Add '<' meta command to read in code from external file

lldb/source/Expression/REPL.cpp

@@ -123,10 +123,11 @@ const char *REPL::IOHandlerGetHelpPrologue() {
          "Valid statements, expressions, and declarations are immediately "
          "compiled and executed.\n\n"
          "The complete set of LLDB debugging commands are also available as "
-         "described below.  Commands "
+         "described below.\n\nCommands "
          "must be prefixed with a colon at the REPL prompt (:quit for "
          "example.)  Typing just a colon "
-         "followed by return will switch to the LLDB prompt.\n\n";
+         "followed by return will switch to the LLDB prompt.\n\n"
+         "Type “< path” to read in code from a text file “path”.\n\n";
 }
 
 bool REPL::IOHandlerIsInputComplete(IOHandler &io_handler, StringList &lines) {
@@ -179,6 +180,36 @@ int REPL::IOHandlerFixIndentation(IOHandler &io_handler,
   return (int)desired_indent - actual_indent;
 }
 
+static bool ReadCode(const std::string &path, std::string &code,
+                     lldb::StreamFileSP &error_sp) {
+  auto &fs = FileSystem::Instance();
+  llvm::Twine pathTwine(path);
+  if (!fs.Exists(pathTwine)) {
+    error_sp->Printf("no such file at path '%s'\n", path.c_str());
+    return false;
+  }
+  if (!fs.Readable(pathTwine)) {
+    error_sp->Printf("could not read file at path '%s'\n", path.c_str());
+    return false;
+  }
+  const size_t file_size = fs.GetByteSize(pathTwine);
+  const size_t max_size = code.max_size();
+  if (file_size > max_size) {
+    error_sp->Printf("file at path '%s' too large: "
+                     "file_size = %llu, max_size = %llu\n",
+                     path.c_str(), file_size, max_size);
+    return false;
+  }
+  auto data_sp = fs.CreateDataBuffer(pathTwine);
+  if (data_sp == nullptr) {
+    error_sp->Printf("could not create buffer for file at path '%s'\n",
+                     path.c_str());
+    return false;
+  }
+  code.assign((const char *)data_sp->GetBytes(), data_sp->GetByteSize());
+  return true;
+}
+
 void REPL::IOHandlerInputComplete(IOHandler &io_handler, std::string &code) {
   lldb::StreamFileSP output_sp(io_handler.GetOutputStreamFileSP());
   lldb::StreamFileSP error_sp(io_handler.GetErrorStreamFileSP());
@@ -257,6 +288,15 @@ void REPL::IOHandlerInputComplete(IOHandler &io_handler, std::string &code) {
         }
       }
     } else {
+      if (code[0] == '<') {
+        // User wants to read code from a file.
+        // Interpret rest of line as a literal path.
+        auto path = llvm::StringRef(code.substr(1)).trim().str();
+        if (!ReadCode(path, code, error_sp)) {
+          return;
+        }
+      }
+
       // Unwind any expression we might have been running in case our REPL
       // expression crashed and the user was looking around
       if (m_dedicated_repl_mode) {