getcwd() no longer throws

This is an example of too-edge-case a runtime error to throw IMO.

Instead there is a safe way to manage the process working directory so that the single error that is possible, ie. there is no working directory, cannot happen.

So we document that you should follow that methodology and instead fatalError in the event that the error does occur.

The consequences here are many situations where try was added to simple functions, and those trys have been removed.

Author: mxcl

Sources/Multitool/directories.swift

@@ -20,7 +20,7 @@ public func directories() throws -> (root: String, build: String) {
 }
 
 private func packageRoot() throws -> String {
-    var rootd = try getcwd()
+    var rootd = getcwd()
     while !Path.join(rootd, Manifest.filename).isFile {
         rootd = rootd.parentDirectory
         guard rootd != "/" else {

Sources/POSIX/getcwd.swift

@@ -8,19 +8,33 @@
  See http://swift.org/CONTRIBUTORS.txt for Swift project authors
 */
 
-
-import var libc.errno
-import func libc.free
 import func libc.getcwd
+import func libc.free
+import func libc.exit
 import var libc.PATH_MAX
+import var libc.stderr
+import var libc.errno
 
 /**
  - Returns: The absolute pathname of the current working directory.
+ - Note: If the current directory does not exist, aborts program,
+   to deal with this you should `opendir(getcwd())` as soon as your
+   program starts and then not `chdir()`, `chdir` is an anti-pattern
+   in tooling anyway.
+ - Warning: As a result of the above note use of POSIX demands that
+   the working directory not change during execution. This requires
+   you to have control over the purity of your dependencies.
 */
-public func getcwd() throws -> String {
+public func getcwd() -> String {
+
+    @noreturn func error() {
+        try! fputs("error: no current directory\n", libc.stderr)
+        exit(2)
+    }
+
     let cwd = libc.getcwd(nil, Int(PATH_MAX))
-    if cwd == nil { throw SystemError.getcwd(errno) }
+    if cwd == nil { error() }
     defer { free(cwd) }
-    guard let path = String(validatingUTF8: cwd) else { throw SystemError.getcwd(-1) }
+    guard let path = String(validatingUTF8: cwd) else { error() }
     return path
 }

Sources/POSIX/mkdir.swift

@@ -28,7 +28,7 @@ public func mkdir(path: [String]) throws -> String {
     let parts = path.flatMap{ $0.characters.split(separator: "/") }
     var prefix = path.first!.hasPrefix("/")
         ? ""
-        : try getcwd()
+        : getcwd()
 
     for dir in parts {
         prefix = "\(prefix)/\(String(dir))"

Sources/Utility/Path.swift

@@ -116,12 +116,8 @@ public struct Path {
         // The above function requires both paths to be either relative
         // or absolute. So if they differ we make them both absolute.
         if abs.0 != abs.1 {
-            do {
-                if !abs.path { path = try path.abspath() }
-                if !abs.pivot { pivot = try pivot.abspath() }
-            } catch {
-                return path.normpath
-            }
+            if !abs.path { path = path.abspath() }
+            if !abs.pivot { pivot = pivot.abspath() }
         }
 
         return go(clean(string), clean(pivot))
@@ -201,10 +197,10 @@ extension String {
     /**
      Return a normalized absolutized version of this path. Equivalent to:
 
-         Path.join(try getcwd(), self).normpath
+         Path.join(getcwd(), self).normpath
      */
-    public func abspath() throws -> String {
-        return Path.join(try getcwd(), self).normpath
+    public func abspath() -> String {
+        return Path.join(getcwd(), self).normpath
     }
 
     /// - Returns: true if the string looks like an absolute path
@@ -295,12 +291,6 @@ extension String {
         not changing during execution.
      */
     public var prettyPath: String {
-        if let wd = try? getcwd() {
-            return Path(self).relative(to: wd)
-        } else if let abspath = try? abspath() {
-            return abspath
-        } else {
-            return self
-        }
+        return Path(self).relative(to: getcwd())
     }
 }

Sources/swift-build/initPackage.swift

@@ -22,11 +22,10 @@ final class InitPackage {
 
     let mode: InitMode
     let pkgname: String
-    let rootd: String
+    let rootd = POSIX.getcwd()
 
-    init(mode: InitMode) throws {
+    init(mode: InitMode) {
         self.mode = mode
-        rootd = try POSIX.getcwd()
         pkgname = rootd.basename
     }
 

Sources/swift-build/main.swift

@@ -22,7 +22,7 @@ import Build
 import Get
 
 
-private let origwd = (try? getcwd()) ?? "/"
+private let origwd = getcwd()
 
 extension String {
     private var prettied: String {
@@ -72,7 +72,7 @@ do {
             try build(YAMLPath: yaml, target: "default")
 
         case .Init(let initMode):
-            let initPackage = try InitPackage(mode: initMode)
+            let initPackage = InitPackage(mode: initMode)
             try initPackage.writePackageStructure()
 
         case .Fetch:

Tests/Functional/Utilities.swift

@@ -87,7 +87,7 @@ func swiftBuildPath() -> String {
     }
     fatalError()
 #else
-    return Path.join(try! Process.arguments.first!.abspath().parentDirectory, "swift-build")
+    return Path.join(Process.arguments.first!.abspath().parentDirectory, "swift-build")
 #endif
 }
 

Tests/Utility/PathTests.swift

@@ -184,7 +184,7 @@ class StatTests: XCTestCase {
     }
 
     func test_realpath() {
-        XCTAssertEqual(try! realpath("."), try! getcwd())
+        XCTAssertEqual(try! realpath("."), getcwd())
     }
 
     func test_basename() {
@@ -208,7 +208,7 @@ class RelativePathTests: XCTestCase {
     }
 
     func testMixed() {
-        XCTAssertEqual("3/4", Path(try! getcwd() + "/1/2/3/4").relative(to: "1/2"))
+        XCTAssertEqual("3/4", Path(getcwd() + "/1/2/3/4").relative(to: "1/2"))
     }
 
     func testRelativeCommonSubprefix() {