Merge pull request #1681 from rstudio/fix/positron-repl-preserve-main

Positron REPL: restore `__main__` members after ipykernel launch

R/thread.R

@@ -53,7 +53,32 @@ py_allow_threads <- function(allow = TRUE) {
 py_run_file_on_thread <- function(file, ..., args = NULL) {
   if (!is.null(args))
     args <- as.list(as.character(args))
-  import("rpytools.run")$`_launch_lsp_server_on_thread`(file, args)
+
+  # TODO: we should have a dedicated entry point in reticulate for this.
+  # Needs to be updated in ark and positron.
+  launching_lsp <- (basename(file) == 'positron_language_server.py' &&
+                      is_positron() &&
+                      basename(dirname(file)) == "positron")
+
+  if (launching_lsp) {
+    main_dict <- py_eval("__import__('__main__').__dict__.copy()", FALSE)
+    py_get_attr(main_dict, "pop")("__annotations__")
+  }
+
+  import("rpytools.run")$run_file_on_thread(file, args, ...)
+
+  if (launching_lsp) {
+
+    PositronIPKernelApp <- import("positron_ipykernel.positron_ipkernel")$PositronIPKernelApp
+    for(i in 1:40) { # Positron timeout is 20 seconds
+      if (PositronIPKernelApp$initialized()) break
+      Sys.sleep(.5)
+    }
+    Sys.sleep(1)
+
+    py_eval("__import__('__main__').__dict__.update", FALSE)(main_dict)
+  }
+  invisible()
 }
 
 ## used in Positron:

inst/python/rpytools/run.py

@@ -38,7 +38,7 @@ def __exit__(self, *_):
         if self.argv is not None:
             # restore sys.argv if it's unmodified from what we set it to.
             # otherwise, leave it as-is.
-            patched_argv = [self.path] + list(self.args)
+            patched_argv = [self.path] + list(self.argv)
             if sys.argv == patched_argv:
                 sys.argv = self._orig_sys_argv
 
@@ -50,12 +50,19 @@ def _launch_lsp_server_on_thread(path, args):
     return run_file_on_thread(path, args)
 
 
-
-def run_file_on_thread(path, args=None):
+def run_file_on_thread(path, argv=None, init_globals=None, run_name="__main__"):
     # for now, leave sys.argv and sys.path permanently modified.
     # Later, revisit if it's desirable/safe to restore after the initial
     # lsp event loop startup.
-    RunMainScriptContext(path, args).__enter__()
     import _thread
-
-    _thread.start_new_thread(run_file, (path,))
+    from runpy import run_path
+
+    RunMainScriptContext(path, argv).__enter__()
+    _thread.start_new_thread(
+        run_path,
+        (path,),
+        {
+            "run_name": run_name,
+            "init_globals": init_globals,
+        },
+    )

tests/testthat/test-python-threads.R

@@ -44,11 +44,13 @@ def write_to_file_from_thread(path, lines):
 test_that("Python calls into R from a background thread are evaluated", {
 
   x <- 0L
-  py$r_func <- function() x <<- x+1
-  on.exit(py_del_attr(py, "r_func"), add = TRUE)
+  r_func <- function() x <<- x+1
   py_file <- withr::local_tempfile(lines = "r_func()", fileext = ".py")
 
-  reticulate:::py_run_file_on_thread(py_file)
+  reticulate:::py_run_file_on_thread(
+    py_file,
+    init_globals = list(r_func = r_func)
+  )
 
   # Simulate the main R thread doing non-Python work (e.g., sleeping)
   for(i in 1:10) {
@@ -62,21 +64,20 @@ test_that("Python calls into R from a background thread are evaluated", {
 
 test_that("Errors from background threads calling into main thread are handled", {
 
-  py$signal_r_error <- function() stop("foo-bar-baz")
-  on.exit(py_del_attr(py, "signal_r_error"), add = TRUE)
+  signal_r_error <- function() stop("foo-bar-baz")
 
-  # when testing, `r` in Python resolves `getOption("rlang_trace_top_env"), not
-  # the R globalenv(). Avoid using it to communicate.
   val <- NULL
-  py$set_val <-  function(v) val <<- v
-  on.exit(py_del_attr(py, "set_val"), add = TRUE)
+  set_val <- function(v) val <<- v
 
   py_file <- withr::local_tempfile(lines = "
 try: signal_r_error()
 except Exception as e: set_val(e.args[0])
 ", fileext = ".py")
 
-  reticulate:::py_run_file_on_thread(py_file)
+  reticulate:::py_run_file_on_thread(py_file, init_globals = list(
+    signal_r_error = signal_r_error,
+    set_val = set_val
+  ))
 
   # Simulate the main R thread doing non-Python work (e.g., sleeping)
   for(i in 1:10) {