Add pager size argument to paginator methods

Fixes #1013

docs/content/extras/pagination.md

@@ -17,7 +17,7 @@ Hugo supports pagination for the home page, sections and taxonomies. It's built
 
 Pagination can be configured in the site configuration (e.g. `config.toml`):
 
-* `Paginate` (default `10`)
+* `Paginate` (default `10`) (this setting can be overridden in the template)
 * `PaginatePath` (default `page`)
 
 Setting `Paginate` to a positive value will split the list pages for the home page, sections and taxonomies into chunks of that size. But note that the generation of the pagination pages for sections, taxonomies and home page is *lazy* --- the pages will not be created if not referenced by a `.Paginator` (see below).
@@ -35,6 +35,12 @@ There are two ways to configure and use a `.Paginator`:
 
 For a given **Node**, it's one of the options above. The `.Paginator` is static and cannot change once created.
 
+
+The global page size setting (`Paginate`) can be overridden by providing a positive integer as the last argument. The examples below will give five items per page:
+
+* `{{ range (.Paginator 5).Pages }}`
+* `{{ $paginator := .Paginate (where .Data.Pages "Type" "post") 5 }}`
+
 ## Build the navigation
 
 The `.Paginator` contains enough information to build a paginator interface.

hugolib/pagination.go

@@ -16,6 +16,7 @@ package hugolib
 import (
 	"errors"
 	"fmt"
+	"github.com/spf13/cast"
 	"github.com/spf13/hugo/helpers"
 	"github.com/spf13/viper"
 	"html/template"
@@ -54,8 +55,8 @@ func (p *pager) URL() template.HTML {
 
 // Url is deprecated. Will be removed in 0.15.
 func (p *pager) Url() template.HTML {
-    helpers.Deprecated("Paginator", ".Url", ".URL")
-    return p.URL()
+	helpers.Deprecated("Paginator", ".Url", ".URL")
+	return p.URL()
 }
 
 // Pages returns the elements on this page.
@@ -139,7 +140,13 @@ func splitPages(pages Pages, size int) []Pages {
 
 // Paginator gets this Node's paginator if it's already created.
 // If it's not, one will be created with all pages in Data["Pages"].
-func (n *Node) Paginator() (*pager, error) {
+func (n *Node) Paginator(options ...interface{}) (*pager, error) {
+
+	pagerSize, err := resolvePagerSize(options...)
+
+	if err != nil {
+		return nil, err
+	}
 
 	var initError error
 
@@ -148,7 +155,7 @@ func (n *Node) Paginator() (*pager, error) {
 			return
 		}
 
-		pagers, err := paginatePages(n.Data["Pages"], n.URL)
+		pagers, err := paginatePages(n.Data["Pages"], pagerSize, n.URL)
 
 		if err != nil {
 			initError = err
@@ -170,19 +177,25 @@ func (n *Node) Paginator() (*pager, error) {
 }
 
 // Paginator on Page isn't supported, calling this yields an error.
-func (p *Page) Paginator() (*pager, error) {
+func (p *Page) Paginator(options ...interface{}) (*pager, error) {
 	return nil, errors.New("Paginators not supported for content pages.")
 }
 
 // Paginate on Page isn't supported, calling this yields an error.
-func (p *Page) Paginate(seq interface{}) (*pager, error) {
+func (p *Page) Paginate(seq interface{}, options ...interface{}) (*pager, error) {
 	return nil, errors.New("Paginators not supported for content pages.")
 }
 
 // Paginate gets this Node's paginator if it's already created.
 // If it's not, one will be created with the qiven sequence.
 // Note that repeated calls will return the same result, even if the sequence is different.
-func (n *Node) Paginate(seq interface{}) (*pager, error) {
+func (n *Node) Paginate(seq interface{}, options ...interface{}) (*pager, error) {
+
+	pagerSize, err := resolvePagerSize(options...)
+
+	if err != nil {
+		return nil, err
+	}
 
 	var initError error
 
@@ -190,7 +203,7 @@ func (n *Node) Paginate(seq interface{}) (*pager, error) {
 		if n.paginator != nil {
 			return
 		}
-		pagers, err := paginatePages(seq, n.URL)
+		pagers, err := paginatePages(seq, pagerSize, n.URL)
 
 		if err != nil {
 			initError = err
@@ -211,12 +224,30 @@ func (n *Node) Paginate(seq interface{}) (*pager, error) {
 	return n.paginator, nil
 }
 
-func paginatePages(seq interface{}, section string) (pagers, error) {
-	paginateSize := viper.GetInt("paginate")
+func resolvePagerSize(options ...interface{}) (int, error) {
+	if len(options) == 0 {
+		return viper.GetInt("paginate"), nil
+	}
 
