[tools] Add a ":load" command to the REPRL helper

With this command, we can run the REPRL with existing files, no need to
convert each file to one line and copy-paste it to the REPRL tool.

Change-Id: Ic78082ce7aeb5977e2f49e07701bd4d5c1b82a45
Reviewed-on: https://chrome-internal-review.googlesource.com/c/v8/fuzzilli/+/9865575
Commit-Queue: Marja Hölttä <marja@google.com>
Reviewed-by: Leon Bettscheider <bettscheider@chromium.org>
Reviewed-by: Raphaël Hérouart <rherouart@google.com>

Author: marjakh

Sources/REPRLRun/main.swift

@@ -104,14 +104,29 @@ if execute("").status != 0 {
 // Run a couple of tests now
 runREPRLTests()
 
-print("Enter code to run, then hit enter to execute it")
+print("Enter code to run, then hit enter to execute it, or enter :load <file> to execute a file")
 while true {
     print("> ", terminator: "")
-    guard let code = readLine(strippingNewline: false) else {
+    guard var code = readLine(strippingNewline: false) else {
         print("Bye")
         break
     }
 
+    // TODO(fuzzilli): If we extend this with more commands, handle them elegantly (e.g., add a "command -> callback" map).
+    let loadCommand = ":load "
+    if code.hasPrefix(loadCommand) {
+        let path = NSString(
+            string: code.dropFirst(loadCommand.count).trimmingCharacters(
+                in: .whitespacesAndNewlines)
+        ).expandingTildeInPath
+        do {
+            code = try String(contentsOfFile: path, encoding: .utf8)
+        } catch {
+            print("Failed to read \(path): \(error.localizedDescription)")
+            continue
+        }
+    }
+
     let (status, exec_time) = execute(code)
 
     if status < 0 {