From c66865dff1747ecd55915ef8c549dc1a088ff168 Mon Sep 17 00:00:00 2001
From: Nikolay Amiantov <ab@fmap.me>
Date: Fri, 4 Mar 2016 13:47:19 +0300
Subject: [PATCH 1/2] builtins.readFile: Propagate path context

Co-authored-by: Shea Levy <shea@shealevy.com>
---
 src/libexpr/primops.cc | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index d7382af6b..1d2a7d5d2 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -1470,7 +1470,11 @@ static void prim_readFile(EvalState & state, const Pos & pos, Value * * args, Va
     string s = readFile(path);
     if (s.find((char) 0) != string::npos)
         throw Error("the contents of the file '%1%' cannot be represented as a Nix string", path);
-    v.mkString(s);
+    auto refs = state.store->isInStore(path) ?
+        state.store->queryPathInfo(state.store->toStorePath(path).first)->references :
+        StorePathSet{};
+    auto context = state.store->printStorePathSet(refs);
+    v.mkString(s, context);
 }
 
 static RegisterPrimOp primop_readFile({

From 120ca245d13708743a59e83da12ec90902636236 Mon Sep 17 00:00:00 2001
From: Nikolay Amiantov <ab@fmap.me>
Date: Sat, 11 Nov 2017 01:51:34 +0300
Subject: [PATCH 2/2] Add test for readFile keeping context

---
 tests/local.mk                    |  3 ++-
 tests/readfile-context.builder.sh |  1 +
 tests/readfile-context.nix        | 19 +++++++++++++++++++
 tests/readfile-context.sh         | 16 ++++++++++++++++
 4 files changed, 38 insertions(+), 1 deletion(-)
 create mode 100644 tests/readfile-context.builder.sh
 create mode 100644 tests/readfile-context.nix
 create mode 100644 tests/readfile-context.sh

diff --git a/tests/local.mk b/tests/local.mk
index c22e779a6..d2a46f22b 100644
--- a/tests/local.mk
+++ b/tests/local.mk
@@ -59,7 +59,8 @@ nix_tests = \
   ca/recursive.sh \
   ca/concurrent-builds.sh \
   ca/nix-copy.sh \
-  eval-store.sh
+  eval-store.sh \
+  readfile-context.sh
   # parallel.sh
 
 ifeq ($(HAVE_LIBCPUID), 1)
diff --git a/tests/readfile-context.builder.sh b/tests/readfile-context.builder.sh
new file mode 100644
index 000000000..7084a08cb
--- /dev/null
+++ b/tests/readfile-context.builder.sh
@@ -0,0 +1 @@
+echo "$input" > $out
diff --git a/tests/readfile-context.nix b/tests/readfile-context.nix
new file mode 100644
index 000000000..600036a94
--- /dev/null
+++ b/tests/readfile-context.nix
@@ -0,0 +1,19 @@
+with import ./config.nix;
+
+let
+
+  input = import ./simple.nix;
+
+  dependent = mkDerivation {
+    name = "dependent";
+    builder = ./readfile-context.builder.sh;
+    input = "${input}/hello";
+  };
+
+  readDependent = mkDerivation {
+    name = "read-dependent";
+    builder = ./readfile-context.builder.sh;
+    input = builtins.readFile dependent;
+  };
+
+in readDependent
diff --git a/tests/readfile-context.sh b/tests/readfile-context.sh
new file mode 100644
index 000000000..31e70ddb1
--- /dev/null
+++ b/tests/readfile-context.sh
@@ -0,0 +1,16 @@
+source common.sh
+
+clearStore
+
+outPath=$(nix-build --no-out-link readfile-context.nix)
+
+# Set a GC root.
+ln -s $outPath "$NIX_STATE_DIR"/gcroots/foo
+
+# Check that file exists.
+[ "$(cat $(cat $outPath))" = "Hello World!" ]
+
+nix-collect-garbage
+
+# Check that file still exists.
+[ "$(cat $(cat $outPath))" = "Hello World!" ]