support PUBLIC_URL during development as well

[PavelPolyakov]

Is this a bug report?

no

Situation

Imagine I want to have the next product structure:

1. SPA (created using create-react-app), which is going to be served as /auth
2. API, which is going to be served as /auth/api/*
3. gateway, which resolves all the requests to the appropriate microservices

Here is a demo repo I prepared.

Problem

In the current version of CRA the variable PUBLIC_URL is ignored during the development.
The closest answer to the question why? which I found was this:
30ee52c#diff-a7f98c18479be87c9f33e7604dbd1a09L33

which was updated by 30ee52c#diff-dc0c4e7c623b73660da1809fc60cf6baR74 (@Timer)

But this is exactly what prevents people from developing CRA applications while being under the gateway. I think it is quite handy in the "microservices" world.

Question

Are there any solutions to this problem? Is this something we can change in the CRA behaviour?

Regards,

[ericclemmons]

I got caught up in this as well. I expected that PUBLIC_URL would be used here:

create-react-app/packages/react-scripts/config/webpackDevServer.config.js

Line 71 in 30ee52c

publicPath: '/',

I don't know enough about CRA to say why it shouldn't, but I definitely expected it to work that way.

(It was natural to me that homepage be a production-only URL, since it goes in the package.json)

[ericclemmons]

Did some quick research into this, and it seems possible, but 1 single line blocked me:

diff --git a/packages/react-scripts/config/webpack.config.js b/packages/react-scripts/config/webpack.config.js
index 25cc88a..a9ac3ca 100644
--- a/packages/react-scripts/config/webpack.config.js
+++ b/packages/react-scripts/config/webpack.config.js
@@ -59,9 +59,8 @@ module.exports = function(webpackEnv) {
   // Webpack uses `publicPath` to determine where the app is being served from.
   // It requires a trailing slash, or the file assets will get an incorrect path.
   // In development, we always serve from the root. This makes config easier.
-  const publicPath = isEnvProduction
-    ? paths.servedPath
-    : isEnvDevelopment && '/';
+  const publicPath = paths.servedPath;
+
   // Some apps do not use client-side routing with pushState.
   // For these, "homepage" can be set to "." to enable relative asset paths.
   const shouldUseRelativeAssetPaths = publicPath === './';
@@ -69,9 +68,8 @@ module.exports = function(webpackEnv) {
   // `publicUrl` is just like `publicPath`, but we will provide it to our app
   // as %PUBLIC_URL% in `index.html` and `process.env.PUBLIC_URL` in JavaScript.
   // Omit trailing slash as %PUBLIC_URL%/xyz looks better than %PUBLIC_URL%xyz.
-  const publicUrl = isEnvProduction
-    ? publicPath.slice(0, -1)
-    : isEnvDevelopment && '';
+  const publicUrl = publicPath.slice(0, -1);
+
   // Get environment variables to inject into our app.
   const env = getClientEnvironment(publicUrl);

@@ -169,7 +167,7 @@ module.exports = function(webpackEnv) {
         : isEnvDevelopment && 'static/js/[name].chunk.js',
       // We inferred the "public path" (such as / or /my-project) from homepage.
       // We use "/" in development.
-      publicPath: publicPath,
+      publicPath,
       // Point sourcemap entries to original disk location (format as URL on Windows)
       devtoolModuleFilenameTemplate: isEnvProduction
         ? info =>
@@ -587,7 +585,7 @@ module.exports = function(webpackEnv) {
       // having to parse `index.html`.
       new ManifestPlugin({
         fileName: 'asset-manifest.json',
-        publicPath: publicPath,
+        publicPath,
       }),
       // Moment.js is an extremely popular library that bundles large locale files
       // by default due to how Webpack interprets its code. This is a practical
diff --git a/packages/react-scripts/config/webpackDevServer.config.js b/packages/react-scripts/config/webpackDevServer.config.js
index 60a9713..21a9428 100644
--- a/packages/react-scripts/config/webpackDevServer.config.js
+++ b/packages/react-scripts/config/webpackDevServer.config.js
@@ -68,7 +68,12 @@ module.exports = function(proxy, allowedHost) {
     hot: true,
     // It is important to tell WebpackDevServer to use the same "root" path
     // as we specified in the config. In development, we always serve from /.
+
+    // ❌ /whatever/static/js/bundle.js doesn't work
+    // ✅ /static/js/bundle.js still does
+    // 🤔 Changing this to /whatever prevents %PUBLIC_URL% from being replaced!?
     publicPath: '/',
+
     // WebpackDevServer is noisy by default so we emit custom message instead
     // by listening to the compiler events with `compiler.hooks[...].tap` calls above.
     quiet: true,
diff --git a/packages/react-scripts/package.json b/packages/react-scripts/package.json
index a9ed5e4..cd62d26 100644
--- a/packages/react-scripts/package.json
+++ b/packages/react-scripts/package.json
@@ -3,6 +3,7 @@
   "version": "2.1.3",
   "description": "Configuration and scripts for Create React App.",
   "repository": "facebook/create-react-app",
+  "homepage": "http://localhost:3000/whatever",
   "license": "MIT",
   "engines": {
     "node": ">=6"

(Tested via a fork & yarn start)

[PavelPolyakov]

@ericclemmons other thing you can try is to set ./ as PUBLIC_URL. This works both on local and on production.

But I still think that PUBLIC_URL should be configurable during the development.

[ericclemmons]

Sorry, I don't fully understand. How would I set PUBLIC_URL as ./ when it's only used in production?

(I may submit that diff as a PR, since it's soooo close to working!)

[PavelPolyakov]

@ericclemmons sorry, I've mixed it up. I used ./ but that was not development mode.
Thanks for your PR, let's see if it'll be accepted.

[Bazzer588]

I have a page action which calls the server like this:

fetch( process.env.PUBLIC_URL + '/upload-data', ...

This works fine if I do a full build
However if I use npm run start then it doesn't work as PUBLIC_URL is ''

I can add a value to the .env file as REACT_APP_PUBLIC_URL but this kind of seems to defeat the purpose of PUBLIC_URL

[blueshirts]

👍

[stale]

This issue has been automatically marked as stale because it has not had any recent activity. It will be closed in 5 days if no further activity occurs.

[PavelPolyakov]

I believe this issue should not be closed. At least it will be good to receive an answer from the create-react-app contributors to understand if it's a feature or bug.

@Timer @gaearon

[ericclemmons]

My PR is slated for v3, so this can be closed when that's merged, right?

…

[prem911]

Following this as I m not able to get parity in my dev and prod environment.
I have 2 react apps which I m trying to host from domain.com/path1 and domain.com/path2
For npm run build, PUBLIC_URL is set to /path1 or /path2 and the index.html neatly uses /path1/static.
However, the same doesnot happen when we do npm start.
How do we get dev/prod parity in this case?

[stale]

This issue has been automatically marked as stale because it has not had any recent activity. It will be closed in 5 days if no further activity occurs.

[PavelPolyakov]

And still, this issue is not stale. But needs an attention of contributors, so we know if it's a bug or a feature.

[iansu]

There's an open PR to address this issue: #6280