feat: adding the ability to force overrides

relates to #489

Author: mrsteele

README.md

@@ -118,6 +118,7 @@ Use the following properties to configure your instance.
 * **defaults** (`false`) - Adds support for `dotenv-defaults`. If set to `true`, uses `./.env.defaults`. If a string, uses that location for a defaults file. Read more at [npm](https://www.npmjs.com/package/dotenv-defaults).
 * **ignoreStub** (`false`) - Override the automatic check whether to stub `process.env`. [Read more here](#user-content-processenv-stubbing--replacing).
 * **prefix** (`'process.env.'`) - The prefix to use before the name of your env variables.
+* **force** (`false`) - This will override existing env variables with anything you pass in from your file.
 
 The following example shows how to set any/all arguments.
 

src/index.js

@@ -57,7 +57,7 @@ class Dotenv {
     const { env, blueprint } = this.getEnvs()
 
     Object.keys(blueprint).forEach(key => {
-      const value = Object.prototype.hasOwnProperty.call(vars, key) ? vars[key] : env[key]
+      const value = !this.config.force && Object.prototype.hasOwnProperty.call(vars, key) ? vars[key] : env[key]
 
       const isMissing = typeof value === 'undefined' || value === null ||
         (!allowEmptyValues && value === '')

test/index.test.js

@@ -236,6 +236,22 @@ describe.each(versions)('%s', (_, DotenvPlugin) => {
     })
   })
 
+  describe('force configuration', () => {
+    test('Should override if forced', (done) => {
+      // defaults
+      // TEST=nope
+      // TEST2=youcanseethis
+
+      // missingone
+      // TEST2=Hello
+      expectResultsToContainReplacements(
+        new DotenvPlugin({ force: true }),
+        {...defaultEnvResult, ...missingOneResult},
+        done
+      )
+    })
+  })
+
   describe('Defaults configuration', () => {
     test('should support default configurations', (done) => {
       expectResultsToContainReplacements(