test(3p/nix): Add test for derivation parse/serialize r/1548

Add a rapidcheck test covering roundtrip parse and serialize for Nix
derivations. This covers a bug we discovered in ef54f5d which broke this
roundtrip.

Change-Id: I72d140334b5f24f79e82e34f98609c695dbfbf93
Reviewed-on: https://cl.tvl.fyi/c/depot/+/1582
Tested-by: BuildkiteCI
Reviewed-by: kanepyork <rikingcoding@gmail.com>

4 files changed, 121 insertions, 2 deletions

diff --git a/third_party/nix/src/libstore/derivations.cc b/third_party/nix/src/libstore/derivations.cc
index 29f929270e9b..8a50f3c85b4d 100644
--- a/third_party/nix/src/libstore/derivations.cc
+++ b/third_party/nix/src/libstore/derivations.cc
@@ -144,7 +144,7 @@ static StringSet parseStrings(std::istream& str, bool arePaths) {
   return res;
 }
 
-static Derivation parseDerivation(const std::string& s) {
+Derivation parseDerivation(const std::string& s) {
   Derivation drv;
   istringstream_nocopy str(s);
   expect(str, "Derive([");
diff --git a/third_party/nix/src/libstore/derivations.hh b/third_party/nix/src/libstore/derivations.hh
index 21ef71372e05..38877780e0c1 100644
--- a/third_party/nix/src/libstore/derivations.hh
+++ b/third_party/nix/src/libstore/derivations.hh
@@ -16,10 +16,10 @@ const std::string drvExtension = ".drv";
 
 struct DerivationOutput {
   Path path;
+  // TODO(grfn): make these two fields a Hash
   std::string hashAlgo; /* hash used for expected hash computation */
   std::string hash;     /* expected hash, may be null */
   DerivationOutput() {}
-  // TODO(grfn): Make explicit
   DerivationOutput(Path path, std::string hashAlgo, std::string hash) {
     this->path = path;
     this->hashAlgo = hashAlgo;
@@ -92,6 +92,8 @@ Path writeDerivation(const ref<Store>& store, const Derivation& drv,
 /* Read a derivation from a file. */
 Derivation readDerivation(const Path& drvPath);
 
+Derivation parseDerivation(const std::string& s);
+
 /* Check whether a file name ends with the extension for
    derivations. */
 bool isDerivation(const std::string& fileName);
diff --git a/third_party/nix/src/tests/CMakeLists.txt b/third_party/nix/src/tests/CMakeLists.txt
index 724a7a95b519..33f4f774a61b 100644
--- a/third_party/nix/src/tests/CMakeLists.txt
+++ b/third_party/nix/src/tests/CMakeLists.txt
@@ -11,6 +11,17 @@ target_link_libraries(attr-set
 
 gtest_discover_tests(attr-set)
 
