tools: move eslint from tools to tools/node_modules

This is required because we need to add the babel-eslint dependency
and it has to be able to resolve "eslint".
babel-eslint is required to support future ES features such as async
iterators and import.meta.

Refs: https://github.com/nodejs/node/pull/17755
PR-URL: https://github.com/nodejs/node/pull/17820
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>

1 files changed, 82 insertions, 0 deletions

diff --git a/tools/node_modules/eslint/lib/rules/no-negated-condition.js b/tools/node_modules/eslint/lib/rules/no-negated-condition.js
new file mode 100644
index 0000000000..8ea8559ea1
--- /dev/null
+++ b/tools/node_modules/eslint/lib/rules/no-negated-condition.js
@@ -0,0 +1,82 @@
+/**
+ * @fileoverview Rule to disallow a negated condition
+ * @author Alberto Rodríguez
+ */
+"use strict";
+
+//------------------------------------------------------------------------------
+// Rule Definition
+//------------------------------------------------------------------------------
+
+module.exports = {
+    meta: {
+        docs: {
+            description: "disallow negated conditions",
+            category: "Stylistic Issues",
+            recommended: false
+        },
+
+        schema: []
+    },
+
+    create(context) {
+
+        /**
+         * Determines if a given node is an if-else without a condition on the else
+         * @param {ASTNode} node The node to check.
+         * @returns {boolean} True if the node has an else without an if.
+         * @private
+         */
+        function hasElseWithoutCondition(node) {
+            return node.alternate && node.alternate.type !== "IfStatement";
+        }
+
+        /**
+         * Determines if a given node is a negated unary expression
+         * @param {Object} test The test object to check.
+         * @returns {boolean} True if the node is a negated unary expression.
+         * @private
+         */
+        function isNegatedUnaryExpression(test) {
+            return test.type === "UnaryExpression" && test.operator === "!";
+        }
+
+        /**
+         * Determines if a given node is a negated binary expression
+         * @param {Test} test The test to check.
+         * @returns {boolean} True if the node is a negated binary expression.
+         * @private
+         */
+        function isNegatedBinaryExpression(test) {
+            return test.type === "BinaryExpression" &&
+                (test.operator === "!=" || test.operator === "!==");
+        }
+
+        /**
+         * Determines if a given node has a negated if expression
+         * @param {ASTNode} node The node to check.
+         * @returns {boolean} True if the node has a negated if expression.
+         * @private
+         */
+        function isNegatedIf(node) {
+            return isNegatedUnaryExpression(node.test) || isNegatedBinaryExpression(node.test);
+        }
+
+        return {
+            IfStatement(node) {
+                if (!hasElseWithoutCondition(node)) {
+                    return;
+                }
+
+                if (isNegatedIf(node)) {
+                    context.report({ node, message: "Unexpected negated condition." });
+                }
+            },
+            ConditionalExpression(node) {
+                if (isNegatedIf(node)) {
+                    context.report({ node, message: "Unexpected negated condition." });
+                }
+            }
+        };
+    }
+};