Merge pull request #127 from kellymclaughlin/xref-provider

Add xref provider for cross reference analysis

2 files changed, 297 insertions, 0 deletions

diff --git a/src/rebar.app.src b/src/rebar.app.src
index 73c1eff..1230436 100644
--- a/src/rebar.app.src
+++ b/src/rebar.app.src
@@ -43,6 +43,7 @@
                      rebar_prv_release,
                      rebar_prv_version,
                      rebar_prv_common_test,
+                     rebar_prv_xref,
                      rebar_prv_help]}
         ]}
  ]}.
diff --git a/src/rebar_prv_xref.erl b/src/rebar_prv_xref.erl
new file mode 100644
index 0000000..32ebf46
--- /dev/null
+++ b/src/rebar_prv_xref.erl
@@ -0,0 +1,296 @@
+%% -*- erlang-indent-level: 4;indent-tabs-mode: nil -*-
+%% ex: ts=4 sw=4 et
+
+-module(rebar_prv_xref).
+
+-behaviour(provider).
+
+-export([init/1,
+         do/1,
+         format_error/1]).
+
+-include("rebar.hrl").
+
+-define(PROVIDER, xref).
+-define(DEPS, [compile]).
+-define(SUPPORTED_XREFS, [undefined_function_calls, undefined_functions,
+                          locals_not_used, exports_not_used,
+                          deprecated_function_calls, deprecated_functions]).
+
+%% ===================================================================
+%% Public API
+%% ===================================================================
+
+-spec init(rebar_state:t()) -> {ok, rebar_state:t()}.
+init(State) ->
+    Provider = providers:create([{name, ?PROVIDER},
+                                 {module, ?MODULE},
+                                 {deps, ?DEPS},
+                                 {bare, false},
+                                 {example, "rebar3 xref"},
+                                 {short_desc, short_desc()},
+                                 {desc, desc()}]),
+    State1 = rebar_state:add_provider(State, Provider),
+    {ok, State1}.
+
+-spec do(rebar_state:t()) -> {ok, rebar_state:t()} | {error, string()}.
+do(State) ->
+    {OriginalPath, XrefChecks} = prepare(State),
+
+    %% Run xref checks
+    ?INFO("Running cross reference analysis...", []),
+    XrefResults = xref_checks(XrefChecks),
+
+    %% Run custom queries
+    QueryChecks = rebar_state:get(State, xref_queries, []),
+    QueryResults = lists:foldl(fun check_query/2, [], QueryChecks),
+
+    ok = cleanup(OriginalPath),
+
+    case XrefResults =:= [] andalso QueryResults =:= [] of
+        true ->
+            {ok, State};
+        false ->
+            {error, {?MODULE, {xref_issues, XrefResults, QueryResults}}}
+    end.
+
+-spec format_error(any()) -> iolist().
+format_error({xref_issues, XrefResults, QueryResults}) ->
+    lists:flatten(display_results(XrefResults, QueryResults));
+format_error(Reason) ->
+    io_lib:format("~p", [Reason]).
+
+%% ===================================================================
+%% Internal functions
+%% ===================================================================
+
+short_desc() ->
+    "Run cross reference analysis".
+
+desc() ->
+    io_lib:format(
+      "~s~n"
+      "~n"
+      "Valid rebar.config options:~n"
+      "  ~p~n"
+      "  ~p~n"
+      "  ~p~n"
+      "  ~p~n",
+      [short_desc(),
+       {xref_warnings, false},
+       {xref_extra_paths,[]},
+       {xref_checks, [undefined_function_calls, undefined_functions,
+                      locals_not_used, exports_not_used,
+                      deprecated_function_calls, deprecated_functions]},
+       {xref_queries,
+        [{"(xc - uc) || (xu - x - b"
+          " - (\"mod\":\".*foo\"/\"4\"))",[]}]}
+      ]).
+
+-spec prepare(rebar_state:t()) -> list(atom()).
