Mark build-support Python files as Pants targets to lint build-support (

pantsbuild#7633)

### Converting to Pants targets
Now that we have two Python scripts, and may have more scripts in the future, there is value in linting our script code.

By making these two scripts as targets, we can now use `./pants fmt`, `./pants lint`, and `./pants mypy` on the build-support folder for little cost.

The pre-commit check will check `./pants fmt` and `./pants lint` automatically on the `build-support` Python files now. It will not do the header check until we explicitly add the folder.

### Add `common.py`
We also add `common.py` to reduce duplication and simplify writing scripts.

See the `NB` in that file about why we only use the stdlib for that file.

build-support/bin/BUILD

@@ -0,0 +1,22 @@
+# Copyright 2019 Pants project contributors (see CONTRIBUTORS.md).
+# Licensed under the Apache License, Version 2.0 (see LICENSE).
+
+python_library(
+  name = 'common',
+  sources = 'common.py',
+  compatibility = ['CPython>=3.6'],
+)
+
+python_binary(
+  name = 'check_header_helper',
+  sources = 'check_header_helper.py',
+)
+
+python_binary(
+  name = 'check_pants_pex_abi',
+  sources = 'check_pants_pex_abi.py',
+  dependencies = [
+    ':common',
+  ],
+  compatibility = ['CPython>=3.6'],
+)

build-support/bin/check_header_helper.py

@@ -16,6 +16,7 @@
 import sys
 from io import open
 
+
 EXPECTED_HEADER="""# coding=utf-8
 # Copyright YYYY Pants project contributors (see CONTRIBUTORS.md).
 # Licensed under the Apache License, Version 2.0 (see LICENSE).

build-support/bin/check_pants_pex_abi.py

@@ -9,10 +9,7 @@
 import zipfile
 from pathlib import Path
 
-
-RED = "\033[31m"
-BLUE = "\033[34m"
-RESET = "\033[0m"
+from common import die, green
 
 
 def main() -> None:
@@ -32,7 +29,7 @@ def main() -> None:
   if not parsed_abis.issubset(expected_abis):
     die("pants.pex was built with the incorrect ABI. Expected wheels with: {}, found: {}."
         .format(' or '.join(sorted(expected_abis)), ', '.join(sorted(parsed_abis))))
-  success("Success. The pants.pex was built with wheels carrying the expected ABIs: {}."
+  green("Success. The pants.pex was built with wheels carrying the expected ABIs: {}."
           .format(', '.join(sorted(parsed_abis))))
 
 
@@ -52,13 +49,5 @@ def parse_abi_from_filename(filename: str) -> str:
   return filename.split("-")[-2]
 
 
-def success(message: str) -> None:
-  print(f"{BLUE}{message}{RESET}")
-
-
-def die(message: str) -> None:
-  raise SystemExit(f"{RED}{message}{RESET}")
-
-
 if __name__ == "__main__":
   main()

