watch: fix --env-file-if-exists crashing on linux if the file is missing

lib/internal/main/watch_mode.js

@@ -24,6 +24,7 @@ const { green, blue, red, white, clear } = require('internal/util/colors');
 const { convertToValidSignal } = require('internal/util');
 
 const { spawn } = require('child_process');
+const { existsSync } = require('fs');
 const { inspect } = require('util');
 const { setTimeout, clearTimeout } = require('timers');
 const { resolve } = require('path');
@@ -34,10 +35,8 @@ markBootstrapComplete();
 
 const kKillSignal = convertToValidSignal(getOptionValue('--watch-kill-signal'));
 const kShouldFilterModules = getOptionValue('--watch-path').length === 0;
-const kEnvFiles = [
-  ...getOptionValue('--env-file'),
-  ...getOptionValue('--env-file-if-exists'),
-];
+const kEnvFiles = getOptionValue('--env-file');
+const kOptionalEnvFiles = 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);
@@ -105,6 +104,14 @@ function start() {
   if (kEnvFiles.length > 0) {
     ArrayPrototypeForEach(kEnvFiles, (file) => watcher.filterFile(resolve(file)));
   }
+  if (kOptionalEnvFiles.length > 0) {
+    ArrayPrototypeForEach(kOptionalEnvFiles, (file) => {
+      const resolvedPath = resolve(file);
+      if (existsSync(resolvedPath)) {
+        watcher.filterFile(resolvedPath);
+      }
+    });
+  }
   child.once('exit', (code) => {
     exited = true;
     const waitingForChanges = 'Waiting for file changes before restarting...';

test/sequential/test-watch-mode.mjs

@@ -277,6 +277,27 @@ describe('watch mode', { concurrency: !process.env.TEST_PARALLEL, timeout: 60_00
     }
   });
 
+  it('should not crash when --env-file-if-exists points to a missing file', async () => {
+    const envKey = `TEST_ENV_${Date.now()}`;
+    const jsFile = createTmpFile(`console.log('ENV: ' + process.env.${envKey});`);
+    const missingEnvFile = path.join(tmpdir.path, `missing-${Date.now()}.env`);
+    const { done, restart } = runInBackground({
+      args: ['--watch-path', tmpdir.path, `--env-file-if-exists=${missingEnvFile}`, jsFile],
+    });
+
+    try {
+      const { stderr, stdout } = await restart();
+
+      assert.doesNotMatch(stderr, /ENOENT: no such file or directory, watch/);
+      assert.deepStrictEqual(stdout, [
+        'ENV: undefined',
+        `Completed running ${inspect(jsFile)}. Waiting for file changes before restarting...`,
+      ]);
+    } finally {
+      await done();
+    }
+  });
+
   it('should watch changes to a failing file', async () => {
     const file = createTmpFile('throw new Error("fails");');
     const { stderr, stdout } = await runWriteSucceed({