tools: add no-duplicate-requires rule

PR-URL: https://github.com/nodejs/node/pull/21712
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com>
Reviewed-By: Weijia Wang <starkwang@126.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Jon Moss <me@jonathanmoss.me>

1 files changed, 70 insertions, 0 deletions

diff --git a/tools/eslint-rules/no-duplicate-requires.js b/tools/eslint-rules/no-duplicate-requires.js
new file mode 100644
index 0000000000..595c223601
--- /dev/null
+++ b/tools/eslint-rules/no-duplicate-requires.js
@@ -0,0 +1,70 @@
+/**
+ * @fileoverview Ensure modules are not required twice at top level of a module
+ * @author devsnek
+ */
+'use strict';
+
+//------------------------------------------------------------------------------
+// Rule Definition
+//------------------------------------------------------------------------------
+
+
+function isString(node) {
+  return node && node.type === 'Literal' && typeof node.value === 'string';
+}
+
+function isRequireCall(node) {
+  return node.callee.type === 'Identifier' && node.callee.name === 'require';
+}
+
+function isTopLevel(node) {
+  do {
+    if (node.type === 'FunctionDeclaration' ||
+        node.type === 'FunctionExpression' ||
+        node.type === 'ArrowFunctionExpression' ||
+        node.type === 'ClassBody' ||
+        node.type === 'MethodDefinition') {
+      return false;
+    }
+  } while (node = node.parent);
+  return true;
+}
+
+module.exports = (context) => {
+  if (context.parserOptions.sourceType === 'module') {
+    return {};
+  }
+
+  function getRequiredModuleNameFromCall(node) {
+    // node has arguments and first argument is string
+    if (node.arguments.length && isString(node.arguments[0])) {
+      return node.arguments[0].value.trim();
+    }
+
+    return undefined;
+  }
+
+  const required = new Set();
+
+  const rules = {
+    CallExpression: (node) => {
+      if (isRequireCall(node) && isTopLevel(node)) {
+        const moduleName = getRequiredModuleNameFromCall(node);
+        if (moduleName === undefined) {
+          return;
+        }
+        if (required.has(moduleName)) {
+          context.report(
+            node,
+            '\'{{moduleName}}\' require is duplicated.',
+            { moduleName }
+          );
+        } else {
+          required.add(moduleName);
+        }
+      }
+    },
+  };
+
+  return rules;
+};