Add cachebusters to CSS and JS

support/shake/1lab-shake.cabal

@@ -77,6 +77,7 @@ executable shake
       HTML.Emit
     , Shake.AgdaCompile
     , Shake.Diagram
+    , Shake.Digest
     , Shake.Git
     , Shake.KaTeX
     , Shake.LinkGraph

support/shake/app/Main.hs

@@ -33,6 +33,7 @@ import Shake.LinkGraph
 import Shake.Markdown
 import Shake.Modules
 import Shake.Diagram
+import Shake.Digest
 import Shake.KaTeX
 import Shake.Git
 import Shake.Utils
@@ -48,6 +49,7 @@ import Timer
 rules :: Rules ()
 rules = do
   agdaRules
+  digestRules
   gitRules
   katexRules
   moduleRules

support/shake/app/Shake/Digest.hs

@@ -0,0 +1,29 @@
+{-# LANGUAGE BlockArguments, GeneralizedNewtypeDeriving, TypeFamilies #-}
+
+-- | Compute a truncated hash of a file, useful for computing cache-busters
+-- (or other unique ids) for a file.
+module Shake.Digest (digestRules, getFileDigest) where
+
+import qualified Data.ByteString.Lazy as LazyBS
+import Data.Digest.Pure.SHA
+import Data.Typeable
+
+import Development.Shake.Classes (Hashable, Binary, NFData)
+import Development.Shake
+
+newtype FileDigest = FileDigest FilePath
+  deriving (Show, Typeable, Eq, Hashable, Binary, NFData)
+
+type instance RuleResult FileDigest = String
+
+-- | Shake rules required for computing file digest.
+digestRules :: Rules ()
+digestRules = versioned 1 do
+  _ <- addOracle \(FileDigest f) -> do
+    need [f]
+    take 8 . showDigest . sha256 <$> liftIO (LazyBS.readFile f)
+  pure ()
+
+-- | Compute a short digest of a file.
+getFileDigest :: FilePath -> Action String
+getFileDigest = askOracle . FileDigest

support/shake/app/Shake/Markdown.hs

@@ -47,6 +47,7 @@ import Shake.LinkReferences
 import Shake.SearchData
 import Shake.Highlights
 import Shake.Options
+import Shake.Digest
 import Shake.KaTeX
 import Shake.Git
 
@@ -198,8 +199,18 @@ buildMarkdown modname input output = do
   need dependencies
 
   baseUrl <- getBaseUrl
+  digest <- do
+    cssDigest <- getFileDigest "_build/html/css/default.css"
+    startJsDigest <- getFileDigest "_build/html/start.js"
+    mainJsDigest <- getFileDigest "_build/html/main.js"
+    pure . Context . Map.fromList $
+      [ ("css",       toVal (Text.pack cssDigest))
+      , ("start-js",  toVal (Text.pack startJsDigest))
+      , ("main-js",   toVal (Text.pack mainJsDigest))
+      ]
+
   text <- liftIO $ either (fail . show) pure =<<
-    runIO (renderMarkdown authors references modname baseUrl markdown)
+    runIO (renderMarkdown authors references modname baseUrl digest markdown)
 
   let tags = foldEquations False (parseTags text)
   tags <- renderHighlights tags
@@ -343,8 +354,9 @@ renderMarkdown :: PandocMonad m
                -> [Val Text]   -- ^ List of references
                -> String       -- ^ Name of the current module
                -> String       -- ^ Base URL
+               -> Context Text -- ^ Digests of the various files.
                -> Pandoc -> m Text
-renderMarkdown authors references modname baseUrl markdown = do
+renderMarkdown authors references modname baseUrl digest markdown = do
   template <- getTemplate templateName >>= runWithPartials . compileTemplate templateName
                 >>= either (throwError . PandocTemplateError . Text.pack) pure
   let
@@ -358,6 +370,7 @@ renderMarkdown authors references modname baseUrl markdown = do
       , ("authors",      toVal authors')
       , ("reference",    toVal references)
       , ("base-url",     toVal (Text.pack baseUrl))
+      , ("digest",       toVal digest)
       ]
 
     options = def { writerTemplate        = Just template

support/web/template.html

@@ -7,7 +7,7 @@
 
   <title>$pagetitle$ - 1Lab</title>
 
-  <link rel="stylesheet" href="$base-url$/css/default.css" />
+  <link rel="stylesheet" href="$base-url$/css/default.css?v=$digest.css$" />
   <link rel="stylesheet" href="$base-url$/css/katex.min.css" />
 
   <meta name="twitter:card" content="summary" />
@@ -29,8 +29,8 @@
   <meta name="description" content="A formalised, explorable online resource for Homotopy Type Theory." />
   $endif$
 
-  <script src="$base-url$/start.js"></script>
-  <script defer src="$base-url$/main.js"></script>
+  <script src="$base-url$/start.js?v=$digest.start-js$"></script>
+  <script defer src="$base-url$/main.js?v=$digest.main-js$"></script>
 
   <noscript>
     <style>