feat: Add prefix option (#176)

djdmbrwsk · Jul 4, 2021 · 4c402cc · 4c402cc
1 parent 6594a1d
commit 4c402cc
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Showing 3 changed files with 57 additions and 1 deletion.
diff --git a/README.md b/README.md
@@ -80,6 +80,18 @@ files you load on `NODE_ENV`. For example, you may want `NODE_ENV` set to
 dotenvCra.config({ env: process.env.AWS_ENV });
 ```
 
+### Prefix
+
+Default: none
+
+You may specify a required prefix for your dotenv variables. For example, you
+may want to prefix your variables with `WEB_API_` to ensure there aren't any
+collisions with other environment variables.
+
+```ts
+dotenvCra.config({ prefix: 'WEB_API_' });
+```
+
 ### Path
 
 Default: `path.resolve(process.cwd(), '.env')`

diff --git a/src/main.ts b/src/main.ts
@@ -4,6 +4,7 @@ import { basename, resolve } from 'path';
 import {
   DotenvConfigOptions,
   DotenvConfigOutput,
+  DotenvParseOutput,
   config as dotenvConfig,
 } from 'dotenv';
 import dotenvExpand from 'dotenv-expand';
@@ -13,6 +14,10 @@ export interface DotenvCraOptions extends DotenvConfigOptions {
    * You may specify a custom environment if NODE_ENV isn't sufficient.
    */
   env?: string;
+  /**
+   * You may specify a required prefix for your dotenv variables (ex. `REACT_APP_`).
+   */
+  prefix?: string;
 }
 
 export function config(options?: DotenvCraOptions): DotenvConfigOutput {
@@ -42,7 +47,7 @@ export function config(options?: DotenvCraOptions): DotenvConfigOutput {
 
   // Reference:
   // https://github.com/facebook/create-react-app/blob/8b7b819b4b9e6ba457e011e92e33266690e26957/packages/react-scripts/config/env.js#L36-L49
-  let parsed: { [name: string]: string } = {};
+  let parsed: DotenvParseOutput = {};
   for (const dotenvFile of dotenvFiles) {
     if (!dotenvFile) {
       continue;
@@ -68,6 +73,26 @@ export function config(options?: DotenvCraOptions): DotenvConfigOutput {
     parsed = { ...result.parsed, ...parsed };
   }
 
+  // Reference:
+  // https://github.com/facebook/create-react-app/blob/8b7b819b4b9e6ba457e011e92e33266690e26957/packages/react-scripts/config/env.js#L72-L89
+  if (options?.prefix) {
+    const prefixRegExp = new RegExp(`^${options.prefix}`, 'i');
+    parsed = Object.keys(parsed)
+      .filter((key) => {
+        const match = prefixRegExp.test(key);
+        log(
+          `Prefix for key \`${key}\` ${
+            match ? 'matches' : 'does not match'
+          } \`${options.prefix}\``,
+        );
+        return match;
+      })
+      .reduce((obj, key) => {
+        obj[key] = parsed[key];
+        return obj;
+      }, {} as DotenvParseOutput);
+  }
+
   return {
     parsed,
   };

diff --git a/test/main.test.ts b/test/main.test.ts
@@ -117,6 +117,25 @@ test('should exclude .env.local when NODE_ENV set to test', () => {
   expect(secondCallPath?.endsWith('.env.local')).toEqual(true);
 });
 
+test('should filter out values when provided prefix does not match', () => {
+  process.env.NODE_ENV = 'development';
+  jest.spyOn(fs, 'existsSync').mockReturnValue(true);
+  jest.spyOn(dotenv, 'config').mockImplementation(
+    makeMockDotenvConfig({
+      '.env.local': { parsed: { MY_APP_SETTING: 'FOO' } },
+      '.env': { parsed: { NOT_MY_SETTING: 'BAR', MY_APP_SETTING_2: 'BAZ' } },
+    }),
+  );
+
+  const output = config({ prefix: 'MY_APP_' });
+  expect(output.error).toBeFalsy();
+  expect(output.parsed).toBeTruthy();
+  expect(output.parsed).toEqual({
+    MY_APP_SETTING: 'FOO',
+    MY_APP_SETTING_2: 'BAZ',
+  });
+});
+
 test('should return error objects', () => {
   jest.spyOn(fs, 'existsSync').mockReturnValue(true);
   jest.spyOn(dotenv, 'config').mockReturnValue({ error: new Error('foobar') });