Essential environment variable parsing ^& validation

src/env/schema.mjs

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+// @ts-check
+import { z } from "zod";
+
+/**
+ * Specify your server-side environment variables schema here.
+ * This way you can ensure the app isn't built with invalid env vars.
+ */
+export const serverSchema = z.object({
+  API_KEY: z.string(),
+  CRONITOR_ACCOUNT_ID: z.string(),
+  CRONITOR_JOB_ID: z.string(),
+  LIFE360_USERNAME: z.string(),
+  LIFE360_PASSWORD: z.string(),
+  LIFE360_MEMBER_ID: z.string(),
+  MAX_DISTANCE: z.coerce.number().positive(),
+  CENTER_LATITUDE: z.coerce.number().min(-90).max(90),
+  CENTER_LONGITUDE: z.coerce.number().min(-180).max(180),
+});

src/env/server.mjs

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+// @ts-check
+/**
+ * This file is included in `/next.config.mjs` which ensures the app isn't built with invalid env vars.
+ * It has to be a `.mjs`-file to be imported there.
+ */
+import { serverSchema } from "./schema.mjs";
+import { formatErrors } from "./util.mjs";
+
+const _serverEnv = serverSchema.safeParse({
+  API_KEY: process.env.API_KEY,
+  CRONITOR_ACCOUNT_ID: process.env.CRONITOR_ACCOUNT_ID,
+  CRONITOR_JOB_ID: process.env.CRONITOR_JOB_ID,
+  LIFE360_USERNAME: process.env.LIFE360_USERNAME,
+  LIFE360_PASSWORD: process.env.LIFE360_PASSWORD,
+  LIFE360_MEMBER_ID: process.env.LIFE360_MEMBER_ID,
+  MAX_DISTANCE: process.env.MAX_DISTANCE,
+  CENTER_LATITUDE: process.env.CENTER_LATITUDE,
+  CENTER_LONGITUDE: process.env.CENTER_LONGITUDE,
+});
+
+if (_serverEnv.success === false) {
+  console.error(
+    "❌ Invalid environment variables:\n",
+    ...formatErrors(_serverEnv.error.format())
+  );
+  throw new Error("Invalid environment variables");
+}
+
+/**
+ * Validate that server-side environment variables are not exposed to the client.
+ */
+for (let key of Object.keys(_serverEnv.data)) {
+  if (key.startsWith("NEXT_PUBLIC_")) {
+    console.warn("❌ You are exposing a server-side env-variable:", key);
+
+    throw new Error("You are exposing a server-side env-variable");
+  }
+}
+
+export const env = { ..._serverEnv.data };

src/env/util.mjs

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+export const formatErrors = (
+    /** @type {import('zod').ZodFormattedError<Map<string,string>,string>} */
+    errors,
+  ) =>
+    Object.entries(errors)
+      .map(([name, value]) => {
+        if (value && "_errors" in value)
+          return `${name}: ${value._errors.join(", ")}\n`;
+      })
+      .filter(Boolean);