fix: Extraneous error message in usage output in Python 3.10

* Fixes extraneous error message in usage output
  when using Python 3.10.
  Python 3.10's `argparse` usage messages were tweaked
  in a way that weren't fully backwards compatible
  with earlier Python versions.

closes #36

DESCRIPTION

@@ -1,7 +1,7 @@
 Package: argparse
 Type: Package
 Title: Command Line Optional and Positional Argument Parser
-Version: 2.1.2
+Version: 2.1.3
 Authors@R: c(person("Trevor L", "Davis", role=c("aut", "cre"), email="[email protected]"),
     person("Allen", "Day", role="ctb", comment="Some documentation and examples ported from the getopt package."),
     person("Python Software Foundation", role="ctb", comment="Some documentation from the optparse Python module."),

NEWS.md

@@ -1,3 +1,10 @@
+argparse 2.1.3
+==============
+
+* Prevents extraneous error message from being included in usage message 
+  when using Python 3.10 (#36).
+  Thanks @dariober for bug report.
+
 argparse 2.1.2
 ==============
 

R/argparse.R

@@ -190,7 +190,7 @@ Parser <- R6Class("Parser", # nolint
 parse_args_output <- function(output) {
     if (grepl("^usage:", output[1])) {
         has_positional_arguments <- any(grepl("^positional arguments:", output))
-        has_optional_arguments <- any(grepl("^optional arguments:", output))
+        has_optional_arguments <- any(grepl("^optional arguments:|^options:", output))
         if (has_positional_arguments || has_optional_arguments) {
             .print_message_and_exit(output, "help requested:")
         } else {

tests/testthat/test-argparse.R

@@ -26,7 +26,7 @@ test_that("print_help works as expected", {
     skip_if_not(detects_python())
     parser <- ArgumentParser(description = "Process some integers.")
     expect_output(parser$print_help(), "usage:")
-    expect_output(parser$print_help(), "optional arguments:")
+    expect_output(parser$print_help(), "optional arguments:|options:")
     expect_output(parser$print_help(), "Process some integers.")
     expect_output(parser$print_usage(), "usage:")
 
@@ -324,7 +324,6 @@ test_that("Paths that quit()", {
 
     help <- system2(cmd, c("scripts/test_help.R", "--help"),
                     stdout = TRUE, stderr = TRUE)
-    expect_equal(help,
-                 c("usage: scripts/test_help.R [-h]", "", "optional arguments:",
-                   "  -h, --help  show this help message and exit"))
+    expect_equal("usage: scripts/test_help.R [-h]", help[2])
+    expect_equal("  -h, --help  show this help message and exit", help[5])
 })