Merge pull request #1026 from elixir-lang/jv-no-warn-unused-imports

Warn on unused imports

Author: José Valim

lib/elixir/src/elixir_import.erl

@@ -4,6 +4,7 @@
 -module(elixir_import).
 -export([import/5, recorded_locals/1, format_error/1,
   ensure_no_import_conflict/4, ensure_no_local_conflict/4,
+  ensure_all_imports_used/3,
   build_table/1, delete_table/1, record/3]).
 -include("elixir.hrl").
 
@@ -25,6 +26,21 @@ record(Tuple, Receiver, Module) ->
     error:badarg -> false
   end.
 
+record_warn(_Meta, _Ref, _Opts, #elixir_scope{module=nil}) -> false;
+
+record_warn(Meta, Ref, Opts, S) ->
+  Table = table(S#elixir_scope.module),
+  ets:delete(Table, Ref),
+
+  Warn =
+    case keyfind(warn, Opts) of
+      { warn, false } -> false;
+      { warn, true } -> true;
+      false -> S#elixir_scope.check_clauses
+    end,
+
+  Warn andalso ets:insert(Table, { Ref, ?line(Meta) }).
+
 recorded_locals(Module) ->
   Table  = table(Module),
   Match  = { '$1', Module },
@@ -61,6 +77,7 @@ import(Meta, Ref, Opts, Selector, S) ->
       SF#elixir_scope{macros=Macros, macro_macros=TempM}
   end,
 
+  record_warn(Meta, Ref, Opts, S),
   SM.
 
 %% IMPORT FUNCTION RELATED HELPERS
@@ -188,6 +205,16 @@ ensure_no_import_conflict(Meta, File, Module, AllDefined) ->
       ok
   end.
 
+ensure_all_imports_used(_Line, File, Module) ->
+  Table = table(Module),
+  [begin
+    elixir_errors:handle_file_warning(File, { L, ?MODULE, { unused_import, M } })
+   end || [M, L] <- ets:select(Table, module_line_spec()),
+          ets:match(Table, { '$1', M }) == []].
+
+module_line_spec() ->
+  [{ { '$1', '$2' }, [{ is_integer, '$2' }], ['$$'] }].
+
 %% Ensure the given functions don't clash with any
 %% of Elixir non overridable macros.
 
@@ -225,6 +252,9 @@ format_error({internal_conflict,{Receiver, Name, Arity}}) ->
   io_lib:format("cannot import ~ts.~ts/~B because it conflicts with Elixir special forms",
     [elixir_errors:inspect(Receiver), Name, Arity]);
 
+format_error({ unused_import, Module }) ->
+  io_lib:format("unused import ~ts", [elixir_errors:inspect(Module)]);
+
 format_error({ no_macros, Module }) ->
   io_lib:format("could not load macros from module ~ts", [elixir_errors:inspect(Module)]).
 

lib/elixir/src/elixir_macros.erl

@@ -213,7 +213,7 @@ translate({defmodule, Meta, [Ref, KV]}, S) ->
       { TRef, S }
   end,
 
-  MS = FS#elixir_scope{check_clauses=true,local=nil},
+  MS = FS#elixir_scope{local=nil},
   { elixir_module:translate(Meta, FRef, Block, MS), FS };
 
 translate({Kind, Meta, [Call]}, S) when ?FUNS(Kind) ->

lib/elixir/src/elixir_module.erl

@@ -66,6 +66,7 @@ compile(Line, Module, Block, Vars, #elixir_scope{} = S) when is_atom(Module) ->
     Forms1          = specs_form(Line, Module, Private, Defmacro, Forms0, C),
     Forms2          = attributes_form(Line, File, Module, Forms1),
 
+    elixir_import:ensure_all_imports_used(Line, File, Module),
     elixir_import:ensure_no_local_conflict(Line, File, Module, All),
     elixir_import:ensure_no_import_conflict(Line, File, Module, All),
 

lib/elixir/src/elixir_translator.erl

@@ -35,13 +35,10 @@ translate(Forms, S) ->
 %% Those macros are "low-level". They are the basic mechanism
 %% that makes the language work and cannot be partially applied
 %% nor overwritten.
-%%
-%% =, ^, import, require and alias could be made non-special
-%% forms without causing any side effects.
 
 %% Assignment operator
 
-translate_each({'=', Meta, [Left, Right]}, S) ->
+translate_each({ '=', Meta, [Left, Right] }, S) ->
   assert_no_guard_scope(Meta, '=', S),
   { TRight, SR } = translate_each(Right, S),
   { TLeft, SL } = elixir_clauses:assigns(fun translate_each/2, Left, SR),
@@ -190,7 +187,7 @@ translate_each({ import, Meta, [Left, Right, Opts] }, S) ->
     _ -> syntax_error(Meta, S#elixir_scope.file, "invalid name for import, expected an atom or alias")
   end,
 
-  validate_opts(Meta, import, [as, only, except], Opts, S),
+  validate_opts(Meta, import, [as, only, except, warn], Opts, S),
 
   As = case lists:keyfind(as, 1, Opts) of
     false -> false;

lib/mix/lib/mix/tasks/app.start.ex

@@ -1,8 +1,6 @@
 defmodule Mix.Tasks.App.Start do
   use Mix.Task
 
-  import Mix.Deps, only: [all: 0, ok?: 1]
-
   @hidden true
   @shortdoc "Start registered apps"
   @recursive true

lib/mix/lib/mix/tasks/deps.unlock.ex

@@ -9,8 +9,6 @@ defmodule Mix.Tasks.Deps.Unlock do
   are given, unlock all.
   """
 
-  import Mix.Deps, only: [all: 0, by_name!: 1]
-
   def run([]) do
     Mix.Deps.Lock.write([])
   end