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buildfiles/app/node_modules/eslint/lib/rules/no-duplicate-imports.js

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+/**
+ * @fileoverview Restrict usage of duplicate imports.
+ * @author Simen Bekkhus
+ */
+"use strict";
+
+//------------------------------------------------------------------------------
+// Rule Definition
+//------------------------------------------------------------------------------
+
+/**
+ * Returns the name of the module imported or re-exported.
+ * @param {ASTNode} node A node to get.
+ * @returns {string} the name of the module, or empty string if no name.
+ */
+function getValue(node) {
+    if (node && node.source && node.source.value) {
+        return node.source.value.trim();
+    }
+
+    return "";
+}
+
+/**
+ * Checks if the name of the import or export exists in the given array, and reports if so.
+ * @param {RuleContext} context The ESLint rule context object.
+ * @param {ASTNode} node A node to get.
+ * @param {string} value The name of the imported or exported module.
+ * @param {string[]} array The array containing other imports or exports in the file.
+ * @param {string} messageId A messageId to be reported after the name of the module
+ *
+ * @returns {void} No return value
+ */
+function checkAndReport(context, node, value, array, messageId) {
+    if (array.indexOf(value) !== -1) {
+        context.report({
+            node,
+            messageId,
+            data: {
+                module: value
+            }
+        });
+    }
+}
+
+/**
+ * @callback nodeCallback
+ * @param {ASTNode} node A node to handle.
+ */
+
+/**
+ * Returns a function handling the imports of a given file
+ * @param {RuleContext} context The ESLint rule context object.
+ * @param {boolean} includeExports Whether or not to check for exports in addition to imports.
+ * @param {string[]} importsInFile The array containing other imports in the file.
+ * @param {string[]} exportsInFile The array containing other exports in the file.
+ *
+ * @returns {nodeCallback} A function passed to ESLint to handle the statement.
+ */
+function handleImports(context, includeExports, importsInFile, exportsInFile) {
+    return function(node) {
+        const value = getValue(node);
+
+        if (value) {
+            checkAndReport(context, node, value, importsInFile, "import");
+
+            if (includeExports) {
+                checkAndReport(context, node, value, exportsInFile, "importAs");
+            }
+
+            importsInFile.push(value);
+        }
+    };
+}
+
+/**
+ * Returns a function handling the exports of a given file
+ * @param {RuleContext} context The ESLint rule context object.
+ * @param {string[]} importsInFile The array containing other imports in the file.
+ * @param {string[]} exportsInFile The array containing other exports in the file.
+ *
+ * @returns {nodeCallback} A function passed to ESLint to handle the statement.
+ */
+function handleExports(context, importsInFile, exportsInFile) {
+    return function(node) {
+        const value = getValue(node);
+
+        if (value) {
+            checkAndReport(context, node, value, exportsInFile, "export");
+            checkAndReport(context, node, value, importsInFile, "exportAs");
+
+            exportsInFile.push(value);
+        }
+    };
+}
+
+module.exports = {
+    meta: {
+        type: "problem",
+
+        docs: {
+            description: "disallow duplicate module imports",
+            category: "ECMAScript 6",
+            recommended: false,
+            url: "https://eslint.org/docs/rules/no-duplicate-imports"
+        },
+
+        schema: [{
+            type: "object",
+            properties: {
+                includeExports: {
+                    type: "boolean",
+                    default: false
+                }
+            },
+            additionalProperties: false
+        }],
+        messages: {
+            import: "'{{module}}' import is duplicated.",
+            importAs: "'{{module}}' import is duplicated as export.",
+            export: "'{{module}}' export is duplicated.",
+            exportAs: "'{{module}}' export is duplicated as import."
+        }
+    },
+
+    create(context) {
+        const includeExports = (context.options[0] || {}).includeExports,
+            importsInFile = [],
+            exportsInFile = [];
+
+        const handlers = {
+            ImportDeclaration: handleImports(context, includeExports, importsInFile, exportsInFile)
+        };
+
+        if (includeExports) {
+            handlers.ExportNamedDeclaration = handleExports(context, importsInFile, exportsInFile);
+            handlers.ExportAllDeclaration = handleExports(context, importsInFile, exportsInFile);
+        }
+
+        return handlers;
+    }
+};