Check allowedStartRules exist. (#532)

Fixes #524

lib/compiler/passes/report-undefined-rules.js

@@ -5,7 +5,7 @@ let asts = require("../asts");
 let visitor = require("../visitor");
 
 // Checks that all referenced rules exist.
-function reportUndefinedRules(ast) {
+function reportUndefinedRules(ast, options) {
   let check = visitor.build({
     rule_ref(node) {
       if (!asts.findRule(ast, node.name)) {
@@ -18,6 +18,15 @@ function reportUndefinedRules(ast) {
   });
 
   check(ast);
+
+  if (options.allowedStartRules) {
+    options.allowedStartRules.forEach(rule => {
+      if (!asts.findRule(ast, rule)) {
+        throw new GrammarError(
+          "Start rule \"" + rule + "\" is not defined.");
+      }
+    });
+  }
 }
 
 module.exports = reportUndefinedRules;

test/api/pegjs-api.spec.js

@@ -30,6 +30,12 @@ describe("PEG.js API", function() {
         "c = 'x'"
       ].join("\n");
 
+      it("throws an error on missing rule", function() {
+        expect(() => peg.generate(grammar, {
+          allowedStartRules: ["missing"]
+        })).to.throw();
+      });
+
       // The |allowedStartRules| option is implemented separately for each
       // optimization mode, so we need to test it in both.
 

test/unit/compiler/passes/helpers.js

@@ -57,13 +57,15 @@ module.exports = function(chai, utils) {
     );
   });
 
-  Assertion.addMethod("reportError", function(grammar, props) {
+  Assertion.addMethod("reportError", function(grammar, props, options) {
+    options = options !== undefined ? options : {};
+
     let ast = parser.parse(grammar);
 
     let passed, result;
 
     try {
-      utils.flag(this, "object")(ast);
+      utils.flag(this, "object")(ast, options);
       passed = true;
     } catch (e) {
       result = e;

test/unit/compiler/passes/report-undefined-rules.spec.js

@@ -18,4 +18,12 @@ describe("compiler pass |reportUndefinedRules|", function() {
       }
     });
   });
+
+  it("checks allowedStartRules", function() {
+    expect(pass).to.reportError("start = 'a'", {
+      message: "Start rule \"missing\" is not defined."
+    }, {
+      allowedStartRules: ["missing"]
+    });
+  });
 });