+prepare(State) ->
+    {ok, _} = xref:start(xref),
+    ok = xref:set_library_path(xref, code_path(State)),
+
+    xref:set_default(xref, [{warnings,
+                             rebar_state:get(State, xref_warnings, false)},
+                            {verbose, rebar_log:is_verbose(State)}]),
+
+    {ok, _} = xref:add_directory(xref, "ebin"),
+
+    %% Save the code path prior to doing any further code path
+    %% manipulation
+    OriginalPath = code:get_path(),
+    true = code:add_path(rebar_dir:ebin_dir()),
+
+    %% Get list of xref checks we want to run
+    ConfXrefChecks = rebar_state:get(State, xref_checks,
+                                     [exports_not_used,
+                                      undefined_function_calls]),
+
+    XrefChecks = sets:to_list(sets:intersection(
+                                sets:from_list(?SUPPORTED_XREFS),
+                                sets:from_list(ConfXrefChecks))),
+    {OriginalPath, XrefChecks}.
+
+cleanup(Path) ->
+    %% Restore the code path using the provided path
+    true = rebar_utils:cleanup_code_path(Path),
+
+    %% Stop xref
+    stopped = xref:stop(xref),
+    ok.
+
+xref_checks(XrefChecks) ->
+    lists:foldl(fun run_xref_check/2, [], XrefChecks).
+
+run_xref_check(XrefCheck, Acc) ->
+    {ok, Results} = xref:analyze(xref, XrefCheck),
+    case filter_xref_results(XrefCheck, Results) of
+        [] ->
+            Acc;
+        FilterResult ->
+            [{XrefCheck, FilterResult} | Acc]
+    end.
+
+check_query({Query, Value}, Acc) ->
+    {ok, Answer} = xref:q(xref, Query),
+    case Answer =:= Value of
+        false ->
+            [{Query, Value, Answer} | Acc];
+        _     ->
+            Acc
+    end.
+
+code_path(State) ->
+    [P || P <- code:get_path() ++
+              rebar_state:get(State, xref_extra_paths, []),
+          filelib:is_dir(P)].
+
+%% Ignore behaviour functions, and explicitly marked functions
+%%
+%% Functions can be ignored by using
+%% -ignore_xref([{F, A}, {M, F, A}...]).
+get_xref_ignorelist(Mod, XrefCheck) ->
+    %% Get ignore_xref attribute and combine them in one list
+    Attributes =
+        try
+            Mod:module_info(attributes)
+        catch
+            _Class:_Error -> []
+        end,
+
+    IgnoreXref = keyall(ignore_xref, Attributes),
+
+    BehaviourCallbacks = get_behaviour_callbacks(XrefCheck, Attributes),
+
+    %% And create a flat {M,F,A} list
+    lists:foldl(
+      fun({F, A}, Acc) -> [{Mod,F,A} | Acc];
+         ({M, F, A}, Acc) -> [{M,F,A} | Acc]
+      end, [], lists:flatten([IgnoreXref, BehaviourCallbacks])).
+
+keyall(Key, List) ->
+    lists:flatmap(fun({K, L}) when Key =:= K -> L; (_) -> [] end, List).
+
+get_behaviour_callbacks(exports_not_used, Attributes) ->
+    [B:behaviour_info(callbacks) || B <- keyall(behaviour, Attributes)];
+get_behaviour_callbacks(_XrefCheck, _Attributes) ->
+    [].
+
+parse_xref_result({_, MFAt}) -> MFAt;
+parse_xref_result(MFAt) -> MFAt.
+
+filter_xref_results(XrefCheck, XrefResults) ->
+    SearchModules = lists:usort(
+                      lists:map(
+                        fun({Mt,_Ft,_At}) -> Mt;
+                           ({{Ms,_Fs,_As},{_Mt,_Ft,_At}}) -> Ms;
+                           (_) -> undefined
+                        end, XrefResults)),
+
+    Ignores = lists:flatmap(fun(Module) ->
+                                    get_xref_ignorelist(Module, XrefCheck)
+                            end, SearchModules),
+
+    [Result || Result <- XrefResults,
+               not lists:member(parse_xref_result(Result), Ignores)].
