From 81761d53fe2ae2a10c4c281581498163cbb60f4c Mon Sep 17 00:00:00 2001
From: Toru Nagashima <star.ctor@gmail.com>
Date: Thu, 8 Nov 2018 22:05:00 +0900
Subject: [PATCH] Breaking: throw syntax error on solo `const` keyword (fixes
 #531)

---
 package.json                            |  9 ++++++
 parser.js                               | 43 ++++++++++++++++++++++---
 tests/fixtures/basics/solo-const.src.js |  1 +
 tests/lib/__snapshots__/basics.js.snap  |  2 ++
 4 files changed, 51 insertions(+), 4 deletions(-)
 create mode 100644 tests/fixtures/basics/solo-const.src.js

diff --git a/package.json b/package.json
index efa7b8b..8799fec 100644
--- a/package.json
+++ b/package.json
@@ -63,6 +63,15 @@
     "collectCoverage": true,
     "coverageReporters": [
       "text-summary"
+    ],
+    "collectCoverageFrom": [
+      "**/*.js",
+      "!**/coverage/**",
+      "!**/node_modules/**",
+      "!**/tests/**",
+      "!**/tools/**",
+      "!**/Makefile.js",
+      "!**/test.js"
     ]
   }
 }
diff --git a/parser.js b/parser.js
index 32b4e7c..28bc3cb 100644
--- a/parser.js
+++ b/parser.js
@@ -13,6 +13,21 @@ const astNodeTypes = require("typescript-estree").AST_NODE_TYPES;
 const traverser = require("eslint/lib/util/traverser");
 const visitorKeys = require("./visitor-keys");
 
+/**
+ * Create a syntax error object.
+ * @param {ASTNode} node The node that caused the error.
+ * @param {string} message The error message.
+ * @returns {SyntaxError} The created error.
+ */
+function newSyntaxError(node, message) {
+    const error = new SyntaxError(message);
+    error.index = node.range[0];
+    error.lineNumber = node.loc.start.line;
+    error.column = node.loc.start.column + 1;
+
+    return error;
+}
+
 //------------------------------------------------------------------------------
 // Public
 //------------------------------------------------------------------------------
@@ -23,10 +38,30 @@ exports.parseForESLint = function parseForESLint(code, options) {
     const ast = parse(code, options);
     traverser.traverse(ast, {
         enter: node => {
-            if (node.type === "DeclareFunction" || node.type === "FunctionExpression" || node.type === "FunctionDeclaration") {
-                if (!node.body) {
-                    node.type = `TSEmptyBody${node.type}`;
-                }
+            switch (node.type) {
+                // Just for backword compatibility.
+                case "DeclareFunction":
+                    if (!node.body) {
+                        node.type = `TSEmptyBody${node.type}`;
+                    }
+                    break;
+
+                // Function#body cannot be null in ESTree spec.
+                case "FunctionExpression":
+                case "FunctionDeclaration":
+                    if (!node.body) {
+                        node.type = `TSEmptyBody${node.type}`;
+                    }
+                    break;
+
+                // VariableDeclaration that doesn't have any declarations is syntax error.
+                case "VariableDeclaration":
+                    if (node.declarations.length === 0) {
+                        throw newSyntaxError(node, `'${node.kind}' declarations require one or more declarator(s).`);
+                    }
+                    break;
+
+                // no default
             }
         }
     });
diff --git a/tests/fixtures/basics/solo-const.src.js b/tests/fixtures/basics/solo-const.src.js
new file mode 100644
index 0000000..aaae4e1
--- /dev/null
+++ b/tests/fixtures/basics/solo-const.src.js
@@ -0,0 +1 @@
+const
diff --git a/tests/lib/__snapshots__/basics.js.snap b/tests/lib/__snapshots__/basics.js.snap
index d952c5a..d9fc279 100644
--- a/tests/lib/__snapshots__/basics.js.snap
+++ b/tests/lib/__snapshots__/basics.js.snap
@@ -2162,6 +2162,8 @@ Object {
 }
 `;
 
+exports[`basics fixtures/solo-const.src 1`] = `"'const' declarations require one or more declarator(s)."`;
+
 exports[`basics fixtures/typeof-expression.src 1`] = `
 Object {
   "body": Array [