Fix broken Chroma CSS styles (#23174)

The CSS styles in Gitea themes are out-of-sync of Chroma's styles.

This PR introduces a `chroma-style-diff.go` tool to compare the diff.
The missing CSS styles have been added manually. They are left as empty
to reduce arguments because there was no color for them before.

And this PR fixes #22348, with just 2 lines changed: `.chroma .kt & .n`,
these colors are taken from GitHub.

It's good enough for #22348


![image](https://user-images.githubusercontent.com/2114189/221551941-0d27d11d-e71e-498f-8e88-92b558fe4a18.png)

---------

Co-authored-by: silverwind <me@silverwind.io>

5 files changed, 105 insertions, 8 deletions

diff --git a/.stylelintrc.yaml b/.stylelintrc.yaml
index ca0f16b07..c488d0677 100644
--- a/.stylelintrc.yaml
+++ b/.stylelintrc.yaml
@@ -1,12 +1,18 @@
 plugins:
   - stylelint-declaration-strict-value
 
+ignoreFiles:
+  - "**/*.go"
+
 overrides:
   - files: ["**/*.less"]
     customSyntax: postcss-less
   - files: ["**/chroma/*", "**/codemirror/*", "**/standalone/*", "**/console/*"]
     rules:
       scale-unlimited/declaration-strict-value: null
+  - files: ["**/chroma/*", "**/codemirror/*"]
+    rules:
+      block-no-empty: null
 
