Merge of #12044

src/libstore-c/nix_api_store.cc

@@ -67,6 +67,17 @@ nix_err nix_store_get_uri(nix_c_context * context, Store * store, nix_get_string
     NIXC_CATCH_ERRS
 }
 
+nix_err
+nix_store_get_storedir(nix_c_context * context, Store * store, nix_get_string_callback callback, void * user_data)
+{
+    if (context)
+        context->last_err_code = NIX_OK;
+    try {
+        return call_nix_get_string_callback(store->ptr->storeDir, callback, user_data);
+    }
+    NIXC_CATCH_ERRS
+}
+
 nix_err
 nix_store_get_version(nix_c_context * context, Store * store, nix_get_string_callback callback, void * user_data)
 {
@@ -89,6 +100,18 @@ bool nix_store_is_valid_path(nix_c_context * context, Store * store, StorePath *
     NIXC_CATCH_ERRS_RES(false);
 }
 
+nix_err nix_store_real_path(
+    nix_c_context * context, Store * store, StorePath * path, nix_get_string_callback callback, void * user_data)
+{
+    if (context)
+        context->last_err_code = NIX_OK;
+    try {
+        auto res = store->ptr->toRealPath(path->path);
+        return call_nix_get_string_callback(res, callback, user_data);
+    }
+    NIXC_CATCH_ERRS
+}
+
 StorePath * nix_store_parse_path(nix_c_context * context, Store * store, const char * path)
 {
     if (context)

src/libstore-c/nix_api_store.h

@@ -48,12 +48,27 @@ nix_err nix_libstore_init_no_load_config(nix_c_context * context);
  * Store instances may share state and resources behind the scenes.
  *
  * @param[out] context Optional, stores error information
- * @param[in] uri URI of the Nix store, copied. See [*Store URL format* in the Nix Reference
+ *
+ * @param[in] uri @parblock
+ *   URI of the Nix store, copied.
+ *
+ *   If `NULL`, the store from the settings will be used.
+ *   Note that `"auto"` holds a strange middle ground, reading part of the general environment, but not all of it. It
+ * ignores `NIX_REMOTE` and the `store` option. For this reason, `NULL` is most likely the better choice.
+ *
+ *   For supported store URLs, see [*Store URL format* in the Nix Reference
  * Manual](https://nixos.org/manual/nix/stable/store/types/#store-url-format).
- * @param[in] params optional, null-terminated array of key-value pairs, e.g. {{"endpoint",
- * "https://s3.local"}}. See [*Store Types* in the Nix Reference
- * Manual](https://nixos.org/manual/nix/stable/store/types).
+ * @endparblock
+ *
+ * @param[in] params @parblock
+ *   optional, null-terminated array of key-value pairs, e.g. {{"endpoint",
+ * "https://s3.local"}}.
+ *
+ *   See [*Store Types* in the Nix Reference Manual](https://nixos.org/manual/nix/stable/store/types).
+ * @endparblock
+ *
  * @return a Store pointer, NULL in case of errors
+ *
  * @see nix_store_free
  */
 Store * nix_store_open(nix_c_context * context, const char * uri, const char *** params);
@@ -78,7 +93,18 @@ void nix_store_free(Store * store);
  */
 nix_err nix_store_get_uri(nix_c_context * context, Store * store, nix_get_string_callback callback, void * user_data);
 
