Add render template hooks for links and images

This commit also revises the change detection for templates used by content files in server mode.

Fixes gohugoio#6545
Fixes gohugoio#4663
Closes gohugoio#6043

docs/content/en/functions/RenderString.md

@@ -0,0 +1,37 @@
+---
+title: .RenderString
+description: "Renders markup to HTML."
+godocref:
+date: 2019-12-18
+categories: [functions]
+menu:
+  docs:
+    parent: "functions"
+keywords: [markdown,goldmark,render]
+signature: [".RenderString MARKUP"]
+---
+
+{{< new-in "0.62.0" >}} 
+
+`.RenderString` is a method on `Page` that renders some markup to HTML using the content renderer defined for that page (if not set in the options).
+
+The method takes an optional map argument with these options:
+
+display ("inline")
+: `inline` or `block`. If `inline` (default), surrounding ´<p></p>` on short snippets will be trimmed.
+
+markup (defaults to the Page's markup)
+: See identifiers in [List of content formats](/content-management/formats/#list-of-content-formats).
+
+Some examples:
+
+```go-html-template
+{{ $optBlock := dict "display" "block" }}
+{{ $optOrg := dict "markup" "org" }}
+{{ "**Bold Markdown**" | $p.RenderString }}
+{{  "**Bold Block Markdown**" | $p.RenderString  $optBlock }}
+{{  "/italic org mode/" | $p.RenderString  $optOrg }}:REND
+```
+
+
+**Note** that this method is more powerful than the similar [markdownify](functions/markdownify/) function as it also supports [Render Hooks](/getting-started/configuration-markup/#markdown-render-hooks) and it has options to render other markup formats.

docs/content/en/getting-started/configuration-markup.md

@@ -74,3 +74,62 @@ endLevel
 
 ordered
 : Whether or not to generate an ordered list instead of an unordered list.
+
+
+## Markdown Render Hooks
+
+{{< new-in "0.62.0" >}}
+
+Note that this is only supported with the [Goldmark](#goldmark) renderer.
+
+These Render Hooks allow custom templates to render links and images from markdown.
+
+You can do this by creating templates with base names `render-link` and/or `render-image` inside `layouts/_default`.
+
+You can define [Output Format](/templates/output-formats) specific templates if needed.[^1] Your `layouts` folder may then look like this:
+
+```bash
+layouts
+└── _default
+    └── markup
+        ├── render-image.html
+        ├── render-image.rss.xml
+        └── render-link.html
+```
+
+Some use cases for the above:
+
+* Resolve link references using `.GetPage`. This would make links more portable as you could translate `./my-post.md` (and similar constructs that would work on GitHub) into `/blog/2019/01/01/my-post/` etc.
+* Add `target=blank` to external links.
+* Resolve (look in the page bundle, inside `/assets` etc.) and [transform](/content-management/image-processing) images.
+
+
+[^1]: It's currently only possible to have one set of render hook templates, e.g. not per `Type` or `Section`. We may consider that in a future version.
+
+### Render Hook Templates
+
+Both `render-link` and `render-image` templates will receive this context:
+
+Page
+: The [Page](/variables/page/) being rendered.
+
+Destination
+: The URL.
+
+Title
+: The title attribute.
+
+Text
+: The link text.
+
+A Markdown example for a inline-style link with title:
+
+```md
+[Text](https://www.gohugo.io "Title")
+```
+
+A very simple template example given the above:
+
+{{< code file="layouts/_default/render-link.html" >}}
+<a href="{{ .Destination | safeURL }}"{{ with .Title}}title="{{ . }}"{{ end }}>{{ .Text }}{{ with .Page }} (in page {{ .Title }}){{ end }}"</a>
+{{< /code >}}

helpers/content.go

@@ -25,13 +25,14 @@ import (
 
 	"github.com/gohugoio/hugo/common/loggers"
 
+	"github.com/spf13/afero"
+
 	"github.com/gohugoio/hugo/markup/converter"
 
 	"github.com/gohugoio/hugo/markup"
 
 	bp "github.com/gohugoio/hugo/bufferpool"
 	"github.com/gohugoio/hugo/config"
-	"github.com/spf13/afero"
 
 	"strings"
 )
@@ -78,6 +79,7 @@ func NewContentSpec(cfg config.Provider, logger *loggers.Logger, contentFs afero
 		ContentFs: contentFs,
 		Logger:    logger,
 	})
+
 	if err != nil {
 		return nil, err
 	}