-	if paginateSize <= 0 {
+	if len(options) > 1 {
+		return -1, errors.New("too many arguments, 'pager size' is currently the only option")
+	}
+
+	pas, err := cast.ToIntE(options[0])
+
+	if err != nil || pas <= 0 {
+		return -1, errors.New(("'pager size' must be a positive integer"))
+	}
+
+	return pas, nil
+}
+
+func paginatePages(seq interface{}, pagerSize int, section string) (pagers, error) {
+
+	if pagerSize <= 0 {
 		return nil, errors.New("'paginate' configuration setting must be positive to paginate")
 	}
+
 	var pages Pages
 	switch seq.(type) {
 	case Pages:
@@ -232,7 +263,7 @@ func paginatePages(seq interface{}, section string) (pagers, error) {
 	}
 
 	urlFactory := newPaginationURLFactory(section)
-	paginator, _ := newPaginator(pages, paginateSize, urlFactory)
+	paginator, _ := newPaginator(pages, pagerSize, urlFactory)
 	pagers := paginator.Pagers()
 
 	return pagers, nil

hugolib/pagination_test.go

@@ -44,6 +44,7 @@ func TestPager(t *testing.T) {
 
 	first := paginatorPages[0]
 	assert.Equal(t, "page/1/", first.URL())
+	assert.Equal(t, first.URL(), first.Url())
 	assert.Equal(t, first, first.First())
 	assert.True(t, first.HasNext())
 	assert.Equal(t, paginatorPages[1], first.Next())
@@ -110,14 +111,32 @@ func TestPaginationURLFactory(t *testing.T) {
 }
 
 func TestPaginator(t *testing.T) {
-	viper.Set("paginate", 5)
+	for _, useViper := range []bool{false, true} {
+		doTestPaginator(t, useViper)
+	}
+}
+
+func doTestPaginator(t *testing.T, useViper bool) {
+	pagerSize := 5
+	if useViper {
+		viper.Set("paginate", pagerSize)
+	} else {
+		viper.Set("paginate", -1)
+	}
 	pages := createTestPages(12)
 	s := &Site{}
 	n1 := s.newHomeNode()
 	n2 := s.newHomeNode()
 	n1.Data["Pages"] = pages
 
-	paginator1, err := n1.Paginator()
+	var paginator1 *pager
+	var err error
+
+	if useViper {
+		paginator1, err = n1.Paginator()
+	} else {
+		paginator1, err = n1.Paginator(pagerSize)
+	}
 
 	assert.Nil(t, err)
 	assert.NotNil(t, paginator1)
@@ -146,13 +165,33 @@ func TestPaginatorWithNegativePaginate(t *testing.T) {
 }
 
 func TestPaginate(t *testing.T) {
-	viper.Set("paginate", 5)
+	for _, useViper := range []bool{false, true} {
+		doTestPaginate(t, useViper)
+	}
+}
+
+func doTestPaginate(t *testing.T, useViper bool) {
+
+	pagerSize := 5
+	if useViper {
+		viper.Set("paginate", pagerSize)
+	} else {
+		viper.Set("paginate", -1)
+	}
+
 	pages := createTestPages(6)
 	s := &Site{}
 	n1 := s.newHomeNode()
 	n2 := s.newHomeNode()
 
-	paginator1, err := n1.Paginate(pages)
+	var paginator1 *pager
+	var err error
+
+	if useViper {
+		paginator1, err = n1.Paginate(pages)
+	} else {
+		paginator1, err = n1.Paginate(pages, pagerSize)
+	}
 
 	assert.Nil(t, err)
 	assert.NotNil(t, paginator1)
@@ -172,6 +211,17 @@ func TestPaginate(t *testing.T) {
 	assert.NotNil(t, err)
 }
 
+func TestInvalidOptions(t *testing.T) {
+	s := &Site{}
+	n1 := s.newHomeNode()
+	_, err := n1.Paginate(createTestPages(1), 1, 2)
+	assert.NotNil(t, err)
+	_, err = n1.Paginator(1, 2)
+	assert.NotNil(t, err)
+	_, err = n1.Paginator(-1)
+	assert.NotNil(t, err)
+}
+
 func TestPaginateWithNegativePaginate(t *testing.T) {
 	viper.Set("paginate", -1)
 	s := &Site{}
@@ -180,13 +230,12 @@ func TestPaginateWithNegativePaginate(t *testing.T) {
 }
 
 func TestPaginatePages(t *testing.T) {
-	viper.Set("paginate", 11)
 	for i, seq := range []interface{}{createTestPages(11), WeightedPages{}, PageGroup{}, &Pages{}} {
-		v, err := paginatePages(seq, "t")
+		v, err := paginatePages(seq, 11, "t")
 		assert.NotNil(t, v, "Val %d", i)
 		assert.Nil(t, err, "Err %d", i)
 	}
-	_, err := paginatePages(Site{}, "t")
+	_, err := paginatePages(Site{}, 11, "t")
 	assert.NotNil(t, err)
 
 }