chore: warn if wkhtmltopdf is invalid (#26174)

* chore: warn if wkhtmltopdf is invalid

wkhtmltopdf ( with patched qt ) is required to generate pdfs properly.
when user clicks on PDF, pdf will be generated and downloaded.
however, on print preview page warning will be shown.

* chore: refactor based on review comments

* chore: return False incase of exception

* chore: refactor and better naming

Co-authored-by: Ankush Menat <ankushmenat@gmail.com>
(cherry picked from commit 6a6ded1)

frappe/printing/page/print/print.js

@@ -603,7 +603,24 @@ frappe.ui.form.PrintView = class {
 			},
 		});
 	}
-
+	async is_wkhtmltopdf_valid() {
+		const is_valid = await frappe.xcall("frappe.utils.pdf.is_wkhtmltopdf_valid");
+		// function returns true or false
+		if (is_valid) return;
+		frappe.msgprint({
+			title: __("Invalid wkhtmltopdf version"),
+			message:
+				__("PDF generation may not work as expected.") +
+				"<hr/>" +
+				__("Please contact your system manager to install correct version.") +
+				"<br/>" +
+				__("Correct version :") +
+				" <b><a href ='https://wkhtmltopdf.org/downloads.html'>" +
+				__("wkhtmltopdf 0.12.x (with patched qt).") +
+				"</a></b>",
+			indicator: "red",
+		});
+	}
 	render_pdf() {
 		let print_format = this.get_print_format();
 		if (print_format.print_format_builder_beta) {
@@ -619,6 +636,7 @@ frappe.ui.form.PrintView = class {
 				return;
 			}
 		} else {
+			this.is_wkhtmltopdf_valid();
 			this.render_page("/api/method/frappe.utils.print_format.download_pdf?");
 		}
 	}

frappe/utils/pdf.py

@@ -18,6 +18,7 @@
 from frappe import _
 from frappe.core.doctype.file.utils import find_file_by_url
 from frappe.utils import cstr, scrub_urls
+from frappe.utils.caching import redis_cache
 from frappe.utils.jinja_globals import bundled_asset, is_rtl
 
 PDF_CONTENT_ERRORS = [
@@ -352,6 +353,16 @@ def toggle_visible_pdf(soup):
 		tag.extract()
 
 
+@frappe.whitelist()
+@redis_cache(ttl=60 * 60)
+def is_wkhtmltopdf_valid():
+	try:
+		output = subprocess.check_output(["wkhtmltopdf", "--version"])
+		return "qt" in output.decode("utf-8").lower()
+	except Exception:
+		return False
+
+
 def get_wkhtmltopdf_version():
 	wkhtmltopdf_version = frappe.cache.hget("wkhtmltopdf_version", None)