inaka · elbrujohalcon · Jun 6, 2025 · Jun 6, 2025
diff --git a/doc_rules/elvis_style/operator_spaces.md b/doc_rules/elvis_style/operator_spaces.md
@@ -41,6 +41,8 @@ compromised without adequate spacing.
 
 `{left, "!"}, {right, "!"}` was added in [4.0.0](https://github.com/inaka/elvis_core/releases/tag/4.0.0)).
 
+`{left, "?="}, {right, "?="}` was added in [4.1.0](https://github.com/inaka/elvis_core/releases/tag/4.1.0)).
+
 ## Example configuration
 
 ```erlang

diff --git a/src/elvis_style.erl b/src/elvis_style.erl
@@ -345,7 +345,9 @@ default(operator_spaces) ->
                 {left, "->"},
                 {right, ","},
                 {left, "!"},
-                {right, "!"}
+                {right, "!"},
+                {right, "?="},
+                {left, "?="}
             ]
     };
 default(no_space) ->
@@ -871,7 +873,7 @@ operator_spaces(Config, Target, RuleConfig) ->
     Zipper = elvis_code:code_zipper(Root),
     OpNodes = zipper:filter(fun is_operator_node/1, Zipper),
 
-    PunctuationTokens = elvis_code:find_by_types_in_tokens(?PUNCTUATION_SYMBOLS, Root),
+    PunctuationTokens = elvis_code:find_by_types_in_tokens(['=' | ?PUNCTUATION_SYMBOLS], Root),
 
     Lines = elvis_utils:split_all_lines(Src),
     AllNodes = OpNodes ++ PunctuationTokens,
@@ -883,7 +885,14 @@ operator_spaces(Config, Target, RuleConfig) ->
 %% @doc Returns true when the node is an operator with more than one operand
 -spec is_operator_node(ktn_code:tree_node()) -> boolean().
 is_operator_node(Node) ->
-    ktn_code:type(Node) =:= op andalso length(ktn_code:content(Node)) > 1.
+    NodeType = ktn_code:type(Node),
+    OpOrMatch = [op | match_operators()],
+    ExtraOpsTypes = [map_field_exact, generate, b_generate, map_field_assoc],
+    (length(ktn_code:content(Node)) > 1 andalso lists:member(NodeType, OpOrMatch)) orelse
+        lists:member(NodeType, ExtraOpsTypes).
+
+match_operators() ->
+    [match, maybe_match].
 
 -type no_space_config() ::
     #{ignore => [ignorable()], rules => [{right | left, string()}]}.
@@ -1915,11 +1924,11 @@ is_match_in_condition(Node) ->
                 ktn_code:content(Node)
             )).
 
+is_match(Node) ->
+    lists:member(ktn_code:type(Node), match_operators()).
+
 has_match_child(Node) ->
-    IsMatch = fun(InnerNode) ->
-        ktn_code:type(InnerNode) =:= match orelse ktn_code:type(InnerNode) =:= maybe_match
-    end,
-    lists:any(IsMatch, ktn_code:content(Node)).
+    lists:any(fun is_match/1, ktn_code:content(Node)).
 
 -type numeric_format_config() ::
     #{
@@ -2654,12 +2663,9 @@ check_parent_match_or_macro(Zipper) ->
             false;
         ParentZipper ->
             Parent = zipper:node(ParentZipper),
-            case ktn_code:type(Parent) of
-                match ->
-                    zipper:down(ParentZipper) =:= Zipper;
-                macro ->
-                    zipper:down(ParentZipper) =:= Zipper;
-                maybe_match ->
+            IsMatchOrMacro = lists:member(ktn_code:type(Parent), [macro | match_operators()]),
+            case IsMatchOrMacro of
+                true ->
                     zipper:down(ParentZipper) =:= Zipper;
                 _ ->
                     check_parent_match_or_macro(ParentZipper)

diff --git a/test/examples/fail_operator_spaces.erl b/test/examples/fail_operator_spaces.erl
@@ -2,6 +2,8 @@
 %% Another initial comment
 -module(fail_operator_spaces).
 
+-feature(maybe_expr, enable).
+
 -dialyzer({nowarn_function, function7/0}).
 
 -export([ function1/2
@@ -21,6 +23,7 @@
         , pass_more_operators/0
         , fail_more_operators/0
         , fail_no_space_excl/0
+        , fail_maybe/0
         ]).
 
 %% No space before and after coma,on a comment.
@@ -154,3 +157,12 @@ fail_more_operators()->
 
 fail_no_space_excl() ->
     self()!'a'.
+
+fail_maybe() ->
+    maybe
+        A = 2,
+        A?=throw(error)
+    else
+        _ ->
+            ok
+    end.
diff --git a/test/style_SUITE.erl b/test/style_SUITE.erl
@@ -676,6 +676,10 @@ verify_operator_spaces(Config) ->
         #{info := [right, "->" | _]},
         #{info := [left, "->" | _]},
         #{info := [left, "->" | _]},
+        #{info := [right, "=" | _]},
+        #{info := [left, "=" | _]},
+        #{info := [right, "=" | _]},
+        #{info := [left, "=" | _]},
         #{info := [right, "+" | _]},
         #{info := [left, "+" | _]},
         #{info := [right, "-" | _]},
@@ -684,6 +688,12 @@ verify_operator_spaces(Config) ->
         #{info := [left, "*" | _]},
         #{info := [right, "/" | _]},
         #{info := [left, "/" | _]},
+        #{info := [right, "=" | _]},
+        #{info := [left, "=" | _]},
+        #{info := [right, "=>" | _]},
+        #{info := [right, "=>" | _]},
+        #{info := [left, "=>" | _]},
+        #{info := [left, "=>" | _]},
         #{info := [right, "=<" | _]},
         #{info := [left, "=<" | _]},
         #{info := [right, "<" | _]},
@@ -702,14 +712,23 @@ verify_operator_spaces(Config) ->
         #{info := [left, "=/=" | _]},
         #{info := [right, "--" | _]},
         #{info := [left, "--" | _]},
+        #{info := [right, "=>" | _]},
+        #{info := [left, "=>" | _]},
+        #{info := [right, ":=" | _]},
+        #{info := [left, ":=" | _]},
+        #{info := [left, "<-" | _]},
         #{info := [right, "||" | _]},
         #{info := [left, "||" | _]},
+        #{info := [right, "<=" | _]},
+        #{info := [left, "<=" | _]},
         #{info := [right, "||" | _]},
         #{info := [left, "||" | _]},
         #{info := [right, "|" | _]},
         #{info := [left, "|" | _]},
         #{info := [left, "!" | _]},
-        #{info := [right, "!" | _]}
+        #{info := [right, "!" | _]},
+        #{info := [right, "?=" | _]},
+        #{info := [left, "?=" | _]}
     ] =
         elvis_core_apply_rule(Config, elvis_style, operator_spaces, DefaultOptions, Path).