Ensure nested configs can be loaded from env file (#4360)

.changeset/late-pants-wash.md

@@ -0,0 +1,5 @@
+---
+"@effect/platform": patch
+---
+
+Ensure that nested configuration values can be properly loaded from an env file

packages/platform/src/internal/platformConfigProvider.ts

@@ -17,13 +17,17 @@ import * as Layer from "effect/Layer"
 
 /** @internal */
 export const fromDotEnv = (
-  path: string
+  path: string,
+  config?: Partial<ConfigProvider.ConfigProvider.FromMapConfig>
 ): Effect.Effect<ConfigProvider.ConfigProvider, PlatformError, FileSystem.FileSystem> =>
   Effect.gen(function*() {
     const fs = yield* FileSystem.FileSystem
     const content = yield* fs.readFileString(path)
     const obj = parseDotEnv(content)
-    return ConfigProvider.fromJson(obj)
+    return ConfigProvider.fromMap(
+      new Map(Object.entries(obj)),
+      Object.assign({}, { pathDelim: "_", seqDelim: "," }, config)
+    )
   })
 
 /** @internal */

packages/platform/test/ConfigProvider.test.ts

@@ -0,0 +1,28 @@
+import * as FileSystem from "@effect/platform/FileSystem"
+import * as PlatformConfigProvider from "@effect/platform/PlatformConfigProvider"
+import { assert, describe, it } from "@effect/vitest"
+import * as Config from "effect/Config"
+import * as Effect from "effect/Effect"
+import * as Layer from "effect/Layer"
+
+const ConfigProviderLive = Layer.unwrapEffect(
+  PlatformConfigProvider.fromDotEnv(".env").pipe(
+    Effect.map(Layer.setConfigProvider)
+  )
+)
+
+describe("PlatformConfigProvider", () => {
+  it.effect("should properly load configuration values from an env file", () =>
+    Effect.gen(function*() {
+      const fileSystem = FileSystem.layerNoop({
+        readFileString: () => Effect.succeed("NESTED_CONFIG=nested_config")
+      })
+
+      const result = yield* Config.string("CONFIG").pipe(
+        Config.nested("NESTED"),
+        Effect.provide(Layer.provide(ConfigProviderLive, fileSystem))
+      )
+
+      assert.strictEqual(result, "nested_config")
+    }))
+})