treeprinter: add DotDotDot

Add a feature to add a vertical ellipsis indicating that a node has
more hidden children.

Author: RaduBerinde

internal/treeprinter/tree_printer.go

@@ -11,11 +11,12 @@ import (
 )
 
 var (
-	edgeLinkChr = rune('│')
-	edgeMidChr  = rune('├')
-	edgeLastChr = rune('└')
-	horLineChr  = rune('─')
-	bulletChr   = rune('•')
+	edgeLinkChr  = rune('│')
+	edgeMidChr   = rune('├')
+	edgeLastChr  = rune('└')
+	horLineChr   = rune('─')
+	bulletChr    = rune('•')
+	dotDotDotChr = rune('⋮')
 )
 
 // Node is a handle associated with a specific depth in a tree. See below for
@@ -250,6 +251,33 @@ func (n Node) Child(text string) Node {
 	return n.childLine(text)
 }
 
+// DotDotDot adds an indication that this node has children that are not shown.
+func (n Node) DotDotDot() {
+	t := n.tree
+	t.rows = append(t.rows, nil)
+	rowIdx := len(t.rows) - 1
+	edgePos := (n.level - 1) * len(t.edgeLast)
+	if len(t.stack) <= n.level {
+		// No siblings; Connect to parent.
+		if len(t.stack) != n.level {
+			panic("misuse of node")
+		}
+		parentRow := t.stack[n.level-1].firstChildConnectRow
+		for i := parentRow + 1; i < rowIdx; i++ {
+			t.set(i, edgePos, t.edgeLink)
+		}
+		t.set(rowIdx, edgePos, []rune{' ', dotDotDotChr})
+	} else {
+		// Case 3: non-first child. Connect to sibling.
+		siblingRow := t.stack[n.level].nextSiblingConnectRow
+		t.set(siblingRow, edgePos, t.edgeMid)
+		for i := siblingRow + 1; i < rowIdx; i++ {
+			t.set(i, edgePos, t.edgeLink)
+		}
+		t.set(rowIdx, edgePos, []rune{' ', dotDotDotChr})
+	}
+}
+
 // AddLine adds a new line to a node without an edge.
 func (n Node) AddLine(text string) {
 	t := n.tree

internal/treeprinter/tree_printer_test.go

@@ -227,3 +227,35 @@ tree of trees
 		t.Errorf("incorrect result:\n%s", res)
 	}
 }
+
+func TestTreePrinterDotDotDot(t *testing.T) {
+	tp := New()
+	r1 := tp.Child("root")
+	r11 := r1.Child("1.1")
+	r11.DotDotDot()
+	r12 := r1.Child("1.2")
+	r12.Child("1.2.1")
+	r122 := r12.Child("1.2.2")
+	r122.Child("1.2.2.1")
+	r122.Child("1.2.2.2")
+	r122.Child("1.2.2.3")
+	r12.DotDotDot()
+	res := tp.String()
+
+	exp := `
+root
+ ├── 1.1
+ │    ⋮
+ └── 1.2
+      ├── 1.2.1
+      ├── 1.2.2
+      │    ├── 1.2.2.1
+      │    ├── 1.2.2.2
+      │    └── 1.2.2.3
+      ⋮
+`
+	exp = strings.TrimLeft(exp, "\n")
+	if res != exp {
+		t.Errorf("incorrect result:\n%s", res)
+	}
+}