fmt: add linebreak after const decl (fix #20157) (#20162)

vlib/v/fmt/fmt.v

@@ -422,6 +422,11 @@ fn (f Fmt) should_insert_newline_before_node(node ast.Node, prev_node ast.Node)
 			ast.Import {
 				return false
 			}
+			ast.ConstDecl {
+				if node !is ast.ConstDecl && !(node is ast.ExprStmt && node.expr is ast.Comment) {
+					return true
+				}
+			}
 			else {}
 		}
 		match node {

vlib/v/fmt/tests/consts_after_linebreak_expected.vv

@@ -0,0 +1,18 @@
+import os
+
+const foo = 'foo'
+const bar = 1
+// ...
+const a = 1
+
+fn baz() {
+}
+
+const b = ''
+
+fn foobar() {
+}
+
+const c = '' // ...
+
+struct Struct {}

vlib/v/fmt/tests/consts_after_linebreak_input.vv

@@ -0,0 +1,15 @@
+import os
+
+const foo = 'foo'
+const bar = 1
+// ...
+const a = 1
+fn baz() {
+}
+
+const b = ''
+fn foobar() {
+}
+
+const c = '' // ...
+struct Struct {}

vlib/v/fmt/tests/donut_card_expected.vv

@@ -4,6 +4,7 @@ import strings
 import time { sleep }
 
 const alt = '.,-~:;=!*#$@'
+
 fn rd(cs int, ls int, a f64, b f64) {
 	tt_spacing, p_spacing := 0.07, 0.02
 	r1, r2, k2 := 1, 2, 5