From f5e17d425a6fe2b7cfa06369fe81a189a5cfc3d2 Mon Sep 17 00:00:00 2001
From: Arkadiusz Czekajski <aczekajski@gmail.com>
Date: Thu, 12 Jun 2025 21:55:02 +0900
Subject: [PATCH] feat: support optional env var replacements in .npmrc

---
 docs/lib/content/configuring-npm/npmrc.md | 5 ++++-
 workspaces/config/lib/env-replace.js      | 8 +++++---
 workspaces/config/test/env-replace.js     | 6 ++++++
 3 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/docs/lib/content/configuring-npm/npmrc.md b/docs/lib/content/configuring-npm/npmrc.md
index cd31ae886f132..b0ee60bcb9686 100644
--- a/docs/lib/content/configuring-npm/npmrc.md
+++ b/docs/lib/content/configuring-npm/npmrc.md
@@ -25,11 +25,14 @@ The four relevant files are:
 * npm builtin config file (`/path/to/npm/npmrc`)
 
 All npm config files are an ini-formatted list of `key = value` parameters.
-Environment variables can be replaced using `${VARIABLE_NAME}`. For
+Environment variables can be replaced using `${VARIABLE_NAME}`. By default
+if the variable is not defined, it is left unreplaced. By adding `?` after
+variable name they can be forced to evaluate to an empty string instead.For
 example:
 
 ```bash
 cache = ${HOME}/.npm-packages
+node-options = "${NODE_OPTIONS?} --use-system-ca"
 ```
 
 Each of these files is loaded, and config options are resolved in priority
diff --git a/workspaces/config/lib/env-replace.js b/workspaces/config/lib/env-replace.js
index c851f6e4d1501..30dbbeefc45ad 100644
--- a/workspaces/config/lib/env-replace.js
+++ b/workspaces/config/lib/env-replace.js
@@ -1,9 +1,11 @@
 // replace any ${ENV} values with the appropriate environ.
+// optional "?" modifier can be used like this: ${ENV?} so in case of the variable being not defined, it evaluates into empty string
 
-const envExpr = /(?<!\\)(\\*)\$\{([^${}]+)\}/g
+const envExpr = /(?<!\\)(\\*)\$\{([^${}?]+)(\?)?\}/g
 
-module.exports = (f, env) => f.replace(envExpr, (orig, esc, name) => {
-  const val = env[name] !== undefined ? env[name] : `$\{${name}}`
+module.exports = (f, env) => f.replace(envExpr, (orig, esc, name, modifier) => {
+  const fallback = modifier === '?' ? '' : `$\{${name}}`
+  const val = env[name] !== undefined ? env[name] : fallback
 
   // consume the escape chars that are relevant.
   if (esc.length % 2) {
diff --git a/workspaces/config/test/env-replace.js b/workspaces/config/test/env-replace.js
index c2b570364de87..ed27238b5887f 100644
--- a/workspaces/config/test/env-replace.js
+++ b/workspaces/config/test/env-replace.js
@@ -8,6 +8,12 @@ const env = {
 
 t.equal(envReplace('\\${foo}', env), '${foo}')
 t.equal(envReplace('\\\\${foo}', env), '\\bar')
+t.equal(envReplace('\\\\\\${foo}', env), '\\${foo}')
 t.equal(envReplace('${baz}', env), '${baz}')
 t.equal(envReplace('\\${baz}', env), '${baz}')
 t.equal(envReplace('\\\\${baz}', env), '\\${baz}')
+t.equal(envReplace('\\${foo?}', env), '${foo?}')
+t.equal(envReplace('\\\\${foo?}', env), '\\bar')
+t.equal(envReplace('${baz?}', env), '')
+t.equal(envReplace('\\${baz?}', env), '${baz?}')
+t.equal(envReplace('\\\\${baz?}', env), '\\')