Check injecting file is readable. (#203)

InjectionBundle/SwiftEval.swift

@@ -433,6 +433,15 @@ public class SwiftEval: NSObject {
  // Objective-C paths can only contain space and '
  // project file itself can only contain spaces
  let isFile = classNameOrFile.hasPrefix("/")
+ if isFile && (try? String(contentsOfFile: classNameOrFile)) == nil {
+ throw evalError("""
+ File \(classNameOrFile) is not readable. This could be because
+ the file is in a secure area of the file system or because the
+ case of the letters in the file name does not match that in the
+ Xcode project. The file system injection uses is case sensitive.
+ """)
+ }
+
  let sourceRegex = isFile ? "\\Q\(classNameOrFile)\\E" : "/\(classNameOrFile)\\.(?:swift|mm?)"
  let swiftEscaped = (isFile ? "" : "[^\"]*?") + sourceRegex.escaping("'$", with: "\\E\\\\*$0\\Q")
  let objcEscaped = (isFile ? "" : "\\S*?") + sourceRegex.escaping("' ")