 rules:
   alpha-value-notation: null
diff --git a/web_src/less/chroma/chroma-style-diff.go b/web_src/less/chroma/chroma-style-diff.go
new file mode 100644
index 000000000..424325968
--- /dev/null
+++ b/web_src/less/chroma/chroma-style-diff.go
@@ -0,0 +1,79 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+//go:build ignore
+
+/*
+This tool is used to compare the CSS names in a chroma builtin styles with the Gitea theme CSS names.
+
+It outputs the difference between the two sets of CSS names, eg:
+
+```
+CSS names not in builtin:
+.chroma .ln
+----
+Builtin CSS names not in file:
+.chroma .vm
+```
+
+Developers could use this tool to re-sync the CSS names in the Gitea theme.
+*/
+
+package main
+
+import (
+	"os"
+	"regexp"
+	"strings"
+
+	"github.com/alecthomas/chroma/v2"
+)
+
+func main() {
+	if len(os.Args) != 2 {
+		println("Usage: chroma-style-diff css-or-less-file")
+		os.Exit(1)
+	}
+
+	data, err := os.ReadFile(os.Args[1])
+	if err != nil {
+		println(err.Error())
+		os.Exit(1)
+	}
+
+	content := string(data)
+
+	// a simple CSS parser to collect CSS names
+	content = regexp.MustCompile("//.*\r?\n").ReplaceAllString(content, "\n")
+	content = regexp.MustCompile("/\\*.*?\\*/").ReplaceAllString(content, "")
+	matches := regexp.MustCompile("\\s*([-.#:\\w\\s]+)\\s*\\{[^}]*}").FindAllStringSubmatch(content, -1)
+
+	cssNames := map[string]bool{}
+	for _, matchGroup := range matches {
+		cssName := strings.TrimSpace(matchGroup[1])
+		cssNames[cssName] = true
+	}
+
+	// collect Chroma builtin CSS names
+	builtin := map[string]bool{}
+	for tokenType, cssName := range chroma.StandardTypes {
+		if tokenType > 0 && cssName != "" {
+			builtin[".chroma ."+cssName] = true
+		}
+	}
+
+	// show the diff
+	println("CSS names not in builtin:")
+	for cssName := range cssNames {
+		if !builtin[cssName] {
+			println(cssName)
+		}
+	}
+	println("----")
+	println("Builtin CSS names not in file:")
+	for cssName := range builtin {
+		if !cssNames[cssName] {
+			println(cssName)
+		}
+	}
+}
diff --git a/web_src/less/chroma/dark.less b/web_src/less/chroma/dark.less
index 4be9cf791..1b0c722a1 100644
--- a/web_src/less/chroma/dark.less
+++ b/web_src/less/chroma/dark.less
@@ -7,17 +7,19 @@
 .chroma .cpf { color: #649bc4; } /* CommentPreprocFile */
 .chroma .cs { color: #9075cd; } /* CommentSpecial */
 .chroma .dl { color: #649bc4; } /* LiteralStringDelimiter */
+.chroma .fm {} /* NameFunctionMagic */
+.chroma .g {} /* Generic */
 .chroma .gd { color: #ffffff; background-color: #5f3737; } /* GenericDeleted */
 .chroma .ge { color: #ddee30; } /* GenericEmph */
 .chroma .gh { color: #ffaa10; } /* GenericHeading */
 .chroma .gi { color: #ffffff; background-color: #3a523a; } /* GenericInserted */
+.chroma .gl {} /* GenericUnderline */
 .chroma .go { color: #777e94; } /* GenericOutput */
 .chroma .gp { color: #ebdbb2; } /* GenericPrompt */
 .chroma .gr { color: #ff4433; } /* GenericError */
 .chroma .gs { color: #ebdbb2; } /* GenericStrong */
 .chroma .gt { color: #ff7540; } /* GenericTraceback */
 .chroma .gu { color: #b8bb26; } /* GenericSubheading */
-.chroma .hl { background-color: #3f424d; } /* LineHighlight */
 .chroma .il { color: #649bc4; } /* LiteralNumberIntegerLong */
 .chroma .k { color: #ff7540; } /* Keyword */
 .chroma .kc { color: #649bc4; } /* KeywordConstant */
@@ -25,16 +27,16 @@
 .chroma .kn { color: #ffaa10; } /* KeywordNamespace */
 .chroma .kp { color: #5f8700; } /* KeywordPseudo */
 .chroma .kr { color: #ff7540; } /* KeywordReserved */
-.chroma .kt { color: #fabd2f; } /* KeywordType */
-.chroma .ln { color: #7f8699; } /* LineNumbers */
-.chroma .lnt { color: #7f8699; } /* LineNumbersTable */
+.chroma .kt { color: #ff7b72; } /* KeywordType */
+.chroma .l {} /* Literal */
+.chroma .ld {} /* LiteralDate */
 .chroma .m { color: #649bc4; } /* LiteralNumber */
 .chroma .mb { color: #649bc4; } /* LiteralNumberBin */
 .chroma .mf { color: #649bc4; } /* LiteralNumberFloat */
 .chroma .mh { color: #649bc4; } /* LiteralNumberHex */
 .chroma .mi { color: #649bc4; } /* LiteralNumberInteger */
 .chroma .mo { color: #649bc4; } /* LiteralNumberOct */
