From cfc38257cfcdabd34151d723906b38873e7ef6d0 Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Tue, 10 Mar 2020 19:21:47 +0100
Subject: [PATCH] Fix flake subdirectory handling

---
 corepkgs/call-flake.nix          | 10 +++++-----
 src/libexpr/flake/flake.cc       | 11 ++++++++---
 src/libexpr/primops/fetchTree.cc |  1 +
 3 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/corepkgs/call-flake.nix b/corepkgs/call-flake.nix
index 29ff41040..c59a0c75f 100644
--- a/corepkgs/call-flake.nix
+++ b/corepkgs/call-flake.nix
@@ -1,14 +1,14 @@
-locks: rootSrc:
+locks: rootSrc: rootSubdir:
 
 let
 
-  callFlake = sourceInfo: locks:
+  callFlake = sourceInfo: subdir: locks:
     let
-      flake = import (sourceInfo + "/flake.nix");
+      flake = import (sourceInfo + "/" + subdir + "/flake.nix");
 
       inputs = builtins.mapAttrs (n: v:
         if v.flake or true
-        then callFlake (fetchTree v.locked) v.inputs
+        then callFlake (fetchTree (removeAttrs v.locked ["dir"])) (v.locked.dir or "") v.inputs
         else fetchTree v.locked) locks;
 
       outputs = flake.outputs (inputs // { self = result; });
@@ -19,4 +19,4 @@ let
 
       result;
 
-in callFlake rootSrc (builtins.fromJSON locks).inputs
+in callFlake rootSrc rootSubdir (builtins.fromJSON locks).inputs
diff --git a/src/libexpr/flake/flake.cc b/src/libexpr/flake/flake.cc
index eac7d026d..9d8a5f950 100644
--- a/src/libexpr/flake/flake.cc
+++ b/src/libexpr/flake/flake.cc
@@ -626,15 +626,20 @@ void callFlake(EvalState & state,
     auto vCallFlake = state.allocValue();
     auto vLocks = state.allocValue();
     auto vRootSrc = state.allocValue();
-    auto vTmp = state.allocValue();
+    auto vRootSubdir = state.allocValue();
+    auto vTmp1 = state.allocValue();
+    auto vTmp2 = state.allocValue();
 
     mkString(*vLocks, lockedInputs.to_string());
 
     emitTreeAttrs(state, *flake.sourceInfo, flake.lockedRef.input, *vRootSrc);
 
+    mkString(*vRootSubdir, flake.lockedRef.subdir);
+
     state.evalFile(canonPath(settings.nixDataDir + "/nix/corepkgs/call-flake.nix", true), *vCallFlake);
-    state.callFunction(*vCallFlake, *vLocks, *vTmp, noPos);
-    state.callFunction(*vTmp, *vRootSrc, vRes, noPos);
+    state.callFunction(*vCallFlake, *vLocks, *vTmp1, noPos);
+    state.callFunction(*vTmp1, *vRootSrc, *vTmp2, noPos);
+    state.callFunction(*vTmp2, *vRootSubdir, vRes, noPos);
 }
 
 void callFlake(EvalState & state,
diff --git a/src/libexpr/primops/fetchTree.cc b/src/libexpr/primops/fetchTree.cc
index 66994c823..47667a1b8 100644
--- a/src/libexpr/primops/fetchTree.cc
+++ b/src/libexpr/primops/fetchTree.cc
@@ -76,6 +76,7 @@ static void prim_fetchTree(EvalState & state, const Pos & pos, Value * * args, V
     if (evalSettings.pureEval && !input->isImmutable())
         throw Error("in pure evaluation mode, 'fetchTree' requires an immutable input");
 
+    // FIXME: use fetchOrSubstituteTree
     auto [tree, input2] = input->fetchTree(state.store);
 
     if (state.allowedPaths)