fix: Use CssParser to correctly pass options to wkhtmltopdf

- Regex incorrectly fetches .print-format's child styles and also extracts the wrong attribute value
- A CssParser is more maintainable and more readable as well as less prone to errors while extracting values
- Method: We extract style tag contents out of the html and tokenize them. We then filter the styles for the right selector and extract the attributes we want from them.
- This way we make sure that the right value is extracted and only the ones applicable to .print-format directly

(cherry picked from commit 5dbcbbb)

frappe/utils/pdf.py

@@ -5,10 +5,10 @@
 import io
 import mimetypes
 import os
-import re
 import subprocess
 from urllib.parse import parse_qs, urlparse
 
+import cssutils
 import pdfkit
 from bs4 import BeautifulSoup
 from packaging.version import Version
@@ -206,7 +206,8 @@ def read_options_from_html(html):
 
 	toggle_visible_pdf(soup)
 
-	# use regex instead of soup-parser
+	valid_styles = get_print_format_styles(soup)
+
 	for attr in (
 		"margin-top",
 		"margin-bottom",
@@ -218,17 +219,51 @@ def read_options_from_html(html):
 		"page-width",
 		"page-height",
 	):
-		try:
-			pattern = re.compile(r"(\.print-format)([\S|\s][^}]*?)(" + str(attr) + r":)(.+)(mm;)")
-			match = pattern.findall(html)
-			if match:
-				options[attr] = str(match[-1][3]).strip()
-		except Exception:
-			pass
+		for style in valid_styles:
+			if attr == style.name:
+				options[attr] = style.value
 
 	return str(soup), options
 
 
+def get_print_format_styles(soup: BeautifulSoup) -> list[cssutils.css.Property]:
+	"""
+	Get styles purely on class 'print-format'.
+	Valid:
+	1) .print-format { ... }
+	2) .print-format, p { ... } | p, .print-format { ... }
+
+	Invalid (applied on child elements):
+	1) .print-format p { ... } | .print-format > p { ... }
+	2) .print-format #abc { ... }
+
+	Returns:
+	[cssutils.css.Property(name='margin-top', value='50mm', priority=''), ...]
+	"""
+	stylesheet = ""
+	style_tags = soup.find_all("style")
+
+	# Prepare a css stylesheet from all the style tags' contents
+	for style_tag in style_tags:
+		stylesheet += style_tag.string
+
+	# Use css parser to tokenize the classes and their styles
+	parsed_sheet = cssutils.parseString(stylesheet)
+
+	# Get all styles that are only for .print-format
+	valid_styles = []
+	for rule in parsed_sheet:
+		if not isinstance(rule, cssutils.css.CSSStyleRule):
+			continue
+
+		# Allow only .print-format { ... } and .print-format, p { ... }
+		# Disallow .print-format p { ... } and .print-format > p { ... }
+		if ".print-format" in [x.strip() for x in rule.selectorText.split(",")]:
+			valid_styles.extend(entry for entry in rule.style)
+
+	return valid_styles
+
+
 def inline_private_images(html) -> str:
 	soup = BeautifulSoup(html, "html.parser")
 	for img in soup.find_all("img"):

pyproject.toml

@@ -35,6 +35,7 @@ dependencies = [
     "chardet~=5.1.0",
     "croniter~=2.0.1",
     "cryptography~=42.0.0",
+    "cssutils~=2.9.0",
     "email-reply-parser~=0.5.12",
     "git-url-parse~=1.2.2",
     "gunicorn~=21.2.0",