-.chroma .n { color: #fabd2f; } /* Name */
+.chroma .n { color: #c9d1d9; } /* Name */
 .chroma .na { color: #b8bb26; } /* NameAttribute */
 .chroma .nb { color: #fabd2f; } /* NameBuiltin */
 .chroma .nc { color: #ffaa10; } /* NameClass */
@@ -51,6 +53,7 @@
 .chroma .o { color: #ff7540; } /* Operator */
 .chroma .ow { color: #5f8700; } /* OperatorWord */
 .chroma .p { color: #d2d4db; } /* Punctuation */
+.chroma .py {} /* NameProperty */
 .chroma .s { color: #b8bb26; } /* LiteralString */
 .chroma .s1 { color: #b8bb26; } /* LiteralStringSingle */
 .chroma .s2 { color: #b8bb26; } /* LiteralStringDouble */
@@ -67,4 +70,5 @@
 .chroma .vc { color: #ff7540; } /* NameVariableClass */
 .chroma .vg { color: #ffaa10; } /* NameVariableGlobal */
 .chroma .vi { color: #ffaa10; } /* NameVariableInstance */
+.chroma .vm {} /* NameVariableMagic */
 .chroma .w { color: #7f8699; } /* TextWhitespace */
diff --git a/web_src/less/chroma/light.less b/web_src/less/chroma/light.less
index 2e811844c..4bfce8fe7 100644
--- a/web_src/less/chroma/light.less
+++ b/web_src/less/chroma/light.less
@@ -7,16 +7,19 @@
 .chroma .cpf { color: #4c4dbc; } /* CommentPreprocFile */
 .chroma .cs { color: #999999; } /* CommentSpecial */
 .chroma .dl { color: #106303; } /* LiteralStringDelimiter */
+.chroma .fm {} /* NameFunctionMagic */
+.chroma .g {} /* Generic */
 .chroma .gd { color: #000000; background-color: #ffdddd; } /* GenericDeleted */
 .chroma .ge { color: #000000; } /* GenericEmph */
 .chroma .gh { color: #999999; } /* GenericHeading */
 .chroma .gi { color: #000000; background-color: #ddffdd; } /* GenericInserted */
+.chroma .gl {} /* GenericUnderline */
 .chroma .go { color: #888888; } /* GenericOutput */
 .chroma .gp { color: #555555; } /* GenericPrompt */
 .chroma .gr { color: #aa0000; } /* GenericError */
+.chroma .gs {} /* GenericStrong */
 .chroma .gt { color: #aa0000; } /* GenericTraceback */
 .chroma .gu { color: #aaaaaa; } /* GenericSubheading */
-.chroma .hl { background-color: #e5e5e5; } /* LineHighlight */
 .chroma .il { color: #009999; } /* LiteralNumberIntegerLong */
 .chroma .k { color: #d73a49; } /* Keyword */
 .chroma .kc { color: #d73a49; } /* KeywordConstant */
@@ -25,14 +28,15 @@
 .chroma .kp { color: #d73a49; } /* KeywordPseudo */
 .chroma .kr { color: #d73a49; } /* KeywordReserved */
 .chroma .kt { color: #445588; } /* KeywordType */
-.chroma .ln { color: #7f7f7f; } /* LineNumbers */
-.chroma .lnt { color: #7f7f7f; } /* LineNumbersTable */
+.chroma .l {} /* Literal */
+.chroma .ld {} /* LiteralDate */
 .chroma .m { color: #009999; } /* LiteralNumber */
 .chroma .mb { color: #009999; } /* LiteralNumberBin */
 .chroma .mf { color: #009999; } /* LiteralNumberFloat */
 .chroma .mh { color: #009999; } /* LiteralNumberHex */
 .chroma .mi { color: #009999; } /* LiteralNumberInteger */
 .chroma .mo { color: #009999; } /* LiteralNumberOct */
+.chroma .n {} /* Name */
 .chroma .na { color: #d73a49; } /* NameAttribute */
 .chroma .nb { color: #005cc5; } /* NameBuiltin */
 .chroma .nc { color: #445588; } /* NameClass */
@@ -48,6 +52,8 @@
 .chroma .nx { color: #24292e; } /* NameOther */
 .chroma .o { color: #d73a49; } /* Operator */
 .chroma .ow { color: #d73a49; } /* OperatorWord */
+.chroma .p {} /* Punctuation */
+.chroma .py {} /* NameProperty */
 .chroma .s { color: #106303; } /* LiteralString */
 .chroma .s1 { color: #cc7a00; } /* LiteralStringSingle */
 .chroma .s2 { color: #106303; } /* LiteralStringDouble */
@@ -64,4 +70,5 @@
 .chroma .vc { color: #008080; } /* NameVariableClass */
 .chroma .vg { color: #008080; } /* NameVariableGlobal */
 .chroma .vi { color: #008080; } /* NameVariableInstance */
+.chroma .vm {} /* NameVariableMagic */
 .chroma .w { color: #bbbbbb; } /* TextWhitespace */
diff --git a/web_src/less/themes/theme-arc-green.less b/web_src/less/themes/theme-arc-green.less
index 2f06f33ac..17b8f9bae 100644
--- a/web_src/less/themes/theme-arc-green.less
+++ b/web_src/less/themes/theme-arc-green.less
@@ -1,3 +1,4 @@
+@import "../chroma/base.less";
 @import "../chroma/dark.less";
 @import "../codemirror/dark.less";