hugolib/content_render_hooks_test.go

@@ -0,0 +1,244 @@
+// Copyright 2019 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 requiredF 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 hugolib
+
+import "testing"
+
+func TestRenderHooks(t *testing.T) {
+	config := `
+baseURL="https://example.org"
+workingDir="/mywork"
+`
+	b := newTestSitesBuilder(t).WithWorkingDir("/mywork").WithConfigFile("toml", config).Running()
+	b.WithTemplatesAdded("_default/single.html", `{{ .Content }}`)
+	b.WithTemplatesAdded("shortcodes/myshortcode1.html", `{{ partial "mypartial1" }}`)
+	b.WithTemplatesAdded("shortcodes/myshortcode2.html", `{{ partial "mypartial2" }}`)
+	b.WithTemplatesAdded("shortcodes/myshortcode3.html", `SHORT3|`)
+	b.WithTemplatesAdded("shortcodes/myshortcode4.html", `
+<div class="foo">
+{{ .Inner | markdownify }}
+</div>
+`)
+	b.WithTemplatesAdded("shortcodes/myshortcode5.html", `
+Inner Inline: {{ .Inner | .Page.RenderString }}
+Inner Block: {{ .Inner | .Page.RenderString (dict "display" "block" ) }}
+`)
+
+	b.WithTemplatesAdded("shortcodes/myshortcode6.html", `.Render: {{ .Page.Render "myrender" }}`)
+	b.WithTemplatesAdded("partials/mypartial1.html", `PARTIAL1`)
+	b.WithTemplatesAdded("partials/mypartial2.html", `PARTIAL2  {{ partial "mypartial3.html" }}`)
+	b.WithTemplatesAdded("partials/mypartial3.html", `PARTIAL3`)
+	b.WithTemplatesAdded("partials/mypartial4.html", `PARTIAL4`)
+	b.WithTemplatesAdded("customview/myrender.html", `myrender: {{ .Title }}|P4: {{ partial "mypartial4" }}`)
+	b.WithTemplatesAdded("_default/_markup/render-link.html", `{{ with .Page }}{{ .Title }}{{ end }}|{{ .Destination | safeURL }}|Title: {{ .Title | safeHTML }}|Text: {{ .Text | safeHTML }}|END`)
+	b.WithTemplatesAdded("docs/_markup/render-link.html", `Link docs section: {{ .Text | safeHTML }}|END`)
+	b.WithTemplatesAdded("_default/_markup/render-image.html", `IMAGE: {{ .Page.Title }}||{{ .Destination | safeURL }}|Title: {{ .Title | safeHTML }}|Text: {{ .Text | safeHTML }}|END`)
+
+	b.WithContent("customview/p1.md", `---
+title: Custom View
+---
+
+{{< myshortcode6 >}}
+
+	`, "blog/p1.md", `---
+title: Cool Page
+---
+
+[First Link](https://www.google.com "Google's Homepage")
+
+{{< myshortcode3 >}}
+
+[Second Link](https://www.google.com "Google's Homepage")
+
+Image:
+
+![Drag Racing](/images/Dragster.jpg "image title")
+
+
+`, "blog/p2.md", `---
+title: Cool Page2
+layout: mylayout
+---
+
+{{< myshortcode1 >}}
+
+[Some Text](https://www.google.com "Google's Homepage")
+
+
+
+`, "blog/p3.md", `---
+title: Cool Page3
+---
+
+{{< myshortcode2 >}}
+
+
+`, "docs/docs1.md", `---
+title: Docs 1
+---
+
+
+[Docs 1](https://www.google.com "Google's Homepage")
+
+
+`, "blog/p4.md", `---
+title: Cool Page With Image
+---
+
+Image:
+
+![Drag Racing](/images/Dragster.jpg "image title")
+
+
+`, "blog/p5.md", `---
+title: Cool Page With Markdownify
+---
+
+{{< myshortcode4 >}}
+Inner Link: [Inner Link](https://www.google.com "Google's Homepage")
+{{< /myshortcode4 >}}
+
+`, "blog/p6.md", `---
+title: With RenderString
+---
+
+{{< myshortcode5 >}}Inner Link: [Inner Link](https://www.gohugo.io "Hugo's Homepage"){{< /myshortcode5 >}}
+
+`)
+	b.Build(BuildCfg{})
+	b.AssertFileContent("public/blog/p1/index.html", `
+<p>Cool Page|https://www.google.com|Title: Google's Homepage|Text: First Link|END</p>
+Text: Second
+SHORT3|
+<p>IMAGE: Cool Page||/images/Dragster.jpg|Title: image title|Text: Drag Racing|END</p>
+`)
+
+	b.AssertFileContent("public/customview/p1/index.html", `.Render: myrender: Custom View|P4: PARTIAL4`)
+	b.AssertFileContent("public/blog/p2/index.html", `PARTIAL`)
+	b.AssertFileContent("public/blog/p3/index.html", `PARTIAL3`)
+	// We may add type template support later, keep this for then. b.AssertFileContent("public/docs/docs1/index.html", `Link docs section: Docs 1|END`)
