Re: [PATCH v3 10/17] qapi/gen: Combine ._add_[user|system]_module

[John Snow]

On 1/20/21 9:20 AM, Markus Armbruster wrote:
> John Snow <jsnow@redhat.com> writes:
>
> > From: Markus Armbruster <armbru@redhat.com>
> >
> > QAPISchemaModularCVisitor attempts to encapsulate the way it splits
> > the module name space between user modules (name can't start with
> > './') and system modules (name is None or starts with './') by
>
> Is this still accurate?

Ah, not exactly; sorry I mangled your patches here. I had written my own 
version of what this patch used to be, but your patch went one step 
further, but the ordering got weird.

> > providing separate ._add_user_module() and ._add_system_module(),
> > where the latter prepends './' to names other than None.
> >
> > Not worthwhile.  Dumb down to a single ._add_module().
> >
> > Signed-off-by: Markus Armbruster <armbru@redhat.com>
> > Signed-off-by: John Snow <jsnow@redhat.com>
> > ---
> >   scripts/qapi/commands.py |  2 +-
> >   scripts/qapi/events.py   |  2 +-
> >   scripts/qapi/gen.py      | 20 +++++++-------------
> >   3 files changed, 9 insertions(+), 15 deletions(-)
> >
> > diff --git a/scripts/qapi/commands.py b/scripts/qapi/commands.py
> > index fc5fe27c472..49111663394 100644
> > --- a/scripts/qapi/commands.py
> > +++ b/scripts/qapi/commands.py
> > @@ -286,7 +286,7 @@ def _begin_user_module(self, name: str) -> None:
> >                                types=types))
> >   
> >       def visit_end(self) -> None:
> > -        self._add_system_module('./init', ' * QAPI Commands initialization')
> > +        self._add_module('./init', ' * QAPI Commands initialization')
> >           self._genh.add(mcgen('''
> >   #include "qapi/qmp/dispatch.h"
> >   
> > diff --git a/scripts/qapi/events.py b/scripts/qapi/events.py
> > index 26faa829898..079c666ec69 100644
> > --- a/scripts/qapi/events.py
> > +++ b/scripts/qapi/events.py
> > @@ -191,7 +191,7 @@ def _begin_user_module(self, name: str) -> None:
> >                                types=types))
> >   
> >       def visit_end(self) -> None:
> > -        self._add_system_module('./emit', ' * QAPI Events emission')
> > +        self._add_module('./emit', ' * QAPI Events emission')
> >           self._genc.preamble_add(mcgen('''
> >   #include "qemu/osdep.h"
> >   #include "%(prefix)sqapi-emit-events.h"
> > diff --git a/scripts/qapi/gen.py b/scripts/qapi/gen.py
> > index 55acd7e080d..b5505685e6e 100644
> > --- a/scripts/qapi/gen.py
> > +++ b/scripts/qapi/gen.py
> > @@ -272,22 +272,15 @@ def _module_filename(self, what: str, name: str) -> str:
> >                               self._module_basename(what, name))
> >   
> >       def _add_module(self, name: str, blurb: str) -> None:
> > +        if QAPISchemaModule.is_user_module(name):
> > +            if self._main_module is None:
> > +                self._main_module = name
> >           basename = self._module_filename(self._what, name)
> >           genc = QAPIGenC(basename + '.c', blurb, self._pydoc)
> >           genh = QAPIGenH(basename + '.h', blurb, self._pydoc)
> >           self._module[name] = (genc, genh)
> >           self._genc, self._genh = self._module[name]
> >   
> > -    def _add_user_module(self, name: str, blurb: str) -> None:
> > -        assert QAPISchemaModule.is_user_module(name)
> > -        if self._main_module is None:
> > -            self._main_module = name
> > -        self._add_module(name, blurb)
> > -
> > -    def _add_system_module(self, name: str, blurb: str) -> None:
> > -        assert QAPISchemaModule.is_system_module(name)
> > -        self._add_module(name, blurb)
> > -
> >       def write(self, output_dir: str, opt_builtins: bool = False) -> None:
> >           for name in self._module:
> >               if QAPISchemaModule.is_builtin_module(name) and not opt_builtins:
> > @@ -303,9 +296,9 @@ def _begin_user_module(self, name: str) -> None:
> >           pass
> >   
> >       def visit_module(self, module: QAPISchemaModule) -> None:
> > -        if module.system_module:
> > +        if module.builtin_module:
>
> Looks like you're fixing a slip-up in PATCH 06.  If yes, squash.  If no,
> I'm confused.

Or patch 7, actually -- where we clarify that we are checking for the 
built-in module and not any old system module.

> >               if self._builtin_blurb:
> > -                self._add_system_module(module.name, self._builtin_blurb)
> > +                self._add_module(module.name, self._builtin_blurb)
> >                   self._begin_builtin_module()
> >               else:
> >                   # The built-in module has not been created.  No code may
> > @@ -313,7 +306,8 @@ def visit_module(self, module: QAPISchemaModule) -> None:
> >                   self._genc = None
> >                   self._genh = None
> >           else:
> > -            self._add_user_module(module.name, self._user_blurb)
> > +            assert module.user_module, "Unexpected system module"
>
> The string provides no value.

That's just, like, your opinion, man. It has value to me.


Compare:

```
#!/usr/bin/env python3

def main():
    assert False

if __name__ == '__main__':
    main()
```

```
# ./foo.py

Traceback (most recent call last):
  File "./foo.py", line 7, in <module>
    main()
  File "./foo.py", line 4, in main
    assert False
AssertionError
```

With:


```
#!/usr/bin/env python3

def main():
    assert False, "Unexpected system module"

if __name__ == '__main__':
    main()
```

```
# ./foo.py

Traceback (most recent call last):
  File "./foo.py", line 7, in <module>
    main()
  File "./foo.py", line 4, in main
    assert False, "Unexpected system module"
AssertionError: Unexpected system module
```

I like the extra string for giving some semantic context as to 
specifically what broke (We don't expect to see system modules here) 
instead of just a stack trace.

> > +            self._add_module(module.name, self._user_blurb)
> >               self._begin_user_module(module.name)
> >   
> >       def visit_include(self, name: str, info: QAPISourceInfo) -> None: