Escape DOT keywords

Author: mattt

Sources/DOT/DOT.swift

@@ -0,0 +1,39 @@
+/**
+ The following is an abstract grammar defining the DOT language.
+
+ Terminals are shown in bold font and nonterminals in italics.
+ Literal characters are given in single quotes.
+ Parentheses ( and ) indicate grouping when needed.
+ Square brackets [ and ] enclose optional items.
+ Vertical bars | separate alternatives.
+
+         graph    :    [ strict ] (graph | digraph) [ ID ] '{' stmt_list '}'
+     stmt_list    :    [ stmt [ ';' ] stmt_list ]
+          stmt    :    node_stmt
+                  |    edge_stmt
+                  |    attr_stmt
+                  |    ID '=' ID
+                  |    subgraph
+     attr_stmt    :    (graph | node | edge) attr_list
+     attr_list    :    '[' [ a_list ] ']' [ attr_list ]
+        a_list    :    ID '=' ID [ (';' | ',') ] [ a_list ]
+     edge_stmt    :    (node_id | subgraph) edgeRHS [ attr_list ]
+       edgeRHS    :    edgeop (node_id | subgraph) [ edgeRHS ]
+     node_stmt    :    node_id [ attr_list ]
+       node_id    :    ID [ port ]
+          port    :    ':' ID [ ':' compass_pt ]
+                  |    ':' compass_pt
+      subgraph    :    [ subgraph [ ID ] ] '{' stmt_list '}'
+    compass_pt    :    (n | ne | e | se | s | sw | w | nw | c | _)
+ */
+enum DOT {
+    /// The keywords node, edge, graph, digraph, subgraph, and strict are case-independent.
+    static let keywords: Set<String> = [
+        "node",
+        "edge",
+        "graph",
+        "digraph",
+        "subgraph",
+        "strict"
+    ]
+}

Sources/DOT/DOTEncoder.swift

@@ -156,7 +156,9 @@ public struct DOTEncoder {
 
     private func escape(_ string: String) -> String {
         var escapedString = string.replacingOccurrences(of: "\"", with: #"\""#)
-        if string.contains(where: { !$0.isLetter && !$0.isNumber && $0 != "_" }) {
+        if string.contains(where: { !$0.isLetter && !$0.isNumber && $0 != "_" }) ||
+            DOT.keywords.contains(where: { escapedString.caseInsensitiveCompare($0) == .orderedSame })
+        {
             escapedString = #""\#(escapedString)""#
         }
 

Tests/GraphVizTests/NodeTests.swift

@@ -31,4 +31,13 @@ final class NodeTests: XCTestCase {
 
         XCTAssertEqual(encoder.encode(node, in: graph), expected)
     }
+
+    func testNodeWithKeywordID() {
+        var node = Node("Node")
+        node.label = "Node"
+
+        let expected = #""Node" [label="Node"]"#
+
+        XCTAssertEqual(encoder.encode(node, in: graph), expected)
+    }
 }