Merge pull request #2 from Rel1cx/no-duplicate-exports

feat(no-duplicate-exports): implement rule to disallow duplicate exports with tests

Author: Rel1cx

packages/tsl-module/src/rules/no-duplicate-exports.test.ts

@@ -0,0 +1,46 @@
+import tsx from "dedent";
+import { ruleTester } from "tsl/ruleTester";
+import { expect, test } from "vitest";
+
+import { messages, noDuplicateExports } from "./no-duplicate-exports";
+
+test("no-duplicate-exports", () => {
+  const ret = ruleTester({
+    invalid: [
+      {
+        code: tsx`
+          export { A } from 'module';
+          export { B } from 'module';
+        `,
+        errors: [
+          {
+            line: 2,
+            message: messages.noDuplicateExports({ source: "'module'" }),
+          },
+        ],
+      },
+      {
+        code: tsx`
+          export type { A } from 'module';
+          export type { B } from 'module';
+        `,
+        errors: [
+          {
+            line: 2,
+            message: messages.noDuplicateExports({ source: "'module'" }),
+          },
+        ],
+      },
+    ],
+    ruleFn: noDuplicateExports,
+    tsx: true,
+    valid: [
+      tsx`
+        export { A } from 'module1';
+        export { A } from 'module2';
+        export { A } from 'module3';
+      `,
+    ],
+  });
+  expect(ret).toBe(false);
+});

packages/tsl-module/src/rules/no-duplicate-exports.ts

@@ -0,0 +1,65 @@
+import { defineRule } from "tsl";
+
+export const messages = {
+  noDuplicateExports: (p: { source: string }) =>
+    `Duplicate export to module ${p.source}. Combine into a single export statement.`,
+} as const;
+
+/**
+ * Rule to disallow duplicate exports to the same module. Combine multiple export statements to the same module into a single statement.
+ *
+ * @todo Add autofix to merge duplicate exports automatically.
+ *
+ * @example
+ *
+ * ```ts
+ * // Incorrect
+ * export { A } from 'module';
+ * export { B } from 'module';
+ * ```
+ *
+ * ```ts
+ * // Incorrect
+ * export type { A } from 'module';
+ * export type { B } from 'module';
+ * ```
+ *
+ * @example
+ *
+ * ```ts
+ * // Correct
+ * export { A, B } from 'module';
+ * ```
+ *
+ * ```ts
+ * // Correct
+ * export { A } from 'moduleA';
+ * export type { B } from 'moduleA';
+ * ```
+ */
+export const noDuplicateExports = defineRule(() => {
+  return {
+    name: "module/no-duplicate-exports",
+    createData() {
+      return [
+        new Set<string>(), // for export
+        new Set<string>(), // for export type
+      ] as const;
+    },
+    visitor: {
+      ExportDeclaration(ctx, node) {
+        if (node.moduleSpecifier == null) return; // skip non-re-export exports
+        const exportSource = node.moduleSpecifier.getText();
+        const seen = ctx.data[node.isTypeOnly ? 1 : 0];
+        if (seen.has(exportSource)) {
+          ctx.report({
+            node,
+            message: messages.noDuplicateExports({ source: exportSource }),
+          });
+          return;
+        }
+        seen.add(exportSource);
+      },
+    },
+  };
+});

packages/tsl-module/src/rules/no-duplicate-imports.ts

@@ -42,7 +42,7 @@ export const messages = {
  */
 export const noDuplicateImports = defineRule(() => {
   return {
-    name: "module/no-duplicate-import",
+    name: "module/no-duplicate-imports",
     createData() {
       return [
         new Set<string>(), // for import