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Safe mechanism for converting strings to existing atoms #200

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Safe mechanism for converting strings to existing atoms #200

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a970358
Safe mechanism for converting strings to existing atoms
macintux Aug 4, 2015
8ac7a94
Awkward grammar is awkward
macintux Aug 5, 2015
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16 changes: 14 additions & 2 deletions src/cuttlefish_datatypes.erl
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Original file line number Diff line number Diff line change
Expand Up @@ -193,10 +193,18 @@ to_string(Value, MaybeExtendedDatatype) ->
{error, {type, {Value, MaybeExtendedDatatype}}}
end.

-spec from_string(term(), datatype()) -> term() | cuttlefish_error:error().
-spec from_string(term(), datatype()|'existing_atom') -> term() | cuttlefish_error:error().
from_string(Atom, atom) when is_atom(Atom) -> Atom;
from_string(String, atom) when is_list(String) -> list_to_atom(String);

from_string(String, existing_atom) when is_list(String) ->
try
list_to_existing_atom(String)
catch
error:badarg ->
{error, {conversion, {String, atom}}}
end;

from_string(Value, {enum, Enum}) ->
cuttlefish_enum:parse(Value, {enum, Enum});

Expand Down Expand Up @@ -338,7 +346,11 @@ to_string_unsupported_datatype_test() ->

from_string_atom_test() ->
?assertEqual(split_the, from_string(split_the, atom)),
?assertEqual(split_the, from_string("split_the", atom)).
?assertEqual(split_the, from_string("split_the", atom)),
?assertMatch({error, {conversion, _}}, from_string("unknown_atom_to_explode_table", existing_atom)),
%% Using `assertEqual' as above introduces the atom to be created,
%% so they don't actually test that unknown atoms work properly.
?assert(is_atom(from_string("unknown_atom_to_explode_table", atom))).

from_string_integer_test() ->
?assertEqual(32, from_string(32, integer)),
Expand Down