hugolib: Allow override of sitemap file name

Closes #12525

hugolib/content_map_page.go

@@ -1881,11 +1881,19 @@ func (sa *sitePagesAssembler) addStandalonePages() error {
 	}
 
 	if sitemapEnabled {
-		addStandalone("/_sitemap", kinds.KindSitemap, output.SitemapFormat)
+		of := output.SitemapFormat
-		skipSitemapIndex := s.Conf.IsMultihost() || !(s.Conf.DefaultContentLanguageInSubdir() || s.Conf.IsMultilingual())
+		if s.conf.Sitemap.Filename != "" {
+			of.BaseName = paths.Filename(s.conf.Sitemap.Filename)
+		}
+		addStandalone("/_sitemap", kinds.KindSitemap, of)
 
+		skipSitemapIndex := s.Conf.IsMultihost() || !(s.Conf.DefaultContentLanguageInSubdir() || s.Conf.IsMultilingual())
 		if !skipSitemapIndex {
-			addStandalone("/_sitemapindex", kinds.KindSitemapIndex, output.SitemapIndexFormat)
+			of = output.SitemapIndexFormat
+			if s.conf.Sitemap.Filename != "" {
+				of.BaseName = paths.Filename(s.conf.Sitemap.Filename)
+			}
+			addStandalone("/_sitemapindex", kinds.KindSitemapIndex, of)
 		}
 	}
 

hugolib/content_map_test.go

@@ -16,6 +16,7 @@ package hugolib
 import (
 	"fmt"
 	"path/filepath"
+	"strings"
 	"testing"
 
 	qt "github.com/frankban/quicktest"
@@ -358,3 +359,41 @@ p1-foo.txt
 	b.AssertFileExists("public/s1/p1-foo.txt", true) // failing test
 	b.AssertFileExists("public/s1/p1/index.html", true)
 }
+
+func TestSitemapOverrideFilename(t *testing.T) {
+	t.Parallel()
+
+	files := `
+-- hugo.toml --
+baseURL = 'https://example.org/'
+disableKinds = ['page','rss','section','taxonomy','term']
+defaultContentLanguage = 'de'
+defaultContentLanguageInSubdir = true
+[languages.de]
+[languages.en]
+[sitemap]
+filename = 'foo.xml'
+-- layouts/index.html --
+irrelevant
+`
+
+	b := Test(t, files)
+
+	b.AssertFileExists("public/de/foo.xml", true)
+	b.AssertFileExists("public/en/foo.xml", true)
+	b.AssertFileContent("public/foo.xml",
+		"<loc>https://example.org/de/foo.xml</loc>",
+		"<loc>https://example.org/en/foo.xml</loc>",
+	)
+
+	files = strings.ReplaceAll(files, "filename = 'foo.xml'", "")
+
+	b = Test(t, files)
+
+	b.AssertFileExists("public/de/sitemap.xml", true)
+	b.AssertFileExists("public/en/sitemap.xml", true)
+	b.AssertFileContent("public/sitemap.xml",
+		"<loc>https://example.org/de/sitemap.xml</loc>",
+		"<loc>https://example.org/en/sitemap.xml</loc>",
+	)
+}