xwayland/ci: Enforce various code style checks

Make sure the code change does not contain tab characters nor stray
newlines.

This is contributed by Peter Hutterer, adapted from the libinput similar
CI check.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Signed-off-by: Olivier Fourdan <ofourdan@redhat.com>
Part-of: <https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/2121>
(cherry picked from commit 9c31b4ad8f)

.gitlab-ci.yml

@@ -334,6 +334,13 @@ check-commits:
       junit: results.xml
   allow_failure: true
 
+check-whitespace:
+  extends:
+    - .fdo.ci-fairy
+  stage: test
+  script:
+    - .gitlab-ci/whitespace-check.py $(git ls-files hw/xwayland)
+
 #
 # Workflow rules needed due to:
 # https://gitlab.freedesktop.org/freedesktop/freedesktop/-/issues/438

.gitlab-ci/whitespace-check.py

@@ -0,0 +1,133 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: MIT
+
+from pathlib import Path
+from dataclasses import dataclass
+
+import argparse
+import itertools
+import os
+import re
+import sys
+
+
+@dataclass
+class WhitespaceError:
+    message: str
+    lineno: int
+    nlines: int = 1
+    column: None | int = None
+    ncolumns: int = 1
+
+
+def test_tab_indent(lines: list[str]) -> list[WhitespaceError]:
+    errors = []
+    for idx, l in enumerate(lines):
+        if re.match("^\t+.*", l):
+            errors.append(
+                WhitespaceError(
+                    "Tab indent", idx, ncolumns=2
+                )
+            )
+    return errors
+
+
+def test_duplicate_empty_lines(lines: list[str]) -> list[WhitespaceError]:
+    errors = []
+    for idx, (l1, l2) in enumerate(itertools.pairwise(lines)):
+        if not l1 and not l2:
+            errors.append(WhitespaceError("Duplicated empty lines", idx, nlines=2))
+    return errors
+
+
+def test_tab_after_space(lines: list[str]) -> list[WhitespaceError]:
+    errors = []
+    for idx, l in enumerate(lines):
+        index = l.find(" \t")
+        if index > -1:
+            errors.append(
+                WhitespaceError(
+                    "Tab after space", idx, nlines=index, column=index, ncolumns=2
+                )
+            )
+    return errors
+
+
+def test_trailing_whitespace(lines: list[str]) -> list[WhitespaceError]:
+    errors = []
+    for idx, l in enumerate(lines):
+        if l.rstrip() != l:
+            errors.append(WhitespaceError("Trailing whitespace", idx))
+    return errors
+
+
+def test_empty_line_between_braces(lines: list[str]) -> list[WhitespaceError]:
+    errors = []
+    for idx in range(len(lines) - 3):
+        l1 = lines[idx]
+        l2 = lines[idx + 1]
+        l3 = lines[idx + 2]
+        if l1.strip() == "}" and l3.strip() == "}" and l2.strip() == "":
+            errors.append(WhitespaceError("Empty line between closing braces", idx + 1))
+    return errors
+
+
+def main():
+    parser = argparse.ArgumentParser(description="Whitespace checker script")
+    parser.add_argument(
+        "files",
+        metavar="FILES",
+        type=Path,
+        nargs="+",
+        help="The files to check",
+    )
+
+    args = parser.parse_args()
+
+    have_errors: bool = False
+
+    if os.isatty(sys.stderr.fileno()):
+        red = "\x1b[0;31m"
+        reset = "\x1b[0m"
+    else:
+        red = ""
+        reset = ""
+
+    for file in args.files:
+        lines = [l.rstrip("\n") for l in file.open().readlines()]
+
+        errors = []
+        errors.extend(test_tab_indent(lines))
+        errors.extend(test_tab_after_space(lines))
+        errors.extend(test_trailing_whitespace(lines))
+        if any(file.name.endswith(suffix) for suffix in [".c", ".h"]):
+            if not file.parts[0] == "include":
+                errors.extend(test_duplicate_empty_lines(lines))
+                errors.extend(test_empty_line_between_braces(lines))
+
+        for e in errors:
+            print(f"{red}ERROR: {e.message} in {file}:{reset}", file=sys.stderr)
+            print(f"{'-' * 72}", file=sys.stderr)
+            lineno = max(0, e.lineno - 5)
+            for idx, l in enumerate(lines[lineno : lineno + 10]):
+                if e.lineno <= lineno + idx < e.lineno + e.nlines:
+                    prefix = "->"
+                    hl = red
+                    nohl = reset
+                else:
+                    prefix = "  "
+                    hl = ""
+                    nohl = ""
+                print(f"{hl}{lineno + idx:3d}: {prefix} {l.rstrip()}{nohl}")
+
+            print(f"{'-' * 72}", file=sys.stderr)
+
+        if errors:
+            have_errors = True
+
+    if have_errors:
+        sys.exit(1)
+
+
+if __name__ == "__main__":
+    main()