feat(3p/nix): add MockBinaryCacheStore

This adds an implementation of BinaryCacheStore to be used by tests exercising both the logic inherent to BinaryCacheStore and more general Store tests.

A new library target, nixstoremock, is created to indicate that this file is intended only for use in tests and not in user-facing code.

Change-Id: Ib68f777238843a4f3a2303db8a69735fbc22d161
Reviewed-on: https://cl.tvl.fyi/c/depot/+/1645
Tested-by: BuildkiteCI
Reviewed-by: glittershark <grfn@gws.fyi>

third_party/nix/src/libstore/CMakeLists.txt

@@ -1,8 +1,11 @@
 # -*- mode: cmake; -*-
 add_library(nixstore SHARED)
+add_library(nixstoremock SHARED)
 set_property(TARGET nixstore PROPERTY CXX_STANDARD 17)
+set_property(TARGET nixstoremock PROPERTY CXX_STANDARD 17)
 include_directories(${PROJECT_BINARY_DIR}) # for config.h
 target_include_directories(nixstore PUBLIC "${nix_SOURCE_DIR}/src")
+target_include_directories(nixstoremock PUBLIC "${nix_SOURCE_DIR}/src")
 
 # The database schema is stored in schema.sql, but needs to be
 # available during the build as static data.
@@ -101,8 +104,24 @@ target_link_libraries(nixstore
   sodium
 )
 
+target_sources(nixstoremock
+  PUBLIC
+    mock-binary-cache-store.hh
+
+  PRIVATE
+    mock-binary-cache-store.cc
+)
+
+target_link_libraries(nixstoremock
+  nixstore
+
+  absl::btree
+  absl::flat_hash_map
+  glog
+)
+
 configure_file("nix-store.pc.in" "${PROJECT_BINARY_DIR}/nix-store.pc" @ONLY)
 INSTALL(FILES "${PROJECT_BINARY_DIR}/nix-store.pc" DESTINATION "${PKGCONFIG_INSTALL_DIR}")
 
 INSTALL(FILES ${HEADER_FILES} DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}/nix/libstore)
-INSTALL(TARGETS nixstore DESTINATION ${CMAKE_INSTALL_LIBDIR})
+INSTALL(TARGETS nixstore nixstoremock DESTINATION ${CMAKE_INSTALL_LIBDIR})

third_party/nix/src/libstore/mock-binary-cache-store.cc

@@ -0,0 +1,91 @@
+#include "libstore/mock-binary-cache-store.hh"
+
+#include <glog/logging.h>
+
+namespace nix {
+
+MockBinaryCacheStore::MockBinaryCacheStore(const Params& params)
+    : BinaryCacheStore(params), contents_(), errorInjections_() {}
+
+std::string MockBinaryCacheStore::getUri() { return "mock://1"; }
+
+bool MockBinaryCacheStore::fileExists(const std::string& path) {
+  ThrowInjectedErrors(path);
+
+  return contents_.find(path) != contents_.end();
+};
+
+void MockBinaryCacheStore::upsertFile(const std::string& path,
+                                      const std::string& data,
+                                      const std::string& mimeType) {
+  ThrowInjectedErrors(path);
+
+  contents_[path] = MemoryFile{data, mimeType};
+}
+
+void MockBinaryCacheStore::getFile(
+    const std::string& path,
+    Callback<std::shared_ptr<std::string>> callback) noexcept {
+  auto eit = errorInjections_.find(path);
+  if (eit != errorInjections_.end()) {
+    try {
+      eit->second();
+      LOG(FATAL) << "thrower failed to throw";
+    } catch (...) {
+      callback.rethrow();
+    }
+    return;
+  }
+
+  auto it = contents_.find(path);
+  if (it == contents_.end()) {
+    try {
+      throw NoSuchBinaryCacheFile(absl::StrCat(
+          "file '", path, "' was not added to the MockBinaryCache"));
+    } catch (...) {
+      callback.rethrow();
+    }
+    return;
+  }
+  callback(std::make_shared<std::string>(it->second.data));
+}
+
+PathSet MockBinaryCacheStore::queryAllValidPaths() {
+  PathSet paths;
+
+  for (auto it : contents_) {
+    paths.insert(it.first);
+  }
+
+  return paths;
+}
+
+void MockBinaryCacheStore::DeleteFile(const std::string& path) {
+  contents_.erase(path);
+}
+
+// Same as upsert, but bypasses injected errors.
+void MockBinaryCacheStore::SetFileContentsForTest(const std::string& path,
+                                                  const std::string& data,
+                                                  const std::string& mimeType) {
+  contents_[path] = MemoryFile{data, mimeType};
+}
+
+void MockBinaryCacheStore::PrepareErrorInjection(
+    const std::string& path, std::function<void()> err_factory) {
+  errorInjections_[path] = err_factory;
+}
+
+void MockBinaryCacheStore::CancelErrorInjection(const std::string& path) {
+  errorInjections_.erase(path);
+}
+
+void MockBinaryCacheStore::ThrowInjectedErrors(const std::string& path) {
+  auto it = errorInjections_.find(path);
+  if (it != errorInjections_.end()) {
+    it->second();
+    LOG(FATAL) << "thrower failed to throw";
+  }
+}
+
+}  // namespace nix

third_party/nix/src/libstore/mock-binary-cache-store.hh

@@ -0,0 +1,59 @@
+#pragma once
+
+#include <absl/container/btree_map.h>
+#include <absl/container/flat_hash_map.h>
+
+#include "libstore/binary-cache-store.hh"
+
+namespace nix {
+
+// MockBinaryCacheStore implements a memory-based BinaryCacheStore, for use in
+// tests.
+class MockBinaryCacheStore : public BinaryCacheStore {
+ public:
+  MockBinaryCacheStore(const Params& params);
+
+  // Store API
+
+  std::string getUri() override;
+
+  bool fileExists(const std::string& path) override;
+
+  void upsertFile(const std::string& path, const std::string& data,
+                  const std::string& mimeType) override;
+
+  void getFile(
+      const std::string& path,
+      Callback<std::shared_ptr<std::string>> callback) noexcept override;
+
+  PathSet queryAllValidPaths() override;
+
+  // Test API
+
+  // Remove a file from the store.
+  void DeleteFile(const std::string& path);
+
+  // Same as upsert, but bypasses injected errors.
+  void SetFileContentsForTest(const std::string& path, const std::string& data,
+                              const std::string& mimeType);
+
+  void PrepareErrorInjection(const std::string& path,
+                             std::function<void()> throw_func);
+
+  void CancelErrorInjection(const std::string& path);
+
+  // Internals
+
+ private:
+  void ThrowInjectedErrors(const std::string& path);
+
+  struct MemoryFile {
+    std::string data;
+    std::string mimeType;
+  };
+
+  absl::btree_map<std::string, MemoryFile> contents_;
+  absl::flat_hash_map<std::string, std::function<void()>> errorInjections_;
+};
+
+}  // namespace nix