Rework markup link rendering (#26745)

Fixes #26548

This PR refactors the rendering of markup links. The old code uses
`strings.Replace` to change some urls while the new code uses more
context to decide which link should be generated.

The added tests should ensure the same output for the old and new
behaviour (besides the bug).

We may need to refactor the rendering a bit more to make it clear how
the different helper methods render the input string. There are lots of
options (resolve links / images / mentions / git hashes / emojis / ...)
but you don't really know what helper uses which options. For example,
we currently support images in the user description which should not be
allowed I think:

<details>
  <summary>Profile</summary> 

https://try.gitea.io/KN4CK3R

![grafik](https://github.com/go-gitea/gitea/assets/1666336/109ae422-496d-4200-b52e-b3a528f553e5)

</details>

---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

1 files changed, 71 insertions, 46 deletions

diff --git a/modules/markup/html_test.go b/modules/markup/html_test.go
index 62fd0f5a85..89ecfc036b 100644
--- a/modules/markup/html_test.go
+++ b/modules/markup/html_test.go
@@ -42,8 +42,10 @@ func TestRender_Commits(t *testing.T) {
 		buffer, err := markup.RenderString(&markup.RenderContext{
 			Ctx:          git.DefaultContext,
 			RelativePath: ".md",
-			URLPrefix:    markup.TestRepoURL,
-			Metas:        localMetas,
+			Links: markup.Links{
+				Base: markup.TestRepoURL,
+			},
+			Metas: localMetas,
 		}, input)
 		assert.NoError(t, err)
 		assert.Equal(t, strings.TrimSpace(expected), strings.TrimSpace(buffer))
@@ -93,8 +95,10 @@ func TestRender_CrossReferences(t *testing.T) {
 		buffer, err := markup.RenderString(&markup.RenderContext{
 			Ctx:          git.DefaultContext,
 			RelativePath: "a.md",
-			URLPrefix:    setting.AppSubURL,
-			Metas:        localMetas,
+			Links: markup.Links{
+				Base: setting.AppSubURL,
+			},
+			Metas: localMetas,
 		}, input)
 		assert.NoError(t, err)
 		assert.Equal(t, strings.TrimSpace(expected), strings.TrimSpace(buffer))
@@ -138,7 +142,9 @@ func TestRender_links(t *testing.T) {
 		buffer, err := markup.RenderString(&markup.RenderContext{
 			Ctx:          git.DefaultContext,
 			RelativePath: "a.md",
-			URLPrefix:    markup.TestRepoURL,
+			Links: markup.Links{
+				Base: markup.TestRepoURL,
+			},
 		}, input)
 		assert.NoError(t, err)
 		assert.Equal(t, strings.TrimSpace(expected), strings.TrimSpace(buffer))
@@ -238,7 +244,9 @@ func TestRender_email(t *testing.T) {
 		res, err := markup.RenderString(&markup.RenderContext{
 			Ctx:          git.DefaultContext,
 			RelativePath: "a.md",
-			URLPrefix:    markup.TestRepoURL,
+			Links: markup.Links{
+				Base: markup.TestRepoURL,
+			},
 		}, input)
 		assert.NoError(t, err)
 		assert.Equal(t, strings.TrimSpace(expected), strings.TrimSpace(res))
@@ -309,7 +317,9 @@ func TestRender_emoji(t *testing.T) {
 		buffer, err := markup.RenderString(&markup.RenderContext{
 			Ctx:          git.DefaultContext,
 			RelativePath: "a.md",
-			URLPrefix:    markup.TestRepoURL,
+			Links: markup.Links{
+				Base: markup.TestRepoURL,
+			},
 		}, input)
 		assert.NoError(t, err)
 		assert.Equal(t, strings.TrimSpace(expected), strings.TrimSpace(buffer))
@@ -371,29 +381,34 @@ func TestRender_ShortLinks(t *testing.T) {
 
