ep

Erlang Protocols

Build

make

Will compile and generate the ep escript, run it to see usage

Test

make test

Using the Script to Test the Parse Transform

The following will run the ep parse transform (ep_pt) on test/ep_pt_SUITE_data/ep_test_1.erl and output protocol metadata to MY_OUTPUT

./ep pt erl MY_OUTPUT test/ep_pt_SUITE_data/ep_test_1.erl

Output:

-file("test/ep_pt_SUITE_data/ep_test_1.erl", 1).

-module(ep_test_1).

-export([printable@to_string/1, consy@first/1,
         consy@rest/1]).

-ep({printable, #{to_string => {my_to_string, 1}}}).

-ep({consy,
     #{first => {first, 1}, rest => {consy_rest, 1}}}).

my_to_string(V) -> io_lib:format("~p", [V]).

first(L = [H | _]) when is_list(L) -> H.

consy_rest([_ | T]) -> T.


printable@to_string(Arg@1) -> my_to_string(Arg@1).

consy@first(Arg@1) -> first(Arg@1).

consy@rest(Arg@1) -> consy_rest(Arg@1).

./ep pt erl MY_OUTPUT test/ep_pt_SUITE_data/ep_test_2.erl

Output:

-file("test/ep_pt_SUITE_data/ep_test_2.erl", 1).

-module(ep_test_2).

-export([]).

-def_ep({printable, #{to_string => {my_to_string, 1}}}).

-def_ep({consy, #{first => 1, rest => 1}}).

my_to_string(V) when is_integer(V) ->
    integer_to_binary(V);
my_to_string(V) when is_float(V) -> float_to_binary(V);
my_to_string(V) when is_atom(V) ->
    atom_to_binary(V, utf8).

Content of MY_OUTPUT:

MY_OUTPUT
└── ep
    ├── consy
    │   ├── ep_test_1.ep
    │   └── ep_test_2.epd
    └── printable
        ├── ep_test_1.ep
        └── ep_test_2.epd

3 directories, 4 files

Using the Script to Consolidate Protocol Implementations

Map Type Structs

Printable (with default implementations)

./ep compile-proto map erl MY_OUTPUT/ep/ printable

Outputs:

-module(printable).

-export([to_string/1]).

to_string(V) when is_integer(V) -> integer_to_binary(V);
to_string(V) when is_float(V) -> float_to_binary(V);
to_string(V) when is_atom(V) -> atom_to_binary(V, utf8);
to_string(Arg@0 = V) ->
    ep_test_1:printable@to_string(Arg@0);
to_string(V = #{'__struct__' := Type}) ->
    Type:printable@to_string(V).

Consy (without default implementations)

./ep compile-proto map erl MY_OUTPUT/ep/ consy

Outputs:

-module(consy).

-export([first/1, rest/1]).

first(L = [H | _]) when is_list(L) ->
    ep_test_1:consy@first(L);
first(V = #{'__struct__' := Type}) ->
    Type:consy@first(V).

rest(Arg@0 = [_ | T]) -> ep_test_1:consy@rest(Arg@0);
rest(V = #{'__struct__' := Type}) -> Type:consy@rest(V).

Tuple Type Structs

Printable (with default implementations)

./ep compile-proto tuple erl MY_OUTPUT/ep/ printable

Outputs:

-module(printable).

-export([to_string/1]).

to_string(V) when is_integer(V) -> integer_to_binary(V);
to_string(V) when is_float(V) -> float_to_binary(V);
to_string(V) when is_atom(V) -> atom_to_binary(V, utf8);
to_string(Arg@0 = V) ->
    ep_test_1:printable@to_string(Arg@0);
to_string(V = {{Type, _Data, _}}) ->
    Type:printable@to_string(V).

Consy (without default implementations)

./ep compile-proto tuple erl MY_OUTPUT/ep/ consy

-module(consy).

-export([first/1, rest/1]).

first(L = [H | _]) when is_list(L) ->
    ep_test_1:consy@first(L);
first(V = {{Type, _Data, _}}) -> Type:consy@first(V).

rest(Arg@0 = [_ | T]) -> ep_test_1:consy@rest(Arg@0);
rest(V = {{Type, _Data, _}}) -> Type:consy@rest(V).

Notes

If I embed the ast of the impl function in the proto module I don't have access to private functions and I have to rewrite local calls to remote ones for the ones that are public.

TODO

• Remove {eof, Line} from module AST in parse transform when appending proto funs

• Validate that proto implementation implements right functions and arities

• Remove .ep and .epd files in output if that module no longer declares or implements protos