From 26dacc09837cb5226b7d97ed70a0fbade5e40304 Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Tue, 11 Feb 2020 23:53:46 +0100
Subject: [PATCH] Add fetchTree builtin function

This allows all supported fetchers to be used, e.g.

  builtins.fetchTree {
    type = "github";
    owner = "NixOS";
    repo = "nix";
    rev = "d4df99a3349cf2228a8ee78dea320afef86eb3ba";
  }
---
 src/libexpr/primops/fetchTree.cc | 61 ++++++++++++++++++++++++++++++++
 tests/tarball.sh                 |  6 ++++
 2 files changed, 67 insertions(+)
 create mode 100644 src/libexpr/primops/fetchTree.cc

diff --git a/src/libexpr/primops/fetchTree.cc b/src/libexpr/primops/fetchTree.cc
new file mode 100644
index 000000000..ccb0cacd5
--- /dev/null
+++ b/src/libexpr/primops/fetchTree.cc
@@ -0,0 +1,61 @@
+#include "primops.hh"
+#include "eval-inline.hh"
+#include "store-api.hh"
+#include "fetchers/fetchers.hh"
+#include "fetchers/registry.hh"
+
+namespace nix {
+
+static void prim_fetchTree(EvalState & state, const Pos & pos, Value * * args, Value & v)
+{
+    std::shared_ptr<const fetchers::Input> input;
+    PathSet context;
+
+    state.forceValue(*args[0]);
+
+    if (args[0]->type == tAttrs) {
+        state.forceAttrs(*args[0], pos);
+
+        fetchers::Input::Attrs attrs;
+
+        for (auto & attr : *args[0]->attrs) {
+            state.forceValue(*attr.value);
+            if (attr.value->type == tString)
+                attrs.emplace(attr.name, attr.value->string.s);
+            else
+                throw Error("unsupported attribute type");
+        }
+
+        if (!attrs.count("type"))
+            throw Error("attribute 'type' is missing in call to 'fetchTree', at %s", pos);
+
+        input = fetchers::inputFromAttrs(attrs);
+    } else
+        input = fetchers::inputFromURL(state.coerceToString(pos, *args[0], context, false, false));
+
+    if (!evalSettings.pureEval && !input->isDirect())
+        input = lookupInRegistries(state.store, input);
+
+    if (evalSettings.pureEval && !input->isImmutable())
+        throw Error("in pure evaluation mode, 'fetchTree' requires an immutable input");
+
+    auto [tree, input2] = input->fetchTree(state.store);
+
+    state.mkAttrs(v, 8);
+    auto storePath = state.store->printStorePath(tree.storePath);
+    mkString(*state.allocAttr(v, state.sOutPath), storePath, PathSet({storePath}));
+    if (input2->getRev()) {
+        mkString(*state.allocAttr(v, state.symbols.create("rev")), input2->getRev()->gitRev());
+        mkString(*state.allocAttr(v, state.symbols.create("shortRev")), input2->getRev()->gitShortRev());
+    }
+    if (tree.info.revCount)
+        mkInt(*state.allocAttr(v, state.symbols.create("revCount")), *tree.info.revCount);
+    v.attrs->sort();
+
+    if (state.allowedPaths)
+        state.allowedPaths->insert(tree.actualPath);
+}
+
+static RegisterPrimOp r("fetchTree", 1, prim_fetchTree);
+
+}
diff --git a/tests/tarball.sh b/tests/tarball.sh
index 8adb8d72f..7c8896b2e 100644
--- a/tests/tarball.sh
+++ b/tests/tarball.sh
@@ -10,6 +10,8 @@ mkdir -p $tarroot
 cp dependencies.nix $tarroot/default.nix
 cp config.nix dependencies.builder*.sh $tarroot/
 
+hash=$(nix hash-path $tarroot)
+
 test_tarball() {
     local ext="$1"
     local compressor="$2"
@@ -25,6 +27,10 @@ test_tarball() {
 
     nix-build -o $TEST_ROOT/result -E "import (fetchTarball file://$tarball)"
 
+    nix-build -o $TEST_ROOT/result -E "import (fetchTree file://$tarball)"
+    nix-build -o $TEST_ROOT/result -E "import (fetchTree { type = \"tarball\"; url = file://$tarball; })"
+    nix-build -o $TEST_ROOT/result -E "import (fetchTree { type = \"tarball\"; url = file://$tarball; narHash = \"$hash\"; })"
+
     nix-instantiate --eval -E '1 + 2' -I fnord=file://no-such-tarball.tar$ext
     nix-instantiate --eval -E 'with <fnord/xyzzy>; 1 + 2' -I fnord=file://no-such-tarball$ext
     (! nix-instantiate --eval -E '<fnord/xyzzy> 1' -I fnord=file://no-such-tarball$ext)