 	test := func(input, expected, expectedWiki string) {
 		buffer, err := markdown.RenderString(&markup.RenderContext{
-			Ctx:       git.DefaultContext,
-			URLPrefix: tree,
+			Ctx: git.DefaultContext,
+			Links: markup.Links{
+				Base:       markup.TestRepoURL,
+				BranchPath: "master",
+			},
 		}, input)
 		assert.NoError(t, err)
 		assert.Equal(t, strings.TrimSpace(expected), strings.TrimSpace(buffer))
 		buffer, err = markdown.RenderString(&markup.RenderContext{
-			Ctx:       git.DefaultContext,
-			URLPrefix: markup.TestRepoURL,
-			Metas:     localMetas,
-			IsWiki:    true,
+			Ctx: git.DefaultContext,
+			Links: markup.Links{
+				Base: markup.TestRepoURL,
+			},
+			Metas:  localMetas,
+			IsWiki: true,
 		}, input)
 		assert.NoError(t, err)
 		assert.Equal(t, strings.TrimSpace(expectedWiki), strings.TrimSpace(buffer))
 	}
 
-	rawtree := util.URLJoin(markup.TestRepoURL, "raw", "master")
+	mediatree := util.URLJoin(markup.TestRepoURL, "media", "master")
 	url := util.URLJoin(tree, "Link")
 	otherURL := util.URLJoin(tree, "Other-Link")
 	encodedURL := util.URLJoin(tree, "Link%3F")
-	imgurl := util.URLJoin(rawtree, "Link.jpg")
-	otherImgurl := util.URLJoin(rawtree, "Link+Other.jpg")
-	encodedImgurl := util.URLJoin(rawtree, "Link+%23.jpg")
-	notencodedImgurl := util.URLJoin(rawtree, "some", "path", "Link+#.jpg")
+	imgurl := util.URLJoin(mediatree, "Link.jpg")
+	otherImgurl := util.URLJoin(mediatree, "Link+Other.jpg")
+	encodedImgurl := util.URLJoin(mediatree, "Link+%23.jpg")
+	notencodedImgurl := util.URLJoin(mediatree, "some", "path", "Link+#.jpg")
 	urlWiki := util.URLJoin(markup.TestRepoURL, "wiki", "Link")
 	otherURLWiki := util.URLJoin(markup.TestRepoURL, "wiki", "Other-Link")
 	encodedURLWiki := util.URLJoin(markup.TestRepoURL, "wiki", "Link%3F")
@@ -475,21 +490,25 @@ func TestRender_ShortLinks(t *testing.T) {
 
 func TestRender_RelativeImages(t *testing.T) {
 	setting.AppURL = markup.TestAppURL
-	tree := util.URLJoin(markup.TestRepoURL, "src", "master")
 
 	test := func(input, expected, expectedWiki string) {
 		buffer, err := markdown.RenderString(&markup.RenderContext{
-			Ctx:       git.DefaultContext,
-			URLPrefix: tree,
-			Metas:     localMetas,
+			Ctx: git.DefaultContext,
+			Links: markup.Links{
+				Base:       markup.TestRepoURL,
+				BranchPath: "master",
+			},
+			Metas: localMetas,
 		}, input)
 		assert.NoError(t, err)
 		assert.Equal(t, strings.TrimSpace(expected), strings.TrimSpace(buffer))
 		buffer, err = markdown.RenderString(&markup.RenderContext{
-			Ctx:       git.DefaultContext,
-			URLPrefix: markup.TestRepoURL,
-			Metas:     localMetas,
-			IsWiki:    true,
+			Ctx: git.DefaultContext,
+			Links: markup.Links{
+				Base: markup.TestRepoURL,
+			},
+			Metas:  localMetas,
+			IsWiki: true,
 		}, input)
 		assert.NoError(t, err)
 		assert.Equal(t, strings.TrimSpace(expectedWiki), strings.TrimSpace(buffer))
@@ -521,9 +540,11 @@ func Test_ParseClusterFuzz(t *testing.T) {
 