-// returns: owned StorePath*
+/**
+ * @brief get the storeDir of a Nix store, typically `"/nix/store"`
+ * @param[out] context Optional, stores error information
+ * @param[in] store nix store reference
+ * @param[in] callback Called with the URI.
+ * @param[in] user_data optional, arbitrary data, passed to the callback when it's called.
+ * @see nix_get_string_callback
+ * @return error code, NIX_OK on success.
+ */
+nix_err
+nix_store_get_storedir(nix_c_context * context, Store * store, nix_get_string_callback callback, void * user_data);
+
 /**
  * @brief Parse a Nix store path into a StorePath
  *
@@ -123,6 +149,26 @@ void nix_store_path_free(StorePath * p);
  * @return true or false, error info in context
  */
 bool nix_store_is_valid_path(nix_c_context * context, Store * store, StorePath * path);
+
+/**
+ * @brief Get the physical location of a store path
+ *
+ * A store may reside at a different location than its `storeDir` suggests.
+ * This situation is called a relocated store.
+ * Relocated stores are used during NixOS installation, as well as in restricted computing environments that don't offer
+ * a writable `/nix/store`.
+ *
+ * Not all types of stores support this operation.
+ *
+ * @param[in] context Optional, stores error information
+ * @param[in] store nix store reference
+ * @param[in] path the path to get the real path from
+ * @param[in] callback called with the real path
+ * @param[in] user_data arbitrary data, passed to the callback when it's called.
+ */
+nix_err nix_store_real_path(
+    nix_c_context * context, Store * store, StorePath * path, nix_get_string_callback callback, void * user_data);
+
 // nix_err nix_store_ensure(Store*, const char*);
 // nix_err nix_store_build_paths(Store*);
 /**

src/libstore-tests/meson.build

@@ -16,8 +16,10 @@ cxx = meson.get_compiler('cpp')
 
 subdir('nix-meson-build-support/deps-lists')
 
+nix_store = dependency('nix-store')
+
 deps_private_maybe_subproject = [
-  dependency('nix-store'),
+  nix_store,
   dependency('nix-store-c'),
   dependency('nix-store-test-support'),
 ]
@@ -90,6 +92,7 @@ this_exe = executable(
   include_directories : include_dirs,
   # TODO: -lrapidcheck, see ../libutil-support/build.meson
   link_args: linker_export_flags + ['-lrapidcheck'],
+  cpp_args : [ '-DNIX_STORE_DIR="' + nix_store.get_variable('storedir') + '"' ],
   # get main from gtest
   install : true,
 )

src/libstore-tests/nix_api_store.cc

@@ -24,6 +24,39 @@ TEST_F(nix_api_store_test, nix_store_get_uri)
     ASSERT_STREQ("local", str.c_str());
 }
 
+TEST_F(nix_api_util_context, nix_store_get_storedir_default)
+{
+    if (nix::getEnv("HOME").value_or("") == "/homeless-shelter") {
+        // skipping test in sandbox because nix_store_open tries to create /nix/var/nix/profiles
+        GTEST_SKIP();
+    }
+    nix_libstore_init(ctx);
+    Store * store = nix_store_open(ctx, nullptr, nullptr);
+    assert_ctx_ok();
+    ASSERT_NE(store, nullptr);
+
+    std::string str;
+    auto ret = nix_store_get_storedir(ctx, store, OBSERVE_STRING(str));
+    assert_ctx_ok();
+    ASSERT_EQ(NIX_OK, ret);
+
+    // These tests run with a unique storeDir, but not a relocated store
+    ASSERT_STREQ(NIX_STORE_DIR, str.c_str());
+
+    nix_store_free(store);
+}
+
+TEST_F(nix_api_store_test, nix_store_get_storedir)
+{
+    std::string str;
+    auto ret = nix_store_get_storedir(ctx, store, OBSERVE_STRING(str));
+    assert_ctx_ok();
+    ASSERT_EQ(NIX_OK, ret);
+
+    // These tests run with a unique storeDir, but not a relocated store
+    ASSERT_STREQ(nixStoreDir.c_str(), str.c_str());
+}
+
 TEST_F(nix_api_store_test, InvalidPathFails)
 {
     nix_store_parse_path(ctx, store, "invalid-path");
@@ -86,4 +119,84 @@ TEST_F(nix_api_store_test, nix_store_is_valid_path_not_in_store)
     ASSERT_EQ(false, nix_store_is_valid_path(ctx, store, path));
 }
 
