hugolib: Fix regression for blank summaries

Fix regression in content summarization so that we can use empty
summary by using the manual summary divider. Since v0.123, there
has been the regression that causes Hugo to use automatic summary
generation when the manual summary results in an empty string,
even if there is a `<!--more-->` summary divider.

2 files changed, 26 insertions, 1 deletions

diff --git a/hugolib/page__content.go b/hugolib/page__content.go
index 62e78c612..54f7be961 100644
--- a/hugolib/page__content.go
+++ b/hugolib/page__content.go
@@ -770,7 +770,7 @@ func (c *cachedContent) contentPlain(ctx context.Context, cp *pageContentOutput)
 			result.readingTime = (result.wordCount + 212) / 213
 		}
 
-		if rendered.summary != "" {
+		if c.pi.hasSummaryDivider || rendered.summary != "" {
 			result.summary = rendered.summary
 			result.summaryTruncated = rendered.summaryTruncated
 		} else if cp.po.p.m.pageConfig.Summary != "" {
diff --git a/hugolib/page_test.go b/hugolib/page_test.go
index f22a4d07c..8919c246c 100644
--- a/hugolib/page_test.go
+++ b/hugolib/page_test.go
@@ -65,6 +65,15 @@ Summary Next Line
 Some more text
 `
 
+	simplePageWithBlankSummary = `---
+title: SimpleWithBlankSummary
+---
+
+<!--more-->
+
+Some text.
+`
+
 	simplePageWithSummaryParameter = `---
 title: SimpleWithSummaryParameter
 summary: "Page with summary parameter and [a link](http://www.example.com/)"
@@ -351,6 +360,9 @@ func normalizeExpected(ext, str string) string {
 
 		return expected
 	case "rst":
+		if str == "" {
+			return "<div class=\"document\"></div>"
+		}
 		return fmt.Sprintf("<div class=\"document\">\n\n\n%s</div>", str)
 	}
 }
@@ -630,6 +642,19 @@ func TestPageWithDelimiter(t *testing.T) {
 	testAllMarkdownEnginesForPages(t, assertFunc, nil, simplePageWithSummaryDelimiter)
 }
 
+func TestPageWithBlankSummary(t *testing.T) {
+	t.Parallel()
+	assertFunc := func(t *testing.T, ext string, pages page.Pages) {
+		p := pages[0]
+		checkPageTitle(t, p, "SimpleWithBlankSummary")
+		checkPageContent(t, p, normalizeExpected(ext, "<p>Some text.</p>\n"), ext)
+		checkPageSummary(t, p, normalizeExpected(ext, ""), ext)
+		checkPageType(t, p, "page")
+	}
+
+	testAllMarkdownEnginesForPages(t, assertFunc, nil, simplePageWithBlankSummary)
+}
+
 func TestPageWithSummaryParameter(t *testing.T) {
 	t.Parallel()
 	assertFunc := func(t *testing.T, ext string, pages page.Pages) {