HMR of env variable is not working

[XantreDev]

Summary

Changing of .env file do not change anything

Problems lays in env expansion code:

  expo:start:server:metro:waitForTypescript Observed change: C:\Users\Xantre\Projects\fleet-mobile\apps\international\.env +2s
  expo:start:server:metro Reloading environment variables... +2s
  expo:env Loaded environment variables from: C:\Users\Xantre\Projects\fleet-mobile\apps\international\.env +2s
before expand {
  EXPO_PUBLIC_SHOW_DEBUG_SCREEN: 'beb',
}
updated env {
  env: {
    EXPO_PUBLIC_SHOW_DEBUG_SCREEN: 'sdfsdf',
}

What platform(s) does this occur on?

Android, iOS

SDK Version

~50.0.17

Environment

expo-env-info 1.2.0 environment info:
System:
OS: Windows 11 10.0.22631
Binaries:
Node: 20.12.0 - ~\scoop\apps\volta\current\appdata\tools\image\node\20.12.0\node.EXE
Yarn: 1.22.21 - ~\scoop\apps\volta\current\appdata\tools\image\yarn\1.22.21\bin\yarn.CMD
npm: 10.5.0 - ~\scoop\apps\volta\current\appdata\tools\image\node\20.12.0\npm.CMD
Watchman: 2024041.112832.0 - C:\Users\Xantre\scoop\shims\watchman.EXE
IDEs:
Android Studio: AI-232.10227.8.2321.11479570
npmPackages:
react-native: * => 0.73.7
Expo Workflow: managed

Minimal reproducible example

https://github.com/XantreDev/no-hmr-env-repro

[XantreDev]

Here is a patch that fixes an issue:

@expo__env@0.2.3.patch

diff --git a/build/env.js b/build/env.js
index f5e5e4efd8609d683d709219acf8b46554e62978..4c1bc0fc8baeae92fff946dcfd31cc60252f968f 100644
--- a/build/env.js
+++ b/build/env.js
@@ -138,24 +138,22 @@ function createControlledEnvironment() {
   function _expandEnv(parsedEnv) {
     const expandedEnv = {};
 
+    const processEnv = {...process.env}
+    for (const key in parsedEnv) {
+      delete processEnv[key]
+    }
     // Pass a clone of `process.env` to avoid mutating the original environment.
     // When the expansion is done, we only store the environment variables that were initially parsed from `parsedEnv`.
-    const allExpandedEnv = (0, _dotenvExpand().expand)({
+    (0, _dotenvExpand().expand)({
       parsed: parsedEnv,
-      processEnv: {
-        ...process.env
-      }
+      processEnv: processEnv
     });
-    if (allExpandedEnv.error) {
-      console.error(`Failed to expand environment variables, using non-expanded environment variables: ${allExpandedEnv.error}`);
-      return parsedEnv;
-    }
 
     // Only store the values that were initially parsed, from `parsedEnv`.
     for (const key of Object.keys(parsedEnv)) {
       var _allExpandedEnv$parse;
-      if ((_allExpandedEnv$parse = allExpandedEnv.parsed) !== null && _allExpandedEnv$parse !== void 0 && _allExpandedEnv$parse[key]) {
-        expandedEnv[key] = allExpandedEnv.parsed[key];
+      if ((_allExpandedEnv$parse = parsedEnv) !== null && _allExpandedEnv$parse !== void 0 && _allExpandedEnv$parse[key]) {
+        expandedEnv[key] = parsedEnv[key];
       }
     }
     return expandedEnv;

We need to allow keys to be overwritten, because existing keys is prefered https://github.com/motdotla/dotenv-expand/blob/ff7e2efd0d9925c7da82c167ae77d22a6c76e878/lib/main.js#L24C10-L31

[XantreDev]

If you want I can provide a pr with this changes. But this do not fixes that change of env vars do not cause automatic server reload

[expo-bot]

Thank you for filing this issue!
This comment acknowledges we believe this may be a bug and there’s enough information to investigate it.
However, we can’t promise any sort of timeline for resolution. We prioritize issues based on severity, breadth of impact, and alignment with our roadmap. If you’d like to help move it more quickly, you can continue to investigate it more deeply and/or you can open a pull request that fixes the cause.

[byCedric]

Hi @XantreDev! Thanks for the issue report.

If you want I can provide a pr with this changes.

Yeah, feel free to open a PR that applies the fix you mentioned. Let's consider the auto-reload, or HMR, issue separate from this one.

[XantreDev]

Ok. @byCedric I will provide it today/tomorrow