Allow cascade to be a slice with a _target discriminator

Fixes #7782

11 files changed, 375 insertions, 29 deletions

diff --git a/docs/content/en/content-management/front-matter.md b/docs/content/en/content-management/front-matter.md
index a14cb3065..097cf0598 100644
--- a/docs/content/en/content-management/front-matter.md
+++ b/docs/content/en/content-management/front-matter.md
@@ -159,6 +159,39 @@ show_comments: false
 
 Any node or section can pass down to descendents a set of Front Matter values as long as defined underneath the reserved `cascade` Front Matter key.
 
+### Target Specific Pages
+
+{{< new-in "0.76.0" >}}
+
+Since Hugo 0.76 the `cascade` block can be a slice with a optional `_target` keyword, allowing for multiple `cascade` values targeting different page sets.
+
+{{< code-toggle copy="false" >}}
+title ="Blog"
+[[cascade]]
+background = "yosemite.jpg"
+[cascade._target]
+path="/blog/**"
+lang="en"
+kind="page"
+[[cascade]]
+background = "goldenbridge.jpg"
+[cascade._target]
+kind="section"
+{{</ code-toggle >}}
+
+Keywords available for `_target`:
+
+path
+: A [Glob](https://github.com/gobwas/glob) pattern matching the content path below /content. Expects Unix-styled slashes. Note that this is the virtual path, so it starts at the mount root.
+
+kind
+: A Glob pattern matching the Page's Kind(s), e.g. "{home,section}".
+
+lang
+: A Glob pattern matching the Page's language, e.g. "{en,sv}".
+
+Any of the above can be omitted. 
+
 ### Example
 
 In `content/blog/_index.md`
@@ -174,6 +207,8 @@ With the above example the Blog section page and its descendents will return `im
 - Said descendent has its own `banner` value set 
 - Or a closer ancestor node has its own `cascade.banner` value set.
 
+
+
 ## Order Content Through Front Matter
 
 You can assign content-specific `weight` in the front matter of your content. These values are especially useful for [ordering][ordering] in list views. You can use `weight` for ordering of content and the convention of [`<TAXONOMY>_weight`][taxweight] for ordering content within a taxonomy. See [Ordering and Grouping Hugo Lists][lists] to see how `weight` can be used to organize your content in list views.
diff --git a/hugofs/glob/glob.go b/hugofs/glob/glob.go
index 124a3d50e..88485e1f0 100644
--- a/hugofs/glob/glob.go
+++ b/hugofs/glob/glob.go
@@ -23,30 +23,36 @@ import (
 	"github.com/gobwas/glob/syntax"
 )
 
+type globErr struct {
+	glob glob.Glob
+	err  error
+}
+
 var (
-	globCache = make(map[string]glob.Glob)
+	globCache = make(map[string]globErr)
 	globMu    sync.RWMutex
 )
 
 func GetGlob(pattern string) (glob.Glob, error) {
-	var g glob.Glob
+	var eg globErr
 
 	globMu.RLock()
-	g, found := globCache[pattern]
+	var found bool
+	eg, found = globCache[pattern]
 	globMu.RUnlock()
-	if !found {
-		var err error
-		g, err = glob.Compile(strings.ToLower(pattern), '/')
-		if err != nil {
-			return nil, err
-		}
-
-		globMu.Lock()
-		globCache[pattern] = g
-		globMu.Unlock()
+	if found {
+		return eg.glob, eg.err
 	}
 
-	return g, nil
+	var err error
+	g, err := glob.Compile(strings.ToLower(pattern), '/')
+	eg = globErr{g, err}
+
+	globMu.Lock()
+	globCache[pattern] = eg
+	globMu.Unlock()
+
+	return eg.glob, eg.err
 
