Add pyright to test suite, pyrightconfig.json (#5059)

Co-authored-by: Sebastian Rittau <srittau@rittau.biz>

tests/pyright_test.py

@@ -0,0 +1,30 @@
+#!/usr/bin/env python3
+
+import subprocess
+import sys
+from pathlib import Path
+
+
+_WELL_KNOWN_FILE = Path("tests", "pyright_test.py")
+_PYRIGHT_COMMAND = ["npx", "-p", "pyright@1.1.114", "pyright"]
+
+
+def main() -> None:
+    assert_npm_is_installed()
+    ret = subprocess.run(_PYRIGHT_COMMAND).returncode
+    sys.exit(ret)
+
+
+def assert_npm_is_installed() -> None:
+    if not _WELL_KNOWN_FILE.exists():
+        print("pyright_test.py must be run from the typeshed root directory", file=sys.stderr)
+        sys.exit(1)
+    try:
+        subprocess.run(["npx", "--version"])
+    except OSError:
+        print("error running npx; is Node.js installed?", file=sys.stderr)
+        sys.exit(1)
+
+
+if __name__ == "__main__":
+    main()