Fix: no-duplicate-imports allow unmergeable (fixes #12758, fixes #12760)

docs/rules/no-duplicate-imports.md

@@ -12,7 +12,7 @@ import { find } from 'module';
 
 ## Rule Details
 
-This rule requires that all imports from a single module exists in a single `import` statement.
+This rule requires that all imports from a single module that can be merged exist in a single `import` statement.
 
 Example of **incorrect** code for this rule:
 
@@ -33,6 +33,16 @@ import { merge, find } from 'module';
 import something from 'another-module';
 ```
 
+Example of **correct** code for this rule:
+
+```js
+/*eslint no-duplicate-imports: "error"*/
+
+// not mergeable
+import { merge } from 'module';
+import * as something from 'module';
+```
+
 ## Options
 
 This rule takes one optional argument, an object with a single key, `includeExports` which is a `boolean`. It defaults to `false`.
@@ -58,3 +68,17 @@ import { merge, find } from 'module';
 
 export { find };
 ```
+
+Example of **correct** code for this rule with the `{ "includeExports": true }` option:
+
+```js
+/*eslint no-duplicate-imports: ["error", { "includeExports": true }]*/
+
+import { merge, find } from 'module';
+
+// cannot be merged with the above import
+export * as something from 'module';
+
+// cannot be written differently
+export * from 'module';
+```

lib/rules/no-duplicate-imports.js

@@ -4,92 +4,225 @@
  */
 "use strict";
 
+//------------------------------------------------------------------------------
+// Helpers
+//------------------------------------------------------------------------------
+
+const NAMED_TYPES = ["ImportSpecifier", "ExportSpecifier"];
+const NAMESPACE_TYPES = [
+    "ImportNamespaceSpecifier",
+    "ExportNamespaceSpecifier"
+];
+
 //------------------------------------------------------------------------------
 // Rule Definition
 //------------------------------------------------------------------------------
 
 /**
- * Returns the name of the module imported or re-exported.
+ * Check if an import/export type belongs to (ImportSpecifier|ExportSpecifier) or (ImportNamespaceSpecifier|ExportNamespaceSpecifier).
+ * @param {string} importExportType An import/export type to check.
+ * @param {string} type Can be "named" or "namespace"
+ * @returns {boolean} True if import/export type belongs to (ImportSpecifier|ExportSpecifier) or (ImportNamespaceSpecifier|ExportNamespaceSpecifier) and false if it doesn't.
+ */
+function isImportExportSpecifier(importExportType, type) {
+    const arrayToCheck = type === "named" ? NAMED_TYPES : NAMESPACE_TYPES;
+
+    return arrayToCheck.includes(importExportType);
+}
+
+/**
+ * Return the type of (import|export).
  * @param {ASTNode} node A node to get.
- * @returns {string} the name of the module, or empty string if no name.
+ * @returns {string} The type of the (import|export).
  */
-function getValue(node) {
-    if (node && node.source && node.source.value) {
-        return node.source.value.trim();
+function getImportExportType(node) {
+    if (node.specifiers && node.specifiers.length > 0) {
+        const nodeSpecifiers = node.specifiers;
+        const index = nodeSpecifiers.findIndex(
+            ({ type }) =>
+                isImportExportSpecifier(type, "named") ||
+                isImportExportSpecifier(type, "namespace")
+        );
+        const i = index > -1 ? index : 0;
+
+        return nodeSpecifiers[i].type;
     }
+    if (node.type === "ExportAllDeclaration") {
+        if (node.exported) {
+            return "ExportNamespaceSpecifier";
+        }
+        return "ExportAll";
+    }
+    return "SideEffectImport";
+}
 
-    return "";
+/**
+ * Returns a boolean indicates if two (import|export) can be merged
+ * @param {ASTNode} node1 A node to check.
+ * @param {ASTNode} node2 A node to check.
+ * @returns {boolean} True if two (import|export) can be merged, false if they can't.
+ */
+function isImportExportCanBeMerged(node1, node2) {
+    const importExportType1 = getImportExportType(node1);
+    const importExportType2 = getImportExportType(node2);
+
+    if (
+        (importExportType1 === "ExportAll" &&
+            importExportType2 !== "ExportAll" &&
+            importExportType2 !== "SideEffectImport") ||
+        (importExportType1 !== "ExportAll" &&
+            importExportType1 !== "SideEffectImport" &&
+            importExportType2 === "ExportAll")
+    ) {
+        return false;
+    }
+    if (
+        (isImportExportSpecifier(importExportType1, "namespace") &&
+            isImportExportSpecifier(importExportType2, "named")) ||
+        (isImportExportSpecifier(importExportType2, "namespace") &&
+            isImportExportSpecifier(importExportType1, "named"))
+    ) {
+        return false;
+    }
+    return true;
 }
 
 /**
- * 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
+ * Returns a boolean if we should report (import|export).
+ * @param {ASTNode} node A node to be reported or not.
+ * @param {[ASTNode]} previousNodes An array contains previous nodes of the module imported or exported.
+ * @returns {boolean} True if the (import|export) should be reported.
  */
-function checkAndReport(context, node, value, array, messageId) {
-    if (array.indexOf(value) !== -1) {
-        context.report({
-            node,
-            messageId,
-            data: {
-                module: value
-            }
-        });
+function shouldReportImportExport(node, previousNodes) {
+    let i = 0;
+
+    while (i < previousNodes.length) {
+        if (isImportExportCanBeMerged(node, previousNodes[i])) {
+            return true;
+        }
+        i++;
     }
+    return false;
 }
 
