Update SWIG typemaps to use new `PythonFile` wrapper

[zturner]

Summary

Handling of Python files is different in Python 3, to the point that it is unwieldy to try to write native C API calls in places that need to use files. A new type of python object PythonFile is created to wrap these implementation details, and the various swig typemaps are updated to use this wrapper instead of the native API calls.

[zturner]

Fixed indentation

scripts/Python/python-typemaps.swig

 %typemap(in) FILE * {
    if ($input == Py_None)
       $1 = NULL;
-   else if (!PyFile_Check($input)) {
+   else if (!lldb_private::PythonFile::Check($input)) {
       int fd = PyObject_AsFileDescriptor($input);
-      PyObject *py_mode = PyObject_GetAttrString($input, "mode");
-      if (!py_mode) {
-         PyErr_SetString(PyExc_TypeError,"not a file-like object");
-         return NULL;
-      }
-      const char *mode = PyString_AsString(py_mode);
-      if (-1 != fd && mode) {
+      lldb_private::PythonString py_mode(lldb_private::PyRefType::Owned,
+      PyObject_GetAttrString($input, "mode"));
+
+      if (-1 != fd && py_mode.IsValid()) {
          FILE *f;
-         if ((f = fdopen(fd, mode)))
+         if ((f = fdopen(fd, py_mode.GetString().str().c_str())))
             $1 = f;
          else
             PyErr_SetString(PyExc_TypeError, strerror(errno));
       } else {
          PyErr_SetString(PyExc_TypeError,"not a file-like object");
-         return NULL;
+         return nullptr;
       }
    }
    else
-      $1 = PyFile_AsFile($input);
+   {
+      lldb_private::File file;
+      lldb_private::PythonFile py_file(lldb_private::PyRefType::Borrowed, $input);
+      if (!py_file.GetUnderlyingFile(file))
+        return nullptr;
+
+      $1 = file.GetStream();
+   }
 }
 
 %typemap(out) FILE * {

    else // if (flags & __SRW)
       mode[i++] = 'a';
 #endif
-   $result = PyFile_FromFile($1, const_cast<char*>(""), mode, fflush);
+   lldb_private::File file($1, false);
+   lldb_private::PythonFile py_file(file, mode);
+   $result = py_file.release();
 }
 
 %typemap(in) (const char* string, int len) {

source/Plugins/ScriptInterpreter/Python/PythonDataObjects.h

 class PythonFile : public PythonObject
 {
   public:
-    explicit PythonFile(File &file, const char *mode);
+    PythonFile(File &file, const char *mode);
+    PythonFile(const char *path, const char *mode);
     PythonFile(PyRefType type, PyObject *o);
     ~PythonFile() override;
 

 
     void Reset(PyRefType type, PyObject *py_obj) override;
     void Reset(File &file, const char *mode);
+
+    bool GetUnderlyingFile(File &file) const;
 };
 
 } // namespace lldb_private

source/Plugins/ScriptInterpreter/Python/PythonDataObjects.cpp

     Reset(file, mode);
 }
 
+PythonFile::PythonFile(const char *path, const char *mode)
+{
+    FILE *fp = nullptr;
+    fp = fopen(path, mode);
+    lldb_private::File file(fp, true);
+    Reset(file, mode);
+}
+
 PythonFile::PythonFile(PyRefType type, PyObject *o)
 {
     Reset(type, o);

 #endif
 }
 
+bool
+PythonFile::GetUnderlyingFile(File &file) const
+{
+    if (!IsValid())
+        return false;
+
+    file.Close();
+    // We don't own the file descriptor returned by this function, make sure the
+    // File object knows about that.
+    file.SetDescriptor(PyObject_AsFileDescriptor(m_py_obj), false);
+    return file.IsValid();
+}
+
+
 #endif