+add_executable(derivations_test derivations_test.cc)
+target_link_libraries(derivations_test
+  nixexpr
+  nixstore
+  rapidcheck
+  rapidcheck_gtest
+  GTest::gtest_main
+)
+
+gtest_discover_tests(derivations_test)
+
 add_executable(hash_test hash_test.cc)
 target_link_libraries(hash_test
   nixutil
diff --git a/third_party/nix/src/tests/derivations_test.cc b/third_party/nix/src/tests/derivations_test.cc
new file mode 100644
index 000000000000..e026fbe3b11c
--- /dev/null
+++ b/third_party/nix/src/tests/derivations_test.cc
@@ -0,0 +1,106 @@
+#include "libstore/derivations.hh"
+
+#include <memory>
+
+#include <absl/strings/str_cat.h>
+#include <gtest/gtest.h>
+#include <rapidcheck.h>
+#include <rapidcheck/Assertions.h>
+#include <rapidcheck/gen/Arbitrary.h>
+#include <rapidcheck/gen/Build.h>
+#include <rapidcheck/gen/Container.h>
+#include <rapidcheck/gen/Tuple.h>
+#include <rapidcheck/gtest.h>
+#include <rapidcheck/state.h>
+
+#include "libexpr/eval.hh"
+#include "libutil/hash.hh"
+#include "libutil/types.hh"
+
+namespace rc {
+
+using nix::Derivation;
+using nix::DerivationOutput;
+
+template <>
+struct Arbitrary<nix::Base> {
+  static Gen<nix::Base> arbitrary() {
+    return gen::element(nix::Base16, nix::Base32, nix::Base64);
+  }
+};
+
+template <>
+struct Arbitrary<DerivationOutput> {
+  static Gen<DerivationOutput> arbitrary() {
+    return gen::apply(
+        [](std::string content, std::string path, std::string hash_algo,
+           bool recursive, bool include_algo_in_hash, nix::Base base) {
+          auto hash_type = nix::parseHashType(hash_algo);
+          auto hash = nix::hashString(hash_type, content);
+          return DerivationOutput(
+              path, recursive ? absl::StrCat("r:", hash_algo) : hash_algo,
+              hash.to_string(base, include_algo_in_hash));
+        },
+        gen::arbitrary<std::string>(),
+        gen::map(gen::arbitrary<std::string>(),
+                 [](std::string s) { return absl::StrCat("/", s); }),
+        gen::element<std::string>("md5", "sha1", "sha256", "sha512"),
+        gen::arbitrary<bool>(), gen::arbitrary<bool>(),
+        gen::arbitrary<nix::Base>());
+  }
+};
+
+template <>
+struct Arbitrary<Derivation> {
+  static Gen<Derivation> arbitrary() {
+    auto gen_path = gen::map(gen::arbitrary<std::string>(), [](std::string s) {
+      return absl::StrCat("/", s);
+    });
+
+    return gen::build<Derivation>(
+        gen::set(&nix::BasicDerivation::outputs),
+        gen::set(&nix::BasicDerivation::inputSrcs,
+                 gen::container<nix::PathSet>(gen_path)),
+        gen::set(&nix::BasicDerivation::platform),
+        gen::set(&nix::BasicDerivation::builder, gen_path),
+        gen::set(&nix::BasicDerivation::args),
+        gen::set(&nix::BasicDerivation::env),
+        gen::set(&Derivation::inputDrvs,
+                 gen::container<nix::DerivationInputs>(
+                     gen_path, gen::arbitrary<nix::StringSet>())));
+  }
+};
+
+}  // namespace rc
+
+namespace nix {
+
+void AssertDerivationsEqual(const Derivation& lhs, const Derivation& rhs) {
+  RC_ASSERT(lhs.outputs.size() == rhs.outputs.size());
+  for (const auto& [k, lhs_v] : lhs.outputs) {
+    auto rhs_v = rhs.outputs.find(k);
+    RC_ASSERT(rhs_v != rhs.outputs.end());
+    RC_ASSERT(lhs_v.path == rhs_v->second.path);
+    RC_ASSERT(lhs_v.hashAlgo == rhs_v->second.hashAlgo);
+    RC_ASSERT(lhs_v.hash == rhs_v->second.hash);
+  }
+
+  RC_ASSERT(lhs.inputSrcs == rhs.inputSrcs);
+  RC_ASSERT(lhs.platform == rhs.platform);
+  RC_ASSERT(lhs.builder == rhs.builder);
+  RC_ASSERT(lhs.args == rhs.args);
+  RC_ASSERT(lhs.env == rhs.env);
+  RC_ASSERT(lhs.inputDrvs == rhs.inputDrvs);
+}
+
+class DerivationsTest : public ::testing::Test {};
+
+// NOLINTNEXTLINE
+RC_GTEST_FIXTURE_PROP(DerivationsTest, UnparseParseRoundTrip,
+                      (Derivation && drv)) {
+  auto unparsed = drv.unparse();
+  auto parsed = parseDerivation(unparsed);
+  AssertDerivationsEqual(drv, parsed);
+}
+
+}  // namespace nix