From 47b9dc226e49f6b3b59bba209665038598dfb439 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Janne=20He=C3=9F?= <janne@hess.ooo>
Date: Wed, 7 Aug 2024 10:31:07 +0200
Subject: [PATCH] Allow overwriting the version with a .version file

---
 MAINTENANCE.md |  3 +++
 main/Main.hs   | 10 +++++++++-
 nixfmt.cabal   |  2 ++
 3 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/MAINTENANCE.md b/MAINTENANCE.md
index 172b9901..ccf58b94 100644
--- a/MAINTENANCE.md
+++ b/MAINTENANCE.md
@@ -1,5 +1,8 @@
 # Maintainer documentation
 
+Writing to .version in the root of the project causes this version to be returned by `nixfmt --version`
+rather than the version from the cabalfile.
+
 ## Making a new release
 
 - Check the commit log if anything is missing from the change log.
diff --git a/main/Main.hs b/main/Main.hs
index 1efb8280..d7348a6e 100644
--- a/main/Main.hs
+++ b/main/Main.hs
@@ -1,11 +1,14 @@
 {-# LANGUAGE DeriveDataTypeable #-}
 {-# LANGUAGE MultiWayIf #-}
 {-# LANGUAGE NamedFieldPuns #-}
+{-# LANGUAGE TemplateHaskell #-}
 
 module Main where
 
 import Control.Concurrent (Chan, forkIO, newChan, readChan, writeChan)
+import Data.ByteString.Char8 (unpack)
 import Data.Either (lefts)
+import Data.FileEmbed
 import Data.List (isSuffixOf)
 import Data.Text (Text)
 import qualified Data.Text.IO as TextIO (getContents, hPutStr, putStr)
@@ -46,6 +49,11 @@ data Nixfmt = Nixfmt
   }
   deriving (Show, Data, Typeable)
 
+versionFromFile :: String
+versionFromFile = case $(embedFileIfExists ".version") of
+  Just ver -> unpack ver
+  _ -> showVersion version
+
 options :: Nixfmt
 options =
   let defaultWidth = 100
@@ -67,7 +75,7 @@ options =
             &= help
               "Pretty print the internal AST, only for debugging"
       }
-      &= summary ("nixfmt v" ++ showVersion version)
+      &= summary ("nixfmt " ++ versionFromFile)
       &= help "Format Nix source code"
 
 data Target = Target
diff --git a/nixfmt.cabal b/nixfmt.cabal
index 35f532f5..33095527 100644
--- a/nixfmt.cabal
+++ b/nixfmt.cabal
@@ -31,7 +31,9 @@ executable nixfmt
   hs-source-dirs:      main
   build-depends:
       base             >= 4.12.0 && < 4.19
+    , bytestring
     , cmdargs          >= 0.10.20 && < 0.11
+    , file-embed
     , nixfmt
     , unix             >= 2.7.2 && < 2.9
     , text             >= 1.2.3 && < 2.2