From 12913ccf454c1bc82a51c59872f8185b40c533c5 Mon Sep 17 00:00:00 2001
From: Linus Heckemann <git@sphalerite.org>
Date: Fri, 16 Mar 2018 22:15:24 +0000
Subject: [PATCH] nix-shell: allow symlinks to .drvs

This makes persistent shell environments easier to use.
---
 src/nix-build/nix-build.cc             |  8 ++++++--
 src/nix-instantiate/nix-instantiate.cc |  2 +-
 tests/nix-shell.sh                     | 12 ++++++++++++
 3 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/src/nix-build/nix-build.cc b/src/nix-build/nix-build.cc
index 99f773451..cf628519c 100755
--- a/src/nix-build/nix-build.cc
+++ b/src/nix-build/nix-build.cc
@@ -271,10 +271,14 @@ void mainWrapped(int argc, char * * argv)
         exprs = {state.parseStdin()};
     else
         for (auto i : left) {
+            auto absolute = i;
+            try {
+                absolute = canonPath(absPath(i), true);
+            } catch (Error e) {};
             if (fromArgs)
                 exprs.push_back(state.parseExprFromString(i, absPath(".")));
-            else if (store->isStorePath(i) && std::regex_match(i, std::regex(".*\\.drv(!.*)?")))
-                drvs.push_back(DrvInfo(state, store, i));
+            else if (store->isStorePath(absolute) && std::regex_match(absolute, std::regex(".*\\.drv(!.*)?")))
+                drvs.push_back(DrvInfo(state, store, absolute));
             else
                 /* If we're in a #! script, interpret filenames
                    relative to the script. */
diff --git a/src/nix-instantiate/nix-instantiate.cc b/src/nix-instantiate/nix-instantiate.cc
index dd262bea0..5049460c7 100644
--- a/src/nix-instantiate/nix-instantiate.cc
+++ b/src/nix-instantiate/nix-instantiate.cc
@@ -70,7 +70,7 @@ void processExpr(EvalState & state, const Strings & attrPaths,
                 if (gcRoot == "")
                     printGCWarning();
                 else {
-                    Path rootName = gcRoot;
+                    Path rootName = indirectRoot ? absPath(gcRoot) : gcRoot;
                     if (++rootNr > 1) rootName += "-" + std::to_string(rootNr);
                     auto store2 = state.store.dynamic_pointer_cast<LocalFSStore>();
                     if (store2)
diff --git a/tests/nix-shell.sh b/tests/nix-shell.sh
index f7cac6ecf..063e97ce2 100644
--- a/tests/nix-shell.sh
+++ b/tests/nix-shell.sh
@@ -17,6 +17,18 @@ output=$(nix-shell --pure shell.nix -A shellDrv --run \
 [[ $(nix-shell --pure $(nix-instantiate shell.nix -A shellDrv) --run \
     'echo "$IMPURE_VAR - $VAR_FROM_STDENV_SETUP - $VAR_FROM_NIX"') = " - foo - bar" ]]
 
+# Test nix-shell on a .drv symlink
+
+# Legacy: absolute path and .drv extension required
+nix-instantiate shell.nix -A shellDrv --indirect --add-root shell.drv
+[[ $(nix-shell --pure $PWD/shell.drv --run \
+    'echo "$IMPURE_VAR - $VAR_FROM_STDENV_SETUP - $VAR_FROM_NIX"') = " - foo - bar" ]]
+
+# New behaviour: just needs to resolve to a derivation in the store
+nix-instantiate shell.nix -A shellDrv --indirect --add-root shell
+[[ $(nix-shell --pure shell --run \
+    'echo "$IMPURE_VAR - $VAR_FROM_STDENV_SETUP - $VAR_FROM_NIX"') = " - foo - bar" ]]
+
 # Test nix-shell -p
 output=$(NIX_PATH=nixpkgs=shell.nix nix-shell --pure -p foo bar --run 'echo "$(foo) $(bar)"')
 [ "$output" = "foo bar" ]