Last Updated: February 25, 2016

pretty print erlang config, using the erl_syntax module

nicely highlighted gist here: http://ly.lefant.net/pretty_erl

code snippet below for your convenience.

#!/usr/bin/env escript
%% -*- erlang -*-

%% * slurp in terms using inlined version of kernels file:consult/1
%% * convert to abstract syntax tree
%% * annotate all tuples
%% * pretty print using a hook to prefix the annotated nodes with newline

main([]) ->
 io:format("%% -*-erlang-*-~n"),
 {ok, Terms} = consult_stream(),
 [pretty_term(Term) || Term <- Terms],
 ok.

pretty_term(Term) ->
 Abstract = erl_syntax:abstract(Term),
 AnnF = fun(Node) -> annotate_tuple(Node) end,
 AnnAbstract = postorder(AnnF, Abstract),
 HookF = fun(Node, Ctxt, Cont) ->
 Doc = Cont(Node, Ctxt),
 prettypr:above(prettypr:empty(), Doc)
 end,
 Io = erl_prettypr:format(AnnAbstract, [{hook, HookF}]),
 io:put_chars(Io),
 io:format(".~n").

annotate_tuple(Node) ->
 case erl_syntax:type(Node) of
 tuple -> erl_syntax:add_ann(tuple, Node);
 _ -> Node
 end.

%% from the erl_syntax manpage
postorder(F, Tree) ->
 F(case erl_syntax:subtrees(Tree) of
 [] -> Tree;
 List -> erl_syntax:update_tree(Tree,
 [[postorder(F, Subtree)
 || Subtree <- Group]
 || Group <- List])
 end).

%% specialized from kernel/file.erl
consult_stream() -> consult_stream([]).
consult_stream(Acc) ->
 case io:read('') of
 {ok, Term} -> consult_stream([Term|Acc]);
 {error, Error} -> {error, Error};
 eof -> {ok, lists:reverse(Acc)}
 end.

#erlang

#config

#pretty

#escript