Add nix-flake-c, nix_flake_init_global, nix_flake_settings_new

meson.build

@@ -34,6 +34,7 @@ endif
 subproject('libutil-c')
 subproject('libstore-c')
 subproject('libexpr-c')
+subproject('libflake-c')
 subproject('libmain-c')
 
 # Language Bindings

packaging/components.nix

@@ -44,6 +44,7 @@ in
   nix-expr-tests = callPackage ../src/libexpr-tests/package.nix { };
 
   nix-flake = callPackage ../src/libflake/package.nix { };
+  nix-flake-c = callPackage ../src/libflake-c/package.nix { };
   nix-flake-tests = callPackage ../src/libflake-tests/package.nix { };
 
   nix-main = callPackage ../src/libmain/package.nix { };

src/external-api-docs/doxygen.cfg.in

@@ -40,6 +40,7 @@ GENERATE_LATEX         = NO
 INPUT                  = \
   @src@/src/libutil-c \
   @src@/src/libexpr-c \
+  @src@/src/libflake-c \
   @src@/src/libstore-c \
   @src@/src/external-api-docs/README.md
 

src/external-api-docs/package.nix

@@ -30,6 +30,7 @@ mkMesonDerivation (finalAttrs: {
       # Source is not compiled, but still must be available for Doxygen
       # to gather comments.
       (cpp ../libexpr-c)
+      (cpp ../libflake-c)
       (cpp ../libstore-c)
       (cpp ../libutil-c)
     ];

src/libflake-c/.version

@@ -0,0 +1 @@
+../../.version

src/libflake-c/build-utils-meson

@@ -0,0 +1 @@
+../../build-utils-meson/

src/libflake-c/meson.build

@@ -0,0 +1,93 @@
+project('nix-flake-c', 'cpp',
+  version : files('.version'),
+  default_options : [
+    'cpp_std=c++2a',
+    # TODO(Qyriad): increase the warning level
+    'warning_level=1',
+    'debug=true',
+    'optimization=2',
+    'errorlogs=true', # Please print logs for tests that fail
+  ],
+  meson_version : '>= 1.1',
+  license : 'LGPL-2.1-or-later',
+)
+
+cxx = meson.get_compiler('cpp')
+
+subdir('build-utils-meson/deps-lists')
+
+configdata = configuration_data()
+
+deps_private_maybe_subproject = [
+  dependency('nix-util'),
+  dependency('nix-store'),
+  dependency('nix-expr'),
+  dependency('nix-flake'),
+]
+deps_public_maybe_subproject = [
+  dependency('nix-util-c'),
+  dependency('nix-store-c'),
+  dependency('nix-expr-c'),
+]
+subdir('build-utils-meson/subprojects')
+
+# TODO rename, because it will conflict with downstream projects
+configdata.set_quoted('PACKAGE_VERSION', meson.project_version())
+
+config_h = configure_file(
+  configuration : configdata,
+  output : 'config-flake.h',
+)
+
+add_project_arguments(
+  # TODO(Qyriad): Yes this is how the autoconf+Make system did it.
+  # It would be nice for our headers to be idempotent instead.
+
+  # From C++ libraries, only for internals
+  '-include', 'config-util.hh',
+  '-include', 'config-store.hh',
+  '-include', 'config-expr.hh',
+  # not generated (yet?)
+  # '-include', 'config-flake.hh',
+
+  # From C libraries, for our public, installed headers too
+  '-include', 'config-util.h',
+  '-include', 'config-store.h',
+  '-include', 'config-expr.h',
+  '-include', 'config-flake.h',
+  language : 'cpp',
+)
+
+subdir('build-utils-meson/common')
+
+sources = files(
+  'nix_api_flake.cc',
+)
+
+include_dirs = [include_directories('.')]
+
+headers = [config_h] + files(
+  'nix_api_flake.h',
+)
+
+# TODO move this header to libexpr, maybe don't use it in tests?
+headers += files('nix_api_flake.h')
+
+subdir('build-utils-meson/export-all-symbols')
+subdir('build-utils-meson/windows-version')
+
+this_library = library(
+  'nixflakec',
+  sources,
+  dependencies : deps_public + deps_private + deps_other,
+  include_directories : include_dirs,
+  link_args: linker_export_flags,
+  prelink : true, # For C++ static initializers
+  install : true,
+)
+
+install_headers(headers, subdir : 'nix', preserve_path : true)
+
+libraries_private = []
+
+subdir('build-utils-meson/export')

