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, 43 insertions, 0 deletions

diff --git a/tools/node_modules/eslint/lib/rules/no-duplicate-case.js b/tools/node_modules/eslint/lib/rules/no-duplicate-case.js
new file mode 100644
index 0000000000..07823f284c
--- /dev/null
+++ b/tools/node_modules/eslint/lib/rules/no-duplicate-case.js
@@ -0,0 +1,43 @@
+/**
+ * @fileoverview Rule to disallow a duplicate case label.
+ * @author Dieter Oberkofler
+ * @author Burak Yigit Kaya
+ */
+
+"use strict";
+
+//------------------------------------------------------------------------------
+// Rule Definition
+//------------------------------------------------------------------------------
+
+module.exports = {
+    meta: {
+        docs: {
+            description: "disallow duplicate case labels",
+            category: "Possible Errors",
+            recommended: true
+        },
+
+        schema: []
+    },
+
+    create(context) {
+        const sourceCode = context.getSourceCode();
+
+        return {
+            SwitchStatement(node) {
+                const mapping = {};
+
+                node.cases.forEach(switchCase => {
+                    const key = sourceCode.getText(switchCase.test);
+
+                    if (mapping[key]) {
+                        context.report({ node: switchCase, message: "Duplicate case label." });
+                    } else {
+                        mapping[key] = switchCase;
+                    }
+                });
+            }
+        };
+    }
+};