Better more complete fix for allowing filename to set date and slug

docs/content/getting-started/configuration.md

@@ -298,6 +298,8 @@ theme =                       ""
 title =                       ""
 # if true, use /filename.html instead of /filename/
 uglyURLs =                    false
+# use dates in filenames e.g. 2017-01-31-mypostname.md
+useFilenameDateAsFallback =  true
 # verbose output
 verbose =                     false
 # verbose logging

docs/content/variables/page.md

@@ -36,7 +36,13 @@ See [`.Scratch`](/functions/scratch/) for page-scoped, writable variables.
 : the data specific to this type of page.
 
 `.Date`
-: the date associated with the page; `.Date` pulls from the `date` field in a content's front matter. See also `.ExpiryDate`, `.PublishDate`, and `.Lastmod`.
+: the date associated with the page; `.Date` pulls from the `date` field in a content's front matter.
+If no `date` field present Hugo will try and extract the date from the filename. For example `2017-01-31-myblog.md`. It will also set `.Slug` to contain the path without the
+date prefix.'
+
+You can disable the automatic date detection and slug modification by setting `useFilenameDateAsFallback` configuration option to false. 
+
+See also `.ExpiryDate`, `.PublishDate`, and `.Lastmod`.
 
 `.Description`
 : the description for the page.

hugolib/config.go

@@ -139,6 +139,7 @@ func loadDefaultSettingsFor(v *viper.Viper) {
 	v.SetDefault("enableEmoji", false)
 	v.SetDefault("pygmentsCodeFencesGuessSyntax", false)
 	v.SetDefault("useModTimeAsFallback", false)
+	v.SetDefault("useFilenameDateAsFallback", true)
 	v.SetDefault("defaultContentLanguage", "en")
 	v.SetDefault("defaultContentLanguageInSubdir", false)
 	v.SetDefault("enableMissingTranslationPlaceholders", false)

hugolib/page.go

@@ -48,6 +48,9 @@ import (
 var (
 	cjk = regexp.MustCompile(`\p{Han}|\p{Hangul}|\p{Hiragana}|\p{Katakana}`)
 
+	// date expression used to find iso date in filename
+	dateExp = regexp.MustCompile("(?P<year>\\d{4})\\-(?P<month>\\d{2})\\-(?P<day>\\d{2})-(?P<slug>.*)\\..*")
+
 	// This is all the kinds we can expect to find in .Site.Pages.
 	allKindsInPages = []string{KindPage, KindHome, KindSection, KindTaxonomy, KindTaxonomyTerm}
 
@@ -963,7 +966,9 @@ func (p *Page) initURLs() error {
 
 var ErrHasDraftAndPublished = errors.New("both draft and published parameters were found in page's frontmatter")
 
-func (p *Page) update(f interface{}) error {
+// should just read metadata - should not handle any default fallback that
+// is done in updateMetadata
+func (p *Page) readMetadata(f interface{}) error {
 	if f == nil {
 		return errors.New("no metadata found")
 	}
@@ -1147,13 +1152,26 @@ func (p *Page) update(f interface{}) error {
 	p.Params["draft"] = p.Draft
 
 	if p.Date.IsZero() && p.s.Cfg.GetBool("useModTimeAsFallback") {
+
 		fi, err := p.s.Fs.Source.Stat(filepath.Join(p.s.PathSpec.AbsPathify(p.s.Cfg.GetString("contentDir")), p.File.Path()))
 		if err == nil {
+			p.s.Log.DEBUG.Printf("using file modification time as fallback for page %s", p.File.Path())
 			p.Date = fi.ModTime()
 			p.Params["date"] = p.Date
 		}
 	}
 
+	if p.Date.IsZero() && p.s.Cfg.GetString("filenameDateFallbackPattern") != "" {
+		dateExp := regexp.MustCompile(p.s.Cfg.GetString("filenameDateFallbackPattern"))
+		dateString := dateExp.FindString(p.File.Path())
+		filenameDate, err := time.Parse(p.s.Cfg.GetString("filenameDateFallbackFormat"), dateString)
+		if err == nil {
+			p.s.Log.DEBUG.Printf("using filename date as fallback for page %s", p.File.Path())
+			p.Date = filenameDate
+			p.Params["date"] = p.Date
+		}
+	}
+
 	if p.Lastmod.IsZero() {
 		if !modified.IsZero() {
 			p.Lastmod = modified
@@ -1181,6 +1199,54 @@ func (p *Page) update(f interface{}) error {
 
