[Fix #3958] Bug of Style/SpaceInsideHashLiteralBraces (#3976)

When checking the braces, it uses the type instead of text to avoid
confusion a brace in a string. This avoid a confusion when token text is
a brace, but the token type is a string.

CHANGELOG.md

@@ -28,6 +28,7 @@
 * [#3959](https://github.com/bbatsov/rubocop/issues/3959): Don't wrap "percent arrays" with extra brackets when autocorrecting `Style/MutableConstant`. ([@mikegee][])
 * [#3978](https://github.com/bbatsov/rubocop/pull/3978): Fix false positive in `Performance/RegexpMatch` with `English` module. ([@pocke][])
 * [#3242](https://github.com/bbatsov/rubocop/issues/3242): Ignore `Errno::ENOENT` during cache cleanup from `File.mtime` too. ([@mikegee][])
+* [#3958](https://github.com/bbatsov/rubocop/issues/3958): `Style/SpaceInsideHashLiteralBraces` doesn't add and offence when checking an hash where a value is a left brace string (e.g. { k: '{' }). ([@nodo][])
 * [#4006](https://github.com/bbatsov/rubocop/issues/4006): Prevent `Style/WhileUntilModifier` from breaking on a multiline modifier. ([@drenmi][])
 
 ## 0.47.1 (2017-01-18)
@@ -2630,5 +2631,6 @@
 [@backus]: https://github.com/backus
 [@pat]: https://github.com/pat
 [@sinsoku]: https://github.com/sinsoku
+[@nodo]: https://github.com/nodo
 [@onk]: https://github.com/onk
 [@dabroz]: https://github.com/dabroz

lib/rubocop/cop/style/space_inside_hash_literal_braces.rb

@@ -48,7 +48,7 @@ def check(t1, t2)
           return if t1.pos.line < t2.pos.line
           return if t2.type == :tCOMMENT # Also indicates there's a line break.
 
-          is_empty_braces = t1.text == '{' && t2.text == '}'
+          is_empty_braces = left_brace?(t1) && right_brace?(t2)
           expect_space    = expect_space?(t1, t2)
 
           if offense?(t1, t2, expect_space)
@@ -59,8 +59,8 @@ def check(t1, t2)
         end
 
         def expect_space?(t1, t2)
-          is_same_braces  = t1.text == t2.text
-          is_empty_braces = t1.text == '{' && t2.text == '}'
+          is_same_braces  = t1.type == t2.type
+          is_empty_braces = left_brace?(t1) && right_brace?(t2)
 
           if is_same_braces && style == :compact
             false

spec/rubocop/cop/style/space_inside_hash_literal_braces_spec.rb

@@ -214,4 +214,12 @@
       expect(cop.offenses).to be_empty
     end
   end
+
+  context 'on { key: "{" }' do
+    # regression test; see GH issue 3958
+    it 'does not register an offense' do
+      inspect_source(cop, '{ key: "{" }')
+      expect(cop.offenses).to be_empty
+    end
+  end
 end