fix: esm conditional imports

fix #791

Author: RebeccaStevens

rollup.config.ts

@@ -12,7 +12,43 @@ const treeshake = {
   unknownGlobalSideEffects: false,
 } satisfies RollupOptions["treeshake"];
 
-const classic = {
+const classicCJS = {
+  input: "src/classic.ts",
+
+  output: [
+    {
+      file: pkg.exports["."].require,
+      format: "cjs",
+      sourcemap: false,
+    },
+  ],
+
+  plugins: [
+    rollupPluginAutoExternal(),
+    rollupPluginTs({
+      transpileOnly: true,
+      tsconfig: {
+        fileName: "tsconfig.build.json",
+        hook: (resolvedConfig) => ({
+          ...resolvedConfig,
+          paths: {
+            ...resolvedConfig.paths,
+            "#eslint-plugin-functional/conditional-imports/*": [
+              "src/utils/conditional-imports/cjs/*",
+            ],
+          },
+        }),
+      },
+    }),
+    rollupPluginDeassert({
+      include: ["**/*.{js,ts}"],
+    }),
+  ],
+
+  treeshake,
+} satisfies RollupOptions;
+
+const classicESM = {
   input: "src/classic.ts",
 
   output: [
@@ -21,8 +57,39 @@ const classic = {
       format: "esm",
       sourcemap: false,
     },
+  ],
+
+  plugins: [
+    rollupPluginAutoExternal(),
+    rollupPluginTs({
+      transpileOnly: true,
+      tsconfig: {
+        fileName: "tsconfig.build.json",
+        hook: (resolvedConfig) => ({
+          ...resolvedConfig,
+          paths: {
+            ...resolvedConfig.paths,
+            "#eslint-plugin-functional/conditional-imports/*": [
+              "src/utils/conditional-imports/esm/*",
+            ],
+          },
+        }),
+      },
+    }),
+    rollupPluginDeassert({
+      include: ["**/*.{js,ts}"],
+    }),
+  ],
+
+  treeshake,
+} satisfies RollupOptions;
+
+const flatCJS = {
+  input: "src/flat.ts",
+
+  output: [
     {
-      file: pkg.exports["."].require,
+      file: pkg.exports["./flat"].require,
       format: "cjs",
       sourcemap: false,
     },
@@ -32,7 +99,18 @@ const classic = {
     rollupPluginAutoExternal(),
     rollupPluginTs({
       transpileOnly: true,
-      tsconfig: "tsconfig.build.json",
+      tsconfig: {
+        fileName: "tsconfig.build.json",
+        hook: (resolvedConfig) => ({
+          ...resolvedConfig,
+          paths: {
+            ...resolvedConfig.paths,
+            "#eslint-plugin-functional/conditional-imports/*": [
+              "src/utils/conditional-imports/cjs/*",
+            ],
+          },
+        }),
+      },
     }),
     rollupPluginDeassert({
       include: ["**/*.{js,ts}"],
@@ -42,7 +120,7 @@ const classic = {
   treeshake,
 } satisfies RollupOptions;
 
-const flat = {
+const flatESM = {
   input: "src/flat.ts",
 
   output: [
@@ -51,18 +129,24 @@ const flat = {
       format: "esm",
       sourcemap: false,
     },
-    {
-      file: pkg.exports["./flat"].require,
-      format: "cjs",
-      sourcemap: false,
-    },
   ],
 
   plugins: [
     rollupPluginAutoExternal(),
     rollupPluginTs({
       transpileOnly: true,
-      tsconfig: "tsconfig.build.json",
+      tsconfig: {
+        fileName: "tsconfig.build.json",
+        hook: (resolvedConfig) => ({
+          ...resolvedConfig,
+          paths: {
+            ...resolvedConfig.paths,
+            "#eslint-plugin-functional/conditional-imports/*": [
+              "src/utils/conditional-imports/esm/*",
+            ],
+          },
+        }),
+      },
     }),
     rollupPluginDeassert({
       include: ["**/*.{js,ts}"],
@@ -72,4 +156,4 @@ const flat = {
   treeshake,
 } satisfies RollupOptions;
 
-export default [classic, flat];
+export default [classicCJS, classicESM, flatCJS, flatESM];

src/utils/conditional-imports/ts-api-utils.ts renamed to src/utils/conditional-imports/cjs/ts-api-utils.ts

@@ -0,0 +1,10 @@
+import type tsApiUtils from "ts-api-utils";
+
+import ts from "#eslint-plugin-functional/conditional-imports/typescript";
+
+export default await ((): Promise<typeof tsApiUtils | undefined> => {
+  if (ts !== undefined) {
+    return import("ts-api-utils").catch(() => undefined);
+  }
+  return Promise.resolve(undefined);
+})();

src/utils/conditional-imports/typescript.ts renamed to src/utils/conditional-imports/cjs/typescript.ts

@@ -0,0 +1,4 @@
+// eslint-disable-next-line unicorn/import-style
+export default await import("typescript")
+  .then((module) => module.default)
+  .catch(() => undefined);

src/utils/conditional-imports/esm/ts-api-utils.ts

@@ -40,7 +40,7 @@
       "#eslint-plugin-functional/settings": ["src/settings"],
       "#eslint-plugin-functional/utils/*": ["src/utils/*"],
       "#eslint-plugin-functional/conditional-imports/*": [
-        "src/utils/conditional-imports/*"
+        "src/utils/conditional-imports/cjs/*"
       ],
       "#eslint-plugin-functional/tests/*": ["tests/*"]
     }