Add support for plaintext system e-mail templates.

If `<!doctype html>` is not found in static/email-templates/base.html, all system e-mail templates are assumed to be plaintext and go out as content-type: plaintext e-mails. With this, all HTML tags can be stripped out of the system e-mail templates (while maintaining Go template tags and logic) to have plaintext system e-mail templates. Closes #546
knadh · Oct 28, 2021 · b290d27 · b290d27
1 parent 1c8ac0f
commit b290d27
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Showing 5 changed files with 45 additions and 12 deletions.
diff --git a/cmd/campaigns.go b/cmd/campaigns.go
@@ -773,7 +773,7 @@ func makeOptinCampaignMessage(o campaignReq, app *App) (campaignReq, error) {
 
 	// Prepare sample opt-in message for the campaign.
 	var b bytes.Buffer
-	if err := app.notifTpls.ExecuteTemplate(&b, "optin-campaign", struct {
+	if err := app.notifTpls.tpls.ExecuteTemplate(&b, "optin-campaign", struct {
 		Lists        []models.List
 		OptinURLAttr template.HTMLAttr
 	}{lists, optinURLAttr}); err != nil {

diff --git a/cmd/init.go b/cmd/init.go
@@ -1,6 +1,7 @@
 package main
 
 import (
+	"bytes"
 	"encoding/json"
 	"fmt"
 	"html/template"
@@ -32,6 +33,7 @@ import (
 	"github.com/knadh/listmonk/internal/messenger/email"
 	"github.com/knadh/listmonk/internal/messenger/postback"
 	"github.com/knadh/listmonk/internal/subimporter"
+	"github.com/knadh/listmonk/models"
 	"github.com/knadh/stuffbin"
 	"github.com/labstack/echo"
 	flag "github.com/spf13/pflag"
@@ -78,6 +80,11 @@ type constants struct {
 	BounceSendgridEnabled bool
 }
 
+type notifTpls struct {
+	tpls        *template.Template
+	contentType string
+}
+
 func initFlags() {
 	f := flag.NewFlagSet("config", flag.ContinueOnError)
 	f.Usage = func() {
@@ -491,7 +498,7 @@ func initMediaStore() media.Store {
 
 // initNotifTemplates compiles and returns e-mail notification templates that are
 // used for sending ad-hoc notifications to admins and subscribers.
-func initNotifTemplates(path string, fs stuffbin.FileSystem, i *i18n.I18n, cs *constants) *template.Template {
+func initNotifTemplates(path string, fs stuffbin.FileSystem, i *i18n.I18n, cs *constants) *notifTpls {
 	// Register utility functions that the e-mail templates can use.
 	funcs := template.FuncMap{
 		"RootURL": func() string {
@@ -505,11 +512,36 @@ func initNotifTemplates(path string, fs stuffbin.FileSystem, i *i18n.I18n, cs *c
 		},
 	}
 
-	tpl, err := stuffbin.ParseTemplatesGlob(funcs, fs, "/static/email-templates/*.html")
+	tpls, err := stuffbin.ParseTemplatesGlob(funcs, fs, "/static/email-templates/*.html")
 	if err != nil {
 		lo.Fatalf("error parsing e-mail notif templates: %v", err)
 	}
-	return tpl
+
+	html, err := fs.Read("/static/email-templates/base.html")
+	if err != nil {
+		lo.Fatalf("error reading static/email-templates/base.html: %v", err)
+	}
+
+	out := &notifTpls{
+		tpls:        tpls,
+		contentType: models.CampaignContentTypeHTML,
+	}
+
+	// Determine whether the notification templates are HTML or plaintext.
+	// Copy the first few (arbitrary) bytes of the template and check if has the <!doctype html> tag.
+	ln := 256
+	if len(html) < ln {
+		ln = len(html)
+	}
+	h := make([]byte, ln)
+	copy(h, html[0:ln])
+
+	if !bytes.Contains(bytes.ToLower(h), []byte("<!doctype html>")) {
+		out.contentType = models.CampaignContentTypePlain
+		lo.Println("system e-mail templates are plaintext")
+	}
+
+	return out
 }
 
 // initBounceManager initializes the bounce manager that scans mailboxes and listens to webhooks

diff --git a/cmd/main.go b/cmd/main.go
@@ -3,7 +3,6 @@ package main
 import (
 	"context"
 	"fmt"
-	"html/template"
 	"io"
 	"log"
 	"os"
@@ -43,7 +42,7 @@ type App struct {
 	media      media.Store
 	i18n       *i18n.I18n
 	bounce     *bounce.Manager
-	notifTpls  *template.Template
+	notifTpls  *notifTpls
 	log        *log.Logger
 	bufLog     *buflog.BufLog
 

diff --git a/cmd/notifications.go b/cmd/notifications.go
@@ -27,12 +27,13 @@ func (app *App) sendNotification(toEmails []string, subject, tplName string, dat
 	}
 
 	var b bytes.Buffer
-	if err := app.notifTpls.ExecuteTemplate(&b, tplName, data); err != nil {
+	if err := app.notifTpls.tpls.ExecuteTemplate(&b, tplName, data); err != nil {
 		app.log.Printf("error compiling notification template '%s': %v", tplName, err)
 		return err
 	}
 
 	m := manager.Message{}
+	m.ContentType = app.notifTpls.contentType
 	m.From = app.constants.FromEmail
 	m.To = toEmails
 	m.Subject = subject

diff --git a/cmd/public.go b/cmd/public.go
@@ -437,7 +437,7 @@ func handleSelfExportSubscriberData(c echo.Context) error {
 
 	// Prepare the attachment e-mail.
 	var msg bytes.Buffer
-	if err := app.notifTpls.ExecuteTemplate(&msg, notifSubscriberData, data); err != nil {
+	if err := app.notifTpls.tpls.ExecuteTemplate(&msg, notifSubscriberData, data); err != nil {
 		app.log.Printf("error compiling notification template '%s': %v", notifSubscriberData, err)
 		return c.Render(http.StatusInternalServerError, tplMessage,
 			makeMsgTpl(app.i18n.T("public.errorTitle"), "",
@@ -447,10 +447,11 @@ func handleSelfExportSubscriberData(c echo.Context) error {
 	// Send the data as a JSON attachment to the subscriber.
 	const fname = "data.json"
 	if err := app.messengers[emailMsgr].Push(messenger.Message{
-		From:    app.constants.FromEmail,
-		To:      []string{data.Email},
-		Subject: "Your data",
-		Body:    msg.Bytes(),
+		ContentType: app.notifTpls.contentType,
+		From:        app.constants.FromEmail,
+		To:          []string{data.Email},
+		Subject:     "Your data",
+		Body:        msg.Bytes(),
 		Attachments: []messenger.Attachment{
 			{
 				Name:    fname,