Allow dotenv files from different environments for SSR and SSG in Next.js

CHANGELOG.md

@@ -1 +1,4 @@
+- Implemented a check in the Next.js build function to verify if
+  `.env.<PROJECT-ID>` file exists and make its variables available for the build
+  process.
 - Fix esbuild path used to bundle next.config.js on Windows (#7555)

src/frameworks/next/index.ts

@@ -6,7 +6,7 @@ import type { NextConfig } from "next";
 import type { PrerenderManifest } from "next/dist/build";
 import type { DomainLocale } from "next/dist/server/config";
 import type { PagesManifest } from "next/dist/build/webpack/plugins/pages-manifest-plugin";
-import { copy, mkdirp, pathExists, pathExistsSync } from "fs-extra";
+import { copy, mkdirp, pathExists, pathExistsSync, readFile } from "fs-extra";
 import { pathToFileURL, parse } from "url";
 import { gte } from "semver";
 import { IncomingMessage, ServerResponse } from "http";
@@ -82,6 +82,7 @@ import {
 } from "./constants";
 import { getAllSiteDomains, getDeploymentDomain } from "../../hosting/api";
 import { logger } from "../../logger";
+import { parseStrict } from "../../functions/env";
 
 const DEFAULT_BUILD_SCRIPT = ["next build"];
 const PUBLIC_DIR = "public";
@@ -126,7 +127,19 @@ export async function build(
     process.env.__NEXT_REACT_ROOT = "true";
   }
 
-  const env = { ...process.env };
+  let env = { ...process.env };
+
+  // Check if the .env.<PROJECT-ID> file exists and make it available for the build process
+  if (context?.projectId) {
+    const projectEnvPath = join(dir, `.env.${context.projectId}`);
+
+    if (await pathExists(projectEnvPath)) {
+      const projectEnvVars = parseStrict((await readFile(projectEnvPath)).toString());
+
+      // Merge the parsed variables with the existing environment variables
+      env = { ...projectEnvVars, ...env };
+    }
+  }
 
   if (context?.projectId && context?.site) {
     const deploymentDomain = await getDeploymentDomain(

src/functions/env.spec.ts

@@ -696,4 +696,51 @@ FOO=foo
       }).to.throw("Failed to load");
     });
   });
+
+  describe("parseStrict", () => {
+    it("should parse valid environment variables", () => {
+      const input = `
+	FOO=foo
+	BAR="bar"
+	BAZ='baz'
+	`;
+      const expected = { FOO: "foo", BAR: "bar", BAZ: "baz" };
+      expect(env.parseStrict(input)).to.deep.equal(expected);
+    });
+
+    it("should throw an error for invalid lines", () => {
+      const input = `
+	FOO=foo
+	INVALID LINE
+	BAR=bar
+	`;
+      expect(() => env.parseStrict(input)).to.throw(FirebaseError, /Invalid dotenv file/);
+    });
+
+    it("should throw an error for reserved keys", () => {
+      const input = `
+	FIREBASE_CONFIG=config
+	FOO=foo
+	`;
+      expect(() => env.parseStrict(input)).to.throw(FirebaseError, /Validation failed/);
+    });
+
+    it("should throw an error for invalid key formats", () => {
+      const input = `
+	foo=bar
+	BAR=baz
+	`;
+      expect(() => env.parseStrict(input)).to.throw(FirebaseError, /Validation failed/);
+    });
+
+    it("should handle escape sequences correctly", () => {
+      const input = `
+	FOO="foo\\nbar"
+	BAR="bar\\tfoo"
+	BAZ="baz\\rfoo"
+	`;
+      const expected = { FOO: "foo\nbar", BAR: "bar\tfoo", BAZ: "baz\rfoo" };
+      expect(env.parseStrict(input)).to.deep.equal(expected);
+    });
+  });
 });