Revert "fix: CJS detection regression for packages with "export" in comments (#3793)"

This reverts commit 838f41a.

Author: bartlomieju

packages/plugin-vite/demo/routes/tests/cjs_npm.tsx

@@ -23,37 +23,6 @@ export function deno(): Plugin {
 
   let isDev = false;
 
-  // Cache for package.json "type" field lookups. Per Node.js semantics,
-  // .js files in node_modules are CJS unless the nearest package.json
-  // has "type": "module".
-  const pkgTypeCache = new Map<string, boolean>();
-  async function isEsmPackage(filePath: string): Promise<boolean> {
-    let dir = path.dirname(filePath);
-    while (true) {
-      const cached = pkgTypeCache.get(dir);
-      if (cached !== undefined) return cached;
-
-      try {
-        const text = await Deno.readTextFile(path.join(dir, "package.json"));
-        const isEsm = JSON.parse(text).type === "module";
-        pkgTypeCache.set(dir, isEsm);
-        return isEsm;
-      } catch {
-        const parent = path.dirname(dir);
-        if (parent === dir) break;
-        dir = parent;
-      }
-    }
-    return false;
-  }
-
-  // Detect actual ESM export/import statements at the statement level.
-  // More robust than code.includes("export ") which matches comments
-  // and strings (e.g. "// Remove export in next version" would trick it).
-  // Handles both formatted and minified ESM (e.g. "import{" with no space).
-  const ESM_STMT_RE =
-    /(?:^|[\n;])\s*(?:export\s*[{*]|export\s+(?:default|const|let|var|function|class|async)\b|import\s*[{*"']|import\s+[a-zA-Z_$])/;
-
   return {
     name: "deno",
     sharedDuringBuild: true,
@@ -217,33 +186,27 @@ export function deno(): Plugin {
       // - SSR: module runner evaluates as ESM, needs module/exports/require
       // - Client: browser evaluates as ESM, needs module/exports
       // In build mode, Rollup's @rollup/plugin-commonjs handles CJS.
-      //
-      // CJS detection uses Node.js semantics (package.json "type" field)
-      // instead of content heuristics, which can be fooled by comments
-      // or strings containing "export"/"import".
       if (
         isDev &&
         !id.startsWith("\0") &&
         id.includes("node_modules") &&
         /\.(c?js|cjs)$/.test(id)
       ) {
-        // .cjs is always CJS. For .js files, check the nearest
-        // package.json "type" field first (Node.js semantics), then
-        // fall back to content-based detection for dual CJS/ESM
-        // packages that ship ESM in .js without "type": "module".
-        if (id.endsWith(".cjs") || !(await isEsmPackage(id))) {
-          try {
-            const code = await Deno.readTextFile(id);
-
-            // Skip if the file contains actual ESM syntax. Some packages
-            // (e.g. @opentelemetry/api) ship both CJS and ESM as .js
-            // without "type": "module" in package.json.
-            if (!ESM_STMT_RE.test(code)) {
-              const isServer = this.environment.config.consumer === "server";
-
-              if (isServer) {
-                // SSR: use Node.js createRequire for full CJS compat
-                const wrapped = `
+        try {
+          const code = await Deno.readTextFile(id);
+          // Quick heuristic: if file has CJS patterns and no ESM
+          if (
+            !code.includes("export ") &&
+            !code.includes("import ") &&
+            (code.includes("module.exports") ||
+              code.includes("exports.") ||
+              code.includes("require("))
+          ) {
+            const isServer = this.environment.config.consumer === "server";
+
+            if (isServer) {
+              // SSR: use Node.js createRequire for full CJS compat
+              const wrapped = `
 import { createRequire as __cjs_createRequire } from "node:module";
 import { fileURLToPath as __cjs_fileURLToPath } from "node:url";
 import { dirname as __cjs_dirname } from "node:path";
@@ -257,26 +220,26 @@ ${code}
 
 export default module.exports;
 `;
-                return { code: wrapped };
-              }
-
-              // Client: convert require() calls to ESM imports so
-              // browsers can load them. Hoist static require() calls
-              // to import statements at the top.
-              const imports: string[] = [];
-              let idx = 0;
-              const transformed = code.replace(
-                /\brequire\(["']([^"']+)["']\)/g,
-                (_match: string, spec: string) => {
-                  const varName = `__cjs_import_${idx++}`;
-                  imports.push(
-                    `import ${varName} from ${JSON.stringify(spec)};`,
-                  );
-                  return `(${varName}.default ?? ${varName})`;
-                },
-              );
-
-              const wrapped = `${imports.join("\n")}
+              return { code: wrapped };
+            }
+
+            // Client: convert require() calls to ESM imports so
+            // browsers can load them. Hoist static require() calls
+            // to import statements at the top.
+            const imports: string[] = [];
+            let idx = 0;
+            const transformed = code.replace(
+              /\brequire\(["']([^"']+)["']\)/g,
+              (_match: string, spec: string) => {
+                const varName = `__cjs_import_${idx++}`;
+                imports.push(
+                  `import ${varName} from ${JSON.stringify(spec)};`,
+                );
+                return `(${varName}.default ?? ${varName})`;
+              },
+            );
+
+            const wrapped = `${imports.join("\n")}
 var module = { exports: {} };
 var exports = module.exports;
 var __filename = "";
@@ -286,11 +249,10 @@ ${transformed}
 
 export default module.exports;
 `;
-              return { code: wrapped };
-            }
-          } catch {
-            // Fall through to default loading
+            return { code: wrapped };
           }
+        } catch {
+          // Fall through to default loading
         }
       }
 

packages/plugin-vite/src/plugins/deno.ts

@@ -452,17 +452,6 @@ Deno.test({
   sanitizeResources: false,
 });
 
-Deno.test({
-  name: "vite dev - CJS npm package (qs)",
-  fn: async () => {
-    const res = await fetch(`${demoServer.address()}/tests/cjs_npm`);
-    const text = await res.text();
-    expect(text).toContain("<h1>qs-ok</h1>");
-  },
-  sanitizeOps: false,
-  sanitizeResources: false,
-});
-
 // issue: https://github.com/denoland/fresh/issues/3666
 integrationTest(
   "vite dev - basePath does not intercept Vite URLs",