+
+display_results(XrefResults, QueryResults) ->
+    [lists:map(fun display_xref_results_for_type/1, XrefResults),
+     lists:map(fun display_query_result/1, QueryResults)].
+
+display_query_result({Query, Answer, Value}) ->
+    io_lib:format("Query ~s~n answer ~p~n did not match ~p~n",
+                  [Query, Answer, Value]).
+
+display_xref_results_for_type({Type, XrefResults}) ->
+    lists:map(display_xref_result_fun(Type), XrefResults).
+
+display_xref_result_fun(Type) ->
+    fun(XrefResult) ->
+            {Source, SMFA, TMFA} =
+                case XrefResult of
+                    {MFASource, MFATarget} ->
+                        {format_mfa_source(MFASource),
+                         format_mfa(MFASource),
+                         format_mfa(MFATarget)};
+                    MFATarget ->
+                        {format_mfa_source(MFATarget),
+                         format_mfa(MFATarget),
+                         undefined}
+                end,
+            case Type of
+                undefined_function_calls ->
+                    io_lib:format("~sWarning: ~s calls undefined function ~s (Xref)\n",
+                                  [Source, SMFA, TMFA]);
+                undefined_functions ->
+                    io_lib:format("~sWarning: ~s is undefined function (Xref)\n",
+                                  [Source, SMFA]);
+                locals_not_used ->
+                    io_lib:format("~sWarning: ~s is unused local function (Xref)\n",
+                                  [Source, SMFA]);
+                exports_not_used ->
+                    io_lib:format("~sWarning: ~s is unused export (Xref)\n",
+                                  [Source, SMFA]);
+                deprecated_function_calls ->
+                    io_lib:format("~sWarning: ~s calls deprecated function ~s (Xref)\n",
+                                  [Source, SMFA, TMFA]);
+                deprecated_functions ->
+                    io_lib:format("~sWarning: ~s is deprecated function (Xref)\n",
+                                  [Source, SMFA]);
+                Other ->
+                    io_lib:format("~sWarning: ~s - ~s xref check: ~s (Xref)\n",
+                                  [Source, SMFA, TMFA, Other])
+            end
+    end.
+
+format_mfa({M, F, A}) ->
+    ?FMT("~s:~s/~w", [M, F, A]).
+
+format_mfa_source(MFA) ->
+    case find_mfa_source(MFA) of
+        {module_not_found, function_not_found} -> "";
+        {Source, function_not_found} -> ?FMT("~s: ", [Source]);
+        {Source, Line} -> ?FMT("~s:~w: ", [Source, Line])
+    end.
+
+%%
+%% Extract an element from a tuple, or undefined if N > tuple size
+%%
+safe_element(N, Tuple) ->
+    case catch(element(N, Tuple)) of
+        {'EXIT', {badarg, _}} ->
+            undefined;
+        Value ->
+            Value
+    end.
+
+%%
+%% Given a MFA, find the file and LOC where it's defined. Note that
+%% xref doesn't work if there is no abstract_code, so we can avoid
+%% being too paranoid here.
+%%
+find_mfa_source({M, F, A}) ->
+    case code:get_object_code(M) of
+        error -> {module_not_found, function_not_found};
+        {M, Bin, _} -> find_function_source(M,F,A,Bin)
+    end.
+
+find_function_source(M, F, A, Bin) ->
+    AbstractCode = beam_lib:chunks(Bin, [abstract_code]),
+    {ok, {M, [{abstract_code, {raw_abstract_v1, Code}}]}} = AbstractCode,
+    %% Extract the original source filename from the abstract code
+    [{attribute, 1, file, {Source, _}} | _] = Code,
+    %% Extract the line number for a given function def
+    Fn = [E || E <- Code,
+               safe_element(1, E) == function,
+               safe_element(3, E) == F,
+               safe_element(4, E) == A],
+    case Fn of
+        [{function, Line, F, _, _}] -> {Source, Line};
+        %% do not crash if functions are exported, even though they
+        %% are not in the source.
+        %% parameterized modules add new/1 and instance/1 for example.
+        [] -> {Source, function_not_found}
+    end.