 }
 
diff --git a/hugofs/glob/glob_test.go b/hugofs/glob/glob_test.go
index cca8e4e0f..5a6ef5b7e 100644
--- a/hugofs/glob/glob_test.go
+++ b/hugofs/glob/glob_test.go
@@ -73,5 +73,14 @@ func TestGetGlob(t *testing.T) {
 	g, err := GetGlob("**.JSON")
 	c.Assert(err, qt.IsNil)
 	c.Assert(g.Match("data/my.json"), qt.Equals, true)
+}
+
+func BenchmarkGetGlob(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		_, err := GetGlob("**/foo")
+		if err != nil {
+			b.Fatal(err)
+		}
+	}
 
 }
diff --git a/hugolib/cascade_test.go b/hugolib/cascade_test.go
index 33fc7ceec..336acdcf3 100644
--- a/hugolib/cascade_test.go
+++ b/hugolib/cascade_test.go
@@ -229,7 +229,7 @@ Banner: post.jpg`,
 
 		counters := &testCounters{}
 		b.Build(BuildCfg{testCounters: counters})
-		// As we only changed the content, not the cascade front matter, make
+		// As we only changed the content, not the cascade front matter,
 		// only the home page is re-rendered.
 		b.Assert(int(counters.contentRenderCounter), qt.Equals, 1)
 
@@ -392,3 +392,71 @@ defaultContentLanguageInSubDir = false
 
 	return b
 }
+
+func TestCascadeTarget(t *testing.T) {
+	t.Parallel()
+
+	c := qt.New(t)
+
+	newBuilder := func(c *qt.C) *sitesBuilder {
+		b := newTestSitesBuilder(c)
+
+		b.WithTemplates("index.html", `
+{{ $p1 := site.GetPage "s1/p1" }}
+{{ $s1 := site.GetPage "s1" }}
+
+P1|p1:{{ $p1.Params.p1 }}|p2:{{ $p1.Params.p2 }}|
+S1|p1:{{ $s1.Params.p1 }}|p2:{{ $s1.Params.p2 }}|
+`)
+		b.WithContent("s1/_index.md", "---\ntitle: s1 section\n---")
+		b.WithContent("s1/p1/index.md", "---\ntitle: p1\n---")
+		b.WithContent("s1/p2/index.md", "---\ntitle: p2\n---")
+		b.WithContent("s2/p1/index.md", "---\ntitle: p1_2\n---")
+
+		return b
+
+	}
+
+	c.Run("slice", func(c *qt.C) {
+		b := newBuilder(c)
+		b.WithContent("_index.md", `+++
+title = "Home"
+[[cascade]]
+p1 = "p1"
+[[cascade]]
+p2 = "p2"
++++
+`)
+
+		b.Build(BuildCfg{})
+
+		b.AssertFileContent("public/index.html", "P1|p1:p1|p2:p2")
+
+	})
+
+	c.Run("slice with _target", func(c *qt.C) {
+		b := newBuilder(c)
+
+		b.WithContent("_index.md", `+++
+title = "Home"
+[[cascade]]
+p1 = "p1"
+[cascade._target]
+path="**p1**"
+[[cascade]]
+p2 = "p2"
+[cascade._target]
+kind="section"
++++
+`)
+
+		b.Build(BuildCfg{})
+
+		b.AssertFileContent("public/index.html", `
+P1|p1:p1|p2:|
+S1|p1:|p2:p2|
+`)
+
+	})
+
+}
diff --git a/hugolib/content_map_page.go b/hugolib/content_map_page.go
index b32f808c9..b2a8fda7e 100644
--- a/hugolib/content_map_page.go
+++ b/hugolib/content_map_page.go
@@ -789,7 +789,7 @@ func (m *pageMaps) withMaps(fn func(pm *pageMap) error) error {
 
 type pagesMapBucket struct {
 	// Cascading front matter.
-	cascade maps.Params
+	cascade map[page.PageMatcher]maps.Params
 
 	owner *pageState // The branch node
 
diff --git a/hugolib/page__meta.go b/hugolib/page__meta.go
index 0e16292f0..c7a8db3d5 100644
--- a/hugolib/page__meta.go
+++ b/hugolib/page__meta.go
@@ -308,12 +308,22 @@ func (p *pageMeta) Weight() int {
 
