From ee00a1ae6ade63bce007e3849cbe6c7ef4e0e72d Mon Sep 17 00:00:00 2001
From: felix <felix8a@gmail.com>
Date: Tue, 12 Sep 2017 13:21:35 -0700
Subject: [PATCH] Check allowedStartRules exist. (#532)

Fixes #524
---
 lib/compiler/passes/report-undefined-rules.js         | 11 ++++++++++-
 test/api/pegjs-api.spec.js                            |  6 ++++++
 test/unit/compiler/passes/helpers.js                  |  6 ++++--
 .../compiler/passes/report-undefined-rules.spec.js    |  8 ++++++++
 4 files changed, 28 insertions(+), 3 deletions(-)

diff --git a/lib/compiler/passes/report-undefined-rules.js b/lib/compiler/passes/report-undefined-rules.js
index 0f5d941..4108432 100644
--- a/lib/compiler/passes/report-undefined-rules.js
+++ b/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;
diff --git a/test/api/pegjs-api.spec.js b/test/api/pegjs-api.spec.js
index 75a4cbb..f06f28d 100644
--- a/test/api/pegjs-api.spec.js
+++ b/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.
 
diff --git a/test/unit/compiler/passes/helpers.js b/test/unit/compiler/passes/helpers.js
index 1eed9aa..0232b79 100644
--- a/test/unit/compiler/passes/helpers.js
+++ b/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;
diff --git a/test/unit/compiler/passes/report-undefined-rules.spec.js b/test/unit/compiler/passes/report-undefined-rules.spec.js
index 5fc37f5..bfaa43a 100644
--- a/test/unit/compiler/passes/report-undefined-rules.spec.js
+++ b/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"]
+    });
+  });
 });