 /**
- * @callback nodeCallback
- * @param {ASTNode} node A node to handle.
+ * Returns array contains only nodes with declarations types equal to type.
+ * @param {[{node: ASTNode, declarationType: string}]} nodes An array contains objects, each object contains a node and a declaration type.
+ * @param {string} type Declaration type.
+ * @returns {[ASTNode]} An array contains only nodes with declarations types equal to type.
+ */
+function getNodesByDeclarationType(nodes, type) {
+    return nodes
+        .filter(({ declarationType }) => declarationType === type)
+        .map(({ node }) => node);
+}
+
+/**
+ * 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 getModule(node) {
+    if (node && node.source && node.source.value) {
+        return node.source.value.trim();
+    }
+    return "";
+}
 
 /**
- * Returns a function handling the imports of a given file
+ * Checks if the (import|export) can be merged with at least one import or one export, and reports if so.
  * @param {RuleContext} context The ESLint rule context object.
+ * @param {ASTNode} node A node to get.
+ * @param {Map} modules A Map object contains as a key a module name and as value an array contains objects, each object contains a node and a declaration type.
+ * @param {string} declarationType A declaration type can be an import or export.
  * @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.
+ * @returns {void} No return value.
  */
-function handleImports(context, includeExports, importsInFile, exportsInFile) {
-    return function(node) {
-        const value = getValue(node);
+function checkAndReport(
+    context,
+    node,
+    modules,
+    declarationType,
+    includeExports
+) {
+    const module = getModule(node);
 
-        if (value) {
-            checkAndReport(context, node, value, importsInFile, "import");
+    if (modules.has(module)) {
+        const previousNodes = modules.get(module);
+        const messagesIds = [];
+        const importNodes = getNodesByDeclarationType(previousNodes, "import");
+        let exportNodes;
 
+        if (includeExports) {
+            exportNodes = getNodesByDeclarationType(previousNodes, "export");
+        }
+        if (declarationType === "import") {
+            if (shouldReportImportExport(node, importNodes)) {
+                messagesIds.push("import");
+            }
             if (includeExports) {
-                checkAndReport(context, node, value, exportsInFile, "importAs");
+                if (shouldReportImportExport(node, exportNodes)) {
+                    messagesIds.push("importAs");
+                }
+            }
+        } else if (declarationType === "export") {
+            if (shouldReportImportExport(node, exportNodes)) {
+                messagesIds.push("export");
+            }
+            if (shouldReportImportExport(node, importNodes)) {
+                messagesIds.push("exportAs");
             }
-
-            importsInFile.push(value);
         }
-    };
+        messagesIds.forEach(messageId =>
+            context.report({
+                node,
+                messageId,
+                data: {
+                    module
+                }
+            }));
+    }
 }
 
 /**
- * Returns a function handling the exports of a given file
+ * @callback nodeCallback
+ * @param {ASTNode} node A node to handle.
+ */
+
+/**
+ * Returns a function handling the (imports|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.
- *
+ * @param {Map} modules A Map object contains as a key a module name and as value an array contains objects, each object contains a node and a declaration type.
+ * @param {string} declarationType A declaration type can be an import or export.
+ * @param {boolean} includeExports Whether or not to check for exports in addition to imports.
  * @returns {nodeCallback} A function passed to ESLint to handle the statement.
  */
-function handleExports(context, importsInFile, exportsInFile) {
+function handleImportsExports(
+    context,
+    modules,
+    declarationType,
+    includeExports
+) {
     return function(node) {
-        const value = getValue(node);
+        const module = getModule(node);
+
+        if (module) {
+            checkAndReport(
+                context,
+                node,
+                modules,
+                declarationType,
+                includeExports
+            );
+            const currentNode = { node, declarationType };
+            let nodes = [currentNode];
 
-        if (value) {
-            checkAndReport(context, node, value, exportsInFile, "export");
-            checkAndReport(context, node, value, importsInFile, "exportAs");
+            if (modules.has(module)) {
+                const previousNodes = modules.get(module);
 
-            exportsInFile.push(value);
+                nodes = [...previousNodes, currentNode];
+            }
+            modules.set(module, nodes);
         }
     };
 }
@@ -105,16 +238,19 @@ module.exports = {
             url: "https://eslint.org/docs/rules/no-duplicate-imports"
         },
 
-        schema: [{
-            type: "object",
-            properties: {
-                includeExports: {
-                    type: "boolean",
-                    default: false
-                }
-            },
-            additionalProperties: false
-        }],
+        schema: [
+            {
+                type: "object",
+                properties: {
+                    includeExports: {
+                        type: "boolean",
+                        default: false
+                    }
+                },
+                additionalProperties: false
+            }
+        ],
+
         messages: {
             import: "'{{module}}' import is duplicated.",
             importAs: "'{{module}}' import is duplicated as export.",
@@ -125,18 +261,30 @@ module.exports = {
 
     create(context) {
         const includeExports = (context.options[0] || {}).includeExports,
-            importsInFile = [],
-            exportsInFile = [];
-
+            modules = new Map();
         const handlers = {
-            ImportDeclaration: handleImports(context, includeExports, importsInFile, exportsInFile)
+            ImportDeclaration: handleImportsExports(
+                context,
+                modules,
+                "import",
+                includeExports
+            )
         };
 
         if (includeExports) {
-            handlers.ExportNamedDeclaration = handleExports(context, importsInFile, exportsInFile);
-            handlers.ExportAllDeclaration = handleExports(context, importsInFile, exportsInFile);
+            handlers.ExportNamedDeclaration = handleImportsExports(
+                context,
+                modules,
+                "export",
+                includeExports
+            );
+            handlers.ExportAllDeclaration = handleImportsExports(
+                context,
+                modules,
+                "export",
+                includeExports
+            );
         }
-
         return handlers;
     }
 };