From 04821bc1718aff975b51e98ce7bfb91888167c6d Mon Sep 17 00:00:00 2001
From: Matthew Kenigsberg <matthewkenigsberg@gmail.com>
Date: Tue, 5 May 2020 10:49:39 -0600
Subject: use flake's nixpkgs to find bashInteractive

---
 src/nix/dev-shell.cc    |  3 +--
 src/nix/installables.cc | 12 ++++++++++++
 src/nix/installables.hh |  7 +++++++
 3 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/src/nix/dev-shell.cc b/src/nix/dev-shell.cc
index d842be79f..b3314021f 100644
--- a/src/nix/dev-shell.cc
+++ b/src/nix/dev-shell.cc
@@ -286,9 +286,8 @@ struct CmdDevShell : Common, MixEnvironment
 
     std::string getBashPath(ref<Store> store)
     {
-        auto flakeRef = FlakeRef::fromAttrs({{"type","indirect"}, {"id", "nixpkgs"}});
         auto state = getEvalState();
-        auto lockedFlake = std::make_shared<flake::LockedFlake>(lockFlake(*state, flakeRef, lockFlags));
+        auto lockedFlake = std::make_shared<flake::LockedFlake>(lockFlake(*state, installable->nixpkgsFlakeRef(), lockFlags));
         auto cache = openEvalCache(*state, lockedFlake, true);
         auto root = cache->getRoot();
 
diff --git a/src/nix/installables.cc b/src/nix/installables.cc
index cae85b34e..4e38876ca 100644
--- a/src/nix/installables.cc
+++ b/src/nix/installables.cc
@@ -493,6 +493,18 @@ InstallableFlake::getCursor(EvalState & state, bool useEvalCache)
     return res;
 }
 
+FlakeRef InstallableFlake::nixpkgsFlakeRef() const
+{
+    auto lockedFlake = lockFlake(*(cmd.getEvalState()), flakeRef, cmd.lockFlags);
+
+    auto nixpkgsInput = lockedFlake.flake.inputs.find("nixpkgs");
+    if (nixpkgsInput != lockedFlake.flake.inputs.end()) {
+        return std::move(nixpkgsInput->second.ref);
+    }
+
+    return Installable::nixpkgsFlakeRef();
+}
+
 std::vector<std::shared_ptr<Installable>> SourceExprCommand::parseInstallables(
     ref<Store> store, std::vector<std::string> ss)
 {
diff --git a/src/nix/installables.hh b/src/nix/installables.hh
index 531720de6..57e3d6c8e 100644
--- a/src/nix/installables.hh
+++ b/src/nix/installables.hh
@@ -57,6 +57,11 @@ struct Installable
 
     virtual std::vector<std::pair<std::shared_ptr<eval_cache::AttrCursor>, std::string>>
     getCursor(EvalState & state, bool useEvalCache);
+
+    virtual FlakeRef nixpkgsFlakeRef() const
+    {
+        return std::move(FlakeRef::fromAttrs({{"type","indirect"}, {"id", "nixpkgs"}}));
+    }
 };
 
 struct InstallableValue : Installable
@@ -104,6 +109,8 @@ struct InstallableFlake : InstallableValue
 
     std::vector<std::pair<std::shared_ptr<eval_cache::AttrCursor>, std::string>>
     getCursor(EvalState & state, bool useEvalCache) override;
+
+    FlakeRef nixpkgsFlakeRef() const override;
 };
 
 ref<eval_cache::EvalCache> openEvalCache(
-- 
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