Raise an error when referencing a nonexistent pyi file in another pyi…

… file.

PiperOrigin-RevId: 448589096

pytype/load_pytd.py

@@ -624,13 +624,17 @@ def finish_and_verify_ast(self, mod_ast):
     if mod_ast:
       try:
         self._resolver.verify(mod_ast)
-      except (BadDependencyError, visitors.ContainerError):
+      except (BadDependencyError, visitors.ContainerError) as e:
         # In the case of a circular import, an external type may be left
         # unresolved, so we re-resolve lookups in this module and its direct
         # dependencies. Technically speaking, we should re-resolve all
         # transitive imports, but lookups are expensive.
         dependencies = self._resolver.collect_dependencies(mod_ast)
         for k in dependencies:
+          if k not in self._modules:
+            raise (
+                BadDependencyError("Can't find pyi for %r" % k, mod_ast.name)
+            ) from e
           self._modules[k].ast = self._resolve_external_types(
               self._modules[k].ast)
         mod_ast = self._resolve_external_types(mod_ast)

pytype/tests/test_pyi1.py

@@ -898,6 +898,19 @@ class X:
         import bad  # pyi-error
       """, pythonpath=[d.path])
 
+  def test_nonexistent_import(self):
+    with file_utils.Tempdir() as d:
+      d.create_file("bad.pyi", """
+        import nonexistent
+        x = nonexistent.x
+      """)
+      err = self.CheckWithErrors("""
+        import bad  # pyi-error[e]
+      """, pythonpath=[d.path])
+      self.assertErrorSequences(err, {
+          "e": ["Couldn't import pyi", "nonexistent", "referenced from", "bad"]
+      })
+
 
 if __name__ == "__main__":
   test_base.main()