build-support/bin/common.py

@@ -0,0 +1,81 @@
+# Copyright 2019 Pants project contributors (see CONTRIBUTORS.md).
+# Licensed under the Apache License, Version 2.0 (see LICENSE).
+
+"""Utils for scripts to interface with the outside world.
+
+NB: We intentionally only use the standard library here, rather than using
+Pants code and/or 3rd-party dependencies like `colors`, to ensure that all
+scripts that import this file may still be invoked directly, rather than having
+to run via `./pants run`.
+
+We want to allow direct invocation of scripts for these reasons:
+1) Consistency with how we invoke Bash scripts, which notably may _not_ be ran via `./pants run`.
+2) More ergonomic command line arguments, e.g. `./build-support/bin/check_header.py src tests`,
+   rather than `./pants run build-support/bin:check_header -- src tests`.
+3) Avoid undesired dependencies on Pants for certain scripts. For example, `shellcheck.py`
+   lints the `./pants` script, and we would like the script to still work even if `./pants`
+   breaks. If we had to rely on invoking via `./pants run`, this would not be possible.
+
+Callers of this file, however, are free to dogfood Pants as they'd like, and any script
+may be called via `./pants run` instead of direct invocation if desired."""
+
+import time
+from contextlib import contextmanager
+from pathlib import Path
+from typing import Iterator, Tuple
+
+
+_SCRIPT_START_TIME = time.time()
+
+_CLEAR_LINE = "\x1b[K"
+_COLOR_BLUE = "\x1b[34m"
+_COLOR_RED = "\x1b[31m"
+_COLOR_GREEN = "\x1b[32m"
+_COLOR_RESET = "\x1b[0m"
+
+
+def die(message: str) -> None:
+  raise SystemExit(f"{_COLOR_RED}{message}{_COLOR_RESET}")
+
+
+def green(message: str) -> None:
+  print(f"{_COLOR_GREEN}{message}{_COLOR_RESET}")
+
+
+def banner(message: str) -> None:
+  minutes, seconds = elapsed_time()
+  print(f"{_COLOR_BLUE}[=== {minutes:02d}:{seconds:02d} {message} ===]{_COLOR_RESET}")
+
+
+def elapsed_time() -> Tuple[int, int]:
+  now = time.time()
+  elapsed_seconds = int(now - _SCRIPT_START_TIME)
+  return elapsed_seconds // 60, elapsed_seconds % 60
+
+
+@contextmanager
+def travis_section(slug: str, message: str) -> Iterator[None]:
+  travis_fold_state = "/tmp/.travis_fold_current"
+
+  def travis_fold(action: str, target: str) -> None:
+    print(f"travis_fold:{action}:{target}\r{_CLEAR_LINE}", end="")
+
+  def read_travis_fold_state() -> str:
+    with open(travis_fold_state, "r") as f:
+      return f.readline()
+
+  def write_slug_to_travis_fold_state() -> None:
+    with open(travis_fold_state, "w") as f:
+      f.write(slug)
+
+  def remove_travis_fold_state() -> None:
+    Path(travis_fold_state).unlink()
+
+  travis_fold("start", slug)
+  write_slug_to_travis_fold_state()
+  banner(message)
+  try:
+    yield
+  finally:
+    travis_fold("end", read_travis_fold_state())
+    remove_travis_fold_state()

build-support/githooks/pre-commit

@@ -18,6 +18,8 @@ DIRS_TO_CHECK=(
   pants-plugins
   examples
   contrib
+  # TODO(6071): Add `build-support/bin` once we update the check_header_helper.py script to
+  # allow Python 3 headers (i.e. without __future__ and coding=utf-8).
 )
 
 # TODO(#7068): Fix all these checks to only act on staged files with

testprojects/src/python/no_build_file/dummy.py

@@ -0,0 +1 @@
+# An empty python file.

tests/python/pants_test/engine/legacy/test_graph_integration.py

@@ -24,6 +24,8 @@ def use_pantsd_env_var(cls):
     """
     return False
 
+  _NO_BUILD_FILE_TARGET_BASE = 'testprojects/src/python/no_build_file'
+
   _SOURCES_TARGET_BASE = 'testprojects/src/python/sources'
 
   _SOURCES_ERR_MSGS = {
@@ -146,10 +148,7 @@ def test_existing_bundles(self):
     self.assertNotIn("WARN]", pants_run.stderr_data)
 
   def test_existing_directory_with_no_build_files_fails(self):
-    options = [
-        '--pants-ignore=+["/build-support/bin/native/src"]',
-      ]
-    pants_run = self.run_pants(options + ['list', 'build-support/bin::'])
+    pants_run = self.run_pants(['list', "{}::".format(self._NO_BUILD_FILE_TARGET_BASE)])
     self.assert_failure(pants_run)
     self.assertIn("does not match any targets.", pants_run.stderr_data)