Add support for pyi_srcs / direct_pyi_files

Introduced in rules_python 1.1.

See:
  * https://github.com/bazelbuild/rules_python/releases/tag/1.1.0
  * bazelbuild/rules_python#2538

mypy/private/mypy.bzl

@@ -103,7 +103,12 @@ def _mypy_impl(target, ctx):
     for import_ in _extract_imports(target):
         imports_dirs[import_] = 1
 
+    pyi_files = []
+    pyi_dirs = {}
     for dep in (ctx.rule.attr.deps + additional_types):
+        if RulesPythonPyInfo in dep and hasattr(dep[RulesPythonPyInfo], "direct_pyi_files"):
+            pyi_files.extend(dep[RulesPythonPyInfo].direct_pyi_files.to_list())
+            pyi_dirs |= {"%s/%s" % (ctx.bin_dir.path, imp): None for imp in _extract_imports(dep) if imp != "site-packages" and imp != "_main"}
         depsets.append(dep.default_runfiles.files)
 
         if PyTypeLibraryInfo in dep:
@@ -140,7 +145,7 @@ def _mypy_impl(target, ctx):
 
     # types need to appear first in the mypy path since the module directories
     # are the same and mypy resolves the first ones, first.
-    mypy_path = ":".join(sorted(types) + sorted(external_deps) + sorted(imports_dirs) + sorted(generated_dirs) + sorted(generated_imports_dirs))
+    mypy_path = ":".join(sorted(types) + sorted(pyi_dirs) + sorted(external_deps) + sorted(imports_dirs) + sorted(generated_dirs) + sorted(generated_imports_dirs))
 
     output_file = ctx.actions.declare_file(ctx.rule.attr.name + ".mypy_stdout")
 
@@ -182,7 +187,7 @@ def _mypy_impl(target, ctx):
         mnemonic = "mypy",
         progress_message = "mypy %{label}",
         inputs = depset(
-            direct = ctx.rule.files.srcs + py_type_files + upstream_caches + config_files,
+            direct = ctx.rule.files.srcs + py_type_files + pyi_files + upstream_caches + config_files,
             transitive = depsets,
         ),
         outputs = outputs,