Run Nu HTML Checker with both HTML and XML parsers

Requires silencing an HTML-only error that isn't actually an error, but
a hint that doesn't apply to polygot markup (warns against trailing
slashes which aren't a problem if you always use quotes).

linter-configs/vnu_filter.jq

@@ -1,26 +1,27 @@
 # Filter false positives from the .messages entry of Nu Validator output
 .messages |= map(
 	. | select(
+		.type == "info" and (
+			.message == "Trailing slash on void elements has no effect and interacts badly with unquoted attribute values."
+			and (.url | test(".html"))
+		) or
 		.type == "error" and (
-			( # See https://github.com/w3c/css-validator/issues/361
-				.message == "CSS: Parse Error."
-				and .extract == "){outline:none}}@media(prefers"
-				and .hiliteLength == 1
-			)
-			or
 			( # See https://github.com/validator/validator/issues/1166
 			  # This false-positive has been fixed; will remove once validator.nu updates
 				# validator.w3.org/nu is up-to-date.
 				.message == "Attribute “media” not allowed on element “meta” at this point."
 				and (.extract | test(" name=\"theme-color\""))
-			)
+			) or
-			or
 			( # see https://github.com/w3c/css-validator/issues/369
 				.message == "CSS: “contain-intrinsic-size”: Property “contain-intrinsic-size” doesn't exist."
-			)
+			) or
-			or
 			( # see https://github.com/w3c/css-validator/issues/370
 				.message == "CSS: “contain”: “inline-size” is not a “contain” value."
+			) or
+			( # See https://github.com/w3c/css-validator/issues/361
+				.message == "CSS: Parse Error."
+				and .extract == "){outline:none}}@media(prefers"
+				and .hiliteLength == 1
 			)
 		) | not
 	)

scripts/vnu.sh

@@ -1,16 +1,28 @@
 #!/bin/sh
+
+# Runs the Nu HTML checker (assumed to be available on your $PATH as `vnu`) on all pages.
+
+#shellcheck disable=SC3040  # This only sets pipefail if it's available and otherwise does nothing
+set -o pipefail 2>/dev/null || true
 set -e -u
 dirname="$(dirname "$0")"
 output_dir="$1"
 
+# List all HTML, XHTML, and SVG files we wish to check.
+# We test both XHTML and HTML files, despite the fact that they are identical, because we want to validate under both an HTML and XML parser. VNU has some HTML-only checks.
 find_files_to_analyze() {
-	find "$output_dir" -type f -name '*.xhtml' -o -name '*.svg' \
+	find "$output_dir" -type f -name '*.html' -o -name '*.xhtml' -o -name '*.svg' \
 		| grep -Ev '(bimi\.svg|search/index\.x?html)$'
 }
 
+# Force a non-zero exit code for vnu. We'll decide the exit status after filtering out false-posives.
+vnu_nofail() {
+	xargs vnu --stdout --format json --also-check-svg || true
+}
+
 # files_to_analyze="$(find_files_to_analyze)"
 
 # we skip the BIMI icon (VNU can't handle SVG 1.2) and the search page (it has raw templates).
 find_files_to_analyze \
-	| xargs vnu --stdout --format json --also-check-svg \
+	| vnu_nofail \
 	| sh "$dirname/filter-vnu.sh"