Add KaTeX rendering to Markdown. (#20571)

This PR adds mathematical rendering with KaTeX.

The first step is to add a Goldmark extension that detects the latex
(and tex) mathematics delimiters.

The second step to make this extension only run if math support is
enabled.

The second step is to then add KaTeX CSS and JS to the head which will
load after the dom is rendered.

Fix #3445

Signed-off-by: Andrew Thornton <art27@cantab.net>

Signed-off-by: Andrew Thornton <art27@cantab.net>
Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

1 files changed, 162 insertions, 0 deletions

diff --git a/modules/markup/markdown/renderconfig_test.go b/modules/markup/markdown/renderconfig_test.go
new file mode 100644
index 0000000000..1027035cda
--- /dev/null
+++ b/modules/markup/markdown/renderconfig_test.go
@@ -0,0 +1,162 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package markdown
+
+import (
+	"testing"
+
+	"gopkg.in/yaml.v3"
+)
+
+func TestRenderConfig_UnmarshalYAML(t *testing.T) {
+	tests := []struct {
+		name     string
+		expected *RenderConfig
+		args     string
+	}{
+		{
+			"empty", &RenderConfig{
+				Meta: "table",
+				Icon: "table",
+				Lang: "",
+			}, "",
+		},
+		{
+			"lang", &RenderConfig{
+				Meta: "table",
+				Icon: "table",
+				Lang: "test",
+			}, "lang: test",
+		},
+		{
+			"metatable", &RenderConfig{
+				Meta: "table",
+				Icon: "table",
+				Lang: "",
+			}, "gitea: table",
+		},
+		{
+			"metanone", &RenderConfig{
+				Meta: "none",
+				Icon: "table",
+				Lang: "",
+			}, "gitea: none",
+		},
+		{
+			"metadetails", &RenderConfig{
+				Meta: "details",
+				Icon: "table",
+				Lang: "",
+			}, "gitea: details",
+		},
+		{
+			"metawrong", &RenderConfig{
+				Meta: "details",
+				Icon: "table",
+				Lang: "",
+			}, "gitea: wrong",
+		},
+		{
+			"toc", &RenderConfig{
+				TOC:  true,
+				Meta: "table",
+				Icon: "table",
+				Lang: "",
+			}, "include_toc: true",
+		},
+		{
+			"tocfalse", &RenderConfig{
+				TOC:  false,
+				Meta: "table",
+				Icon: "table",
+				Lang: "",
+			}, "include_toc: false",
+		},
+		{
+			"toclang", &RenderConfig{
+				Meta: "table",
+				Icon: "table",
+				TOC:  true,
+				Lang: "testlang",
+			}, `
+	include_toc: true
+	lang: testlang
+`,
+		},
+		{
+			"complexlang", &RenderConfig{
+				Meta: "table",
+				Icon: "table",
+				Lang: "testlang",
+			}, `
+	gitea:
+		lang: testlang
+`,
+		},
+		{
+			"complexlang2", &RenderConfig{
+				Meta: "table",
+				Icon: "table",
+				Lang: "testlang",
+			}, `
+	lang: notright
+	gitea:
+		lang: testlang
+`,
+		},
+		{
+			"complexlang", &RenderConfig{
+				Meta: "table",
+				Icon: "table",
+				Lang: "testlang",
+			}, `
+	gitea:
+		lang: testlang
+`,
+		},
+		{
+			"complex2", &RenderConfig{
+				Lang: "two",
+				Meta: "table",
+				TOC:  true,
+				Icon: "smiley",
+			}, `
+	lang: one
+	include_toc: true
+	gitea:
+		details_icon: smiley
+		meta: table
+		include_toc: true
+		lang: two
+`,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := &RenderConfig{
+				Meta: "table",
+				Icon: "table",
+				Lang: "",
+			}
+			if err := yaml.Unmarshal([]byte(tt.args), got); err != nil {
+				t.Errorf("RenderConfig.UnmarshalYAML() error = %v", err)
+				return
+			}
+
+			if got.Meta != tt.expected.Meta {
+				t.Errorf("Meta Expected %s Got %s", tt.expected.Meta, got.Meta)
+			}
+			if got.Icon != tt.expected.Icon {
+				t.Errorf("Icon Expected %s Got %s", tt.expected.Icon, got.Icon)
+			}
+			if got.Lang != tt.expected.Lang {
+				t.Errorf("Lang Expected %s Got %s", tt.expected.Lang, got.Lang)
+			}
+			if got.TOC != tt.expected.TOC {
+				t.Errorf("TOC Expected %t Got %t", tt.expected.TOC, got.TOC)
+			}
+		})
+	}
+}