Mach: introduce Pyrefly for Python type checking, starting with the wpt folder (#37953)

This is the first stage of adopting Pyrefly. It introduces the Python
folder and focuses on fixing issues around it.

Testing: *Describe how this pull request is tested or why it doesn't
require tests*
Fixes: *Link to an issue this pull requests fixes or remove this line if
there is no issue*

---------

Signed-off-by: Jerens Lensun <jerensslensun@gmail.com>

python/tidy/tidy.py

@@ -17,7 +17,8 @@ import os
 import re
 import subprocess
 import sys
-from typing import Any, Dict, List
+from dataclasses import dataclass
+from typing import Any, Dict, Iterator, List, Tuple
 
 import colorama
 import toml
@@ -128,6 +129,10 @@ def is_iter_empty(iterator):
         return False, iterator
 
 
+def normalize_path(path: str) -> str:
+    return os.path.relpath(os.path.abspath(path), TOPDIR)
+
+
 def normilize_paths(paths):
     if isinstance(paths, str):
         return os.path.join(*paths.split("/"))
@@ -376,6 +381,38 @@ def check_ruff_lints():
             )
 
 
+@dataclass
+class PyreflyDiagnostic:
+    """
+    Represents a single diagnostic error reported by Pyrefly.
+    """
+
+    line: int
+    column: int
+    stop_line: int
+    stop_column: int
+    path: str
+    code: int
+    name: str
+    description: str
+    concise_description: str
+
+
+def run_python_type_checker() -> Iterator[Tuple[str, int, str]]:
+    print("\r ➤  Checking type annotations in python files ...")
+    try:
+        result = subprocess.run(["pyrefly", "check", "--output-format", "json"], capture_output=True)
+        parsed_json = json.loads(result.stdout)
+        errors = parsed_json.get("errors", [])
+    except subprocess.CalledProcessError as error:
+        print(f"{colorama.Fore.YELLOW}{error}{colorama.Style.RESET_ALL}")
+        pass
+    else:
+        for error in errors:
+            diagnostic = PyreflyDiagnostic(**error)
+            yield normalize_path(diagnostic.path), diagnostic.line, diagnostic.concise_description
+
+
 def run_cargo_deny_lints():
     print("\r ➤  Running `cargo-deny` checks...")
     result = subprocess.run(
@@ -1003,11 +1040,14 @@ def scan(only_changed_files=False, progress=False, github_annotations=False):
     file_errors = collect_errors_for_files(files_to_check, checking_functions, line_checking_functions)
 
     python_errors = check_ruff_lints()
+    python_type_check = run_python_type_checker()
     cargo_lock_errors = run_cargo_deny_lints()
     wpt_errors = run_wpt_lints(only_changed_files)
 
     # chain all the iterators
-    errors = itertools.chain(config_errors, directory_errors, file_errors, python_errors, wpt_errors, cargo_lock_errors)
+    errors = itertools.chain(
+        config_errors, directory_errors, file_errors, python_errors, python_type_check, wpt_errors, cargo_lock_errors
+    )
 
     colorama.init()
     error = None