 func (pm *pageMeta) mergeBucketCascades(b1, b2 *pagesMapBucket) {
 	if b1.cascade == nil {
-		b1.cascade = make(map[string]interface{})
+		b1.cascade = make(map[page.PageMatcher]maps.Params)
 	}
+
 	if b2 != nil && b2.cascade != nil {
 		for k, v := range b2.cascade {
-			if _, found := b1.cascade[k]; !found {
+
+			vv, found := b1.cascade[k]
+			if !found {
 				b1.cascade[k] = v
+			} else {
+				// Merge
+				for ck, cv := range v {
+					if _, found := vv[ck]; !found {
+						vv[ck] = cv
+					}
+				}
 			}
 		}
 	}
@@ -332,14 +342,44 @@ func (pm *pageMeta) setMetadata(parentBucket *pagesMapBucket, p *pageState, fron
 		if p.bucket != nil {
 			// Check for any cascade define on itself.
 			if cv, found := frontmatter["cascade"]; found {
-				p.bucket.cascade = maps.ToStringMap(cv)
+				switch v := cv.(type) {
+				case []map[string]interface{}:
+					p.bucket.cascade = make(map[page.PageMatcher]maps.Params)
+
+					for _, vv := range v {
+						var m page.PageMatcher
+						if mv, found := vv["_target"]; found {
+							err := page.DecodePageMatcher(mv, &m)
+							if err != nil {
+								return err
+							}
+						}
+						c, found := p.bucket.cascade[m]
+						if found {
+							// Merge
+							for k, v := range vv {
+								if _, found := c[k]; !found {
+									c[k] = v
+								}
+							}
+						} else {
+							p.bucket.cascade[m] = vv
+						}
+
+					}
+				default:
+					p.bucket.cascade = map[page.PageMatcher]maps.Params{
+						page.PageMatcher{}: maps.ToStringMap(cv),
+					}
+				}
+
 			}
 		}
 	} else {
 		frontmatter = make(map[string]interface{})
 	}
 
-	var cascade map[string]interface{}
+	var cascade map[page.PageMatcher]maps.Params
 
 	if p.bucket != nil {
 		if parentBucket != nil {
@@ -351,9 +391,14 @@ func (pm *pageMeta) setMetadata(parentBucket *pagesMapBucket, p *pageState, fron
 		cascade = parentBucket.cascade
 	}
 
-	for k, v := range cascade {
-		if _, found := frontmatter[k]; !found {
-			frontmatter[k] = v
+	for m, v := range cascade {
+		if !m.Matches(p) {
+			continue
+		}
+		for kk, vv := range v {
+			if _, found := frontmatter[kk]; !found {
+				frontmatter[kk] = vv
+			}
 		}
 	}
 
@@ -466,7 +511,7 @@ func (pm *pageMeta) setMetadata(parentBucket *pagesMapBucket, p *pageState, fron
 		case "outputs":
 			o := cast.ToStringSlice(v)
 			if len(o) > 0 {
-				// Output formats are exlicitly set in front matter, use those.
+				// Output formats are explicitly set in front matter, use those.
 				outFormats, err := p.s.outputFormatsConfig.GetByNames(o...)
 
