Remove visitLinksForShortLinks features (#6257)

The visitLinksForShortLinks feature would look inside of an <a> tag and
run shortLinkProcessorFull on any text, which attempts to create links
out of potential 'short links' like [[test]] [[link|example]] etc...
This makes no sense because you can't have nested links within an <a>
tag. Specifically, the html5 standard says <a> tags can't include
interactive content if they contain the href attribute:

 http://w3c.github.io/html/single-page.html#the-a-element

And also defines an <a> element with a href attribute as interactive:

 http://w3c.github.io/html/single-page.html#interactive-content

Therefore you can't really put a link inside of another link. In
practice none of this works anyways since browsers won't render it, it
would probably be broken if they tried, and it is causing a bug
(#4946). No current tests rely on this behavior either.

This removes the feature and also explicitly excludes the
current visitNodeForShortLinks from looking in <a> tags.

2 files changed, 9 insertions, 14 deletions

diff --git a/modules/markup/html.go b/modules/markup/html.go
index 8ce8740748..dab6d4e8e5 100644
--- a/modules/markup/html.go
+++ b/modules/markup/html.go
@@ -171,11 +171,6 @@ type postProcessCtx struct {
 
 	// processors used by this context.
 	procs []processor
-
-	// if set to true, when an <a> is found, instead of just returning during
-	// visitNode, it will recursively visit the node exclusively running
-	// shortLinkProcessorFull with true.
-	visitLinksForShortLinks bool
 }
 
 // PostProcess does the final required transformations to the passed raw HTML
@@ -191,11 +186,10 @@ func PostProcess(
 ) ([]byte, error) {
 	// create the context from the parameters
 	ctx := &postProcessCtx{
-		metas:                   metas,
-		urlPrefix:               urlPrefix,
-		isWikiMarkdown:          isWikiMarkdown,
-		procs:                   defaultProcessors,
-		visitLinksForShortLinks: true,
+		metas:          metas,
+		urlPrefix:      urlPrefix,
+		isWikiMarkdown: isWikiMarkdown,
+		procs:          defaultProcessors,
 	}
 	return ctx.postProcess(rawHTML)
 }
@@ -285,9 +279,6 @@ func (ctx *postProcessCtx) visitNode(node *html.Node) {
 		ctx.textNode(node)
 	case html.ElementNode:
 		if node.Data == "a" || node.Data == "code" || node.Data == "pre" {
-			if node.Data == "a" && ctx.visitLinksForShortLinks {
-				ctx.visitNodeForShortLinks(node)
-			}
 			return
 		}
 		for n := node.FirstChild; n != nil; n = n.NextSibling {
@@ -302,7 +293,7 @@ func (ctx *postProcessCtx) visitNodeForShortLinks(node *html.Node) {
 	case html.TextNode:
 		shortLinkProcessorFull(ctx, node, true)
 	case html.ElementNode:
-		if node.Data == "code" || node.Data == "pre" {
+		if node.Data == "code" || node.Data == "pre" || node.Data == "a" {
 			return
 		}
 		for n := node.FirstChild; n != nil; n = n.NextSibling {
diff --git a/modules/markup/html_test.go b/modules/markup/html_test.go
index f17d00cd67..f430cb04be 100644
--- a/modules/markup/html_test.go
+++ b/modules/markup/html_test.go
@@ -222,4 +222,8 @@ func TestRender_ShortLinks(t *testing.T) {
 		"[[some/path/Link #.jpg]]",
 		`<p><a href="`+notencodedImgurl+`" rel="nofollow"><img src="`+notencodedImgurl+`"/></a></p>`,
 		`<p><a href="`+notencodedImgurlWiki+`" rel="nofollow"><img src="`+notencodedImgurlWiki+`"/></a></p>`)
+	test(
+		"<p><a href=\"https://example.org\">[[foobar]]</a></p>",
+		`<p><a href="https://example.org" rel="nofollow">[[foobar]]</a></p>`,
+		`<p><a href="https://example.org" rel="nofollow">[[foobar]]</a></p>`)
 }