Add Bazel build support (#3709)

BUILD.bazel

@@ -0,0 +1,53 @@
+cc_library(
+    name = "json",
+    hdrs = [
+        "include/nlohmann/adl_serializer.hpp",
+        "include/nlohmann/byte_container_with_subtype.hpp",
+        "include/nlohmann/detail/abi_macros.hpp",
+        "include/nlohmann/detail/conversions/from_json.hpp",
+        "include/nlohmann/detail/conversions/to_chars.hpp",
+        "include/nlohmann/detail/conversions/to_json.hpp",
+        "include/nlohmann/detail/exceptions.hpp",
+        "include/nlohmann/detail/hash.hpp",
+        "include/nlohmann/detail/input/binary_reader.hpp",
+        "include/nlohmann/detail/input/input_adapters.hpp",
+        "include/nlohmann/detail/input/json_sax.hpp",
+        "include/nlohmann/detail/input/lexer.hpp",
+        "include/nlohmann/detail/input/parser.hpp",
+        "include/nlohmann/detail/input/position_t.hpp",
+        "include/nlohmann/detail/iterators/internal_iterator.hpp",
+        "include/nlohmann/detail/iterators/iter_impl.hpp",
+        "include/nlohmann/detail/iterators/iteration_proxy.hpp",
+        "include/nlohmann/detail/iterators/iterator_traits.hpp",
+        "include/nlohmann/detail/iterators/json_reverse_iterator.hpp",
+        "include/nlohmann/detail/iterators/primitive_iterator.hpp",
+        "include/nlohmann/detail/json_custom_base_class.hpp",
+        "include/nlohmann/detail/json_pointer.hpp",
+        "include/nlohmann/detail/json_ref.hpp",
+        "include/nlohmann/detail/macro_scope.hpp",
+        "include/nlohmann/detail/macro_unscope.hpp",
+        "include/nlohmann/detail/meta/call_std/begin.hpp",
+        "include/nlohmann/detail/meta/call_std/end.hpp",
+        "include/nlohmann/detail/meta/cpp_future.hpp",
+        "include/nlohmann/detail/meta/detected.hpp",
+        "include/nlohmann/detail/meta/identity_tag.hpp",
+        "include/nlohmann/detail/meta/is_sax.hpp",
+        "include/nlohmann/detail/meta/std_fs.hpp",
+        "include/nlohmann/detail/meta/type_traits.hpp",
+        "include/nlohmann/detail/meta/void_t.hpp",
+        "include/nlohmann/detail/output/binary_writer.hpp",
+        "include/nlohmann/detail/output/output_adapters.hpp",
+        "include/nlohmann/detail/output/serializer.hpp",
+        "include/nlohmann/detail/string_concat.hpp",
+        "include/nlohmann/detail/string_escape.hpp",
+        "include/nlohmann/detail/value_t.hpp",
+        "include/nlohmann/json.hpp",
+        "include/nlohmann/json_fwd.hpp",
+        "include/nlohmann/ordered_map.hpp",
+        "include/nlohmann/thirdparty/hedley/hedley.hpp",
+        "include/nlohmann/thirdparty/hedley/hedley_undef.hpp",
+    ],
+    includes = ["include"],
+    visibility = ["//visibility:public"],
+    alwayslink = True,
+)

CMakeLists.txt

@@ -43,7 +43,7 @@ option(JSON_Diagnostics                    "Use extended diagnostic messages." O
 option(JSON_GlobalUDLs                     "Place use-defined string literals in the global namespace." ON)
 option(JSON_ImplicitConversions            "Enable implicit conversions." ON)
 option(JSON_DisableEnumSerialization       "Disable default integer enum serialization." OFF)
-option(JSON_LegacyDiscardedValueComparison "Enable legacy discarded value comparison." OFF)           
+option(JSON_LegacyDiscardedValueComparison "Enable legacy discarded value comparison." OFF)
 option(JSON_Install                        "Install CMake targets during install step." ${MAIN_PROJECT})
 option(JSON_MultipleHeaders                "Use non-amalgamated version of the library." ON)
 option(JSON_SystemInclude                  "Include as system headers (skip for clang-tidy)." OFF)

Makefile

@@ -192,6 +192,8 @@ check-amalgamation:
 	@mv $(AMALGAMATED_FILE)~ $(AMALGAMATED_FILE)
 	@mv $(AMALGAMATED_FWD_FILE)~ $(AMALGAMATED_FWD_FILE)
 