 				if err != nil {
diff --git a/hugolib/page_test.go b/hugolib/page_test.go
index 2df679a74..3a30216ed 100644
--- a/hugolib/page_test.go
+++ b/hugolib/page_test.go
@@ -1757,3 +1757,24 @@ $$$
 		`<pre><code class="language-bash {hl_lines=[1]}" data-lang="bash {hl_lines=[1]}">SHORT`,
 	)
 }
+
+func TestPageCaseIssues(t *testing.T) {
+	t.Parallel()
+
+	b := newTestSitesBuilder(t)
+	b.WithConfigFile("toml", `defaultContentLanguage = "no"
+[languages]
+[languages.NO]
+title = "Norsk"
+`)
+	b.WithContent("a/B/C/Page1.md", "---\ntitle: Page1\n---")
+	b.WithTemplates("index.html", `
+{{ $p1 := site.GetPage "a/B/C/Page1" }}
+Lang: {{ .Lang }}
+Page1: {{ $p1.Path }}
+`)
+
+	b.Build(BuildCfg{})
+
+	b.AssertFileContent("public/index.html", "Lang: no", filepath.FromSlash("Page1: a/B/C/Page1.md"))
+}
diff --git a/hugolib/pages_capture.go b/hugolib/pages_capture.go
index ddb4bc495..4ee33992d 100644
--- a/hugolib/pages_capture.go
+++ b/hugolib/pages_capture.go
@@ -137,6 +137,7 @@ func (c *pagesCollector) isCascadingEdit(dir contentDirKey) (bool, string) {
 		hasCascade := n.p.bucket.cascade != nil && len(n.p.bucket.cascade) > 0
 		if !ok {
 			isCascade = hasCascade
+
 			return true
 		}
 
@@ -145,7 +146,12 @@ func (c *pagesCollector) isCascadingEdit(dir contentDirKey) (bool, string) {
 			return true
 		}
 
-		isCascade = !reflect.DeepEqual(cascade1, n.p.bucket.cascade)
+		for _, v := range n.p.bucket.cascade {
+			isCascade = !reflect.DeepEqual(cascade1, v)
+			if isCascade {
+				break
+			}
+		}
 
