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Allow configuring <html lang> via html-lang file #92

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dbee96a
Allow configuring <html lang> via html-lang file
MavenRain Mar 31, 2026
ef41b8f
HTML-escape the html-lang attribute value
MavenRain Apr 8, 2026
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7 changes: 5 additions & 2 deletions compiler/src/Generate/Html.hs
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Original file line number Diff line number Diff line change
Expand Up @@ -71,9 +71,12 @@ sandwich_ root moduleName javascript =
customHead
else
"<title>" <> name <> "</title>"

htmlTag = Lamdera.unsafe $ Lamdera.Live.lamderaHtmlLang root
in
[r|<!DOCTYPE HTML>
<html>
"<!DOCTYPE HTML>\n"
<> htmlTag
<> [r|
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=5.0, minimum-scale=1.0">
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32 changes: 26 additions & 6 deletions extra/Lamdera/Live.hs
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Original file line number Diff line number Diff line change
Expand Up @@ -6,7 +6,8 @@ module Lamdera.Live where

import qualified Data.ByteString as BS
import qualified Data.ByteString.Builder as B
import qualified Data.Text.Encoding as T
import qualified Data.Text as T
import qualified Data.Text.Encoding as TE
import qualified System.Directory as Dir
import System.FilePath as FP
import Control.Exception (finally, throw)
Expand Down Expand Up @@ -40,16 +41,16 @@ lamderaLiveSrc =
overrideM <- readUtf8Text overridePathBuilt
case overrideM of
Just override -> do
pure (T.encodeUtf8Builder override)
pure (TE.encodeUtf8Builder override)
Nothing -> do
Lamdera.debug $ "Couldn't load override " ++ overridePath ++ ", using compiled lamderaLive"
pure (T.encodeUtf8Builder (T.decodeUtf8 lamderaLive))
pure (TE.encodeUtf8Builder (TE.decodeUtf8 lamderaLive))
else do
Lamdera.debug $ "Couldn't find override " ++ overridePath ++ ", using compiled lamderaLive"
pure (T.encodeUtf8Builder (T.decodeUtf8 lamderaLive))
pure (TE.encodeUtf8Builder (TE.decodeUtf8 lamderaLive))
else do
Lamdera.debug $ "🗿 Using compiled lamderaLive"
pure (T.encodeUtf8Builder (T.decodeUtf8 lamderaLive))
pure (TE.encodeUtf8Builder (TE.decodeUtf8 lamderaLive))


-- @TODO means we have to restart live for any changes... how to improve that?
Expand All @@ -58,12 +59,31 @@ lamderaLiveHead root = do
headHtmlM <- readUtf8Text $ root </> "head.html"
case headHtmlM of
Just headHtml ->
pure (True, T.encodeUtf8Builder headHtml)
pure (True, TE.encodeUtf8Builder headHtml)

Nothing ->
pure (False, "")


lamderaHtmlLang :: FilePath -> IO B.Builder
lamderaHtmlLang root = do
langM <- readUtf8Text $ root </> "html-lang"
pure $ maybe "<html>" toHtmlTag langM
where
toHtmlTag lang =
let trimmed = T.strip lang in
if T.null trimmed
then "<html>"
else "<html lang=\"" <> TE.encodeUtf8Builder (escapeHtmlAttr trimmed) <> "\">"

escapeHtmlAttr = T.concatMap $ \c -> case c of
'&' -> "&amp;"
'"' -> "&quot;"
'<' -> "&lt;"
'>' -> "&gt;"
_ -> T.singleton c


lamderaLive :: BS.ByteString
lamderaLive =
$(bsToExp =<< runIO (Lamdera.Relative.readByteString "extra/dist/live.js"))