fix: process.env has a higher loading priority than .env files

Author: vicb

examples/playground14/.env.development

@@ -1 +1,2 @@
-TEST_ENV_VAR=TEST_VALUE
+TEST_ENV_VAR=TEST_VALUE
+PROCESS_ENV_VAR=.ENV_FILE

examples/playground14/e2e/cloudflare.spec.ts

@@ -13,4 +13,9 @@ test.describe("playground/cloudflare", () => {
     const { nextConfig } = await res.json();
     expect(nextConfig.output).toEqual("standalone");
   });
+
+  test("Environment variable defined on process.env are not overridden by .env files", async ({ page }) => {
+    const res = await page.request.get("/api/env");
+    await expect(res.json()).resolves.toEqual(expect.objectContaining({ PROCESS_ENV_VAR: "process.env" }));
+  });
 });

examples/playground14/wrangler.jsonc

@@ -15,6 +15,7 @@
     }
   ],
   "vars": {
-    "hello": "Hello World from the cloudflare context!"
+    "hello": "Hello World from the cloudflare context!",
+    "PROCESS_ENV_VAR": "process.env"
   }
 }

packages/cloudflare/src/cli/templates/worker.ts

@@ -78,7 +78,7 @@ function populateProcessEnv(url: URL, env: CloudflareEnv) {
   const mode = env.NEXTJS_ENV ?? "production";
   if (nextEnvVars[mode]) {
     for (const key in nextEnvVars[mode]) {
-      process.env[key] = nextEnvVars[mode][key];
+      process.env[key] ??= nextEnvVars[mode][key];
     }
   }