From 56b74ecf45f63abefa5b8dddcd70ec78033ee082 Mon Sep 17 00:00:00 2001
From: Tomasz Kalinowski <tomasz@posit.co>
Date: Wed, 7 Aug 2024 15:38:54 -0400
Subject: [PATCH] add `py_allow_threads()` function

---
 R/RcppExports.R        |  4 ++++
 R/threads.R            | 16 ++++++++++++++++
 src/RcppExports.cpp    | 12 ++++++++++++
 src/python.cpp         | 16 +++++++++++++++-
 src/reticulate_types.h |  5 -----
 5 files changed, 47 insertions(+), 6 deletions(-)
 create mode 100644 R/threads.R

diff --git a/R/RcppExports.R b/R/RcppExports.R
index e6eb3dbaf..c5047e3af 100644
--- a/R/RcppExports.R
+++ b/R/RcppExports.R
@@ -365,6 +365,10 @@ py_iterate <- function(x, f, simplify = TRUE) {
     .Call(`_reticulate_py_iterate`, x, f, simplify)
 }
 
+py_allow_threads_impl <- function(allow) {
+    .Call(`_reticulate_py_allow_threads_impl`, allow)
+}
+
 readline <- function(prompt) {
     .Call(`_reticulate_readline`, prompt)
 }
diff --git a/R/threads.R b/R/threads.R
new file mode 100644
index 000000000..c3ee58bee
--- /dev/null
+++ b/R/threads.R
@@ -0,0 +1,16 @@
+
+
+py_allow_threads <- function(allow = TRUE) {
+  if (allow) {
+    reticulate_ns <- environment(sys.function())
+    for (f in sys.frames()) {
+      if (identical(parent.env(f), reticulate_ns) &&
+          !identical(f, environment()))
+        # Can't release the gil as unlocked while we're holding it
+        # elsewhere on the callstack.
+        stop("Unblocking python threads only allowed from as a top-level reticulate call")
+    }
+  }
+  invisible(py_allow_threads_impl(allow))
+}
+
diff --git a/src/RcppExports.cpp b/src/RcppExports.cpp
index 3750cd3c1..7c1affef1 100644
--- a/src/RcppExports.cpp
+++ b/src/RcppExports.cpp
@@ -812,6 +812,17 @@ BEGIN_RCPP
     return rcpp_result_gen;
 END_RCPP
 }
+// py_allow_threads_impl
+bool py_allow_threads_impl(bool allow);
+RcppExport SEXP _reticulate_py_allow_threads_impl(SEXP allowSEXP) {
+BEGIN_RCPP
+    Rcpp::RObject rcpp_result_gen;
+    Rcpp::RNGScope rcpp_rngScope_gen;
+    Rcpp::traits::input_parameter< bool >::type allow(allowSEXP);
+    rcpp_result_gen = Rcpp::wrap(py_allow_threads_impl(allow));
+    return rcpp_result_gen;
+END_RCPP
+}
 // readline
 SEXP readline(const std::string& prompt);
 RcppExport SEXP _reticulate_readline(SEXP promptSEXP) {
@@ -895,6 +906,7 @@ static const R_CallMethodDef CallEntries[] = {
     {"_reticulate_as_iterator", (DL_FUNC) &_reticulate_as_iterator, 1},
     {"_reticulate_py_iter_next", (DL_FUNC) &_reticulate_py_iter_next, 2},
     {"_reticulate_py_iterate", (DL_FUNC) &_reticulate_py_iterate, 3},
+    {"_reticulate_py_allow_threads_impl", (DL_FUNC) &_reticulate_py_allow_threads_impl, 1},
     {"_reticulate_readline", (DL_FUNC) &_reticulate_readline, 1},
     {NULL, NULL, 0}
 };
diff --git a/src/python.cpp b/src/python.cpp
index a5a673a41..85a652d76 100644
--- a/src/python.cpp
+++ b/src/python.cpp
@@ -2868,7 +2868,7 @@ void py_initialize(const std::string& python,
 
   s_main_thread = tthread::this_thread::get_id();
   s_is_python_initialized = true;
-  GILScope scope(/*restore=*/ PyGILState_UNLOCKED);
+  GILScope _gil;
 
   // initialize type objects
   initialize_type_objects(is_python3());
@@ -4477,3 +4477,17 @@ SEXP py_exception_as_condition(PyObject* object, SEXP refenv) {
   UNPROTECT(1);
   return out;
 }
+
+
+// [[Rcpp::export]]
+bool py_allow_threads_impl(bool allow) {
+  PyGILState_STATE gstate = PyGILState_Ensure();
+  if (allow) {
+    PyGILState_Release(PyGILState_UNLOCKED);
+  } else {
+    PyGILState_Release(PyGILState_LOCKED);
+  }
+  return gstate == PyGILState_UNLOCKED;
+}
+
+
diff --git a/src/reticulate_types.h b/src/reticulate_types.h
index 277bd993d..3ae1c7dfe 100644
--- a/src/reticulate_types.h
+++ b/src/reticulate_types.h
@@ -164,11 +164,6 @@ class GILScope {
       gstate = PyGILState_Ensure();
     }
 
-  GILScope(PyGILState_STATE restore_state) {
-      PyGILState_Ensure();
-      gstate = restore_state;
-    }
-
   ~GILScope() {
      PyGILState_Release(gstate);
   }