OSWebWriter: raise OSWebCompatibilityError when script contains unsupported syntax

Author: smathot

opensesame_extensions/osweb/oswebext/oswebext.py

@@ -293,7 +293,7 @@ def event_osweb_run(self, fullscreen=False, subject_nr=0,
                 welcome_text=cfg.oswebext_welcome_text,
                 external_js=self._external_js(),
                 intro_click=cfg.oswebext_intro_click)
-        except PythonToJavaScriptError as e:
+        except (OSWebCompatibilityError, PythonToJavaScriptError) as e:
             return e
         else:
             webbrowser.open('file://{}'.format(index_path))

osweb/oswebwriter.py

@@ -20,7 +20,7 @@
 from libopensesame.osexpfile import OSExpWriter
 from libopensesame.oslogging import oslogger
 from metapensiero.pj.__main__ import transform_string as py2js
-from .oswebexceptions import PythonToJavaScriptError
+from .oswebexceptions import PythonToJavaScriptError, OSWebCompatibilityError
 import re
 
 RE_VAR = re.compile('(?<!\w)var\.', re.MULTILINE)
@@ -68,7 +68,14 @@ def parse_cmd(self):
     def script(self):
         script = self._exp.to_string()
         for m in RE_RUN_IF.finditer(script):
-            _, (item, cond), _ = self.parse_cmd(m.group('cmd'))
+            try:
+                _, (item, cond), _ = self.parse_cmd(m.group('cmd'))
+            except ValueError:
+                # This mainly happens for coroutines, which have a slightly
+                # deviant run statement
+                raise OSWebCompatibilityError(
+                    f'The following OpenSesame script is not supported in '
+                    f'OSWeb:\n\n```\n{m.group("cmd")}\n```')
             cond = self.transform(cond)
             cmd = self.create_cmd('run', (item, cond))
             oslogger.debug(f'rewriting {m.group("cmd")} to {cmd}')