feat(fmt): use template substitution instead of +=

release-notes/4.11.0.md

@@ -83,3 +83,7 @@ You might be happy, or fairly upset about this development. But it was important
 This meant you could use `bot.on("message")`, or `bot.on("text")` (text here is a message type, and not an update type, so this was really making sure that `update.message.text` existed). However, when polls were introduced, this caused a conflict. `bot.on("poll")` would match both `update.poll` (update about stopped polls sent by the bot) and `update.message.poll` (a message that is a native poll). At type-level, both objects will show as available, which was wrong.
 
 Besides, this type of filters really limited how far we could go with Telegraf. That's why we introduced filters, which are way more powerful and flexible!
+
+## Minor changes
+
+* Format helpers (`"telegraf/format"`) now use template string substitution instead of naively using `+=`. ([Discussion](https://t.me/TelegrafJSChat/87251))

src/core/helpers/formatting.ts

@@ -49,16 +49,20 @@ export function _fmt(kind: Types.Text | 'very-plain', opts?: object) {
     parts = typeof parts === 'string' ? [parts] : parts
     for (let i = 0; i < parts.length; i++) {
       // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
-      text += parts[i]!
+      text = `${text}${parts[i]!}`
+
       const item = items[i]
       if (item == null) continue
       if (!(item instanceof FmtString)) {
-        text += item
+        // item is some value that's not FmtString
+        text = `${text}${item}`
         continue
       }
+
+      // item is FmtString
       for (const child of item.entities || [])
         entities.push({ ...child, offset: text.length + child.offset })
-      text += item.text
+      text = `${text}${item.text}`
     }
     if (kind !== 'very-plain')
       entities.unshift({ type: kind, offset: 0, length: text.length, ...opts })