Webpack/Express - environment variables not found by server - node.js

Question

In my Express/React app, I am using Webpack to handle server-side rendering. However, I am experiencing a build error related to environment variables that I'm trying to access in my Express server script.
In the server script, index.js, I am setting a few variables like so:
const gitCommit = process.env.GIT_COMMIT || require("./gitignore/git_commit.js"),
buildDate = process.env.BUILD_DATE || require("./gitignore/build_date.js")
And since I am running a test production build on my local machine, I delete the gitignore/ directory and set those environment variables:
$ export GIT_COMMIT="test commit hash"
$ export BUILD_DATE="test build date"
Then I npm run build, which executes the following scripts:
"build:client": "webpack --config webpack.config.js",
"build:server": "webpack --config webpack.server.config.js",
"build": "npm run build:client && npm run build:server"
build:client executes with no problem, but build:server throws errors...
ERROR in ./index.js
Module not found: Error: Can't resolve './gitignore/git_commit.js' in '/Users/filepath'
# ./index.js 12:38-74
ERROR in ./index.js
Module not found: Error: Can't resolve './gitignore/build_date.js' in '/Users/filepath'
# ./index.js 13:42-78
implying that the two environment variables referenced in index.js can't be found, and so it's looking for the gitignore/ instead, which shouldn't exist (I mean, it does exist locally, but I've deleted since I'm simulating a production build).
Here is the complete webpack.server.config.js:
const fs = require("fs"),
path = require("path")// ,
// ExtractTextPlugin = require("extract-text-webpack-plugin")
module.exports = {
"entry": path.resolve(__dirname, "index.js"),
// keep node_module paths out of the bundle
"externals": fs.readdirSync(path.resolve(__dirname, "node_modules")).concat(["react-dom/server", "react/addons"]).reduce((ext, mod) => {
ext[mod] = `commonjs ${mod}`
return ext
}, {}),
"module": {
"loaders": [
{
"exclude": /node_modules/,
"loader": "babel-loader",
"query": { "presets": ["react", "es2015", "stage-2"] },
"test": /\.jsx$/
},
{
"exclude": /node_modules/,
"loader": "babel-loader",
"query": { "presets": ["react", "es2015", "stage-2"] },
"test": /\.js$/
}
]
},
"node": {
"__dirname": true,
"__filename": true
},
"output": {
"filename": "server.bundle.js"
},
"target": "node"
}
Now I expect that gitignore/ would not be found, but what I don't understand is why the two environment variables that I set are not being detected by index.js - they are definitely set in the console before I even run the build command. If I console.log() them in the beginning of webpack.server.config.js, it logs them correctly, and if I run my development version instead (which doesn't use the server config), I can log them correctly in index.js. What gives?
Node version 6.11.1, NPM version 3.10.10, Webpack version 2.6.0.

Answer 1

Your environment variables are only available when Webpack runs, but not when you execute your index.js.
You will need to use the EnvironmentPlugin in your Webpack config like that:
plugins: [new webpack.EnvironmentPlugin(['GIT_COMMIT ', 'BUILD_DATE'])]
That plugin will replace the variables by their actual values.
HINT: Do not use ||. Webpack does not know how to optimize it. Try the ternary operator:
const gitCommit = (process.env.GIT_COMMIT) ? (
process.env.GIT_COMMIT
) : (
require('./gitignore/git_commit.js')
);
Webpack will bundle this to:
const gitCommit = (true) ? (
"test commit hash"
) : (
require('./gitignore/git_commit.js')
);
No IgnorePlugin is needed. Even better, with the UglifyJSPlugin, your code will be optimized to const gitCommit = "test commit hash";. In some cases gitCommit is removed completely as a variable. Its string value will be used instead anywhere where you applied gitCommit.