 		return true
 
@@ -187,6 +193,7 @@ func (c *pagesCollector) Collect() (collectErr error) {
 				collectErr = c.collectDir(dir.dirname, true, nil)
 			case bundleBranch:
 				isCascading, section := c.isCascadingEdit(dir)
+
 				if isCascading {
 					c.contentMap.deleteSection(section)
 				}
diff --git a/resources/page/page_matcher.go b/resources/page/page_matcher.go
new file mode 100644
index 000000000..881f76e33
--- /dev/null
+++ b/resources/page/page_matcher.go
@@ -0,0 +1,91 @@
+// Copyright 2020 The Hugo Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package page
+
+import (
+	"path/filepath"
+	"strings"
+
+	"github.com/pkg/errors"
+
+	"github.com/gohugoio/hugo/hugofs/glob"
+	"github.com/mitchellh/mapstructure"
+)
+
+// A PageMatcher can be used to match a Page with Glob patterns.
+// Note that the pattern matching is case insensitive.
+type PageMatcher struct {
+	// A Glob pattern matching the content path below /content.
+	// Expects Unix-styled slashes.
+	// Note that this is the virtual path, so it starts at the mount root
+	// with a leading "/".
+	Path string
+
+	// A Glob pattern matching the Page's Kind(s), e.g. "{home,section}"
+	Kind string
+
+	// A Glob pattern matching the Page's language, e.g. "{en,sv}".
+	Lang string
+}
+
+// Matches returns whether p matches this matcher.
+func (m PageMatcher) Matches(p Page) bool {
+
+	if m.Kind != "" {
+		g, err := glob.GetGlob(m.Kind)
+		if err == nil && !g.Match(p.Kind()) {
+			return false
+		}
+	}
+
+	if m.Lang != "" {
+		g, err := glob.GetGlob(m.Lang)
+		if err == nil && !g.Match(p.Lang()) {
+			return false
+		}
+	}
+
+	if m.Path != "" {
+		g, err := glob.GetGlob(m.Path)
+		// TODO(bep) Path() vs filepath vs leading slash.
+		p := strings.ToLower(filepath.ToSlash(p.Path()))
+		if !(strings.HasPrefix(p, "/")) {
+			p = "/" + p
+		}
+		if err == nil && !g.Match(p) {
+			return false
+		}
+	}
+
+	return true
+}
+
+// DecodePageMatcher decodes m into v.
+func DecodePageMatcher(m interface{}, v *PageMatcher) error {
+	if err := mapstructure.WeakDecode(m, v); err != nil {
+		return err
+	}
+
+	v.Kind = strings.ToLower(v.Kind)
+	if v.Kind != "" {
+		if _, found := kindMap[v.Kind]; !found {
+			return errors.Errorf("%q is not a valid Page Kind", v.Kind)
+		}
+	}
+
+	v.Path = filepath.ToSlash(strings.ToLower(v.Path))
+
+	return nil
+
+}
diff --git a/resources/page/page_matcher_test.go b/resources/page/page_matcher_test.go
new file mode 100644
index 000000000..24b304772
--- /dev/null
+++ b/resources/page/page_matcher_test.go
@@ -0,0 +1,63 @@
+// Copyright 2020 The Hugo Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package page
+
+import (
+	"path/filepath"
+	"testing"
+
+	qt "github.com/frankban/quicktest"
+)
+
+func TestPageMatcher(t *testing.T) {
+	c := qt.New(t)
+
+	p1, p2, p3 := &testPage{path: "/p1", kind: "section", lang: "en"}, &testPage{path: "p2", kind: "page", lang: "no"}, &testPage{path: "p3", kind: "page", lang: "en"}
+
+	c.Run("Matches", func(c *qt.C) {
+		m := PageMatcher{Kind: "section"}
+
+		c.Assert(m.Matches(p1), qt.Equals, true)
+		c.Assert(m.Matches(p2), qt.Equals, false)
+
+		m = PageMatcher{Kind: "page"}
+		c.Assert(m.Matches(p1), qt.Equals, false)
+		c.Assert(m.Matches(p2), qt.Equals, true)
+		c.Assert(m.Matches(p3), qt.Equals, true)
+
+		m = PageMatcher{Kind: "page", Path: "/p2"}
+		c.Assert(m.Matches(p1), qt.Equals, false)
+		c.Assert(m.Matches(p2), qt.Equals, true)
+		c.Assert(m.Matches(p3), qt.Equals, false)
+
+		m = PageMatcher{Path: "/p*"}
+		c.Assert(m.Matches(p1), qt.Equals, true)
+		c.Assert(m.Matches(p2), qt.Equals, true)
+		c.Assert(m.Matches(p3), qt.Equals, true)
+
+		m = PageMatcher{Lang: "en"}
+		c.Assert(m.Matches(p1), qt.Equals, true)
+		c.Assert(m.Matches(p2), qt.Equals, false)
+		c.Assert(m.Matches(p3), qt.Equals, true)
+
+	})
+
+	c.Run("Decode", func(c *qt.C) {
+		var v PageMatcher
+		c.Assert(DecodePageMatcher(map[string]interface{}{"kind": "foo"}, &v), qt.Not((qt.IsNil)))
+		c.Assert(DecodePageMatcher(map[string]interface{}{"kind": "home", "path": filepath.FromSlash("/a/b/**")}, &v), qt.IsNil)
+		c.Assert(v, qt.Equals, PageMatcher{Kind: "home", Path: "/a/b/**"})
+	})
+
+}
diff --git a/resources/page/testhelpers_test.go b/resources/page/testhelpers_test.go
index 17a795a20..54a908d3b 100644
--- a/resources/page/testhelpers_test.go
+++ b/resources/page/testhelpers_test.go
@@ -85,11 +85,12 @@ func newTestPathSpecFor(cfg config.Provider) *helpers.PathSpec {
 }
 
 type testPage struct {
+	kind        string
 	description string
 	title       string
 	linkTitle   string
-
-	section string
+	lang        string
+	section     string
 
 	content string
 
@@ -297,11 +298,11 @@ func (p *testPage) Keywords() []string {
 }
 
 func (p *testPage) Kind() string {
-	panic("not implemented")
+	return p.kind
 }
 
 func (p *testPage) Lang() string {
-	panic("not implemented")
+	return p.lang
 }
 
 func (p *testPage) Language() *langs.Language {