Add JSON support for Erlang and Elixir

CHANGELOG.md

@@ -7,6 +7,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## [0.7.0-alpha.1] - Unreleased
 
 ### Added
+- Added `json` module to estdlib, compatible with Erlang/OTP `json` API
+- Added `Keyword.put_new/3` to exavmlib
+- Added `JSON` module to exavmlib (Elixir wrapper for estdlib `json`)
 - Added `erlang:node/1` BIF
 - Added `erts_internal:cmp_term/2`
 - Added `short` option to `erlang:float_to_binary/2` and `erlang:float_to_list/2`
@@ -32,6 +35,9 @@ strict format validation
 - Fixed `erlang:binary_to_float/1` and `erlang:list_to_float/1` returning `inf` for overflow instead
 of raising `badarg`
 
+### Removed
+- Removed old `json_encoder` module (now standard Erlang/OTP `json` module is available)
+
 ## [0.7.0-alpha.0] - 2026-03-20
 
 ### Added

CMakeModules/BuildElixir.cmake

@@ -18,10 +18,75 @@
 # SPDX-License-Identifier: Apache-2.0 OR LGPL-2.1-or-later
 #
 
+# Compile a single .ex source that defines multiple modules.
+# All module names must be listed, and OUTPUT names the variable
+# that receives the beam paths (for passing to pack_archive).
+#
+# Usage:
+#     compile_multi(json.ex
+#         JSON
+#         JSON.Encoder
+#         JSON.Encoder.Atom
+#         OUTPUT JSON_BEAMS
+#     )
+#     pack_archive(mylib ${MODULES} EXTRA_BEAMS ${JSON_BEAMS})
+#
+macro(compile_multi source_file)
+    find_package(Elixir REQUIRED)
+    set(_cm_modules "")
+    set(_cm_outputs "")
+    set(_cm_outvar "")
+    set(_cm_in_output FALSE)
+    foreach(_arg ${ARGN})
+        if(_arg STREQUAL "OUTPUT")
+            set(_cm_in_output TRUE)
+        elseif(_cm_in_output)
+            set(_cm_outvar "${_arg}")
+        else()
+            list(APPEND _cm_modules "${_arg}")
+            list(APPEND _cm_outputs
+                "${CMAKE_CURRENT_BINARY_DIR}/beams/Elixir.${_arg}.beam"
+            )
+        endif()
+    endforeach()
+    add_custom_command(
+        OUTPUT ${_cm_outputs}
+        COMMAND mkdir -p
+            ${CMAKE_CURRENT_BINARY_DIR}/beams
+            ${CMAKE_CURRENT_BINARY_DIR}/beams.tmp.multi.${_cm_outvar}
+        COMMAND elixirc --no-docs --no-debug-info
+            --ignore-module-conflict
+            -o ${CMAKE_CURRENT_BINARY_DIR}/beams.tmp.multi.${_cm_outvar}/
+            ${CMAKE_CURRENT_SOURCE_DIR}/${source_file}
+        COMMAND sh -c
+            "mv ${CMAKE_CURRENT_BINARY_DIR}/beams.tmp.multi.${_cm_outvar}/Elixir.*.beam ${CMAKE_CURRENT_BINARY_DIR}/beams/"
+        COMMAND rmdir
+            ${CMAKE_CURRENT_BINARY_DIR}/beams.tmp.multi.${_cm_outvar}
+        DEPENDS ${CMAKE_CURRENT_SOURCE_DIR}/${source_file}
+        COMMENT "Compiling ${source_file}"
+        VERBATIM
+    )
+    set(${_cm_outvar} ${_cm_outputs})
+endmacro()
+
 macro(pack_archive avm_name)
     find_package(Elixir REQUIRED)
 
