fix(oxlint,oxfmt): Skip vite.config.ts exports defineConfig(fn) (#20260)

leaysgur · leaysgur · commit 4ea67decf50f · 2026-03-12T04:56:57.000Z
`vite.config.ts` may return function from `defineConfig(({ mode }) =&gt; ({ ... }))`, but we can't evaluate.

Just skip it like no `.lint|fmt` config.
diff --git a/apps/oxfmt/src-js/cli/js_config.ts b/apps/oxfmt/src-js/cli/js_config.ts
@@ -1,6 +1,8 @@
 import { basename as pathBasename } from "node:path";
 import { pathToFileURL } from "node:url";
 
+const isObject = (v: unknown) => typeof v === "object" && v !== null && !Array.isArray(v);
+
 const VITE_CONFIG_NAME = "vite.config.ts";
 const VITE_OXFMT_CONFIG_FIELD = "fmt";
 
@@ -23,23 +25,29 @@ export async function loadJsConfig(path: string): Promise<object | null> {
   const { default: config } = await import(fileUrl.href);
 
   if (config === undefined) throw new Error(`Configuration file has no default export: ${path}`);
-  if (typeof config !== "object" || config === null || Array.isArray(config)) {
-    throw new Error(`Configuration file must have a default export that is an object: ${path}`);
-  }
 
   // Vite config: extract `.fmt` field
   if (pathBasename(path) === VITE_CONFIG_NAME) {
+    // NOTE: Vite configs may export a function via `defineConfig(() => ({ ... }))`,
+    // but we don't know the arguments to call the function.
+    // Treat non-object exports as "no config" and skip.
+    if (!isObject(config)) return null;
+
     const fmtConfig = (config as Record<string, unknown>)[VITE_OXFMT_CONFIG_FIELD];
     // NOTE: return `null` if missing (signals "skip" to Rust side)
     if (fmtConfig === undefined) return null;
 
-    if (typeof fmtConfig !== "object" || fmtConfig === null || Array.isArray(fmtConfig)) {
+    if (!isObject(fmtConfig)) {
       throw new Error(
         `The \`${VITE_OXFMT_CONFIG_FIELD}\` field in the default export must be an object: ${path}`,
       );
     }
     return fmtConfig;
   }
 
+  if (!isObject(config)) {
+    throw new Error(`Configuration file must have a default export that is an object: ${path}`);
+  }
+
   return config;
 }
diff --git a/apps/oxfmt/test/cli/vite_config/__snapshots__/vite_config.test.ts.snap b/apps/oxfmt/test/cli/vite_config/__snapshots__/vite_config.test.ts.snap
@@ -47,6 +47,21 @@ Finished in <variable>ms on 1 files using 1 threads.
 --------------------"
 `;
 
+exports[`vite_config > skip: auto-discovered vite.config.ts with function export uses defaults 1`] = `
+"--------------------
+arguments: --check test.ts
+working directory: vite_config/fixtures/skip_fn_export
+exit code: 0
+--- STDOUT ---------
+Checking formatting...
+
+All matched files use the correct format.
+Finished in <variable>ms on 1 files using 1 threads.
+--- STDERR ---------
+
+--------------------"
+`;
+
 exports[`vite_config > skip: auto-discovered vite.config.ts without fmt field uses defaults 1`] = `
 "--------------------
 arguments: --check test.ts
diff --git a/apps/oxfmt/test/cli/vite_config/fixtures/skip_fn_export/test.ts b/apps/oxfmt/test/cli/vite_config/fixtures/skip_fn_export/test.ts
@@ -0,0 +1 @@
+const a = 1;
diff --git a/apps/oxfmt/test/cli/vite_config/fixtures/skip_fn_export/vite.config.ts b/apps/oxfmt/test/cli/vite_config/fixtures/skip_fn_export/vite.config.ts
@@ -0,0 +1,5 @@
+const defineConfig = (config: unknown) => config;
+
+export default defineConfig(() => ({
+  plugins: [],
+}));
diff --git a/apps/oxfmt/test/cli/vite_config/vite_config.test.ts b/apps/oxfmt/test/cli/vite_config/vite_config.test.ts
@@ -34,6 +34,12 @@ describe("vite_config", () => {
     expect(snapshot).toMatchSnapshot();
   });
 
