internal/graph: Escape labels to support double quotes

Fixes syntax errors when trying to render pprof profiles that have
double quotes in tags. These can be created with Go's pprof labels
feature, for example with:

Fixes syntax errors when trying to render pprof profiles that have
double quotes in tags. These can be created with Go's pprof labels
feature, for example with:

pprof.Labels("key", "label \"double quote\"\nline two")

Trying to display a graph generated with this lable will fail:

Error: <stdin>: syntax error in line 5 near 'quote'

The double quote (") was never escaped in the label strings. Add
a new escaping function that replaces newlines with centered lines
(\n) because the existing one replaces newline with left-justified
lines (\l).

internal/graph/dotgraph.go

@@ -247,7 +247,7 @@ func (b *builder) addNodelets(node *Node, nodeID int) bool {
 			continue
 		}
 		weight := b.config.FormatValue(w)
-		nodelets += fmt.Sprintf(`N%d_%d [label = "%s" id="N%d_%d" fontsize=8 shape=box3d tooltip="%s"]`+"\n", nodeID, i, t.Name, nodeID, i, weight)
+		nodelets += fmt.Sprintf(`N%d_%d [label = "%s" id="N%d_%d" fontsize=8 shape=box3d tooltip="%s"]`+"\n", nodeID, i, escapeForDotCentered(t.Name), nodeID, i, weight)
 		nodelets += fmt.Sprintf(`N%d -> N%d_%d [label=" %s" weight=100 tooltip="%s" labeltooltip="%s"]`+"\n", nodeID, nodeID, i, weight, weight, weight)
 		if nts := lnts[t.Name]; nts != nil {
 			nodelets += b.numericNodelets(nts, maxNodelets, flatTags, fmt.Sprintf(`N%d_%d`, nodeID, i))
@@ -274,7 +274,7 @@ func (b *builder) numericNodelets(nts []*Tag, maxNumNodelets int, flatTags bool,
 		}
 		if w != 0 {
 			weight := b.config.FormatValue(w)
-			nodelets += fmt.Sprintf(`N%s_%d [label = "%s" id="N%s_%d" fontsize=8 shape=box3d tooltip="%s"]`+"\n", source, j, t.Name, source, j, weight)
+			nodelets += fmt.Sprintf(`N%s_%d [label = "%s" id="N%s_%d" fontsize=8 shape=box3d tooltip="%s"]`+"\n", source, j, escapeForDotCentered(t.Name), source, j, weight)
 			nodelets += fmt.Sprintf(`%s -> N%s_%d [label=" %s" weight=100 tooltip="%s" labeltooltip="%s"%s]`+"\n", source, source, j, weight, weight, weight, attr)
 		}
 	}
@@ -483,9 +483,16 @@ func escapeAllForDot(in []string) []string {
 	return out
 }
 
-// escapeForDot escapes double quotes and backslashes, and replaces Graphviz's
-// "center" character (\n) with a left-justified character.
+// escapeForDot escapes double quotes and backslashes, and replaces newlines
+// with a left-justified escape (\l).
 // See https://graphviz.org/docs/attr-types/escString/ for more info.
 func escapeForDot(str string) string {
 	return strings.ReplaceAll(strings.ReplaceAll(strings.ReplaceAll(str, `\`, `\\`), `"`, `\"`), "\n", `\l`)
 }
+
+// escapeForDotCentered escapes double quotes and backslashes, and replaces
+// newlines with Graphviz's center escape (\n).
+// See https://graphviz.org/docs/attr-types/escString/ for more info.
+func escapeForDotCentered(str string) string {
+	return strings.ReplaceAll(strings.ReplaceAll(strings.ReplaceAll(str, `\`, `\\`), `"`, `\"`), "\n", `\n`)
+}

internal/graph/dotgraph_test.go

@@ -150,6 +150,30 @@ func TestComposeWithNamesThatNeedEscaping(t *testing.T) {
 	compareGraphs(t, buf.Bytes(), "compose7.dot")
 }
 
