Fix: [no-duplicate-imports] ignore namespace imports (fixes #12758)

docs/rules/no-duplicate-imports.md

@@ -12,7 +12,9 @@ import { find } from 'module';
 
 ## Rule Details
 
-This rule requires that all imports from a single module exists in a single `import` statement.
+an import that can be merged with another is a duplicate of that other
+
+This rule requires that all imports from a single module that can be merged exists in a single `import` statement.
 
 Example of **incorrect** code for this rule:
 
@@ -33,6 +35,16 @@ import { merge, find } from 'module';
 import something from 'another-module';
 ```
 
+Example of **correct** code for this rule (namespace imports can't be merged):
+
+```js
+/*eslint no-duplicate-imports: "error"*/
+
+import * as Namespace from 'module';
+import { merge } from 'module';
+import something from 'another-module';
+```
+
 ## Options
 
 This rule takes one optional argument, an object with a single key, `includeExports` which is a `boolean`. It defaults to `false`.

lib/rules/no-duplicate-imports.js

@@ -21,6 +21,20 @@ function getValue(node) {
     return "";
 }
 
+/**
+ * Checks if the import's type is a namespace import.
+ * @param {ASTNode} node A node to get.
+ *
+ * @returns {boolean} Whether or not the import's type is "ImportNamespaceSpecifier".
+ */
+function isNamespaceImport(node) {
+    return (
+        node.specifiers &&
+        node.specifiers[0] &&
+        node.specifiers[0].type === "ImportNamespaceSpecifier"
+    );
+}
+
 /**
  * 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.
@@ -61,7 +75,7 @@ function handleImports(context, includeExports, importsInFile, exportsInFile) {
     return function(node) {
         const value = getValue(node);
 
-        if (value) {
+        if (value && !isNamespaceImport(node)) {
             checkAndReport(context, node, value, importsInFile, "import");
 
             if (includeExports) {

tests/lib/rules/no-duplicate-imports.js

@@ -20,6 +20,7 @@ const ruleTester = new RuleTester({ parserOptions: { ecmaVersion: 6, sourceType:
 
 ruleTester.run("no-duplicate-imports", rule, {
     valid: [
+        "import * as Lodash from \"lodash-es\";import { merge } from \"lodash-es\";;",
         "import os from \"os\";\nimport fs from \"fs\";",
         "import { merge } from \"lodash-es\";",
         "import _, { merge } from \"lodash-es\";",