+  it("skip: auto-discovered vite.config.ts with function export uses defaults", async () => {
+    const cwd = join(fixturesDir, "skip_fn_export");
+    const snapshot = await runAndSnapshot(cwd, [["--check", "test.ts"]]);
+    expect(snapshot).toMatchSnapshot();
+  });
+
   it("priority: oxfmt.config.ts takes precedence over vite.config.ts", async () => {
     // `oxfmt.config.ts` has `semi: false`, `vite.config.ts` has `semi: true`
     // oxfmt.config.ts should win, so `const a = 1;` (with semicolon) should be flagged
diff --git a/apps/oxlint/src-js/js_config.ts b/apps/oxlint/src-js/js_config.ts
@@ -9,6 +9,8 @@ interface JsConfigResult {
   config: unknown; // Will be validated as Oxlintrc on Rust side, `null` means "skip this config"
 }
 
+const isObject = (v: unknown) => typeof v === "object" && v !== null && !Array.isArray(v);
+
 const VITE_CONFIG_NAME = "vite.config.ts";
 const VITE_OXLINT_CONFIG_FIELD = "lint";
 
@@ -57,7 +59,7 @@ function validateConfigExtends(root: object): void {
       }
       for (let i = 0; i < maybeExtends.length; i++) {
         const item = maybeExtends[i];
-        if (typeof item !== "object" || item === null || Array.isArray(item)) {
+        if (!isObject(item)) {
           throw new Error(
             `\`extends[${i}]\` must be a config object (strings/paths are not supported).`,
           );
@@ -106,19 +108,22 @@ export async function loadJsConfigs(paths: string[]): Promise<string> {
           throw new Error(`Configuration file has no default export.`);
         }
 
-        if (typeof config !== "object" || config === null || Array.isArray(config)) {
-          throw new Error(`Configuration file must have a default export that is an object.`);
-        }
-
         // Vite config: extract `.lint` field, skip `defineConfig()` validation
         if (pathBasename(path) === VITE_CONFIG_NAME) {
+          // NOTE: Vite configs may export a function via `defineConfig(() => ({ ... }))`,
+          // but we don't know the arguments to call the function.
+          // Treat non-object exports as "no config" and skip.
+          if (!isObject(config)) {
+            return { path, config: null };
+          }
+
           const lintConfig = (config as Record<string, unknown>)[VITE_OXLINT_CONFIG_FIELD];
           // NOTE: return `null` if `.lint` is missing which signals "skip" this
           if (lintConfig === undefined) {
             return { path, config: null };
           }
 
-          if (typeof lintConfig !== "object" || lintConfig === null || Array.isArray(lintConfig)) {
+          if (!isObject(lintConfig)) {
             throw new Error(
               `The \`${VITE_OXLINT_CONFIG_FIELD}\` field in the default export must be an object.`,
             );
@@ -127,6 +132,10 @@ export async function loadJsConfigs(paths: string[]): Promise<string> {
           return { path, config: lintConfig };
         }
 
+        if (!isObject(config)) {
+          throw new Error(`Configuration file must have a default export that is an object.`);
+        }
+
         if (!isDefineConfig(config)) {
           throw new Error(
             `Configuration file must wrap its default export with defineConfig() from "oxlint".`,
diff --git a/apps/oxlint/test/fixtures/vite_config_fn_export/files/test.js b/apps/oxlint/test/fixtures/vite_config_fn_export/files/test.js
@@ -0,0 +1 @@
+debugger;
diff --git a/apps/oxlint/test/fixtures/vite_config_fn_export/options.json b/apps/oxlint/test/fixtures/vite_config_fn_export/options.json
@@ -0,0 +1,3 @@
+{
+  "singleThread": true
+}
diff --git a/apps/oxlint/test/fixtures/vite_config_fn_export/output.snap.md b/apps/oxlint/test/fixtures/vite_config_fn_export/output.snap.md
@@ -0,0 +1,19 @@
+# Exit code
+0
+
+# stdout
+```
+  ! eslint(no-debugger): `debugger` statement is not allowed
+   ,-[files/test.js:1:1]
+ 1 | debugger;
+   : ^^^^^^^^^
+   `----
+  help: Remove the debugger statement
+
+Found 1 warning and 0 errors.
+Finished in Xms on 1 file with 93 rules using X threads.
+```
+
+# stderr
+```
+```
diff --git a/apps/oxlint/test/fixtures/vite_config_fn_export/vite.config.ts b/apps/oxlint/test/fixtures/vite_config_fn_export/vite.config.ts
@@ -0,0 +1,5 @@
+const defineConfig = (config: unknown) => config;
+
+export default defineConfig(() => ({
+  plugins: [],
+}));
