From fb5f062589c377c00ba0de7691da6425ad7ada1c Mon Sep 17 00:00:00 2001
From: Martin Quinson <martin.quinson@ens-rennes.fr>
Date: Tue, 14 Mar 2023 00:43:27 +0100
Subject: [PATCH] Test for JSON before using it

---
 CMakeLists.txt                                | 10 ++++++++++
 docs/source/Installing_SimGrid.rst            |  3 +++
 include/simgrid/config.h.in                   |  2 ++
 src/dag/loaders.cpp                           | 11 ++++++++---
 tools/cmake/MakeLib.cmake                     |  4 ++++
 tools/cmake/Modules/nlohmann_jsonConfig.cmake | 15 +++++++++++++++
 6 files changed, 42 insertions(+), 3 deletions(-)
 create mode 100644 tools/cmake/Modules/nlohmann_jsonConfig.cmake

diff --git a/CMakeLists.txt b/CMakeLists.txt
index f702831160..ac8fa34e57 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -231,6 +231,16 @@ else()
   message(STATUS "Disabling model BMF because Eigen3 was not found. If it's installed, use EIGEN3_HINT to hint cmake about the location of Eigen3Config.cmake")
 endif()
 
+# Check for our JSON dependency
+set(SIMGRID_HAVE_JSON 0)
+find_package(nlohmann_json 3.11.2
+             HINTS ${nlohmann_json_HINT})
+if (nlohmann_json_FOUND)
+  set(SIMGRID_HAVE_JSON 1)
+  message(STATUS "Found nlohmann_json: ${NLOHMANN_JSON_INCLUDE_DIR}")
+  include_directories(${NLOHMANN_JSON_INCLUDE_DIR})
+endif()
+
 set(HAVE_PAPI 0)
 if(enable_smpi_papi)
   include(FindPAPI)
diff --git a/docs/source/Installing_SimGrid.rst b/docs/source/Installing_SimGrid.rst
index adfb90ee6e..5cb50fbe0d 100644
--- a/docs/source/Installing_SimGrid.rst
+++ b/docs/source/Installing_SimGrid.rst
@@ -107,6 +107,9 @@ Eigen3 (optional)
   - On CentOS / Fedora: ``dnf install eigen3-devel``
   - On macOS with homebrew: ``brew install eigen``
   - Use EIGEN3_HINT to specify where it's installed if cmake doesn't find it automatically.
+JSON (optional, for the DAG wfcommons loader)
+  - On Debian / Ubuntu: ``apt install nlohmann-json3-dev``
+  - Use nlohmann_json_HINT to specify where it's installed if cmake doesn't find it automatically.
 
 For platform-specific details, please see below.
 
diff --git a/include/simgrid/config.h.in b/include/simgrid/config.h.in
index 2995c8d460..6ef3fd76b1 100644
--- a/include/simgrid/config.h.in
+++ b/include/simgrid/config.h.in
@@ -18,4 +18,6 @@
 #cmakedefine NS3_MINOR_VERSION @NS3_MINOR_VERSION@
 /* Was the Eigen3 support compiled in? */
 #cmakedefine01 SIMGRID_HAVE_EIGEN3
+/* Was the JSON support compiled in? */
+#cmakedefine01 SIMGRID_HAVE_JSON
 #endif /* SIMGRID_PUBLIC_CONFIG_H */
diff --git a/src/dag/loaders.cpp b/src/dag/loaders.cpp
index e78e7169a0..676b98b07f 100644
--- a/src/dag/loaders.cpp
+++ b/src/dag/loaders.cpp
@@ -1,5 +1,4 @@
-/* Copyright (c) 2009-2023. The SimGrid Team.
- * All rights reserved.                                                     */
+/* Copyright (c) 2009-2023. The SimGrid Team. All rights reserved.          */
 
 /* This program is free software; you can redistribute it and/or modify it
  * under the terms of the license (GNU LGPL) which comes with this package. */
@@ -21,7 +20,9 @@
 #include "dax_dtd.h"
 #include "dax_dtd.c"
 
+#if SIMGRID_HAVE_JSON
 #include <nlohmann/json.hpp>
+#endif
 
 #if HAVE_GRAPHVIZ
 #include <graphviz/cgraph.h>
@@ -89,6 +90,7 @@ static ExecPtr current_job;
  */
 std::vector<ActivityPtr> create_DAG_from_json(const std::string& filename)
 {
+#if SIMGRID_HAVE_JSON
   std::ifstream f(filename);
   auto data = nlohmann::json::parse(f);
   std::vector<ActivityPtr> dag = {};
@@ -149,8 +151,11 @@ std::vector<ActivityPtr> create_DAG_from_json(const std::string& filename)
       activity->start();
   }
   return dag;
+#else
+  xbt_die("JSON support was not compiled in, probably because nlohmann/json was not found. Please install "
+          "nlohmann-json3-dev and recompile SimGrid to use this feature.");
+#endif
 }
-
 /** @brief loads a DAX file describing a DAG
  *
  * See https://confluence.pegasus.isi.edu/display/pegasus/WorkflowGenerator for more details.
diff --git a/tools/cmake/MakeLib.cmake b/tools/cmake/MakeLib.cmake
index 4afca47839..11cf6b9c28 100644
--- a/tools/cmake/MakeLib.cmake
+++ b/tools/cmake/MakeLib.cmake
@@ -95,6 +95,10 @@ if(HAVE_GRAPHVIZ)
   endif()
 endif()
 
+if(SIMGRID_HAVE_JSON)
+  target_link_libraries(simgrid  nlohmann_json::nlohmann_json)
+endif()
+
 if(NOT ${DL_LIBRARY} STREQUAL "")
   SET(SIMGRID_DEP "${SIMGRID_DEP} ${DL_LIBRARY}")
 endif()
diff --git a/tools/cmake/Modules/nlohmann_jsonConfig.cmake b/tools/cmake/Modules/nlohmann_jsonConfig.cmake
new file mode 100644
index 0000000000..27b0a864a8
--- /dev/null
+++ b/tools/cmake/Modules/nlohmann_jsonConfig.cmake
@@ -0,0 +1,15 @@
+include(FindPackageHandleStandardArgs)
+set(${CMAKE_FIND_PACKAGE_NAME}_CONFIG ${CMAKE_CURRENT_LIST_FILE})
+find_package_handle_standard_args(nlohmann_json CONFIG_MODE)
+
+if(NOT TARGET nlohmann_json::nlohmann_json)
+    include("${CMAKE_CURRENT_LIST_DIR}/nlohmann_jsonTargets.cmake")
+    if((NOT TARGET nlohmann_json) AND
+       (NOT nlohmann_json_FIND_VERSION OR
+        nlohmann_json_FIND_VERSION VERSION_LESS 3.2.0))
+        add_library(nlohmann_json INTERFACE IMPORTED)
+        set_target_properties(nlohmann_json PROPERTIES
+            INTERFACE_LINK_LIBRARIES nlohmann_json::nlohmann_json
+        )
+    endif()
+endif()
-- 
2.20.1