src/libflake-c/nix_api_flake.cc

@@ -0,0 +1,32 @@
+#include "nix_api_flake.h"
+#include "nix_api_flake_internal.hh"
+#include "nix_api_util_internal.h"
+
+#include "flake/flake.hh"
+
+nix_flake_settings * nix_flake_settings_new(nix_c_context * context)
+{
+    try {
+        auto settings = nix::make_ref<nix::flake::Settings>();
+        return new nix_flake_settings{settings};
+    }
+    NIXC_CATCH_ERRS_NULL
+}
+
+void nix_flake_settings_free(nix_flake_settings * settings)
+{
+    delete settings;
+}
+
+nix_err nix_flake_init_global(nix_c_context * context, nix_flake_settings * settings)
+{
+    static std::shared_ptr<nix::flake::Settings> registeredSettings;
+    try {
+        if (registeredSettings)
+            throw nix::Error("nix_flake_init_global already initialized");
+
+        registeredSettings = settings->settings;
+        nix::flake::initLib(*registeredSettings);
+    }
+    NIXC_CATCH_ERRS
+}

src/libflake-c/nix_api_flake.h

@@ -0,0 +1,44 @@
+#ifndef NIX_API_FLAKE_H
+#define NIX_API_FLAKE_H
+/** @defgroup libflake libflake
+ * @brief Bindings to the Nix Flakes library
+ *
+ * @{
+ */
+/** @file
+ * @brief Main entry for the libflake C bindings
+ */
+
+#include "nix_api_store.h"
+#include "nix_api_util.h"
+#include "nix_api_expr.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+// cffi start
+
+typedef struct nix_flake_settings nix_flake_settings;
+
+// Function prototypes
+/**
+ * Create a nix_flake_settings initialized with default values.
+ * @param[out] context Optional, stores error information
+ * @return A new nix_flake_settings or NULL on failure.
+ * @see nix_flake_settings_free
+ */
+nix_flake_settings * nix_flake_settings_new(nix_c_context * context);
+
+/**
+ * @brief Release the resources associated with a nix_flake_settings.
+ */
+void nix_flake_settings_free(nix_flake_settings * settings);
+
+/**
+ * @brief Register Flakes support process-wide.
+ */
+nix_err nix_flake_init_global(nix_c_context * context, nix_flake_settings * settings);
+
+} // extern "C"
+
+#endif

src/libflake-c/nix_api_flake_internal.hh

@@ -0,0 +1,9 @@
+#pragma once
+
+#include "ref.hh"
+#include "flake/settings.hh"
+
+struct nix_flake_settings
+{
+    nix::ref<nix::flake::Settings> settings;
+};

src/libflake-c/package.nix

@@ -0,0 +1,60 @@
+{ lib
+, stdenv
+, mkMesonLibrary
+
+, nix-store-c
+, nix-expr-c
+, nix-flake
+
+# Configuration Options
+
+, version
+}:
+
+let
+  inherit (lib) fileset;
+in
+
+mkMesonLibrary (finalAttrs: {
+  pname = "nix-flake-c";
+  inherit version;
+
+  workDir = ./.;
+  fileset = fileset.unions [
+    ../../build-utils-meson
+    ./build-utils-meson
+    ../../.version
+    ./.version
+    ./meson.build
+    # ./meson.options
+    (fileset.fileFilter (file: file.hasExt "cc") ./.)
+    (fileset.fileFilter (file: file.hasExt "hh") ./.)
+    (fileset.fileFilter (file: file.hasExt "h") ./.)
+  ];
+
+  propagatedBuildInputs = [
+    nix-expr-c
+    nix-store-c
+    nix-flake
+  ];
+
+  preConfigure =
+    # "Inline" .version so it's not a symlink, and includes the suffix.
+    # Do the meson utils, without modification.
+    ''
+      chmod u+w ./.version
+      echo ${version} > ../../.version
+    '';
+
+  mesonFlags = [
+  ];
+
+  env = lib.optionalAttrs (stdenv.isLinux && !(stdenv.hostPlatform.isStatic && stdenv.system == "aarch64-linux")) {
+    LDFLAGS = "-fuse-ld=gold";
+  };
+
+  meta = {
+    platforms = lib.platforms.unix ++ lib.platforms.windows;
+  };
+
+})

