1 files changed, 130 insertions, 0 deletions
diff --git a/tools/eslint/lib/rules/semi.js b/tools/eslint/lib/rules/semi.js
new file mode 100644
index 0000000000..a9f841cd73
--- /dev/null
+++ b/tools/eslint/lib/rules/semi.js
@@ -0,0 +1,130 @@
+/**
+ * @fileoverview Rule to flag missing semicolons.
+ * @author Nicholas C. Zakas
+ */
+"use strict";
+
+//------------------------------------------------------------------------------
+// Rule Definition
+//------------------------------------------------------------------------------
+module.exports = function(context) {
+
+    var OPT_OUT_PATTERN = /[\[\(\/\+\-]/; // One of [(/+-
+
+    var always = context.options[0] !== "never";
+
+    //--------------------------------------------------------------------------
+    // Helpers
+    //--------------------------------------------------------------------------
+
+    /**
+     * Reports a semicolon error with appropriate location and message.
+     * @param {ASTNode} node The node with an extra or missing semicolon.
+     * @returns {void}
+     */
+    function report(node) {
+        var message = always ? "Missing semicolon." : "Extra semicolon.";
+        context.report(node, context.getLastToken(node).loc.end, message);
+    }
+
+    /**
+     * Checks whether a token is a semicolon punctuator.
+     * @param {Token} token The token.
+     * @returns {boolean} True if token is a semicolon punctuator.
+     */
+    function isSemicolon(token) {
+        return (token.type === "Punctuator" && token.value === ";");
+    }
+
+    /**
+     * Check if a semicolon is unnecessary, only true if:
+     *   - next token is on a new line and is not one of the opt-out tokens
+     *   - next token is a valid statement divider
+     * @param {Token} lastToken last token of current node.
+     * @returns {boolean} whether the semicolon is unnecessary.
+     */
+    function isUnnecessarySemicolon(lastToken) {
+        var isDivider, isOptOutToken, lastTokenLine, nextToken, nextTokenLine;
+
+        if (!isSemicolon(lastToken)) {
+            return false;
+        }
+
+        nextToken = context.getTokenAfter(lastToken);
+
+        if (!nextToken) {
+            return true;
+        }
+
+        lastTokenLine = lastToken.loc.end.line;
+        nextTokenLine = nextToken.loc.start.line;
+        isOptOutToken = OPT_OUT_PATTERN.test(nextToken.value);
+        isDivider = (nextToken.value === "}" || nextToken.value === ";");
+
+        return (lastTokenLine !== nextTokenLine && !isOptOutToken) || isDivider;
+    }
+
+    /**
+     * Checks a node to see if it's followed by a semicolon.
+     * @param {ASTNode} node The node to check.
+     * @returns {void}
+     */
+    function checkForSemicolon(node) {
+        var lastToken = context.getLastToken(node);
+
+        if (always) {
+            if (!isSemicolon(lastToken)) {
+                report(node);
+            }
+        } else {
+            if (isUnnecessarySemicolon(lastToken)) {
+                report(node);
+            }
+        }
+    }
+
+    /**
+     * Checks to see if there's a semicolon after a variable declaration.
+     * @param {ASTNode} node The node to check.
+     * @returns {void}
+     */
+    function checkForSemicolonForVariableDeclaration(node) {
+        var ancestors = context.getAncestors(),
+            parentIndex = ancestors.length - 1,
+            parent = ancestors[parentIndex];
+
+        if ((parent.type !== "ForStatement" || parent.init !== node) &&
+            (!/^For(?:In|Of)Statement/.test(parent.type) || parent.left !== node)
+        ) {
+            checkForSemicolon(node);
+        }
+    }
+
+    //--------------------------------------------------------------------------
+    // Public API
+    //--------------------------------------------------------------------------
+
+    return {
+
+        "VariableDeclaration": checkForSemicolonForVariableDeclaration,
+        "ExpressionStatement": checkForSemicolon,
+        "ReturnStatement": checkForSemicolon,
+        "ThrowStatement": checkForSemicolon,
+        "DebuggerStatement": checkForSemicolon,
+        "BreakStatement": checkForSemicolon,
+        "ContinueStatement": checkForSemicolon,
+        "ImportDeclaration": checkForSemicolon,
+        "ExportAllDeclaration": checkForSemicolon,
+        "ExportNamedDeclaration": function (node) {
+            if (!node.declaration) {
+                checkForSemicolon(node);
+            }
+        },
+        "ExportDefaultDeclaration": function (node) {
+            if (!/(?:Class|Function)Declaration/.test(node.declaration.type)) {
+                checkForSemicolon(node);
+            }
+        }
+    };
+
+};