feat: added option to throw on missing env (#664)

* feat: added option to throw on missing env

* fix: passing tests for throwOnMissing

README.md

@@ -556,6 +556,8 @@ Options:
   Default is `false`.
 * `dangerousExtend`: Disable security checks for `extend` query.
   Default is `false`.
+* `throwOnMissing`: throw a error if env is not found.
+  Default is `false`.
 * `mobileToDesktop`: Use desktop browsers if Can I Use doesn’t have data
   about this mobile version. Can I Use has only data only about
   latest versions of mobile browsers. By default, `last 2 and_ff versions`

index.js

@@ -397,6 +397,7 @@ var cache = {}
  *                                                     version in direct query.
  * @param {boolean} [opts.dangerousExtend] Disable security checks
  *                                         for extend query.
+ * @param {boolean} [opts.throwOnMissing] Throw error on missing env.
  * @param {boolean} [opts.mobileToDesktop] Alias mobile browsers to the desktop
  *                                         version when Can I Use doesn't have
  *                                         data about the specified version.

node.js

@@ -82,6 +82,14 @@ function pickEnv(config, opts) {
     name = 'production'
   }
 
+  if (opts.throwOnMissing) {
+    if (name && name !== 'defaults' && !config[name]) {
+      throw new BrowserslistError(
+        'Missing config for Browserslist environment `' + name + '`.'
+      )
+    }
+  }
+
   return config[name] || config.defaults
 }
 

test/main.test.js

@@ -260,4 +260,23 @@ test('correctly works with not and one-version browsers', () => {
   equal(browserslist('last 1 Baidu version, not <2% in AT'), ['baidu 7.12'])
 })
 
+test('throws error on missing env', () => {
+  throws(
+    () => browserslist(null, { path: PACKAGE, throwOnMissing: true, env: 'test' }),
+    "Missing config for Browserslist environment 'test'."
+  )
+})
+
+test('does not throw error on missing defaults env', () => {
+  equal(
+    browserslist(null, { path: PACKAGE, throwOnMissing: true, env: 'defaults' }), DEFAULTS
+  )
+})
+
+test('does not throw error on missing env', () => {
+  equal(
+    browserslist(null, { path: PACKAGE, throwOnMissing: false, env: 'test' }), DEFAULTS
+  )
+})
+
 test.run()