From 8e0aa7bc156ef813841f258b8c29a3202684fe05 Mon Sep 17 00:00:00 2001
From: Richard Marko <srk@48.io>
Date: Thu, 25 Feb 2021 14:31:12 +0100
Subject: [PATCH] repl: use pushScope to pass results from --eval -E

Improve my slopy `input` prototype from f7704b4.

```
hnix --repl --eval -E '{ a = 42; }'
hnix> a
42
```

In a case when argument passed to `-E` is not an attribute set,
we can't push it to scope directly, so we wrap it
in attribute set under `input` attribute, like previous version.

```
hnix --repl --eval -E '42'
hnix> input
42
```

Related to #292 #172.
---
 main/Main.hs | 15 ++++++++++++++-
 main/Repl.hs | 17 ++++-------------
 2 files changed, 18 insertions(+), 14 deletions(-)

diff --git a/main/Main.hs b/main/Main.hs
index c7c29bb87..9e4454de3 100644
--- a/main/Main.hs
+++ b/main/Main.hs
@@ -29,6 +29,7 @@ import qualified Nix.Eval                      as Eval
 import           Nix.Fresh.Basic
 import           Nix.Json
 import           Nix.Options.Parser
+import           Nix.Scope
 import           Nix.Standard
 import           Nix.Thunk.Basic
 import qualified Nix.Type.Env                  as Env
@@ -102,7 +103,19 @@ main = do
         if evaluate opts
           then do
             val <- Nix.nixEvalExprLoc mpath expr
-            withNixContext mempty (Repl.main' $ pure val)
+            fromValueMay val >>= \case
+              -- val is an AttrsSet, use pushScope to pass it to repl
+              -- XXX: be explicit about this? infered via pushScope
+              --Just (as :: AttrSet (StdValue (StandardT (StdIdT IO)))) -> do
+              Just as ->
+                withNixContext mempty
+                  $ pushScope as
+                  $ Repl.main
+              Nothing ->
+                -- pass value as `input`
+                withNixContext mempty
+                  $ pushScope (M.singleton "input" val)
+                  $ Repl.main
           else withNixContext mempty Repl.main
 
   process opts mpath expr
diff --git a/main/Repl.hs b/main/Repl.hs
index 7143f82e1..6b4d9cd94 100644
--- a/main/Repl.hs
+++ b/main/Repl.hs
@@ -19,7 +19,6 @@
 
 module Repl
   ( main
-  , main'
   ) where
 
 import           Nix                     hiding ( exec
@@ -30,7 +29,6 @@ import           Nix.Utils
 import           Nix.Value.Monad                (demand)
 
 import qualified Data.List
-import qualified Data.Maybe
 import qualified Data.HashMap.Lazy
 import           Data.Text                      (Text)
 import qualified Data.Text
@@ -65,13 +63,7 @@ import qualified System.IO.Error
 
 -- | Repl entry point
 main :: (MonadNix e t f m, MonadIO m, MonadMask m) =>  m ()
-main = main' Nothing
-
--- | Principled version allowing to pass initial value for context.
---
--- Passed value is stored in context with "input" key.
-main' :: (MonadNix e t f m, MonadIO m, MonadMask m) => Maybe (NValue t f m) -> m ()
-main' iniVal = initState iniVal >>= \s -> flip evalStateT s
+main = initState >>= \s -> flip evalStateT s
     $ System.Console.Repline.evalRepl
         banner
         cmd
@@ -148,8 +140,8 @@ defReplConfig = ReplConfig
   }
 
 -- | Create initial IState for REPL
-initState :: MonadNix e t f m => Maybe (NValue t f m) -> m (IState t f m)
-initState mIni = do
+initState :: MonadNix e t f m => m (IState t f m)
+initState = do
 
   builtins <- evalText "builtins"
 
@@ -157,8 +149,7 @@ initState mIni = do
 
   pure $ IState
     Nothing
-    (Data.HashMap.Lazy.fromList
-      $ ("builtins", builtins) : fmap ("input",) (Data.Maybe.maybeToList mIni))
+    (Data.HashMap.Lazy.fromList $ pure ("builtins", builtins))
     defReplConfig
       { cfgStrict = strict opts
       , cfgValues = values opts