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lefant/pretty_config.erl

Last active June 22, 2020 08:49
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a little escript snippet to pretty print erlang config, using the erl_syntax module
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pretty_config.erl
#!/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.
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