fix: parse built asset tags from the document and render every entry stylesheet

go.mod

@@ -64,6 +64,7 @@ require (
 	go.uber.org/mock v0.6.0
 	golang.org/x/crypto v0.53.0
 	golang.org/x/image v0.20.0
+	golang.org/x/net v0.56.0
 	golang.org/x/term v0.44.0
 	golang.org/x/text v0.39.0
 	gopkg.in/gomail.v2 v2.0.0-20160411212932-81ebce5c23df
@@ -170,7 +171,6 @@ require (
 	go.uber.org/zap v1.27.0 // indirect
 	golang.org/x/arch v0.10.0 // indirect
 	golang.org/x/exp v0.0.0-20240909161429-701f63a606c0 // indirect
-	golang.org/x/net v0.56.0 // indirect
 	golang.org/x/sys v0.46.0 // indirect
 	golang.org/x/tools v0.47.0 // indirect
 	google.golang.org/protobuf v1.34.2 // indirect

internal/controller/template_controller.go

@@ -20,6 +20,7 @@
 package controller
 
 import (
+	"bytes"
 	"encoding/json"
 	"fmt"
 	"html/template"
@@ -50,13 +51,17 @@ import (
 	"github.com/apache/answer/ui"
 	"github.com/gin-gonic/gin"
 	"github.com/segmentfault/pacman/log"
+	"golang.org/x/net/html"
 )
 
 var SiteUrl = ""
 
 type TemplateController struct {
-	scriptPath               []string
-	cssPath                  string
+	scriptPath []string
+	// cssPath lists every stylesheet the frontend build emits, in document
+	// order; a build that emits more than one entry stylesheet needs all of
+	// them, not just the first, or server-rendered pages come back unstyled.
+	cssPath                  []string
 	templateRenderController *templaterender.TemplateRenderController
 	siteInfoService          siteinfo_common.SiteInfoCommonService
 	eventQueueService        eventqueue.Service
@@ -83,24 +88,64 @@ func NewTemplateController(
 		questionService:          questionService,
 	}
 }
-func GetStyle() (script []string, css string) {
+func GetStyle() (script []string, css []string) {
 	file, err := ui.Build.ReadFile("build/index.html")
 	if err != nil {
 		return
 	}
-	scriptRegexp := regexp.MustCompile(`<script defer="defer" src="([^"]*)"></script>`)
-	scriptData := scriptRegexp.FindAllStringSubmatch(string(file), -1)
-	for _, s := range scriptData {
-		if len(s) == 2 {
-			script = append(script, s[1])
+
+	// Script and stylesheet tags are read from the parsed document, so
+	// attribute order, attribute set (module vs classic scripts), and
+	// quoting do not matter. That shape has already changed once; a
+	// bundler change that breaks it now fails the guarding test instead
+	// of silently shipping pages with no JS or CSS.
+	doc, err := html.Parse(bytes.NewReader(file))
+	if err != nil {
+		return
+	}
+
+	attr := func(n *html.Node, key string) (string, bool) {
+		for _, a := range n.Attr {
+			if a.Key == key {
+				return a.Val, true
+			}
 		}
+		return "", false
+	}
+	isStylesheet := func(n *html.Node) bool {
+		rel, ok := attr(n, "rel")
+		if !ok {
+			return false
+		}
+		for tok := range strings.FieldsSeq(rel) {
+			if strings.EqualFold(tok, "stylesheet") {
+				return true
+			}
+		}
+		return false
 	}
 
-	cssRegexp := regexp.MustCompile(`<link href="(.*)" rel="stylesheet">`)
-	cssListData := cssRegexp.FindStringSubmatch(string(file))
-	if len(cssListData) == 2 {
-		css = cssListData[1]
+	var walk func(*html.Node)
+	walk = func(n *html.Node) {
+		if n.Type == html.ElementNode {
+			switch n.Data {
+			case "script":
+				if src, ok := attr(n, "src"); ok && src != "" {
+					script = append(script, src)
+				}
+			case "link":
+				if isStylesheet(n) {
+					if href, ok := attr(n, "href"); ok && href != "" {
+						css = append(css, href)
+					}
+				}
+			}
+		}
+		for c := n.FirstChild; c != nil; c = c.NextSibling {
+			walk(c)
+		}
 	}
+	walk(doc)
 	return
 }
 func (tc *TemplateController) SiteInfo(ctx *gin.Context) *schema.TemplateSiteInfoResp {
@@ -560,7 +605,7 @@ func (tc *TemplateController) Page404(ctx *gin.Context) {
 
 func (tc *TemplateController) html(ctx *gin.Context, code int, tpl string, siteInfo *schema.TemplateSiteInfoResp, data gin.H) {
 	prefix := ""
-	cssPath := ""
+	cssPath := make([]string, len(tc.cssPath))
 	scriptPath := make([]string, len(tc.scriptPath))
 