+BUILD.bazel: $(SRCS)
+	cmake -P cmake/scripts/gen_bazel_build_file.cmake
 
 ##########################################################################
 # ChangeLog

README.md

@@ -1310,7 +1310,9 @@ endif()
 
 If you are using the [Meson Build System](https://mesonbuild.com), add this source tree as a [meson subproject](https://mesonbuild.com/Subprojects.html#using-a-subproject). You may also use the `include.zip` published in this project's [Releases](https://github.com/nlohmann/json/releases) to reduce the size of the vendored source tree. Alternatively, you can get a wrap file by downloading it from [Meson WrapDB](https://wrapdb.mesonbuild.com/nlohmann_json), or simply use `meson wrap install nlohmann_json`. Please see the meson project for any issues regarding the packaging.
 
-The provided `meson.build` can also be used as an alternative to cmake for installing `nlohmann_json` system-wide in which case a pkg-config file is installed. To use it, simply have your build system require the `nlohmann_json` pkg-config dependency. In Meson, it is preferred to use the [`dependency()`](https://mesonbuild.com/Reference-manual.html#dependency) object with a subproject fallback, rather than using the subproject directly.
+The provided `meson.build` can also be used as an alternative to CMake for installing `nlohmann_json` system-wide in which case a pkg-config file is installed. To use it, simply have your build system require the `nlohmann_json` pkg-config dependency. In Meson, it is preferred to use the [`dependency()`](https://mesonbuild.com/Reference-manual.html#dependency) object with a subproject fallback, rather than using the subproject directly.
+
+If you are using [Bazel](https://bazel.build/) you can simply reference this repository using `http_archive` or `git_repository` and depend on `@nlohmann_json//:json`.
 
 If you are using [Conan](https://www.conan.io/) to manage your dependencies, merely add [`nlohmann_json/x.y.z`](https://conan.io/center/nlohmann_json) to your `conanfile`'s requires, where `x.y.z` is the release version you want to use. Please file issues [here](https://github.com/conan-io/conan-center-index/issues) if you experience problems with the packages.
 

WORKSPACE.bazel

@@ -0,0 +1 @@
+workspace(name = "nlohmann_json")

cmake/scripts/gen_bazel_build_file.cmake

@@ -0,0 +1,24 @@
+# generate Bazel BUILD file
+
+set(PROJECT_ROOT "${CMAKE_CURRENT_LIST_DIR}/../..")
+set(BUILD_FILE "${PROJECT_ROOT}/BUILD.bazel")
+
+file(GLOB_RECURSE HEADERS LIST_DIRECTORIES false RELATIVE "${PROJECT_ROOT}" "include/*.hpp")
+
+file(WRITE "${BUILD_FILE}" [=[
+cc_library(
+    name = "json",
+    hdrs = [
+]=])
+
+foreach(header ${HEADERS})
+    file(APPEND "${BUILD_FILE}" "        \"${header}\",\n")
+endforeach()
+
+file(APPEND "${BUILD_FILE}" [=[
+    ],
+    includes = ["include"],
+    visibility = ["//visibility:public"],
+    alwayslink = True,
+)
+]=])

docs/mkdocs/docs/integration/package_managers.md

@@ -62,6 +62,10 @@ If you are using the [Meson Build System](http://mesonbuild.com), add this sourc
 
 The provided `meson.build` can also be used as an alternative to cmake for installing `nlohmann_json` system-wide in which case a pkg-config file is installed. To use it, simply have your build system require the `nlohmann_json` pkg-config dependency. In Meson, it is preferred to use the [`dependency()`](https://mesonbuild.com/Reference-manual.html#dependency) object with a subproject fallback, rather than using the subproject directly.
 
+## Bazel
+
+This repository provides a [Bazel](https://bazel.build/) `WORKSPACE.bazel` and a corresponding `BUILD.bazel` file. Therefore, this repository can be referenced by workspace rules such as `http_archive`, `git_repository`, or `local_repository` from other Bazel workspaces. To use the library you only need to depend on the target `@nlohmann_json//:json` (e.g. via `deps` attribute).
+
 ## Conan
 
 If you are using [Conan](https://www.conan.io/) to manage your dependencies, merely add `nlohmann_json/x.y.z` to your `conanfile`'s requires, where `x.y.z` is the release version you want to use. Please file issues [here](https://github.com/conan-io/conan-center-index/issues) if you experience problems with the packages.