src/libflake-tests/meson.build

@@ -19,6 +19,7 @@ subdir('build-utils-meson/deps-lists')
 deps_private_maybe_subproject = [
   dependency('nix-expr-test-support'),
   dependency('nix-flake'),
+  dependency('nix-flake-c'),
 ]
 deps_public_maybe_subproject = [
 ]
@@ -46,6 +47,7 @@ subdir('build-utils-meson/common')
 
 sources = files(
   'flakeref.cc',
+  'nix_api_flake.cc',
   'url-name.cc',
 )
 
@@ -68,6 +70,7 @@ test(
   this_exe,
   env : {
     '_NIX_TEST_UNIT_DATA': meson.current_source_dir() / 'data',
+    'NIX_CONFIG': 'extra-experimental-features = flakes',
   },
   protocol : 'gtest',
 )

src/libflake-tests/nix_api_flake.cc

@@ -0,0 +1,51 @@
+#include "nix_api_store.h"
+#include "nix_api_store_internal.h"
+#include "nix_api_util.h"
+#include "nix_api_util_internal.h"
+#include "nix_api_expr.h"
+#include "nix_api_value.h"
+#include "nix_api_flake.h"
+
+#include "tests/nix_api_expr.hh"
+#include "tests/string_callback.hh"
+
+#include <gmock/gmock.h>
+#include <gtest/gtest.h>
+
+namespace nixC {
+
+TEST_F(nix_api_store_test, nix_api_init_global_getFlake_exists)
+{
+    nix_libstore_init(ctx);
+    assert_ctx_ok();
+    nix_libexpr_init(ctx);
+    assert_ctx_ok();
+
+    auto settings = nix_flake_settings_new(ctx);
+    assert_ctx_ok();
+    ASSERT_NE(nullptr, settings);
+
+    nix_flake_init_global(ctx, settings);
+    assert_ctx_ok();
+
+    nix_eval_state_builder * builder = nix_eval_state_builder_new(ctx, store);
+    ASSERT_NE(nullptr, builder);
+    assert_ctx_ok();
+
+    auto state = nix_eval_state_build(ctx, builder);
+    assert_ctx_ok();
+    ASSERT_NE(nullptr, state);
+
+    nix_eval_state_builder_free(builder);
+
+    auto value = nix_alloc_value(ctx, state);
+    assert_ctx_ok();
+    ASSERT_NE(nullptr, value);
+
+    nix_err err = nix_expr_eval_from_string(ctx, state, "builtins.getFlake", ".", value);
+    assert_ctx_ok();
+    ASSERT_EQ(NIX_OK, err);
+    ASSERT_EQ(NIX_TYPE_FUNCTION, nix_get_type(ctx, value));
+}
+
+} // namespace nixC

src/libflake-tests/package.nix

@@ -4,6 +4,7 @@
 , mkMesonExecutable
 
 , nix-flake
+, nix-flake-c
 , nix-expr-test-support
 
 , rapidcheck
@@ -38,6 +39,7 @@ mkMesonExecutable (finalAttrs: {
 
   buildInputs = [
     nix-flake
+    nix-flake-c
     nix-expr-test-support
     rapidcheck
     gtest
@@ -67,6 +69,7 @@ mkMesonExecutable (finalAttrs: {
         mkdir -p "$HOME"
       '' + ''
         export _NIX_TEST_UNIT_DATA=${resolvePath ./data}
+        export NIX_CONFIG="extra-experimental-features = flakes"
         ${stdenv.hostPlatform.emulator buildPackages} ${lib.getExe finalAttrs.finalPackage}
         touch $out
       '');