 	_ = plugin.CallCDN(func(fn plugin.CDN) error {
@@ -572,7 +617,9 @@ func (tc *TemplateController) html(ctx *gin.Context, code int, tpl string, siteI
 		if prefix[len(prefix)-1:] == "/" {
 			prefix = strings.TrimSuffix(prefix, "/")
 		}
-		cssPath = prefix + tc.cssPath
+		for i, path := range tc.cssPath {
+			cssPath[i] = prefix + path
+		}
 		for i, path := range tc.scriptPath {
 			scriptPath[i] = prefix + path
 		}

internal/controller/template_controller_test.go

@@ -0,0 +1,78 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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 required 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 controller
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/apache/answer/ui"
+	"github.com/stretchr/testify/require"
+)
+
+// GetStyle scrapes the script and stylesheet paths out of the built
+// index.html and every server-rendered page reuses them. The scrape is
+// coupled to the exact attribute order and attribute set that the frontend
+// build tool writes into those tags, and nothing in the system reports a
+// mismatch: the frontend build still succeeds, the dev server still works,
+// the binary still compiles, and the server-rendered pages simply come back
+// with no script tags and no stylesheet.
+//
+// Assert the coupling directly so a change to the emitted tag shape fails
+// here instead of shipping.
+func TestGetStyleResolvesBuiltAssets(t *testing.T) {
+	const builtIndexPath = "build/index.html"
+
+	raw, err := ui.Build.ReadFile(builtIndexPath)
+	if err != nil {
+		t.Skipf("no frontend build embedded at %s; build the frontend and re-run: %v", builtIndexPath, err)
+	}
+
+	scripts, css := GetStyle()
+
+	require.NotEmpty(t, scripts,
+		"no script sources parsed out of %s; server-rendered pages would load without any JavaScript", builtIndexPath)
+	for i, src := range scripts {
+		require.NotEmpty(t, src, "script source %d parsed out of %s is empty", i, builtIndexPath)
+	}
+
+	require.NotEmpty(t, css,
+		"no stylesheet href parsed out of %s; server-rendered pages would load unstyled", builtIndexPath)
+	for i, href := range css {
+		require.NotEmpty(t, href,
+			"stylesheet href %d parsed out of %s is empty; server-rendered pages would load unstyled", i, builtIndexPath)
+	}
+
+	// Finding every stylesheet matters as much as finding one. The build emits
+	// more than a single entry stylesheet, and a parser that stopped at the
+	// first one would still satisfy every assertion above while half the page's
+	// CSS silently stopped loading. That regression has happened once already.
+	//
+	// Count them again by a deliberately different and cruder method than the
+	// parser uses, so the two have to agree. It is a lower bound: a build that
+	// quotes attributes differently drives this to zero and the comparison
+	// simply stops constraining, which is why it supplements the assertions
+	// above rather than replacing them.
+	declared := strings.Count(string(raw), `rel="stylesheet"`)
+	require.GreaterOrEqual(t, len(css), declared,
+		"%s declares at least %d stylesheets but only %d were parsed out of it; "+
+			"server-rendered pages would load missing part of their CSS",
+		builtIndexPath, declared, len(css))
+}

ui/template/header.html

@@ -34,7 +34,9 @@
     <link rel="canonical" href="{{.siteinfo.Canonical}}" />
     <link rel="manifest" href="{{$.baseURL}}/manifest.json" />
     <link rel="search" type="application/opensearchdescription+xml" href="{{$.baseURL}}/opensearch.xml" title="{{.siteinfo.General.Name}}" />
-    <link href="{{.cssPath}}" rel="stylesheet" />
+    {{range $path := .cssPath}}
+    <link href="{{$path}}" rel="stylesheet" />
+    {{end}}
     <link href="{{$.baseURL}}/custom.css" rel="stylesheet" />
     <link
       rel="icon"