fix(eventlog-live-otelcol): add automatic flag to switch between using template-haskell and template-haskell-lift

Author: wenkokke

eventlog-live-otelcol/eventlog-live-otelcol.cabal

@@ -88,6 +88,14 @@ source-repository head
   location: https://github.com/well-typed/eventlog-live.git
   subdir:   eventlog-live-otelcol
 
+-- 2025-11-06:
+-- This flag should enable switching between template-haskell and
+-- template-haskell-lift, because the latter is not on nixpkgs.
+flag use-template-haskell-lift
+  description: Use template-haskell-lift in place of template-haskell
+  default:     False
+  manual:      False
+
 common language
   ghc-options:
     -Wall -Wcompat -Widentities -Wprepositive-qualified-module
@@ -140,6 +148,7 @@ library
     GHC.Eventlog.Live.Otelcol.Config.Default
     GHC.Eventlog.Live.Otelcol.Config.Default.Raw
     GHC.Eventlog.Live.Otelcol.Config.Types
+    Language.Haskell.TH.Lift.Compat
     Options.Applicative.Compat
     Paths_eventlog_live_otelcol
     System.Random.Compat
@@ -167,12 +176,18 @@ library
     , random                 >=1.2    && <1.4
     , strict-list            >=0.1    && <0.2
     , table-layout           >=1.0    && <1.1
-    , template-haskell-lift  >=0.1    && <0.2
     , text                   >=1.2    && <2.2
     , unordered-containers   >=0.2.20 && <0.3
     , vector                 >=0.11   && <0.14
     , yaml                   >=0.11   && <0.12
 
+  if flag(use-template-haskell-lift)
+    build-depends: template-haskell-lift >=0.1 && <0.2
+    cpp-options:   -DEVENTLOG_LIVE_OTELCOL_USE_TEMPLATE_HASKELL_LIFT
+
+  else
+    build-depends: template-haskell >=2.2 && <3.0
+
 executable eventlog-live-otelcol
   import:         language
   main-is:        Main.hs

eventlog-live-otelcol/src/GHC/Eventlog/Live/Otelcol/Config/Default.hs

@@ -27,7 +27,7 @@ import GHC.Eventlog.Live.Otelcol.Config.Default.Raw (defaultConfigByteString)
 import GHC.Eventlog.Live.Otelcol.Config.Types (Config)
 import GHC.Records (HasField (..))
 import GHC.TypeLits (KnownSymbol, Symbol, symbolVal)
-import Language.Haskell.TH.Lift (Exp, Lift (..), Q)
+import Language.Haskell.TH.Lift.Compat (Exp, Lift (..), Q)
 
 {- |
 Internal helper.

eventlog-live-otelcol/src/GHC/Eventlog/Live/Otelcol/Config/Types.hs

@@ -26,7 +26,7 @@ module GHC.Eventlog.Live.Otelcol.Config.Types (
 import Data.Aeson.Types (Encoding, FromJSON (..), Options (..), Parser, SumEncoding (..), ToJSON (..), Value (..), camelTo2, defaultOptions, genericParseJSON, genericToEncoding, genericToJSON)
 import Data.Text (Text)
 import GHC.Generics (Generic)
-import Language.Haskell.TH.Lift (Lift)
+import Language.Haskell.TH.Lift.Compat (Lift)
 
 {- |
 The configuration for @eventlog-live-otelcol@.

eventlog-live-otelcol/src/Language/Haskell/TH/Lift/Compat.hs

@@ -0,0 +1,13 @@
+{-# LANGUAGE CPP #-}
+
+module Language.Haskell.TH.Lift.Compat (
+  Exp,
+  Lift (..),
+  Q,
+) where
+
+#if defined(EVENTLOG_LIVE_OTELCOL_USE_TEMPLATE_HASKELL_LIFT)
+import Language.Haskell.TH.Lift (Exp, Lift (..), Q)
+#else
+import Language.Haskell.TH.Syntax (Exp, Lift (..), Q)
+#endif