feat: add ability to use multiple env prefixes

lib/locator.js

@@ -17,10 +17,22 @@ function parseArgv(argv, cliPrefix) {
 module.exports = function({options, env, argv, envPrefix = '', cliPrefix = '--'}) {
     const parsedArgv = parseArgv(argv, cliPrefix);
 
+    function getEnvName(prefixes, subKey) {
+        if (typeof prefixes === 'string') {
+            return prefixes + subKey;
+        }
+
+        const relatedEnvPrefixIndex = prefixes.findIndex((prefix => Object.hasOwnProperty.call(env, prefix + subKey)));
+        const envPrefix = relatedEnvPrefixIndex >= 0 ? prefixes[relatedEnvPrefixIndex] : prefixes[0];
+
+        return envPrefix + subKey;
+    }
+
     function getNested(option, {namePrefix, envPrefix, cliPrefix}) {
         return (subKey) => {
-            const envName = envPrefix + _.snakeCase(subKey);
+            const envSubKey = _.snakeCase(subKey);
             const cliFlag = cliPrefix + _.kebabCase(subKey);
+            const envName = getEnvName(envPrefix, envSubKey);
 
             const argIndex = parsedArgv.lastIndexOf(cliFlag);
             const subOption = _.get(option, subKey);

test/locator.js

@@ -216,4 +216,27 @@ describe('locator', () => {
         assert.propertyVal(childPointer, 'envVar', 'env value');
         assert.propertyVal(childPointer, 'cliOption', 'cli value');
     });
+
+    it('should support multiple envPrefix values', () => {
+        const pointer = locatorWithEnv(
+            {'bar_some_option': 'env value'},
+            {envPrefix: ['foo_', 'bar_']}
+        );
+        const childPointer = pointer.nested('someOption');
+
+        assert.propertyVal(childPointer, 'envVar', 'env value');
+    });
+
+    it('should use first existing envPrefix value', () => {
+        const pointer = locatorWithEnv(
+            {
+                'bar_some_option': 'another env value',
+                'foo_some_option': 'some env value'
+            },
+            {envPrefix: ['foo_', 'bar_']}
+        );
+        const childPointer = pointer.nested('someOption');
+
+        assert.propertyVal(childPointer, 'envVar', 'some env value');
+    });
 });

typings/index.d.ts

@@ -9,7 +9,8 @@ declare module "gemini-configparser" {
   export type Parser<T> = (locator: Locator, config: PartialConfig) => T;
 
   type RootPrefixes = {
-      envPrefix: string;
+      // If defined as an array and multiple prefixes match, first defined in the array will be used
+      envPrefix: string | string[];
       cliPrefix: string;
   };