+TEST_F(nix_api_store_test, nix_store_real_path)
+{
+    StorePath * path = nix_store_parse_path(ctx, store, (nixStoreDir + PATH_SUFFIX).c_str());
+    std::string rp;
+    auto ret = nix_store_real_path(ctx, store, path, OBSERVE_STRING(rp));
+    assert_ctx_ok();
+    ASSERT_EQ(NIX_OK, ret);
+    // Assumption: we're not testing with a relocated store
+    ASSERT_STREQ((nixStoreDir + PATH_SUFFIX).c_str(), rp.c_str());
+
+    nix_store_path_free(path);
 }
+
+TEST_F(nix_api_util_context, nix_store_real_path_relocated)
+{
+    if (nix::getEnv("HOME").value_or("") == "/homeless-shelter") {
+        // Can't open default store from within sandbox
+        GTEST_SKIP();
+    }
+    auto tmp = nix::createTempDir();
+    std::string storeRoot = tmp + "/store";
+    std::string stateDir = tmp + "/state";
+    std::string logDir = tmp + "/log";
+    const char * rootkv[] = {"root", storeRoot.c_str()};
+    const char * statekv[] = {"state", stateDir.c_str()};
+    const char * logkv[] = {"log", logDir.c_str()};
+    // const char * rokv[] = {"read-only", "true"};
+    const char ** kvs[] = {rootkv, statekv, logkv, NULL};
+
+    nix_libstore_init(ctx);
+    assert_ctx_ok();
+
+    Store * store = nix_store_open(ctx, "local", kvs);
+    assert_ctx_ok();
+    ASSERT_NE(store, nullptr);
+
+    std::string nixStoreDir;
+    auto ret = nix_store_get_storedir(ctx, store, OBSERVE_STRING(nixStoreDir));
+    ASSERT_EQ(NIX_OK, ret);
+    ASSERT_STREQ(NIX_STORE_DIR, nixStoreDir.c_str());
+
+    StorePath * path = nix_store_parse_path(ctx, store, (nixStoreDir + PATH_SUFFIX).c_str());
+    assert_ctx_ok();
+    ASSERT_NE(path, nullptr);
+
+    std::string rp;
+    ret = nix_store_real_path(ctx, store, path, OBSERVE_STRING(rp));
+    assert_ctx_ok();
+    ASSERT_EQ(NIX_OK, ret);
+
+    // Assumption: we're not testing with a relocated store
+    ASSERT_STREQ((storeRoot + NIX_STORE_DIR + PATH_SUFFIX).c_str(), rp.c_str());
+
+    nix_store_path_free(path);
+}
+
+TEST_F(nix_api_util_context, nix_store_real_path_binary_cache)
+{
+    if (nix::getEnv("HOME").value_or("") == "/homeless-shelter") {
+        // TODO: override NIX_CACHE_HOME?
+        // skipping test in sandbox because narinfo cache can't be written
+        GTEST_SKIP();
+    }
+
+    Store * store = nix_store_open(ctx, "https://cache.nixos.org", nullptr);
+    assert_ctx_ok();
+    ASSERT_NE(store, nullptr);
+
+    std::string path_raw = std::string(NIX_STORE_DIR) + PATH_SUFFIX;
+    StorePath * path = nix_store_parse_path(ctx, store, path_raw.c_str());
+    assert_ctx_ok();
+    ASSERT_NE(path, nullptr);
+
+    std::string rp;
+    auto ret = nix_store_real_path(ctx, store, path, OBSERVE_STRING(rp));
+    assert_ctx_ok();
+    ASSERT_EQ(NIX_OK, ret);
+    ASSERT_STREQ(path_raw.c_str(), rp.c_str());
+}
+
+} // namespace nixC

src/libutil-c/nix_api_util.h

@@ -47,7 +47,7 @@ extern "C" {
  */
 // Error codes
 /**
- * @brief Type for error codes in the NIX system
+ * @brief Type for error codes in the Nix system
  *
  * This type can have one of several predefined constants:
  * - NIX_OK: No error occurred (0)