watch: fix interaction with multiple env files

lib/internal/main/watch_mode.js

@@ -34,7 +34,10 @@ markBootstrapComplete();
 
 const kKillSignal = convertToValidSignal(getOptionValue('--watch-kill-signal'));
 const kShouldFilterModules = getOptionValue('--watch-path').length === 0;
-const kEnvFile = getOptionValue('--env-file') || getOptionValue('--env-file-if-exists');
+const kEnvFiles = [
+  ...getOptionValue('--env-file'),
+  ...getOptionValue('--env-file-if-exists'),
+];
 const kWatchedPaths = ArrayPrototypeMap(getOptionValue('--watch-path'), (path) => resolve(path));
 const kPreserveOutput = getOptionValue('--watch-preserve-output');
 const kCommand = ArrayPrototypeSlice(process.argv, 1);
@@ -100,8 +103,8 @@ function start() {
     },
   });
   watcher.watchChildProcessModules(child);
-  if (kEnvFile) {
-    watcher.filterFile(resolve(kEnvFile));
+  if (kEnvFiles.length > 0) {
+    ArrayPrototypeForEach(kEnvFiles, (file) => watcher.filterFile(resolve(file)));
   }
   child.once('exit', (code) => {
     exited = true;

src/node_options.h

@@ -185,8 +185,8 @@ class EnvironmentOptions : public Options {
 #endif  // HAVE_INSPECTOR
   std::string redirect_warnings;
   std::string diagnostic_dir;
-  std::string env_file;
-  std::string optional_env_file;
+  std::vector<std::string> env_file;
+  std::vector<std::string> optional_env_file;
   bool has_env_file_string = false;
   bool test_runner = false;
   uint64_t test_runner_concurrency = 0;

test/parallel/test-dotenv-edge-cases.js

@@ -39,6 +39,17 @@ describe('.env supports edge cases', () => {
     })));
   });
 
+  it('should not support comma-separated env files', async () => {
+    const code = 'assert.strictEqual(1, 1)';
+    const child = await common.spawnPromisified(
+      process.execPath,
+      [`--env-file=${validEnvFilePath},${nodeOptionsEnvFilePath}`, '--eval', code],
+      { cwd: __dirname },
+    );
+    assert.notStrictEqual(child.stderr, '');
+    assert.strictEqual(child.code, 9);
+  });
+
   it('supports absolute paths', async () => {
     const code = `
       assert.strictEqual(process.env.BASIC, 'basic');

test/sequential/test-watch-mode.mjs

@@ -860,4 +860,28 @@ process.on('message', (message) => {
       `Completed running ${inspect(file)}. Waiting for file changes before restarting...`,
     ]);
   });
+
+  it('should support multiple --env-file flags', async () => {
+    const envKey = `TEST_ENV_A_${Date.now()}`;
+    const envKey2 = `TEST_ENV_B_${Date.now()}`;
+    const jsFile = createTmpFile(`console.log('ENV_A: ' + process.env.${envKey} + '\\n' + 'ENV_B: ' + process.env.${envKey2});`);
+    const envFileA = createTmpFile(`${envKey}=123`, '.env');
+    const envFileB = createTmpFile(`${envKey2}=456`, '.env');
+    const { done, restart } = runInBackground({
+      args: ['--watch', `--env-file=${envFileA}`, `--env-file=${envFileB}`, jsFile]
+    });
+
+    try {
+      const { stderr, stdout } = await restart();
+
+      assert.strictEqual(stderr, '');
+      assert.deepStrictEqual(stdout, [
+        'ENV_A: 123',
+        'ENV_B: 456',
+        `Completed running ${inspect(jsFile)}. Waiting for file changes before restarting...`,
+      ]);
+    } finally {
+      await done();
+    }
+  });
 });