+func TestComposeWithTagsThatNeedEscaping(t *testing.T) {
+	g := baseGraph()
+	a, c := baseAttrsAndConfig()
+	// Tag names are normally escaped by joinLabels.
+	g.Nodes[0].LabelTags["a"] = &Tag{
+		Name: `label"quote"` + "\nline2",
+		Cum:  10,
+		Flat: 10,
+	}
+	g.Nodes[0].NumericTags[""] = TagMap{
+		"b": &Tag{
+			Name: `numeric"quote"` + "\nline2",
+			Cum:  20,
+			Flat: 20,
+			Unit: "ms",
+		},
+	}
+
+	var buf bytes.Buffer
+	ComposeDot(&buf, g, a, c)
+
+	compareGraphs(t, buf.Bytes(), "compose8.dot")
+}
+
 func TestComposeWithCommentsWithNewlines(t *testing.T) {
 	g := baseGraph()
 	a, c := baseAttrsAndConfig()

internal/graph/graph.go

@@ -519,6 +519,8 @@ func (g *Graph) TrimTree(kept NodePtrSet) {
 	g.RemoveRedundantEdges()
 }
 
+// joinLabels returns the labels as a string. Newlines in the labels are
+// replaced with "\n". Separate labels are joined with newlines.
 func joinLabels(s *profile.Sample) string {
 	if len(s.Label) == 0 {
 		return ""
@@ -527,11 +529,13 @@ func joinLabels(s *profile.Sample) string {
 	var labels []string
 	for key, vals := range s.Label {
 		for _, v := range vals {
-			labels = append(labels, key+":"+v)
+			joined := key + ":" + v
+			escaped := strings.ReplaceAll(joined, "\n", `\n`)
+			labels = append(labels, escaped)
 		}
 	}
 	sort.Strings(labels)
-	return strings.Join(labels, `\n`)
+	return strings.Join(labels, "\n")
 }
 
 // isNegative returns true if the node is considered as "negative" for the

internal/graph/graph_test.go

@@ -531,3 +531,18 @@ func TestShortenFunctionName(t *testing.T) {
 		}
 	}
 }
+
+func TestJoinLabels(t *testing.T) {
+	input := &profile.Sample{
+		Label: map[string][]string{
+			"key1": {"v1", "v2"},
+			// value with an embedded newline: is escaped to \n
+			"key2": {"value line1\nline2"},
+		},
+	}
+	const expected = "key1:v1\nkey1:v2\nkey2:value line1\\nline2"
+	output := joinLabels(input)
+	if output != expected {
+		t.Errorf("output=%#v != expected=%#v", output, expected)
+	}
+}

internal/graph/testdata/compose8.dot

@@ -0,0 +1,11 @@
+digraph "testtitle" {
+node [style=filled fillcolor="#f8f8f8"]
+subgraph cluster_L { "label1" [shape=box fontsize=16 label="label1\llabel2\llabel3: \"foo\"\l" tooltip="testtitle"] }
+N1 [label="src\n10 (10.00%)\nof 25 (25.00%)" id="node1" fontsize=22 shape=box tooltip="src (25)" color="#b23c00" fillcolor="#edddd5"]
+N1_0 [label = "label\"quote\"\nline2" id="N1_0" fontsize=8 shape=box3d tooltip="10"]
+N1 -> N1_0 [label=" 10" weight=100 tooltip="10" labeltooltip="10"]
+NN1_0 [label = "numeric\"quote\"\nline2" id="NN1_0" fontsize=8 shape=box3d tooltip="20"]
+N1 -> NN1_0 [label=" 20" weight=100 tooltip="20" labeltooltip="20"]
+N2 [label="dest\n15 (15.00%)\nof 25 (25.00%)" id="node2" fontsize=24 shape=box tooltip="dest (25)" color="#b23c00" fillcolor="#edddd5"]
+N1 -> N2 [label=" 10" weight=11 color="#b28559" tooltip="src -> dest (10)" labeltooltip="src -> dest (10)" minlen=2]
+}