How can I use erl_lint to syntax check an Erlang module? - syntax

Question

I'm trying to use erl_lint() to build a simple Erlang syntax and style checker. I've gotten far enough to load the file and parse it into Forms and to get erl_lint to partially understand it, but then erl_lint complains about undefined functions that are defined. What am I doing wrong?
erlint.erl :
-module(erlint).
-export([lint/1]).
% based on http://stackoverflow.com/a/28086396/13675
lint(File) ->
{ok, B} = file:read_file(File),
Forms = scan(erl_scan:tokens([],binary_to_list(B),1),[]),
F = fun(X) -> {ok,Y} = erl_parse:parse_form(X), Y end,
erl_lint:module([F(X) || X <- Forms],File).
scan({done,{ok,T,N},S},Res) ->
scan(erl_scan:tokens([],S,N),[T|Res]);
scan(_,Res) ->
lists:reverse(Res).
hello.erl :
-module(hello).
-export([hello_world/0]).
hello_world() -> io:fwrite("hello, world\n").
attempt to use :
1> c(erlint).
{ok,erlint}
2> erlint:lint("hello.erl").
{error,[{"hello.erl",
[{2,erl_lint,{undefined_function,{hello_world,0}}}]}],
[]}

Answer 1

I'm not sure this approach fits with your overall plan, but you could instead compile the input file, extract its abstract forms from the resulting beam, and pass them to erl_lint:
-module(erlint).
-export([lint/1]).
lint(File) ->
{ok,_,Bin} = compile:file(File,[debug_info,binary]),
{ok,{_,[{abstract_code,{_,AC}}]}} = beam_lib:chunks(Bin,[abstract_code]),
erl_lint:module(AC,File).
Let's change your hello.erl to include an unused variable:
-module(hello).
-export([hello_world/0]).
hello_world() ->
X = io:fwrite("hello, world\n").
We see that this version of erlint:lint/1 correctly reports it:
1> erlint:lint("hello.erl").
{ok,[{"hello.erl",[{5,erl_lint,{unused_var,'X'}}]}]}
If you need them for your overall purposes, note that you can retrieve source code forms from the abstract forms variable AC by calling erl_syntax:form_list(AC).