fix: return deno env object (#432)

Fixes yargs/yargs#2136

.github/workflows/ci.yaml

@@ -61,7 +61,9 @@ jobs:
           deno-version: v1.x
       - run: |
           deno --version
-          deno test --allow-read test/deno/yargs-test.ts
+          deno test --allow-read --allow-env test/deno/yargs-test.ts
+        env:
+          MY_PREFIX_MY_KEY: "my value"
   browser:
     runs-on: ubuntu-latest
     steps:

deno.ts

@@ -10,7 +10,7 @@ import type { Arguments, ArgsInput, Parser, Options, DetailedArguments } from '.
 const parser = new YargsParser({
   cwd: Deno.cwd,
   env: () => {
-    Deno.env.toObject()
+    return Deno.env.toObject()
   },
   format: (str: string, arg: string) => { return str.replace('%s', arg) },
   normalize: path.posix.normalize,

test/deno/yargs-test.ts

@@ -63,3 +63,8 @@ Deno.test('it detects strings that could be parsed as numbers', () => {
   assertEquals(parser.looksLikeNumber('0100'), false)
   assertEquals(parser.looksLikeNumber('apple'), false)
 })
+
+Deno.test('should load values from environment variables', () => {
+  const argv = parser([], { envPrefix: 'MY_PREFIX_' })
+  assertEquals(argv.myKey, 'my value')
+})