it.branches.len == 2 && it.has_else && it.branches[0].stmts.len == 1 &&
-		it.branches[1].stmts.len == 1 &&
+	single_line := it.branches.len == 2 && it.has_else && branch_is_single_line(it.branches[0]) &&
+		branch_is_single_line(it.branches[1]) &&
 		(it.is_expr || f.is_assign)
 	f.single_line_if = single_line
 	for i, branch in it.branches {
@@ -1488,6 +1488,13 @@ pub fn (mut f Fmt) if_expr(it ast.IfExpr) {
 	}
 }
 
+fn branch_is_single_line(b ast.IfBranch) bool {
+	if b.stmts.len == 1 && b.comments.len == 0 && stmt_is_single_line(b.stmts[0]) {
+		return true
+	}
+	return false
+}
+
 pub fn (mut f Fmt) at_expr(node ast.AtExpr) {
 	f.write(node.name)
 }
@@ -1713,7 +1720,7 @@ fn expr_is_single_line(expr ast.Expr) bool {
 			return false
 		}
 		ast.StructInit {
-			if expr.fields.len > 0 || expr.pre_comments.len > 0 {
+			if !expr.is_short && (expr.fields.len > 0 || expr.pre_comments.len > 0) {
 				return false
 			}
 		}

vlib/v/fmt/tests/if_keep.vv

@@ -0,0 +1,17 @@
+fn main() {
+	a := if foo { 'TMP1/${b.nexpected_steps:1d}' } else { '${b.cstep:1d}/${b.nexpected_steps:1d}' }
+	b := if bar {
+		// comment
+		'some str'
+	} else {
+		'other str'
+	}
+	_ := if true {
+		Foo{}
+	} else {
+		Foo{
+			x: 5
+		}
+	}
+	_ := if false { Foo{} } else { Foo{5, 6} }
+}