scripts: check-variable-fonts.sh: convert to Python

This script handle errors when trying to build translations
with make pdfdocs.

As part of our cleanup work to remove hacks from docs Makefile,
convert this to python, preparing it to be part of a library
to be called by sphinx-build-wrapper.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Message-ID: <d438fb01d2c00e2c2b4ac16f999d9a8ce848251b.1758196090.git.mchehab+huawei@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/Makefile

@@ -149,7 +149,7 @@ pdfdocs: DENY_VF = XDG_CONFIG_HOME=$(FONTS_CONF_DENY_VF)
 pdfdocs: latexdocs
 	@$(srctree)/scripts/sphinx-pre-install --version-check
 	$(foreach var,$(SPHINXDIRS), \
-	   $(MAKE) PDFLATEX="$(PDFLATEX)" LATEXOPTS="$(LATEXOPTS)" $(DENY_VF) -C $(BUILDDIR)/$(var)/latex || sh $(srctree)/scripts/check-variable-fonts.sh || exit; \
+	   $(MAKE) PDFLATEX="$(PDFLATEX)" LATEXOPTS="$(LATEXOPTS)" $(DENY_VF) -C $(BUILDDIR)/$(var)/latex || $(PYTHON3) $(srctree)/scripts/check-variable-fonts.py || exit; \
 	   mkdir -p $(BUILDDIR)/$(var)/pdf; \
 	   mv $(subst .tex,.pdf,$(wildcard $(BUILDDIR)/$(var)/latex/*.tex)) $(BUILDDIR)/$(var)/pdf/; \
 	)

MAINTAINERS

@@ -7301,7 +7301,7 @@ S:	Maintained
 P:	Documentation/doc-guide/maintainer-profile.rst
 T:	git git://git.lwn.net/linux.git docs-next
 F:	Documentation/
-F:	scripts/check-variable-fonts.sh
+F:	scripts/check-variable-fonts.py
 F:	scripts/checktransupdate.py
 F:	scripts/documentation-file-ref-check
 F:	scripts/get_abi.py

scripts/check-variable-fonts.py

@@ -1,7 +1,9 @@
-#!/bin/sh
+#!/usr/bin/env python3
 # SPDX-License-Identifier: GPL-2.0-only
 # Copyright (C) Akira Yokosawa, 2024
 #
+# Ported to Python by (c) Mauro Carvalho Chehab, 2025
+#
 # For "make pdfdocs", reports of build errors of translations.pdf started
 # arriving early 2024 [1, 2].  It turned out that Fedora and openSUSE
 # tumbleweed have started deploying variable-font [3] format of "Noto CJK"
@@ -87,29 +89,77 @@
 #     Denylisting should be less invasive, as it is effective only while
 #     XeLaTeX runs in "make pdfdocs".
 
-# Default per-user fontconfig path (overridden by env variable)
-: ${FONTS_CONF_DENY_VF:=$HOME/deny-vf}
+import os
+import re
+import subprocess
+import sys
+import textwrap
 
-export XDG_CONFIG_HOME=${FONTS_CONF_DENY_VF}
+class LatexFontChecker:
+    """
+    Detect problems with CJK variable fonts that affect PDF builds for
+    translations.
+    """
 
-notocjkvffonts=`fc-list : file family variable | \
-		grep 'variable=True' | \
-		grep -E -e 'Noto (Sans|Sans Mono|Serif) CJK' | \
-		sed -e 's/^/    /' -e 's/: Noto S.*$//' | sort | uniq`
+    def __init__(self):
+        deny_vf = os.environ.get('FONTS_CONF_DENY_VF', "~/deny-vf")
 
-if [ "x$notocjkvffonts" != "x" ] ; then
-	echo '============================================================================='
-	echo 'XeTeX is confused by "variable font" files listed below:'
-	echo "$notocjkvffonts"
-	echo
-	echo 'For CJK pages in PDF, they need to be hidden from XeTeX by denylisting.'
-	echo 'Or, CJK pages can be skipped by uninstalling texlive-xecjk.'
-	echo
-	echo 'For more info on denylisting, other options, and variable font, see header'
-	echo 'comments of scripts/check-variable-fonts.sh.'
-	echo '============================================================================='
-fi
+        self.environ = os.environ.copy()
+        self.environ['XDG_CONFIG_HOME'] = os.path.expanduser(deny_vf)
 
-# As this script is invoked from Makefile's error path, always error exit
-# regardless of whether any variable font is discovered or not.
-exit 1
+        self.re_cjk = re.compile(r"([^:]+):\s*Noto\s+(Sans|Sans Mono|Serif) CJK")
+
+    def get_noto_cjk_vf_fonts(self):
+        """Get Noto CJK fonts"""
+
+        cjk_fonts = set()
+        cmd = ["fc-list", ":", "file", "family", "variable"]
+        try:
+            result = subprocess.run(cmd,stdout=subprocess.PIPE,
+                                    stderr=subprocess.PIPE,
+                                    universal_newlines=True,
+                                    env=self.environ,
+                                    check=True)
+
+        except subprocess.CalledProcessError as exc:
+            sys.exit(f"Error running fc-list: {repr(exc)}")
+
+        for line in result.stdout.splitlines():
+            if 'variable=True' not in line:
+                continue
+
+            match = self.re_cjk.search(line)
+            if match:
+                cjk_fonts.add(match.group(1))
+
+        return sorted(cjk_fonts)
+
+    def check(self):
+        """Check for problems with CJK fonts"""
+
+        fonts = textwrap.indent("\n".join(self.get_noto_cjk_vf_fonts()), "    ")
+        if not fonts:
+            return None
+
+        rel_file = os.path.relpath(__file__, os.getcwd())
+
+        msg = "=" * 77 + "\n"
+        msg += 'XeTeX is confused by "variable font" files listed below:\n'
+        msg += fonts + "\n"
+        msg += textwrap.dedent(f"""
+                For CJK pages in PDF, they need to be hidden from XeTeX by denylisting.
+                Or, CJK pages can be skipped by uninstalling texlive-xecjk.
+
+                For more info on denylisting, other options, and variable font, see header
+                comments of {rel_file}.
+            """)
+        msg += "=" * 77
+
+        return msg
+
+if __name__ == "__main__":
+    msg = LatexFontChecker().check()
+    if msg:
+        print(msg)
+
+    sys.exit(1)