 	var res strings.Builder
 	err := markup.PostProcess(&markup.RenderContext{
-		Ctx:       git.DefaultContext,
-		URLPrefix: "https://example.com",
-		Metas:     localMetas,
+		Ctx: git.DefaultContext,
+		Links: markup.Links{
+			Base: "https://example.com",
+		},
+		Metas: localMetas,
 	}, strings.NewReader(data), &res)
 	assert.NoError(t, err)
 	assert.NotContains(t, res.String(), "<html")
@@ -532,9 +553,11 @@ func Test_ParseClusterFuzz(t *testing.T) {
 
 	res.Reset()
 	err = markup.PostProcess(&markup.RenderContext{
-		Ctx:       git.DefaultContext,
-		URLPrefix: "https://example.com",
-		Metas:     localMetas,
+		Ctx: git.DefaultContext,
+		Links: markup.Links{
+			Base: "https://example.com",
+		},
+		Metas: localMetas,
 	}, strings.NewReader(data), &res)
 
 	assert.NoError(t, err)
@@ -543,6 +566,7 @@ func Test_ParseClusterFuzz(t *testing.T) {
 
 func TestPostProcess_RenderDocument(t *testing.T) {
 	setting.AppURL = markup.TestAppURL
+	setting.StaticURLPrefix = markup.TestAppURL // can't run standalone
 
 	localMetas := map[string]string{
 		"user": "go-gitea",
@@ -553,9 +577,11 @@ func TestPostProcess_RenderDocument(t *testing.T) {
 	test := func(input, expected string) {
 		var res strings.Builder
 		err := markup.PostProcess(&markup.RenderContext{
-			Ctx:       git.DefaultContext,
-			URLPrefix: "https://example.com",
-			Metas:     localMetas,
+			Ctx: git.DefaultContext,
+			Links: markup.Links{
+				Base: "https://example.com",
+			},
+			Metas: localMetas,
 		}, strings.NewReader(input), &res)
 		assert.NoError(t, err)
 		assert.Equal(t, strings.TrimSpace(expected), strings.TrimSpace(res.String()))
@@ -594,9 +620,8 @@ func TestIssue16020(t *testing.T) {
 
 	var res strings.Builder
 	err := markup.PostProcess(&markup.RenderContext{
-		Ctx:       git.DefaultContext,
-		URLPrefix: "https://example.com",
-		Metas:     localMetas,
+		Ctx:   git.DefaultContext,
+		Metas: localMetas,
 	}, strings.NewReader(data), &res)
 	assert.NoError(t, err)
 	assert.Equal(t, data, res.String())
@@ -611,9 +636,8 @@ func BenchmarkEmojiPostprocess(b *testing.B) {
 	for i := 0; i < b.N; i++ {
 		var res strings.Builder
 		err := markup.PostProcess(&markup.RenderContext{
-			Ctx:       git.DefaultContext,
-			URLPrefix: "https://example.com",
-			Metas:     localMetas,
+			Ctx:   git.DefaultContext,
+			Metas: localMetas,
 		}, strings.NewReader(data), &res)
 		assert.NoError(b, err)
 	}
@@ -622,8 +646,10 @@ func BenchmarkEmojiPostprocess(b *testing.B) {
 func TestFuzz(t *testing.T) {
 	s := "t/l/issues/8#/../../a"
 	renderContext := markup.RenderContext{
-		Ctx:       git.DefaultContext,
-		URLPrefix: "https://example.com/go-gitea/gitea",
+		Ctx: git.DefaultContext,
+		Links: markup.Links{
+			Base: "https://example.com/go-gitea/gitea",
+		},
 		Metas: map[string]string{
 			"user": "go-gitea",
 			"repo": "gitea",
@@ -640,9 +666,8 @@ func TestIssue18471(t *testing.T) {
 
 	var res strings.Builder
 	err := markup.PostProcess(&markup.RenderContext{
-		Ctx:       git.DefaultContext,
-		URLPrefix: "https://example.com",
-		Metas:     localMetas,
+		Ctx:   git.DefaultContext,
+		Metas: localMetas,
 	}, strings.NewReader(data), &res)
 
 	assert.NoError(t, err)