Add initial mypy configuration and types

As a first step, add type hints to variables whose type `mypy` cannot
infer automatically. This is the minimal set of type hints that allow
running `mypy` without any arguments, and having it not fail.

We currently ignore C extensions that mypy can't process directly.
Later, we can look into generating stubs for such modules (potentially
automatically).

1 files changed, 19 insertions, 0 deletions

diff --git a/setup.cfg b/setup.cfg
index 4a0dfb54d..7a62f9282 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -29,3 +29,22 @@ markers =
 max-line-length = 119
 ignore = E129,E125,W504,W605
 exclude = .git/**,.tox/**,.eggs/**,build/**,doc/source/conf.py,src/buildstream/_fuse/fuse.py,src/buildstream/_protos/**/*py,tmp/**
+
+[mypy]
+files = src
+warn_unused_configs = True
+warn_no_return = True
+
+# Ignore missing stubs for third-party packages.
+# In future, these should be re-enabled if/when stubs for them become available.
+[mypy-copyreg,arpy,grpc,pluginbase,psutil,py,pyroaring,pytest,_pytest.*,ruamel]
+ignore_missing_imports=True
+
+# Ignore missing stubs for Cythonized modules.
+# In future, these should be re-enabled by writing stubs for them.
+[mypy-buildstream.node,buildstream._loader.*,buildstream._types,buildstream._utils,buildstream._variables]
+ignore_missing_imports=True
+
+# Ignore issues with generated files and vendored code
+[mypy-buildstream._protos.*,buildstream._fuse.*,buildstream._version]
+ignore_errors = True