fix[lang]: transitive exports (vyperlang#3888)

this commit fixes transitive exports, i.e. where `module1` exports
`module2.foo`, but it was previously not exportable from `module1`. this
is because previously exported functions were not added to the
`ModuleT`'s `exposed_functions` list.

a test had previously been written for this case, but it had been marked
xfail since the desired behavior was not clear until user feedback was
received. this commit removes the `xfail` marker from that test case.

tests/functional/codegen/modules/test_exports.py

@@ -1,6 +1,3 @@
-import pytest
-
-
 def test_simple_export(make_input_bundle, get_contract):
     lib1 = """
 @external
@@ -131,9 +128,7 @@ def foo() -> uint256:
     assert c.foo() == 5
 
 
-# not sure if this one should work
-@pytest.mark.xfail(reason="ambiguous spec")
-def test_recursive_export(make_input_bundle, get_contract):
+def test_transitive_export(make_input_bundle, get_contract):
     lib1 = """
 @external
 def foo() -> uint256:

vyper/exceptions.py

@@ -127,8 +127,9 @@ def format_annotation(self, value):
             return None
 
         if isinstance(node, vy_ast.VyperNode):
-            module_node = node.get_ancestor(vy_ast.Module)
+            module_node = node.module_node
 
+            # TODO: handle cases where module is None or vy_ast.Module
             if module_node.get("path") not in (None, "<unknown>"):
                 node_msg = f'{node_msg}contract "{module_node.path}:{node.lineno}", '
 

vyper/semantics/analysis/module.py

@@ -524,7 +524,7 @@ def visit_ExportsDecl(self, node):
                 decl_node = func_t.decl_node
 
             if not isinstance(func_t, ContractFunctionT):
-                raise StructureException("not a function!", decl_node, item)
+                raise StructureException(f"not a function: `{func_t}`", decl_node, item)
             if not func_t.is_external:
                 raise StructureException("can't export non-external functions!", decl_node, item)
 

vyper/semantics/types/module.py

@@ -296,6 +296,10 @@ def __init__(self, module: vy_ast.Module, name: Optional[str] = None):
             # note: this checks for collisions
             self.add_member(f.name, f._metadata["func_type"])
 
+        for item in self.exports_decls:
+            for fn_t in item._metadata["exports_info"].functions:
+                self.add_member(fn_t.name, fn_t)
+
         for e in self.event_defs:
             # add the type of the event so it can be used in call position
             self.add_member(e.name, TYPE_T(e._metadata["event_type"]))  # type: ignore