+	b.AssertFileContent("public/blog/p4/index.html", `<p>IMAGE: Cool Page With Image||/images/Dragster.jpg|Title: image title|Text: Drag Racing|END</p>`)
+	// The regular markdownify func currently gets regular links.
+	b.AssertFileContent("public/blog/p5/index.html", "Inner Link: <a href=\"https://www.google.com\" title=\"Google's Homepage\">Inner Link</a>\n</div>")
+
+	b.AssertFileContent("public/blog/p6/index.html",
+		"Inner Inline: Inner Link: With RenderString|https://www.gohugo.io|Title: Hugo's Homepage|Text: Inner Link|END",
+		"Inner Block: <p>Inner Link: With RenderString|https://www.gohugo.io|Title: Hugo's Homepage|Text: Inner Link|END</p>",
+	)
+
+	b.EditFiles(
+		"layouts/_default/_markup/render-link.html", `EDITED: {{ .Destination | safeURL }}|`,
+		"layouts/_default/_markup/render-image.html", `IMAGE EDITED: {{ .Destination | safeURL }}|`,
+		"layouts/docs/_markup/render-link.html", `DOCS EDITED: {{ .Destination | safeURL }}|`,
+		"layouts/partials/mypartial1.html", `PARTIAL1_EDITED`,
+		"layouts/partials/mypartial3.html", `PARTIAL3_EDITED`,
+		"layouts/partials/mypartial4.html", `PARTIAL4_EDITED`,
+		"layouts/shortcodes/myshortcode3.html", `SHORT3_EDITED|`,
+	)
+
+	b.Build(BuildCfg{})
+	b.AssertFileContent("public/customview/p1/index.html", `.Render: myrender: Custom View|P4: PARTIAL4_EDITED`)
+	b.AssertFileContent("public/blog/p1/index.html", `<p>EDITED: https://www.google.com|</p>`, "SHORT3_EDITED|")
+	b.AssertFileContent("public/blog/p2/index.html", `PARTIAL1_EDITED`)
+	b.AssertFileContent("public/blog/p3/index.html", `PARTIAL3_EDITED`)
+	// We may add type template support later, keep this for then. b.AssertFileContent("public/docs/docs1/index.html", `DOCS EDITED: https://www.google.com|</p>`)
+	b.AssertFileContent("public/blog/p4/index.html", `IMAGE EDITED: /images/Dragster.jpg|`)
+	b.AssertFileContent("public/blog/p6/index.html", "<p>Inner Link: EDITED: https://www.gohugo.io|</p>")
+
+}
+
+func TestRenderHooksRSS(t *testing.T) {
+
+	b := newTestSitesBuilder(t)
+
+	b.WithTemplates("index.html", `
+{{ $p := site.GetPage "p1.md" }}
+
+P1: {{ $p.Content }}
+	
+	`, "index.xml", `
+
+{{ $p2 := site.GetPage "p2.md" }}
+{{ $p3 := site.GetPage "p3.md" }}
+
+P2: {{ $p2.Content }}
+P3: {{ $p3.Content }}
+
+	
+	`,
+		"_default/_markup/render-link.html", `html-link: {{ .Destination | safeURL }}|`,
+		"_default/_markup/render-link.rss.xml", `xml-link: {{ .Destination | safeURL }}|`,
+	)
+
+	b.WithContent("p1.md", `---
+title: "p1"
+---
+P1. [I'm an inline-style link](https://www.gohugo.io)
+
+
+`, "p2.md", `---
+title: "p2"
+---
+P1. [I'm an inline-style link](https://www.bep.is)
+
+
+`,
+		"p3.md", `---
+title: "p2"
+outputs: ["rss"]
+---
+P3. [I'm an inline-style link](https://www.example.org)
+
+`,
+	)
+
+	b.Build(BuildCfg{})
+
+	b.AssertFileContent("public/index.html", "P1: <p>P1. html-link: https://www.gohugo.io|</p>")
+	b.AssertFileContent("public/index.xml", `
+P2: <p>P1. xml-link: https://www.bep.is|</p>
+P3: <p>P3. xml-link: https://www.example.org|</p>
+`)
+
+}
+
+func TestRenderString(t *testing.T) {
+
+	b := newTestSitesBuilder(t)
+
+	b.WithTemplates("index.html", `
+{{ $p := site.GetPage "p1.md" }}
+{{ $optBlock := dict "display" "block" }}
+{{ $optOrg := dict "markup" "org" }}
+RSTART:{{ "**Bold Markdown**" | $p.RenderString }}:REND
+RSTART:{{  "**Bold Block Markdown**" | $p.RenderString  $optBlock }}:REND
+RSTART:{{  "/italic org mode/" | $p.RenderString  $optOrg }}:REND
+
+`)
+
+	b.WithContent("p1.md", `---
+title: "p1"
+---
+`,
+	)
+
+	b.Build(BuildCfg{})
+
+	b.AssertFileContent("public/index.html", `
+RSTART:<strong>Bold Markdown</strong>:REND
+RSTART:<p><strong>Bold Block Markdown</strong></p>
+RSTART:<em>italic org mode</em>:REND
+`)
+
+}