Output more context on error (#60)

* Fix our spec.s as per elvis_core and output more context on error

The test is a dumb one, not unlike the prior version of it,
but it makes sure we don't crash on function call (mimics
rebar3) and on io:format'ing it

* Bump elvis_core from 3.2.0 to 3.2.1

rebar.config

@@ -12,7 +12,7 @@
 
 %% == Dependencies and plugins ==
 
-{deps, [{elvis_core, "3.2.0"}]}.
+{deps, [{elvis_core, "3.2.1"}]}.
 
 {project_plugins,
  [{rebar3_hank, "~> 1.4.0"},

rebar.lock

@@ -1,14 +1,14 @@
 {"1.2.0",
-[{<<"elvis_core">>,{pkg,<<"elvis_core">>,<<"3.2.0">>},0},
+[{<<"elvis_core">>,{pkg,<<"elvis_core">>,<<"3.2.1">>},0},
  {<<"katana_code">>,{pkg,<<"katana_code">>,<<"2.1.0">>},1},
  {<<"zipper">>,{pkg,<<"zipper">>,<<"1.0.1">>},1}]}.
 [
 {pkg_hash,[
- {<<"elvis_core">>, <<"1B8DD3190903ED7520D03DD53E7535574CFC7354C89FA580BE8FD3F65A70C248">>},
+ {<<"elvis_core">>, <<"D5EFDBC55D14521BAB9337FA6822EB41085377BDB1059B2E6794333F40AE4DC1">>},
  {<<"katana_code">>, <<"0C42BDCD7E59995876AED9F678CF62E3D12EF42E0FBB2190556E64BFEBDD15C6">>},
  {<<"zipper">>, <<"3CCB4F14B97C06B2749B93D8B6C204A1ECB6FAFC6050CACC3B93B9870C05952A">>}]},
 {pkg_hash_ext,[
- {<<"elvis_core">>, <<"05EBF8D4840F4A81721907E1DDCE2F3455BE8EA0F0FB280D50C8DE85C40060FA">>},
+ {<<"elvis_core">>, <<"4F1996776BB53EF35D0CDA0A6799FC14CDB9190BA89F07883AFCA734D464AE3C">>},
  {<<"katana_code">>, <<"AE3BBACA187511588F69695A9FF22251CB2CC672FDCCC180289779BDD25175EF">>},
  {<<"zipper">>, <<"6A1FD3E1F0CC1D1DF5642C9A0CE2178036411B0A5C9642851D1DA276BD737C2D">>}]}
 ].

src/rebar3_lint_prv.erl

@@ -22,23 +22,25 @@ init(State) ->
                           {desc, "A rebar linter plugin based on elvis"}]),
     {ok, rebar_state:add_provider(State, Provider)}.
 
--spec do(rebar_state:t()) -> {ok, rebar_state:t()} | {error, string()}.
+-spec do(rebar_state:t()) -> {ok, rebar_state:t()} | {error, {string(), any()}}.
 do(State) ->
     Elvis = get_elvis_config(State),
     _ = rebar_log:log(info, "elvis analysis starting, this may take a while...", []),
     try elvis_core:rock(Elvis) of
         ok ->
             {ok, State};
-        {fail, _} ->
-            {error, "Linting failed"}
+        {fail, [{throw, Error} | _]} ->
+            rebar_api:abort("elvis_core threw an exception: ~p", [Error]);
+        {fail, Reason} ->
+            {error, {"Linting failed with ~p", Reason}}
     catch
         Error ->
             rebar_api:abort("elvis_core threw an exception: ~p", [Error])
     end.
 
--spec format_error(any()) -> iolist().
-format_error(Reason) ->
-    io_lib:format("~p", [Reason]).
+-spec format_error({string(), any()}) -> iolist().
+format_error({Message, Reason}) ->
+    io_lib:format(Message, [Reason]).
 
 -spec get_elvis_config(rebar_state:t()) -> elvis_config:configs().
 get_elvis_config(State) ->

test/test_app_SUITE.erl

@@ -19,4 +19,6 @@ test_app(_Config) ->
                         [#{dirs => ["src"],
                            filter => "*.erl",
                            rules => [{elvis_style, max_function_length, #{max_length => 1}}]}]),
-    {error, "Linting failed"} = rebar3_lint_prv:do(BadState).
+    {error, {Message = "Linting failed with ~p", Reason}} = rebar3_lint_prv:do(BadState),
+    % Check that this doesn't throw
+    io:format("~p", [rebar3_lint_prv:format_error({Message, Reason})]).