erl_ts

Erlang Tree-Sitter integration. An OTP library that implements NIFs calls to tree-sitter.

Many tree-sitter APIs were implemented, and other functions were added to ease its consumption. This is in early stage, but most important functions were added.

For now it only supports Erlang/OTP grammar but is possible to extend it.

WHY?

I’m not proficient with C and found this project interesting; helps me to learn C, interoperability between Erlang and C libraries using its built-in NIF framework, and practice elisp. Where is the elisp part? well, I wrote a code generator in less than 1 hour to produce the transformations between Erlang terms arguments and C types.

Build

$ rebar3 compile

tree-sitter and tree-sitter-erlang are sub-repositories that are going to be build and generate the dynamic and static libraries. By default, erl_ts will statically link both libraries into erl_ts.so such that it can be integrated with ease in other projects.

The environment variable ERL_TS_LINKING=dynamic controls the dynamic linking, in such case, ensure libtree-sitter and libtree-sitter-erlang.so are part of LDLIBS

Test

$ rebar3 ct

Develop

$ ./build_c_db.sh to generate c_src/compile_commands.json to be used by clangd to help navigate and highlight errors in the C side

Usage example

Note: call erl_ts:init() only once per execution as it will load erl_ts.so and reloading these libraries are not supported by Erlang/OTP.

$ rebar3 shell

Erlang/OTP 26 [erts-14.2.5.4] [source] [64-bit] [smp:4:4] [ds:4:4:10] [async-threads:1] [jit:ns]

Eshell V14.2.5.4 (press Ctrl+G to abort, type help(). for help)
1> erl_ts:init(),
   {ok, Parser} = erl_ts:parser_new(),
   {ok, Lang} = erl_ts:tree_sitter_erlang(),
   true = erl_ts:parser_set_language(Parser, Lang),
   SC = "a_qt_function({A,B}) -> {A+A, B*B}.    b_qt_function(A,B) -> #{a => A, b =>       B}.",
   Tree = erl_ts:parser_parse_string(Parser, SC),
   RootNode = erl_ts:tree_root_node(Tree),
   RootNodeStr = erl_ts:node_string(RootNode).
<<"(source_file forms_only: (fun_decl clause: (function_clause name: (atom) args: (expr_args args: (tuple expr: (var) e"...>>
2> rp(RootNodeStr).
<<"(source_file forms_only: (fun_decl clause: (function_clause name: (atom) args: (expr_args args: (tuple expr: (var) expr: (var))) body: (clause_body exprs: (tuple expr: (binary_op_expr lhs: (var) rhs: (var)) expr: (binary_op_expr lhs: (var) rhs: (var)))))) forms_only: (fun_decl clause: (function_clause name: (atom) args: (expr_args args: (var) args: (var)) body: (clause_body exprs: (map_expr fields: (map_field key: (atom) value: (var)) fields: (map_field key: (atom) value: (var)))))))">>
ok
3> {Query, _, _} = erl_ts:query_new(Lang, "(function_clause name: (atom) @fun_name)").
{#Ref<0.3646334886.4285399041.132320>,3418416122,error_none}
4> Captures = erl_ts:query_capture(RootNode, Query).
[{"fun_name",#Ref<0.733339053.444203009.70844>},
 {"fun_name",#Ref<0.733339053.444203009.70843>}]
5> [{C, erl_ts:node_text(N, SC)} || {C, N} <- Captures].
[{"fun_name","b_qt_function"},{"fun_name","a_qt_function"}]