From 29edafc1b9663550232531719eb9a371ca0452f7 Mon Sep 17 00:00:00 2001
From: Joe Hildebrand <joe-github@cursive.net>
Date: Mon, 16 Aug 2021 16:29:24 -0600
Subject: [PATCH] Check allowedStartRules.   (#175)

Check allowedStartRules.  Fixes #166.
---
 CHANGELOG.md               |  1 +
 lib/compiler/index.js      | 13 +++++++++++++
 test/cli/run.spec.ts       | 16 +++++++++-------
 test/unit/compiler.spec.js | 33 +++++++++++++++++++++++++++++++++
 4 files changed, 56 insertions(+), 7 deletions(-)
 create mode 100644 test/unit/compiler.spec.js

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8d871179..0801d76b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -13,6 +13,7 @@ Released: TBD
 - New CLI [@hildjj](https://github.com/peggyjs/peggy/pull/167)
   - Backward compatible with the previous
   - New -t/--test and -T/--testfile flags to directly test the generated grammar
+- Check allowedStartRules for validity [@hildjj](https://github.com/peggyjs/peggy/pull/175)
 
 1.2.0
 -----
diff --git a/lib/compiler/index.js b/lib/compiler/index.js
index dd80c44e..d50e9932 100644
--- a/lib/compiler/index.js
+++ b/lib/compiler/index.js
@@ -74,6 +74,19 @@ const compiler = {
       trace: false,
     });
 
+    if (!Array.isArray(options.allowedStartRules)) {
+      throw new Error("allowedStartRules must be an array");
+    }
+    if (options.allowedStartRules.length === 0) {
+      throw new Error("Must have at least one start rule");
+    }
+    const allRules = ast.rules.map(r => r.name);
+    for (const rule of options.allowedStartRules) {
+      if (allRules.indexOf(rule) === -1) {
+        throw new Error(`Unknown start rule "${rule}"`);
+      }
+    }
+
     Object.keys(passes).forEach(stage => {
       passes[stage].forEach(p => { p(ast, options); });
     });
diff --git a/test/cli/run.spec.ts b/test/cli/run.spec.ts
index 0fe725be..e4441887 100644
--- a/test/cli/run.spec.ts
+++ b/test/cli/run.spec.ts
@@ -12,6 +12,12 @@ type Options = {
   stdin?: string | Buffer;
 };
 
+const foobarbaz = `\
+foo = '1'
+bar = '2'
+baz = '3'
+`;
+
 /** Execution failed */
 class ExecError extends Error {
   /** Result error code, always non-zero */
@@ -141,11 +147,7 @@ Options:
   it("handles start rules", async() => {
     await expect(exec({
       args: ["--allowed-start-rules", "foo,bar,baz"],
-      stdin: `\
-foo = "1"
-bar = "2"
-baz = "3"
-`,
+      stdin: foobarbaz,
     })).resolves.toMatch(
       /startRuleFunctions = { foo: [^, ]+, bar: [^, ]+, baz: \S+ }/
     );
@@ -239,7 +241,7 @@ baz = "3"
 
     const res = await exec({
       args: ["--extra-options-file", optFile],
-      stdin: "foo = '1'",
+      stdin: foobarbaz,
     });
     expect(res).toMatch(
       /startRuleFunctions = { foo: [^, ]+, bar: [^, ]+, baz: \S+ }/
@@ -249,7 +251,7 @@ baz = "3"
     // Intentional overwrite
     await expect(exec({
       args: ["-c", optFile, "--format", "amd"],
-      stdin: "foo = '1'",
+      stdin: foobarbaz,
     })).resolves.toMatch(/^define\(/m);
 
     await expect(exec({
diff --git a/test/unit/compiler.spec.js b/test/unit/compiler.spec.js
new file mode 100644
index 00000000..2bf29fb9
--- /dev/null
+++ b/test/unit/compiler.spec.js
@@ -0,0 +1,33 @@
+"use strict";
+
+const chai = require("chai");
+const parser = require("../../lib/parser");
+const compiler = require("../../lib/compiler/index");
+
+const expect = chai.expect;
+
+describe("Peggy compiler", () => {
+  it("checks start rules", () => {
+    const ast = parser.parse("foo='1'");
+    expect(compiler.compile(ast, compiler.passes)).to.be.an("object");
+    expect(() => compiler.compile(ast, compiler.passes, {
+      allowedStartRules: null,
+    })).to.throw("allowedStartRules must be an array");
+    expect(() => compiler.compile(ast, compiler.passes, {
+      allowedStartRules: [],
+    })).to.throw("Must have at least one start rule");
+    expect(() => compiler.compile(ast, compiler.passes, {
+      allowedStartRules: ["bar"],
+    })).to.throw('Unknown start rule "bar"');
+  });
+
+  it("checks ouput type", () => {
+    const ast = parser.parse("foo='1'");
+    expect(compiler.compile(ast, compiler.passes, {
+      output: "source",
+    })).to.be.a("string");
+    expect(() => compiler.compile(ast, compiler.passes, {
+      output: "INVALID OUTPUT TYPE",
+    })).to.throw("Invalid output format: INVALID OUTPUT TYPE.");
+  });
+});