Make emrun work with file names containing space on Windows (emscripten-core#12385)

quantum5 · web-flow · commit 4e1e9fb7b494 · 2020-09-30T21:38:43.000-04:00
Essentially, if the first argument to the `cmd.exe` function `start` has
quotes, it will be interpreted as the title of a new `cmd.exe` window instead
of the command to execute. This can be fixed by specifying `""` as the first
argument.
diff --git a/emrun.py b/emrun.py
@@ -1121,9 +1121,16 @@ def win_get_default_browser():
   except WindowsError:
     logv("Unable to find default browser key in Windows registry. Trying fallback.")
 
-  # Fall back to 'start %1', which we have to treat as if user passed --serve_forever, since
+  # Fall back to 'start "" %1', which we have to treat as if user passed --serve_forever, since
   # for some reason, we are not able to detect when the browser closes when this is passed.
-  return ['cmd', '/C', 'start']
+  #
+  # If the first argument to 'start' is quoted, then 'start' will create a new cmd.exe window with
+  # that quoted string as the title. If the URL contained spaces, it would be quoted by subprocess,
+  # and if we did 'start %1', it would create a new cmd.exe window with the URL as title instead of
+  # actually launching the browser. Therefore, we must pass a dummy quoted first argument for start
+  # to interpret as the title. For this purpose, we use the empty string, which will be quoted
+  # as "". See #9253 for details.
+  return ['cmd', '/C', 'start', '']
 
 
 def find_browser(name):
