Change SummaryLength to be configurable (#3924)

Move SummaryLength into the ContentSpec struct and refactor the
relevant summary functions to be methods of ContentSpec. The new
summaryLength struct member is configurable by the summaryLength config
value, and the default remains 70. Also updates hugolib/page to use the
refactored methods.

Resolves #3734

2 files changed, 25 insertions, 19 deletions

diff --git a/helpers/content.go b/helpers/content.go
index 7f5975869..a79da090b 100644
--- a/helpers/content.go
+++ b/helpers/content.go
@@ -36,9 +36,6 @@ import (
 	"strings"
 )
 
-// SummaryLength is the length of the summary that Hugo extracts from a content.
-var SummaryLength = 70
-
 // SummaryDivider denotes where content summarization should end. The default is "<!--more-->".
 var SummaryDivider = []byte("<!--more-->")
 
@@ -47,6 +44,8 @@ type ContentSpec struct {
 	blackfriday                map[string]interface{}
 	footnoteAnchorPrefix       string
 	footnoteReturnLinkContents string
+	// SummaryLength is the length of the summary that Hugo extracts from a content.
+	summaryLength int
 
 	Highlight            func(code, lang, optsStr string) (string, error)
 	defatultPygmentsOpts map[string]string
@@ -61,6 +60,7 @@ func NewContentSpec(cfg config.Provider) (*ContentSpec, error) {
 		blackfriday:                cfg.GetStringMap("blackfriday"),
 		footnoteAnchorPrefix:       cfg.GetString("footnoteAnchorPrefix"),
 		footnoteReturnLinkContents: cfg.GetString("footnoteReturnLinkContents"),
+		summaryLength:              cfg.GetInt("summaryLength"),
 
 		cfg: cfg,
 	}
@@ -480,20 +480,20 @@ func totalWordsOld(s string) int {
 }
 
 // TruncateWordsByRune truncates words by runes.
-func TruncateWordsByRune(words []string, max int) (string, bool) {
+func (c *ContentSpec) TruncateWordsByRune(words []string) (string, bool) {
 	count := 0
 	for index, word := range words {
-		if count >= max {
+		if count >= c.summaryLength {
 			return strings.Join(words[:index], " "), true
 		}
 		runeCount := utf8.RuneCountInString(word)
 		if len(word) == runeCount {
 			count++
-		} else if count+runeCount < max {
+		} else if count+runeCount < c.summaryLength {
 			count += runeCount
 		} else {
 			for ri := range word {
-				if count >= max {
+				if count >= c.summaryLength {
 					truncatedWords := append(words[:index], word[:ri])
 					return strings.Join(truncatedWords, " "), true
 				}
@@ -507,8 +507,7 @@ func TruncateWordsByRune(words []string, max int) (string, bool) {
 
 // TruncateWordsToWholeSentence takes content and truncates to whole sentence
 // limited by max number of words. It also returns whether it is truncated.
-func TruncateWordsToWholeSentence(s string, max int) (string, bool) {
-
+func (c *ContentSpec) TruncateWordsToWholeSentence(s string) (string, bool) {
 	var (
 		wordCount     = 0
 		lastWordIndex = -1
@@ -519,7 +518,7 @@ func TruncateWordsToWholeSentence(s string, max int) (string, bool) {
 			wordCount++
 			lastWordIndex = i
 
-			if wordCount >= max {
+			if wordCount >= c.summaryLength {
 				break
 			}
 
@@ -551,24 +550,24 @@ func isEndOfSentence(r rune) bool {
 }
 
 // Kept only for benchmark.
-func truncateWordsToWholeSentenceOld(content string, max int) (string, bool) {
+func (c *ContentSpec) truncateWordsToWholeSentenceOld(content string) (string, bool) {
 	words := strings.Fields(content)
 
-	if max >= len(words) {
+	if c.summaryLength >= len(words) {
 		return strings.Join(words, " "), false
 	}
 
-	for counter, word := range words[max:] {
+	for counter, word := range words[c.summaryLength:] {
 		if strings.HasSuffix(word, ".") ||
 			strings.HasSuffix(word, "?") ||
 			strings.HasSuffix(word, ".\"") ||
 			strings.HasSuffix(word, "!") {
-			upper := max + counter + 1
+			upper := c.summaryLength + counter + 1
 			return strings.Join(words[:upper], " "), (upper < len(words))
 		}
 	}
 
-	return strings.Join(words[:max], " "), true
+	return strings.Join(words[:c.summaryLength], " "), true
 }
 
 func getAsciidocExecPath() string {
diff --git a/helpers/content_test.go b/helpers/content_test.go
index b0afb9cbd..8f2d44cd9 100644
--- a/helpers/content_test.go
+++ b/helpers/content_test.go
@@ -76,20 +76,23 @@ func TestBytesToHTML(t *testing.T) {
 var benchmarkTruncateString = strings.Repeat("This is a sentence about nothing.", 20)
 
 func BenchmarkTestTruncateWordsToWholeSentence(b *testing.B) {
+	c := newTestContentSpec()
 	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
-		TruncateWordsToWholeSentence(benchmarkTruncateString, SummaryLength)
+		c.TruncateWordsToWholeSentence(benchmarkTruncateString)
 	}
 }
 
 func BenchmarkTestTruncateWordsToWholeSentenceOld(b *testing.B) {
+	c := newTestContentSpec()
 	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
-		truncateWordsToWholeSentenceOld(benchmarkTruncateString, SummaryLength)
+		c.truncateWordsToWholeSentenceOld(benchmarkTruncateString)
 	}
 }
 
 func TestTruncateWordsToWholeSentence(t *testing.T) {
+	c := newTestContentSpec()
 	type test struct {
 		input, expected string
 		max             int
@@ -104,9 +107,11 @@ func TestTruncateWordsToWholeSentence(t *testing.T) {
 		{"To be. Or not to be. That's the question.", "To be.", 1, true},
 		{" \nThis is not a sentence\nAnd this is another", "This is not a sentence", 4, true},
 		{"", "", 10, false},
+		{"This... is a more difficult test?", "This... is a more difficult test?", 1, false},
 	}
 	for i, d := range data {
-		output, truncated := TruncateWordsToWholeSentence(d.input, d.max)
+		c.summaryLength = d.max
+		output, truncated := c.TruncateWordsToWholeSentence(d.input)
 		if d.expected != output {
 			t.Errorf("Test %d failed. Expected %q got %q", i, d.expected, output)
 		}
@@ -118,6 +123,7 @@ func TestTruncateWordsToWholeSentence(t *testing.T) {
 }
 
 func TestTruncateWordsByRune(t *testing.T) {
+	c := newTestContentSpec()
 	type test struct {
 		input, expected string
 		max             int
@@ -139,7 +145,8 @@ func TestTruncateWordsByRune(t *testing.T) {
 		{" \nThis is    not a sentence\n ", "This is not", 3, true},
 	}
 	for i, d := range data {
-		output, truncated := TruncateWordsByRune(strings.Fields(d.input), d.max)
+		c.summaryLength = d.max
+		output, truncated := c.TruncateWordsByRune(strings.Fields(d.input))
 		if d.expected != output {
 			t.Errorf("Test %d failed. Expected %q got %q", i, d.expected, output)
 		}