add docc comments

.spi.yml

@@ -0,0 +1,4 @@
+version: 1
+builder:
+  configs:
+    - documentation_targets: [EnvironmentDecoder]

.swiftlint.yml

@@ -3,7 +3,7 @@ disabled_rules:
   - file_length
 
 opt_in_rules:
-#  - missing_docs
+  - missing_docs
 
 included:
 

Package.resolved

@@ -0,0 +1,24 @@
+{
+  "originHash" : "f9dd70f40d8a36ca304b84a45f9f357e57d2c0708ffe79b8bb090797742b8601",
+  "pins" : [
+    {
+      "identity" : "swift-docc-plugin",
+      "kind" : "remoteSourceControl",
+      "location" : "https://github.com/apple/swift-docc-plugin",
+      "state" : {
+        "revision" : "26ac5758409154cc448d7ab82389c520fa8a8247",
+        "version" : "1.3.0"
+      }
+    },
+    {
+      "identity" : "swift-docc-symbolkit",
+      "kind" : "remoteSourceControl",
+      "location" : "https://github.com/apple/swift-docc-symbolkit",
+      "state" : {
+        "revision" : "b45d1f2ed151d057b54504d653e0da5552844e34",
+        "version" : "1.0.0"
+      }
+    }
+  ],
+  "version" : 3
+}

Package.swift

@@ -9,6 +9,9 @@ let package = Package(
             name: "EnvironmentDecoder",
             targets: ["EnvironmentDecoder"]),
     ],
+    dependencies: [
+        .package(url: "https://github.com/apple/swift-docc-plugin", from: "1.0.0"),
+    ],
     targets: [
         .target(
             name: "EnvironmentDecoder"),

Sources/EnvironmentDecoder/EnvironmentDecoder.swift

@@ -1,8 +1,17 @@
 import Foundation
 
+/// `EnvironmentDecoder` facilitates the decoding of environment variables into semantic `Decodable` types.
 public final class EnvironmentDecoder {
+    /// Initializes `self` with default configuration.
     public init() {}
 
+    /// Decodes a top-level value of the given type from the given environment representation.
+    /// - Parameters:
+    ///   - type: The type of the value to decode.
+    ///   - environment: The environment dictionary to decode from, defaults to `ProcessInfo.processInfo.environment`
+    /// - Returns: A value of the requested type.
+    /// - Throws: `DecodingError` if an error occurs during decoding
+    /// - Throws: An error if any value throws an error during decoding
     public func decode<T: Decodable>(_ type: T.Type, from environment: [String: String] = ProcessInfo.processInfo.environment) throws -> T {
         let decoder = EnvironmentDecoderImpl(environment: environment, codingPathNode: .root)
         return try type.init(from: decoder)