Added helper method to retrieve Environment variables (#1468)

* Adding a helper method to retrieve Environment variables as their raw value

* Removing chance of a String being optional

* Added default values for both strings and booleans. Updated documentation

* Adding documentation for helper methods

Co-authored-by: Michael Miscampbell <mmiscampbell@dynamicsignal.com>

Sources/ProjectDescription/Environment.swift

@@ -5,6 +5,24 @@ public struct Environment {
     public enum Value {
         case boolean(Bool)
         case string(String)
+
+        /// Retrieve the Environment value as a string or return the specified default string value
+        /// - Parameters:
+        ///   - default: default String value to be returned
+        /// - Returns: String
+        public func getString(default defaultString: String) -> String {
+            if case let .string(value) = self { return value }
+            return defaultString
+        }
+
+        /// Retrieve the Environment value as a boolean or return the specified default boolean value
+        /// - Parameters:
+        ///   - default: default Boolean value to be returned
+        /// - Returns: Bool
+        public func getBoolean(default defaultBoolean: Bool) -> Bool {
+            if case let .boolean(value) = self { return value }
+            return defaultBoolean
+        }
     }
 
     public static subscript(dynamicMember member: String) -> Value? {

website/markdown/docs/usage/projectswift.mdx

@@ -152,6 +152,16 @@ Accessing variables returns an instance of type `Environment.Value?` which can t
   ]}
 />
 
+You can also retrieve the string or boolean Environment variable using either of the helper methods defined below, these methods require a default value to be passed to ensure the user gets consistent results each time. This avoids the need to define the function appName() defined above.
+
+```swift
+Environment.appName?.getString(default: "TuistApp")
+```
+
+```swift
+Environment.isCI?.getBoolean(default: false)
+```
+
 ## Package
 
 You can add Swift Packages very similarly to how you add dependencies in a `Package.swift`: