tpl/fmt: Print suppression help with erroridf

Closes #11506

tpl/fmt/fmt.go

@@ -68,6 +68,8 @@ func (ns *Namespace) Errorf(format string, args ...any) string {
 // an information text that the error with the given id can be suppressed in config.
 // It returns an empty string.
 func (ns *Namespace) Erroridf(id, format string, args ...any) string {
+	format += "\nYou can suppress this error by adding the following to your site configuration:\nignoreErrors = ['%s']"
+	args = append(args, id)
 	ns.logger.Errorsf(id, format, args...)
 	return ""
 }

tpl/fmt/integration_test.go

@@ -0,0 +1,45 @@
+// Copyright 2023 The Hugo Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package fmt_test
+
+import (
+	"testing"
+
+	"github.com/gohugoio/hugo/hugolib"
+)
+
+// Issue #11506
+func TestErroridf(t *testing.T) {
+	t.Parallel()
+
+	files := `
+-- hugo.toml --
+disableKinds = ['page','rss','section','sitemap','taxonomy','term']
+ignoreErrors = ['error-b']
+-- layouts/index.html --
+{{ erroridf "error-a" "%s" "a"}}
+{{ erroridf "error-b" "%s" "b"}}
+  `
+
+	b := hugolib.NewIntegrationTestBuilder(
+		hugolib.IntegrationTestConfig{
+			T:           t,
+			TxtarString: files,
+		},
+	)
+
+	b.BuildE()
+	b.AssertLogMatches(`^ERROR a\nYou can suppress this error by adding the following to your site configuration:\nignoreErrors = \['error-a'\]\n$`)
+
+}