Merge pull request #215 from dvaergiller/trailing_whitespace

Add rule checking for trailing whitespace
inaka · Apr 7, 2015 · 5ad8afd · 5ad8afd
2 parents 70fa2bf + 623af81
commit 5ad8afd
Show file tree

Hide file tree

Showing 6 changed files with 77 additions and 0 deletions.
diff --git a/README.md b/README.md
@@ -176,6 +176,7 @@ environment values in your [configuration][config] file:
         filter => "*.erl",
         rules => [{elvis_style, line_length, #{limit => 80}},
                   {elvis_style, no_tabs},
+                  {elvis_style, no_trailing_whitespace},
                   {elvis_style, macro_names},
                   {elvis_style, macro_module_names},
                   {elvis_style, operator_spaces, #{rules => [{right, ","},

diff --git a/config/elvis.config b/config/elvis.config
@@ -8,6 +8,7 @@
         rules => [{elvis_style, line_length, #{limit => 80,
                                                skip_comments => false}},
                   {elvis_style, no_tabs},
+                  {elvis_style, no_trailing_whitespace},
                   {elvis_style, macro_names},
                   {elvis_style, macro_module_names},
                   {elvis_style, operator_spaces, #{rules => [{right, ","},

diff --git a/config/test.config b/config/test.config
@@ -8,6 +8,7 @@
         rules => [{elvis_style, line_length, #{limit => 80,
                                                skip_comments => false}},
                   {elvis_style, no_tabs},
+                  {elvis_style, no_trailing_whitespace},
                   {elvis_style, macro_names},
                   {elvis_style, macro_module_names},
                   {elvis_style, operator_spaces, #{rules => [{right, ","},

diff --git a/src/elvis_style.erl b/src/elvis_style.erl
@@ -3,6 +3,7 @@
 -export([
          line_length/3,
          no_tabs/3,
+         no_trailing_whitespace/3,
          macro_names/3,
          macro_module_names/3,
          operator_spaces/3,
@@ -21,6 +22,9 @@
 
 -define(NO_TABS_MSG, "Line ~p has a tab at column ~p.").
 
+-define(NO_TRAILING_WHITESPACE_MSG,
+        "Line ~b has ~b trailing whitespace characters.").
+
 -define(INVALID_MACRO_NAME_MSG,
         "Invalid macro name ~s on line ~p. Use UPPER_CASE.").
 
@@ -105,6 +109,15 @@ no_tabs(_Config, Target, _RuleConfig) ->
     {Src, _} = elvis_file:src(Target),
     elvis_utils:check_lines(Src, fun check_no_tabs/3, []).
 
+-spec no_trailing_whitespace(elvis_config:config(),
+                             elvis_file:file(),
+                             map()) ->
+    [elvis_result:item()].
+no_trailing_whitespace(_Config, Target, RuleConfig) ->
+    {Src, _} = elvis_file:src(Target),
+    elvis_utils:check_lines(Src, fun check_no_trailing_whitespace/3,
+                            RuleConfig).
+
 -spec macro_names(elvis_config:config(),
                   elvis_file:file(),
                   empty_rule_config()) ->
@@ -393,6 +406,26 @@ check_no_tabs(Line, Num, _Args) ->
             {ok, Result}
     end.
 
+-spec check_no_trailing_whitespace(binary(), integer(), map()) ->
+    no_result | {ok, elvis_result:item()}.
+check_no_trailing_whitespace(Line, Num, RuleConfig) ->
+    Regex =
+      case RuleConfig of
+        %% Lookbehind assertion: http://erlang.org/doc/man/re.html#sect17
+        #{ignore_empty_lines := true} -> "(?<=\\S)\\s+$";
+        _AnythingElse                 -> "\\s+$"
+      end,
+
+    case re:run(Line, Regex) of
+        nomatch ->
+            no_result;
+        {match, [PosLen]} ->
+            Msg = ?NO_TRAILING_WHITESPACE_MSG,
+            Info = [Num, size(binary:part(Line, PosLen))],
+            Result = elvis_result:new(item, Msg, Info, Num),
+            {ok, Result}
+    end.
+
 -spec check_macro_names(binary(), integer(), [term()]) ->
     no_result | {ok, elvis_result:item()}.
 check_macro_names(Line, Num, _Args) ->

diff --git a/test/examples/fail_no_trailing_whitespace.erl b/test/examples/fail_no_trailing_whitespace.erl
@@ -0,0 +1,21 @@
+-module(fail_no_trailing_whitespace).
+
+-export([one/0, two/0, three/0, four/0, five/0]).
+
+one() ->
+    %% Following line ends with a tab
+    not_ok.	
+
+two() ->
+    %% Following line ends with a space
+    not_ok. 
+
+three() -> 
+    %% Previous line ends with a space
+    not_ok.
+
+four() -> %% Previous (supposedly blank) line has a space
+    not_ok.
+
+five() ->
+    ok. %% This function should be fine
diff --git a/test/style_SUITE.erl b/test/style_SUITE.erl
@@ -9,6 +9,7 @@
 -export([
          verify_line_length_rule/1,
          verify_no_tabs_rule/1,
+         verify_no_trailing_whitespace_rule/1,
          verify_macro_names_rule/1,
          verify_macro_module_names/1,
          verify_operator_spaces/1,
@@ -94,6 +95,25 @@ verify_no_tabs_rule(_Config) ->
 
     [_, _] = elvis_style:no_tabs(ElvisConfig, Path, #{}).
 
+-spec verify_no_trailing_whitespace_rule(config()) -> any().
+verify_no_trailing_whitespace_rule(_Config) ->
+    ElvisConfig = elvis_config:default(),
+    SrcDirs = elvis_config:dirs(ElvisConfig),
+
+    File = "fail_no_trailing_whitespace.erl",
+    {ok, Path} = elvis_test_utils:find_file(SrcDirs, File),
+
+    do_verify_no_trailing_whitespace(Path, ElvisConfig,
+                                     #{ignore_empty_lines => true}, 3),
+    do_verify_no_trailing_whitespace(Path, ElvisConfig,
+                                     #{ignore_empty_lines => false}, 4),
+    do_verify_no_trailing_whitespace(Path, ElvisConfig, #{}, 4).
+
+do_verify_no_trailing_whitespace(Path, Config, RuleConfig, ExpectedNumItems) ->
+    Items = elvis_style:no_trailing_whitespace(Config, Path, RuleConfig),
+    length(Items) == ExpectedNumItems orelse
+        ct:fail("Expected ~b error items. Got: ~p", [ExpectedNumItems, Items]).
+
 -spec verify_macro_names_rule(config()) -> any().
 verify_macro_names_rule(_Config) ->
     ElvisConfig = elvis_config:default(),