fix(defines): resolve package-level from-import symbols to the package module

App/lib/core/Gen/ImportsGenMixin.vp

@@ -735,8 +735,11 @@ novirtual class ImportsGenMixin:
                         if alias.asname is not None:
                             local_name = alias.asname
                             orig_name = alias.name
-                        # For `from . import Y`, _resolve_relative_module returns the package name
-                        # but Y is a submodule, so map local_name -> the full submodule name.
+                        # For `from . import Y`, _resolve_relative_module returns the package name.
+                        # Y may be a real submodule (target package.Y) or a package __init__ symbol
+                        # such as `JSON_NULL` (target the package itself). Only append the name
+                        # when it denotes a submodule; otherwise the DefineT/global lives in the
+                        # package vpi and the synthetic `package.Y` module does not exist.
                         fi_target: str = resolved
                         if impf.module is None and resolved is not None:
                             fl_t: sizet = string.strlen(resolved)
@@ -746,7 +749,8 @@ novirtual class ImportsGenMixin:
                                 string.strcpy(jb_t, resolved)
                                 jb_t[fl_t] = '.'
                                 string.strcpy(jb_t + fl_t + 1, alias.name)
-                                fi_target = jb_t
+                                if StubMergerStore.LookupSha1ByModName(jb_t) is not None or self._is_local_module_file(alias.name) != 0:
+                                    fi_target = jb_t
                         trans._from_imports = self.add_from_import(trans.Pool, trans._from_imports, local_name, fi_target, orig_name)
                         # Static symbols (forbidden cross-module): `from mod import name` hitting one
                         # fail-fasts. Logic stays in _CheckStaticFromImport (inlining breaks inference).