feat(flowchart): Allow default in the node ID

cypress/integration/rendering/flowchart-v2.spec.js

@@ -643,4 +643,15 @@ flowchart RL
       {htmlLabels: true, flowchart: {htmlLabels: true}, securityLevel: 'loose'}
     );
   });
+
+  it('2388: handling default in the node name', () => {
+    imgSnapshotTest(
+      `
+      flowchart LR
+      default-index.js --> dot.template.js
+      index.js --> module-utl.js
+      `,
+      {htmlLabels: true, flowchart: {htmlLabels: true}, securityLevel: 'loose'}
+    )
+  })
 });

src/diagrams/flowchart/parser/flow.jison

@@ -557,7 +557,7 @@ direction
 
 alphaNumToken  : PUNCTUATION | AMP | UNICODE_TEXT | NUM| ALPHA | COLON | COMMA | PLUS | EQUALS | MULT | DOT | BRKT| UNDERSCORE ;
 
-idStringToken  : ALPHA|UNDERSCORE |UNICODE_TEXT | NUM|  COLON | COMMA | PLUS | MINUS | DOWN |EQUALS | MULT | BRKT | DOT | PUNCTUATION | AMP;
+idStringToken  : ALPHA|UNDERSCORE |UNICODE_TEXT | NUM|  COLON | COMMA | PLUS | MINUS | DOWN |EQUALS | MULT | BRKT | DOT | PUNCTUATION | AMP | DEFAULT;
 
 graphCodeTokens: STADIUMSTART | STADIUMEND | SUBROUTINESTART | SUBROUTINEEND | CYLINDERSTART | CYLINDEREND | TRAPSTART | TRAPEND | INVTRAPSTART | INVTRAPEND | PIPE | PS | PE | SQS | SQE | DIAMOND_START | DIAMOND_STOP | TAGSTART | TAGEND | ARROW_CROSS | ARROW_POINT | ARROW_CIRCLE | ARROW_OPEN | QUOTE | SEMI;
 %%

src/diagrams/flowchart/parser/flow.spec.js

@@ -51,6 +51,18 @@ describe('when parsing ', function() {
     expect(edges[0].end).toBe('monograph');
   });
 
+  it('should allow default in the node name/id', function() {
+    const res = flow.parser.parse('graph TD\ndefault --> monograph');
+
+    const vert = flow.parser.yy.getVertices();
+    const edges = flow.parser.yy.getEdges();
+
+    expect(vert['default'].id).toBe('default');
+    expect(vert['monograph'].id).toBe('monograph');
+    expect(edges[0].start).toBe('default');
+    expect(edges[0].end).toBe('monograph');
+  });
+
   describe('special characters should be be handled.', function() {
     const charTest = function(char, result) {
       const res = flow.parser.parse('graph TD;A(' + char + ')-->B;');