commands: handle type errors on startup

fixes #3088
fixes #2787

mitmproxy/command.py

@@ -35,9 +35,11 @@ def typename(t: type) -> str:
     """
         Translates a type to an explanatory string.
     """
+    if t == inspect._empty:  # type: ignore
+        raise exceptions.CommandError("missing type annotation")
     to = mitmproxy.types.CommandTypes.get(t, None)
     if not to:
-        raise NotImplementedError(t)
+        raise exceptions.CommandError("unsupported type: %s" % getattr(t, "__name__", t))
     return to.display
 
 
@@ -58,10 +60,12 @@ class Command:
             if i.kind == i.VAR_POSITIONAL:
                 self.has_positional = True
         self.paramtypes = [v.annotation for v in sig.parameters.values()]
-        if sig.return_annotation == inspect._empty:
+        if sig.return_annotation == inspect._empty:  # type: ignore
             self.returntype = None
         else:
             self.returntype = sig.return_annotation
+        # This fails with a CommandException if types are invalid
+        self.signature_help()
 
     def paramnames(self) -> typing.Sequence[str]:
         v = [typename(i) for i in self.paramtypes]
@@ -136,7 +140,12 @@ class CommandManager(mitmproxy.types._CommandBase):
                     pass  # hasattr may raise if o implements __getattr__.
                 else:
                     if is_command:
-                        self.add(o.command_path, o)
+                        try:
+                            self.add(o.command_path, o)
+                        except exceptions.CommandError as e:
+                            self.master.log.warn(
+                                "Could not load command %s: %s" % (o.command_path, e)
+                            )
 
     def add(self, path: str, func: typing.Callable):
         self.commands[path] = Command(self, path, func)

test/mitmproxy/test_command.py

@@ -1,4 +1,5 @@
 import typing
+import inspect
 from mitmproxy import command
 from mitmproxy import flow
 from mitmproxy import exceptions
@@ -55,19 +56,34 @@ class TAddon:
         pass
 
 
+class Unsupported:
+    pass
+
+
 class TypeErrAddon:
     @command.command("noret")
     def noret(self):
         pass
 
+    @command.command("invalidret")
+    def invalidret(self) -> Unsupported:
+        pass
+
+    @command.command("invalidarg")
+    def invalidarg(self, u: Unsupported):
+        pass
+
 
 class TestCommand:
     def test_typecheck(self):
         with taddons.context(loadcore=False) as tctx:
             cm = command.CommandManager(tctx.master)
             a = TypeErrAddon()
-            c = command.Command(cm, "noret", a.noret)
-            print(c.signature_help())
+            command.Command(cm, "noret", a.noret)
+            with pytest.raises(exceptions.CommandError):
+                command.Command(cm, "invalidret", a.invalidret)
+            with pytest.raises(exceptions.CommandError):
+                command.Command(cm, "invalidarg", a.invalidarg)
 
     def test_varargs(self):
         with taddons.context() as tctx:
@@ -288,6 +304,11 @@ def test_typename():
     assert command.typename(mitmproxy.types.Path) == "path"
     assert command.typename(mitmproxy.types.Cmd) == "cmd"
 
+    with pytest.raises(exceptions.CommandError, match="missing type annotation"):
+        command.typename(inspect._empty)
+    with pytest.raises(exceptions.CommandError, match="unsupported type"):
+        command.typename(None)
+
 
 class DummyConsole:
     @command.command("view.resolve")
@@ -339,7 +360,8 @@ class TCmds(TAttr):
         pass
 
 
-def test_collect_commands():
+@pytest.mark.asyncio
+async def test_collect_commands():
     """
         This tests for the error thrown by hasattr()
     """
@@ -349,6 +371,10 @@ def test_collect_commands():
         c.collect_commands(a)
         assert "empty" in c.commands
 
+        a = TypeErrAddon()
+        c.collect_commands(a)
+        await tctx.master.await_log("Could not load")
+
 
 def test_decorator():
     with taddons.context() as tctx: