From 84157674d955778c806efdafda311b2732242b38 Mon Sep 17 00:00:00 2001
From: Alexander Batischev <eual.jp@gmail.com>
Date: Thu, 12 Nov 2020 17:23:28 +0300
Subject: [PATCH] File.hs: +symlink-based static file compiler; for
 multi-gigabyte sites, this can be a major speedup (see #786) (#810)

Co-authored-by: gwern <gwern@gwern.net>
---
 lib/Hakyll/Core/File.hs | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/lib/Hakyll/Core/File.hs b/lib/Hakyll/Core/File.hs
index 49af6590a..6a5775e8d 100644
--- a/lib/Hakyll/Core/File.hs
+++ b/lib/Hakyll/Core/File.hs
@@ -8,6 +8,8 @@ module Hakyll.Core.File
     , copyFileCompiler
     , TmpFile (..)
     , newTmpFile
+    , SymlinkFile (..)
+    , symlinkFileCompiler
     ) where
 
 
@@ -20,6 +22,7 @@ import           System.Directory              (copyFileWithMetadata)
 import           System.Directory              (copyFile)
 #endif
 import           System.Directory              (doesFileExist,
+                                                createFileLink,
                                                 renameFile)
 import           System.FilePath               ((</>))
 import           System.Random                 (randomIO)
@@ -56,6 +59,19 @@ copyFileCompiler = do
     provider   <- compilerProvider <$> compilerAsk
     makeItem $ CopyFile $ resourceFilePath provider identifier
 
+--------------------------------------------------------------------------------
+-- | This will not copy a file but create a symlink, which can save space & time for static sites with many large static files which would normally be handled by copyFileCompiler. (Note: the user will need to make sure their sync method handles symbolic links correctly!)
+newtype SymlinkFile = SymlinkFile FilePath
+    deriving (Binary, Eq, Ord, Show, Typeable)
+--------------------------------------------------------------------------------
+instance Writable SymlinkFile where
+    write dst (Item _ (SymlinkFile src)) = createFileLink src dst
+--------------------------------------------------------------------------------
+symlinkFileCompiler :: Compiler (Item SymlinkFile)
+symlinkFileCompiler = do
+    identifier <- getUnderlying
+    provider   <- compilerProvider <$> compilerAsk
+    makeItem $ SymlinkFile $ resourceFilePath provider identifier
 
 --------------------------------------------------------------------------------
 newtype TmpFile = TmpFile FilePath