cue/format: prevent vertical tabs from causing extra indentation

nextNeedsFormfeed wasn't aware of parentheses, indexes, and selectors,
meaning that if they were used on a multi-line and indented expression,
we would not notice we needed to skip the vertical tab.

In many cases the vertical tab was harmless, but in this case,
it caused tabwriter to further indent the inner list elements.

Updates #2496.

Signed-off-by: Daniel Martí <mvdan@mvdan.cc>
Change-Id: Iba21684c6e7f794e4e2d5ff007b9d2ba8d75d491
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1196135
TryBot-Result: CUEcueckoo <cueckoo@cuelang.org>
Reviewed-by: Aram Hăvărneanu <aram@cue.works>

cue/format/node.go

@@ -462,10 +462,16 @@ func (f *formatter) nextNeedsFormfeed(n ast.Expr) bool {
 		return strings.IndexByte(x.Value, '\n') >= 0
 	case *ast.ListLit:
 		return true
+	case *ast.ParenExpr:
+		return f.nextNeedsFormfeed(x.X)
 	case *ast.UnaryExpr:
 		return f.nextNeedsFormfeed(x.X)
 	case *ast.BinaryExpr:
 		return f.nextNeedsFormfeed(x.X) || f.nextNeedsFormfeed(x.Y)
+	case *ast.IndexExpr:
+		return f.nextNeedsFormfeed(x.X)
+	case *ast.SelectorExpr:
+		return f.nextNeedsFormfeed(x.X)
 	case *ast.CallExpr:
 		for _, arg := range x.Args {
 			if f.nextNeedsFormfeed(arg) {

cue/format/testdata/expressions.txtar

@@ -566,7 +566,6 @@ import "list"
 	s: [string]: {s: string}
 }
 -- issue2496.input --
-// TODO(mvdan): we indent the list elements too much.
 machine_type: [
 	if arch == "amd" {"n2-standard-2"},
 	if arch == "arm" {"t2a-standard-2"},
@@ -589,19 +588,18 @@ _foo: {
 	// skip_create_image: true
 }
 -- issue2496.golden --
-// TODO(mvdan): we indent the list elements too much.
 machine_type: [
-		if arch == "amd" {"n2-standard-2"},
-		if arch == "arm" {"t2a-standard-2"},
-		"unknown arch",
+	if arch == "amd" {"n2-standard-2"},
+	if arch == "arm" {"t2a-standard-2"},
+	"unknown arch",
 ][0]
 
 long_field_name: ([
-			"foo",
+	"foo",
 ])
 
 long_field_name: [
-			"foo",
+	"foo",
 ].bar
 
 // TODO(mvdan): we insert an empty line between the definitions.

tools/flow/testdata/dep.txtar

@@ -155,7 +155,7 @@ graph TD
 
 -- out/run/t3/value --
 {
-	x:   [0, 1][INDEX]
+	x: [0, 1][INDEX]
 	$id: "valToOut"
 
 	//cue:path: root.concreteValueInGeneratedSubfield.index
@@ -184,7 +184,7 @@ graph TD
 -- out/run/t4/value --
 {
 	$after: {
-		x:   [0, 1][INDEX]
+		x: [0, 1][INDEX]
 		$id: "valToOut"
 	}
 	$id: "valToOut"