Revert "Add an Environment type to represent environment variables"

This reverts commit 7f75d72.

Author: weliveindetail

Sources/SWBUtil/Environment.swift

@@ -12,153 +12,25 @@
 
 import Foundation
 
-public struct Environment {
-    var storage: [EnvironmentKey: String]
-}
-
-// MARK: - Accessors
-
-extension Environment {
-    package init() {
-        self.storage = .init()
-    }
-
-    package subscript(_ key: EnvironmentKey) -> String? {
-        _read { yield self.storage[key] }
-        _modify { yield &self.storage[key] }
-    }
-}
-
-// MARK: - Conversions between Dictionary<String, String>
-
-extension Environment {
-    public init(_ dictionary: [String: String]) {
-        self.storage = .init()
-        let sorted = dictionary.sorted { $0.key < $1.key }
-        for (key, value) in sorted {
-            self.storage[.init(key)] = value
-        }
-    }
-}
-
-extension [String: String] {
-    public init(_ environment: Environment) {
-        self.init()
-        let sorted = environment.sorted { $0.key < $1.key }
-        for (key, value) in sorted {
-            self[key.rawValue] = value
-        }
-    }
-}
-
-// MARK: - Path Modification
-
-extension Environment {
-    package mutating func prependPath(key: EnvironmentKey, value: String) {
-        guard !value.isEmpty else { return }
-        if let existing = self[key] {
-            self[key] = "\(value)\(Path.pathEnvironmentSeparator)\(existing)"
-        } else {
-            self[key] = value
-        }
-    }
-
-    package mutating func appendPath(key: EnvironmentKey, value: String) {
-        guard !value.isEmpty else { return }
-        if let existing = self[key] {
-            self[key] = "\(existing)\(Path.pathEnvironmentSeparator)\(value)"
-        } else {
-            self[key] = value
-        }
-    }
-}
-
-// MARK: - Global Environment
-
-extension Environment {
-    fileprivate static let _cachedCurrent = SWBMutex<Self?>(nil)
+@TaskLocal fileprivate var processEnvironment = ProcessInfo.processInfo.environment
 
-    /// Vends a copy of the current process's environment variables.
-    ///
-    /// Mutations to the current process's global environment are not reflected
-    /// in the returned value.
-    public static var current: Self {
-        Self._cachedCurrent.withLock { cachedValue in
-            if let cachedValue = cachedValue {
-                return cachedValue
-            } else {
-                let current = Self(ProcessInfo.processInfo.environment)
-                cachedValue = current
-                return current
-            }
-        }
-    }
+/// Binds the internal defaults to the specified `environment` for the duration of the synchronous `operation`.
+/// - parameter clean: `true` to start with a clean environment, `false` to merge the input environment over the existing process environment.
+/// - note: This is implemented via task-local values.
+@_spi(Testing) public func withEnvironment<R>(_ environment: [String: String], clean: Bool = false, operation: () throws -> R) rethrows -> R {
+    try $processEnvironment.withValue(clean ? environment : processEnvironment.addingContents(of: environment), operation: operation)
 }
 
-// MARK: - Protocol Conformances
-
-extension Environment: Collection {
-    public struct Index: Comparable {
-        public static func < (lhs: Self, rhs: Self) -> Bool {
-            lhs.underlying < rhs.underlying
-        }
-
-        var underlying: Dictionary<EnvironmentKey, String>.Index
-    }
-
-    public typealias Element = (key: EnvironmentKey, value: String)
-
-    public var startIndex: Index {
-        Index(underlying: self.storage.startIndex)
-    }
-
-    public var endIndex: Index {
-        Index(underlying: self.storage.endIndex)
-    }
-
-    public subscript(index: Index) -> Element {
-        self.storage[index.underlying]
-    }
-
-    public func index(after index: Self.Index) -> Self.Index {
-        Index(underlying: self.storage.index(after: index.underlying))
-    }
-}
-
-extension Environment: CustomStringConvertible {
-    public var description: String {
-        let body = self
-            .sorted { $0.key < $1.key }
-            .map { "\"\($0.rawValue)=\($1)\"" }
-            .joined(separator: ", ")
-        return "[\(body)]"
-    }
-}
-
-extension Environment: Encodable {
-    public func encode(to encoder: any Swift.Encoder) throws {
-        try self.storage.encode(to: encoder)
-    }
-}
-
-extension Environment: Equatable {}
-
-extension Environment: ExpressibleByDictionaryLiteral {
-    public typealias Key = EnvironmentKey
-    public typealias Value = String
-
-    public init(dictionaryLiteral elements: (Key, Value)...) {
-        self.storage = .init()
-        for (key, value) in elements {
-            self.storage[key] = value
-        }
-    }
+/// Binds the internal defaults to the specified `environment` for the duration of the asynchronous `operation`.
+/// - parameter clean: `true` to start with a clean environment, `false` to merge the input environment over the existing process environment.
+/// - note: This is implemented via task-local values.
+@_spi(Testing) public func withEnvironment<R>(_ environment: [String: String], clean: Bool = false, operation: () async throws -> R) async rethrows -> R {
+    try await $processEnvironment.withValue(clean ? environment : processEnvironment.addingContents(of: environment), operation: operation)
 }
 
-extension Environment: Decodable {
-    public init(from decoder: any Swift.Decoder) throws {
-        self.storage = try .init(from: decoder)
-    }
+/// Gets the value of the named variable from the process' environment.
+/// - parameter name: The name of the environment variable.
+/// - returns: The value of the variable as a `String`, or `nil` if it is not defined in the environment.
+public func getEnvironmentVariable(_ name: String) -> String? {
+    processEnvironment[name]
 }
-
-extension Environment: Sendable {}