Add --printUnusedTemplates

Fixes #9502

tpl/tplimpl/integration_test.go

@@ -0,0 +1,61 @@
+package tplimpl_test
+
+import (
+	"path/filepath"
+	"testing"
+
+	qt "github.com/frankban/quicktest"
+	"github.com/gohugoio/hugo/hugolib"
+	"github.com/gohugoio/hugo/tpl"
+)
+
+func TestPrintUnusedTemplates(t *testing.T) {
+	t.Parallel()
+
+	files := `
+-- config.toml --
+baseURL = 'http://example.com/'
+printUnusedTemplates=true
+-- content/p1.md --
+---
+title: "P1"
+---
+{{< usedshortcode >}}
+-- layouts/baseof.html --
+{{ block "main" . }}{{ end }}
+-- layouts/baseof.json --
+{{ block "main" . }}{{ end }}
+-- layouts/index.html --
+{{ define "main" }}FOO{{ end }}
+-- layouts/_default/single.json --
+-- layouts/_default/single.html --
+{{ define "main" }}MAIN{{ end }}
+-- layouts/post/single.html --
+{{ define "main" }}MAIN{{ end }}
+-- layouts/partials/usedpartial.html --
+-- layouts/partials/unusedpartial.html --
+-- layouts/shortcodes/usedshortcode.html --
+{{ partial "usedpartial.html" }}
+-- layouts/shortcodes/unusedshortcode.html --
+
+	`
+
+	b := hugolib.NewIntegrationTestBuilder(
+		hugolib.IntegrationTestConfig{
+			T:           t,
+			TxtarString: files,
+			NeedsOsFS:   true,
+		},
+	)
+	b.Build()
+
+	unused := b.H.Tmpl().(tpl.UnusedTemplatesProvider).UnusedTemplates()
+
+	var names []string
+	for _, tmpl := range unused {
+		names = append(names, tmpl.Name())
+	}
+
+	b.Assert(names, qt.DeepEquals, []string{"_default/single.json", "baseof.json", "partials/unusedpartial.html", "post/single.html", "shortcodes/unusedshortcode.html"})
+	b.Assert(unused[0].Filename(), qt.Equals, filepath.Join(b.Cfg.WorkingDir, "layouts/_default/single.json"))
+}