Quit after command-line parses env var

.gitignore

@@ -56,3 +56,6 @@ testing/src/project_version.h
 .__tmp.log
 .check_syntax.tmp
 .check_syntax2.tmp
+*.venv
+__pycache__
+.DS_Store

core/command.h

@@ -23,6 +23,7 @@
 
 #include "app.h"
 #include "exec_version.h"
+#include "mrtrix.h"
 #ifdef MRTRIX_PROJECT
 namespace MR {
 namespace App {
@@ -92,6 +93,18 @@ int main(int cmdline_argc, char **cmdline_argv) {
     ::MR::GUI::App app(cmdline_argc, cmdline_argv);
 #endif
     ::MR::App::parse();
+
+    // ENVVAR name: MRTRIX_CLI_PARSE_ONLY
+    // ENVVAR Set the command to parse the provided inputs and then quit
+    // ENVVAR if it is set. This can be used in the CI of wrapping code,
+    // ENVVAR such as the automatically generated Pydra interfaces.
+    // ENVVAR Note that it will have no effect for R interfaces
+    char *parse_only = std::getenv("MRTRIX_CLI_PARSE_ONLY");
+    if (parse_only && ::MR::to<bool>(parse_only)) {
+      CONSOLE("Quitting after parsing command-line arguments successfully due to environment variable "
+              "'MRTRIX_CLI_PARSE_ONLY'");
+      return 0;
+    }
     run();
   } catch (::MR::Exception &E) {
     E.display();

core/exception.h

@@ -65,19 +65,19 @@ extern void (*report_to_user_func)(const std::string &msg, int type);
 
 #define CONSOLE(msg)                                                                                                   \
   if (MR::App::log_level >= 1)                                                                                         \
-  report_to_user_func(msg, -1)
+  ::MR::report_to_user_func(msg, -1)
 #define FAIL(msg)                                                                                                      \
   if (MR::App::log_level >= 0)                                                                                         \
-  report_to_user_func(msg, 0)
+  ::MR::report_to_user_func(msg, 0)
 #define WARN(msg)                                                                                                      \
   if (MR::App::log_level >= 1)                                                                                         \
-  report_to_user_func(msg, 1)
+  ::MR::report_to_user_func(msg, 1)
 #define INFO(msg)                                                                                                      \
   if (MR::App::log_level >= 2)                                                                                         \
-  report_to_user_func(msg, 2)
+  ::MR::report_to_user_func(msg, 2)
 #define DEBUG(msg)                                                                                                     \
   if (MR::App::log_level >= 3)                                                                                         \
-  report_to_user_func(msg, 3)
+  ::MR::report_to_user_func(msg, 3)
 
 class Exception {
 public:

docs/reference/environment_variables.rst

@@ -24,6 +24,13 @@ List of MRtrix3 environment variables
      when reading DICOM data, match the StudyName entry against
      the string provided
 
+.. envvar:: MRTRIX_CLI_PARSE_ONLY
+
+     Set the command to parse the provided inputs and then quit
+     if it is set. This can be used in the CI of wrapping code,
+     such as the automatically generated Pydra interfaces.
+     Note that it will have no effect for R interfaces
+
 .. envvar:: MRTRIX_CONFIGFILE
 
      This can be used to set the location of the system-wide

lib/mrtrix3/app.py

@@ -192,6 +192,21 @@ def _execute(module): #pylint: disable=unused-variable
   CMDLINE.print_citation_warning()
 
   return_code = 0
+
+  cli_parse_only = os.getenv('MRTRIX_CLI_PARSE_ONLY')
+  if cli_parse_only:
+    try:
+      if cli_parse_only.lower() in ['yes', 'true'] or int(cli_parse_only):
+        console(
+          'Quitting after parsing command-line arguments successfully due to '
+          'environment variable "MRTRIX_CLI_PARSE_ONLY"'
+        )
+        sys.exit(return_code)
+    except ValueError:
+      warn('Potentially corrupt environment variable "MRTRIX_CLI_PARSE_ONLY" '
+           '= "' + cli_parse_only + '"; ignoring')
+    sys.exit(return_code)
+
   try:
     module.execute()
   except (run.MRtrixCmdError, run.MRtrixFnError) as exception: