scanner: switch to a two-run parsing of the XML file

On the first run we extract the interfaces only, on the second run all
the rest. This allows us to pass the interface to the Argument where
appropriate.

proto/scanner.py

@@ -71,6 +71,12 @@ class Argument:
     signature: str = attr.ib(converter=proto_to_type)
     summary: str = attr.ib()
     enum: Optional["Enum"] = attr.ib()
+    interface: Optional["Interface"] = attr.ib()
+
+    @interface.validator  # type: ignore
+    def _validate_interface(self, attribute, value):
+        if value is not None and self.signature not in ["n", "o"]:
+            raise ValueError("Interface may only be set for object types")
 
     @property
     def as_arg(self) -> str:
@@ -107,9 +113,14 @@ class Argument:
 
     @classmethod
     def create(
-        cls, name: str, signature: str, summary: str = "", enum: Optional["Enum"] = None
+        cls,
+        name: str,
+        signature: str,
+        summary: str = "",
+        enum: Optional["Enum"] = None,
+        interface: Optional["Interface"] = None,
     ) -> "Argument":
-        return cls(name, signature, summary, enum)
+        return cls(name, signature, summary, enum, interface=interface)
 
 
 @attr.s
@@ -291,6 +302,8 @@ class Protocol(xml.sax.handler.ContentHandler):
     current_interface: Optional[Interface] = attr.ib(init=False, default=None)
     current_message: Optional[Union[Message, Enum]] = attr.ib(init=False, default=None)
 
+    run: int = attr.ib(init=False, default=0)
+
     def xmlerror(self, msg) -> None:
         line = self._locator.getLineNumber()  # type: ignore
         col = self._locator.getColumnNumber()  # type: ignore
@@ -303,6 +316,15 @@ class Protocol(xml.sax.handler.ContentHandler):
         col = self._locator.getColumnNumber()  # type: ignore
         return line, col
 
+    def interface_by_name(self, name) -> Interface:
+        try:
+            return [iface for iface in self.interfaces if iface.name == name].pop()
+        except IndexError:
+            raise XmlError(*self.location, f"Unable to find interface {name}")
+
+    def startDocument(self):
+        self.run += 1
+
     def startElement(self, element: str, attrs: dict):
         if element == "interface":
             if self.current_interface is not None:
@@ -321,10 +343,21 @@ class Protocol(xml.sax.handler.ContentHandler):
 
             if name.startswith("ei"):
                 name = f"{self.component}{name[2:]}"
-            intf = Interface.create(name=name, version=version, mode=self.component)
+            # We only create the interface on the first run, in subsequent runs we
+            # re-use them so we can cross reference correctly
+            if self.run > 1:
+                intf = self.interface_by_name(name)
+            else:
+                intf = Interface.create(name=name, version=version, mode=self.component)
+                self.interfaces.append(intf)
+
             self.current_interface = intf
-            self.interfaces.append(intf)
+
-        elif element == "request":
+        # first run only parses interfaces
+        if self.run <= 1:
+            return
+
+        if element == "request":
             if self.current_interface is None:
                 raise XmlError(
                     *self.location,
@@ -419,6 +452,13 @@ class Protocol(xml.sax.handler.ContentHandler):
             name = attrs["name"]
             sig = attrs["type"]
             summary = attrs.get("summary", "")
+            interface_name = attrs.get("interface", None)
+            if interface_name is not None:
+                if interface_name.startswith("ei"):
+                    interface_name = f"{self.component}{interface_name[2:]}"
+                interface = self.interface_by_name(interface_name)
+            else:
+                interface = None
             enum = attrs.get("enum", None)
             if enum is not None and enum not in [
                 e.name for e in self.current_interface.enums
@@ -427,7 +467,13 @@ class Protocol(xml.sax.handler.ContentHandler):
                     *self.location,
                     f"Failed to find enum '{self.current_interface.name}.{enum}'",
                 )
-            arg = Argument.create(name=name, signature=sig, summary=summary, enum=enum)
+            arg = Argument.create(
+                name=name,
+                signature=sig,
+                summary=summary,
+                enum=enum,
+                interface=interface,
+            )
             self.current_message.add_argument(arg)
         elif element == "entry":
             if self.current_interface is None:
@@ -452,7 +498,12 @@ class Protocol(xml.sax.handler.ContentHandler):
         if name == "interface":
             assert self.current_interface is not None
             self.current_interface = None
-        elif name == "request":
+
+        # first run only parses interfaces
+        if self.run <= 1:
+            return
+
+        if name == "request":
             assert isinstance(self.current_message, Request)
             self.current_message = None
         elif name == "event":
@@ -474,6 +525,8 @@ class Protocol(xml.sax.handler.ContentHandler):
 def parse(protofile: Path, component: str) -> Protocol:
     proto = Protocol.create(component=component)
     xml.sax.parse(os.fspath(protofile), proto)
+    # We parse two times, once to fetch all the interfaces, then to parse the details
+    xml.sax.parse(os.fspath(protofile), proto)
     return proto