Move pylint helper from dmlc-core. (#8101)

* Move pylint helper from dmlc-core.

- Move the helper into the XGBoost ci_build.
- Run it with multiprocessing.

* Fix original test.

tests/ci_build/lint_python.py

@@ -2,14 +2,17 @@ import argparse
 import os
 import subprocess
 import sys
+from multiprocessing import Pool, cpu_count
+from typing import Dict, Tuple
 
+from pylint import epylint
 from test_utils import DirectoryExcursion
 
 CURDIR = os.path.normpath(os.path.abspath(os.path.dirname(__file__)))
 PROJECT_ROOT = os.path.normpath(os.path.join(CURDIR, os.path.pardir, os.path.pardir))
 
 
-def run_formatter(rel_path: str):
+def run_formatter(rel_path: str) -> bool:
     path = os.path.join(PROJECT_ROOT, rel_path)
     isort_ret = subprocess.run(["isort", "--check", "--profile=black", path]).returncode
     black_ret = subprocess.run(
@@ -25,7 +28,7 @@ def run_formatter(rel_path: str):
     return True
 
 
-def run_mypy(rel_path: str):
+def run_mypy(rel_path: str) -> bool:
     with DirectoryExcursion(os.path.join(PROJECT_ROOT, "python-package")):
         path = os.path.join(PROJECT_ROOT, rel_path)
         ret = subprocess.run(["mypy", path])
@@ -34,16 +37,85 @@ def run_mypy(rel_path: str):
         return True
 
 
+class PyLint:
+    """A helper for running pylint, mostly copied from dmlc-core/scripts. """
+    def __init__(self) -> None:
+        self.pypackage_root = os.path.join(PROJECT_ROOT, "python-package/")
+        self.pylint_cats = set(["error", "warning", "convention", "refactor"])
+        self.pylint_opts = [
+            "--extension-pkg-whitelist=numpy",
+            "--rcfile=" + os.path.join(self.pypackage_root, ".pylintrc"),
+        ]
+
+    def run(self, path: str) -> Tuple[Dict, str, str]:
+        (pylint_stdout, pylint_stderr) = epylint.py_run(
+            " ".join([str(path)] + self.pylint_opts), return_std=True
+        )
+        emap = {}
+        err = pylint_stderr.read()
+
+        out = []
+        for line in pylint_stdout:
+            out.append(line)
+            key = line.split(":")[-1].split("(")[0].strip()
+            if key not in self.pylint_cats:
+                continue
+            if key not in emap:
+                emap[key] = 1
+            else:
+                emap[key] += 1
+
+        return {path: emap}, err, "\n".join(out)
+
+    def __call__(self) -> bool:
+        all_errors: Dict[str, Dict[str, int]] = {}
+
+        def print_summary_map(result_map: Dict[str, Dict[str, int]]) -> int:
+            """Print summary of certain result map."""
+            if len(result_map) == 0:
+                return 0
+            ftype = "Python"
+            npass = sum(1 for x in result_map.values() if len(x) == 0)
+            print(f"====={npass}/{len(result_map)} {ftype} files passed check=====")
+            for fname, emap in result_map.items():
+                if len(emap) == 0:
+                    continue
+                print(
+                    f"{fname}: {sum(emap.values())} Errors of {len(emap)} Categories map={str(emap)}"
+                )
+            return len(result_map) - npass
+
+        all_scripts = []
+        for root, dirs, files in os.walk(self.pypackage_root):
+            for f in files:
+                if f.endswith(".py"):
+                    all_scripts.append(os.path.join(root, f))
+
+        with Pool(cpu_count()) as pool:
+            error_maps = pool.map(self.run, all_scripts)
+            for emap, err, out in error_maps:
+                print(out)
+                if len(err) != 0:
+                    print(err)
+                all_errors.update(emap)
+
+        nerr = print_summary_map(all_errors)
+        return nerr == 0
+
+
 if __name__ == "__main__":
     parser = argparse.ArgumentParser()
     parser.add_argument("--format", type=int, choices=[0, 1], default=1)
     parser.add_argument("--type-check", type=int, choices=[0, 1], default=1)
+    parser.add_argument("--pylint", type=int, choices=[0, 1], default=1)
     args = parser.parse_args()
     if args.format == 1:
         if not all(
-            [
-                run_formatter("python-package/xgboost/dask.py"),
-                run_formatter("python-package/xgboost/spark"),
+            run_formatter(path)
+            for path in [
+                "python-package/xgboost/dask.py",
+                "python-package/xgboost/spark",
+                "tests/ci_build/lint_python.py",
             ]
         ):
             sys.exit(-1)
@@ -58,6 +130,11 @@ if __name__ == "__main__":
                 "tests/python/test_data_iterator.py",
                 "tests/python-gpu/test_gpu_with_dask.py",
                 "tests/python-gpu/test_gpu_data_iterator.py",
+                "tests/ci_build/lint_python.py",
             ]
         ):
             sys.exit(-1)
+
+    if args.pylint == 1:
+        if not PyLint()():
+            sys.exit(-1)