 }
 
+func (p *Page) updateMetadata() error {
+
+	if p.Date.IsZero() && p.s.Cfg.GetBool("useModTimeAsFallback") {
+
+		fi, err := p.s.Fs.Source.Stat(filepath.Join(p.s.PathSpec.AbsPathify(p.s.Cfg.GetString("contentDir")), p.File.Path()))
+		if err == nil {
+			p.s.Log.DEBUG.Printf("using file modification time as fallback for page %s", p.File.Path())
+			p.Date = fi.ModTime()
+			p.Params["date"] = p.Date
+		}
+	}
+
+	if p.Date.IsZero() && p.s.Cfg.GetBool("useFilenameDateAsFallback") {
+		match := dateExp.FindStringSubmatch(p.File.Path())
+
+		if match != nil {
+			year := match[1]
+			month := match[2]
+			day := match[3]
+			slug := match[4]
+
+			filenameDate, err := time.Parse("2006-01-02", year+"-"+month+"-"+day)
+
+			if err == nil {
+				p.Date = filenameDate
+				p.Params["date"] = p.Date
+				if p.Slug == "" {
+					p.Slug = slug
+					p.s.Log.DEBUG.Printf("Using filename date (%s) and slug (%s) as fallback for page %s", p.Date, p.Slug, p.File.Path())
+
+				} else {
+					p.s.Log.DEBUG.Printf("Using filename date (%s) as fallback for page %s", p.Date, p.File.Path())
+
+				}
+			} else {
+				p.s.Log.WARN.Printf("File has what looks like a date, but the date is invalid for page %s.", p.File.Path())
+			}
+		}
+	}
+
+	if p.Lastmod.IsZero() {
+		p.Lastmod = p.Date
+	}
+	p.Params["lastmod"] = p.Lastmod
+	return nil
+
+}
+
 func (p *Page) GetParam(key string) interface{} {
 	return p.getParam(key, true)
 }
@@ -1419,10 +1485,11 @@ func (p *Page) parse(reader io.Reader) error {
 	}
 
 	if meta != nil {
-		if err = p.update(meta); err != nil {
+		if err = p.readMetadata(meta); err != nil {
 			return err
 		}
 	}
+	p.updateMetadata()
 
 	return nil
 }

hugolib/page_test.go

@@ -81,6 +81,7 @@ Content of the file goes Here
 `
 
 	simplePageRFC3339Date  = "---\ntitle: RFC3339 Date\ndate: \"2013-05-17T16:59:30Z\"\n---\nrfc3339 content"
+	simplePageNoDate       = "---\ntitle: Path Date\n---\n Date param from url"
 	simplePageJSONMultiple = `
 {
 	"title": "foobar",
@@ -515,6 +516,7 @@ func checkPageDate(t *testing.T, page *Page, time time.Time) {
 	if page.Date != time {
 		t.Fatalf("Page date is: %s.  Expected: %s", page.Date, time)
 	}
+
 }
 
 func checkTruncation(t *testing.T, page *Page, shouldBe bool, msg string) {
@@ -854,6 +856,80 @@ func TestPageWithDate(t *testing.T) {
 	d, _ := time.Parse(time.RFC3339, "2013-05-17T16:59:30Z")
 
 	checkPageDate(t, p, d)
+
+}
+
+func TestDateAsFallbackWithDateInFilenameDisabled(t *testing.T) {
+	t.Parallel()
+	cfg, fs := newTestCfg()
+
+	cfg.Set("useFilenameDateAsFallback", false)
+
+	writeSource(t, fs, filepath.Join("content", "2017-01-31-simple.md"), simplePageNoDate)
+
+	s := buildSingleSite(t, deps.DepsCfg{Fs: fs, Cfg: cfg}, BuildCfg{SkipRender: true})
+
+	require.Len(t, s.RegularPages, 1)
+
+	p := s.RegularPages[0]
+
+	assert.True(t, p.Date.IsZero(), "page date should be empty as no date in file nor filename.")
+
+	assert.Equal(t, "", p.Slug, "slug for page should not be set as filename as date is disabled.")
+}
+
+func TestDateAsFallbackWithDateInFilename(t *testing.T) {
+	t.Parallel()
+	cfg, fs := newTestCfg()
+
+	writeSource(t, fs, filepath.Join("content", "2017-01-31-simple.md"), simplePageNoDate)
+
+	s := buildSingleSite(t, deps.DepsCfg{Fs: fs, Cfg: cfg}, BuildCfg{SkipRender: true})
+
+	require.Len(t, s.RegularPages, 1)
+
+	p := s.RegularPages[0]
+	d, err := time.Parse("2006-01-02", "2017-01-31")
+
+	assert.Equal(t, err, nil)
+
+	checkPageDate(t, p, d)
+
+	assert.Equal(t, "simple", p.Slug, "slug for page should be set as there is both date and title in filename")
+}
+
+func TestDateAsFallbackWithOutDateInFilename(t *testing.T) {
+	t.Parallel()
+	cfg, fs := newTestCfg()
+
+	writeSource(t, fs, filepath.Join("content", "simple.md"), simplePageNoDate)
+
+	s := buildSingleSite(t, deps.DepsCfg{Fs: fs, Cfg: cfg}, BuildCfg{SkipRender: true})
+
+	require.Len(t, s.RegularPages, 1)
+
+	p := s.RegularPages[0]
+
+	assert.True(t, p.Date.IsZero(), "page date should be empty as no date in filename")
+	assert.Equal(t, "", p.Slug, "page slug should not be set as no date in filename")
+
+}
+
+func TestDateAsFallbackWithInvalidDateInFilename(t *testing.T) {
+	t.Parallel()
+	cfg, fs := newTestCfg()
+
+	writeSource(t, fs, filepath.Join("content", "2017-31-31-simple.md"), simplePageNoDate)
+
+	s := buildSingleSite(t, deps.DepsCfg{Fs: fs, Cfg: cfg}, BuildCfg{SkipRender: true})
+
+	require.Len(t, s.RegularPages, 1)
+
+	p := s.RegularPages[0]
+
+	assert.True(t, p.Date.IsZero(), "page date should be empty as no valid date in filename")
+	assert.Equal(t, "", p.Slug, "page slug should not be set as no valid date in filename")
+
 }
 
 func TestWordCountWithAllCJKRunesWithoutHasCJKLanguage(t *testing.T) {