-    foreach(module_name ${ARGN})
+    # Parse EXTRA_BEAMS keyword from arguments
+    set(_pa_modules "")
+    set(_pa_extra "")
+    set(_pa_in_extra FALSE)
+    foreach(_arg ${ARGN})
+        if(_arg STREQUAL "EXTRA_BEAMS")
+            set(_pa_in_extra TRUE)
+        elseif(_pa_in_extra)
+            list(APPEND _pa_extra "${_arg}")
+        else()
+            list(APPEND _pa_modules "${_arg}")
+        endif()
+    endforeach()
+
+    foreach(module_name ${_pa_modules})
         add_custom_command(
             OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/beams/Elixir.${module_name}.beam
             COMMAND mkdir -p ${CMAKE_CURRENT_BINARY_DIR}/beams ${CMAKE_CURRENT_BINARY_DIR}/beams.tmp.${module_name}
@@ -35,6 +100,8 @@ macro(pack_archive avm_name)
         set(BEAMS ${BEAMS} ${CMAKE_CURRENT_BINARY_DIR}/beams/Elixir.${module_name}.beam)
     endforeach()
 
+    set(BEAMS ${BEAMS} ${_pa_extra})
+
     add_custom_target(
         ${avm_name}_beams ALL
         DEPENDS ${BEAMS}

UPDATING.md

@@ -30,6 +30,8 @@ rather than copy sdkconfig.release-defaults.in to sdkconfig.defaults.in (which s
 `reconfigure` or `set-target` to be run to pick up the changes), this may also be combined with the
 `ATOMVM_ELIXIR_SUPPORT` option. For example, an Elixir-supported release build is configured using:
 `idf.py -DATOMVM_ELIXIR_SUPPORT=on -DATOMVM_RELEASE=on set-target ${CHIP}`
+- `json_encoder` module has been removed, use new (and standard) `json` module. New module uses
+standard Erlang/OTP API, that takes maps instead of proplists.
 
 ## v0.6.4 -> v0.6.5
 

examples/erlang/system_info_server.erl

@@ -1,7 +1,7 @@
 %
 % This file is part of AtomVM.
 %
-% Copyright 2019-2020 Davide Bettio <davide@uninstall.it>
+% Copyright 2019-2026 Davide Bettio <davide@uninstall.it>
 %
 % Licensed under the Apache License, Version 2.0 (the "License");
 % you may not use this file except in compliance with the License.
@@ -62,18 +62,18 @@ handle_req("GET", [], Conn) ->
     Body = [<<"<html><body><h1>">>, TimeString, <<"</h1></body></html>">>],
     http_server:reply(200, Body, Conn);
 handle_req("GET", ["system", "info"], Conn) ->
-    SysInfo = [
-        {atom_count, erlang:system_info(atom_count)},
-        {process_count, erlang:system_info(process_count)},
-        {port_count, erlang:system_info(port_count)},
-        {word_size, erlang:system_info(wordsize)},
-        {system_architecture, erlang:system_info(system_architecture)}
-    ],
-    Body = json_encoder:encode(SysInfo),
+    SysInfo = #{
+        atom_count => erlang:system_info(atom_count),
+        process_count => erlang:system_info(process_count),
+        port_count => erlang:system_info(port_count),
+        word_size => erlang:system_info(wordsize),
+        system_architecture => erlang:system_info(system_architecture)
+    },
+    Body = json:encode(SysInfo),
     http_server:reply(200, Body, Conn);
 handle_req("GET", ["processes", PidString, "info"], Conn) ->
     {Code, ProcInfo} = try_proc_info_list(PidString),
-    Body = json_encoder:encode(ProcInfo),
+    Body = json:encode(ProcInfo),
     http_server:reply(Code, Body, Conn);
 handle_req(Method, Path, Conn) ->
     io:format("Method: ~p Path: ~p~n", [Method, Path]),

libs/eavmlib/src/CMakeLists.txt

@@ -28,7 +28,6 @@ set(ERLANG_MODULES
     console
     gpio_hal
     i2c_hal
-    json_encoder
     logger_manager
     port
     spi_hal

libs/estdlib/src/CMakeLists.txt

@@ -55,6 +55,7 @@ set(ERLANG_MODULES
     init
     io_lib
     io
+    json
     lists
     maps
     math