Fix JSON.load_file and JSON.load_file! to load on Ruby 2.7.0 through 2.7.2

Since ebf0f29, `load_file` and `load_file!` forward their arguments to
`parse` and `parse!` with `...` after a leading parameter. Ruby 2.7 accepts `...` only on its own;
a leading parameter before it was added in Ruby 3.0 and reached the 2.7 series in 2.7.3, so on Ruby 2.7.0
through 2.7.2 requiring json 3.0 raises a `SyntaxError` at `lib/json/common.rb`, while the gemspec still allows
Ruby 2.7 as a whole.

`parse` and `parse!` take keyword arguments only, so forwarding `**options` passes exactly what `...` passed,
on every Ruby the gem supports.

A `method_missing` helper in the parser tests used the same form; it takes an anonymous splat now,
so the test suite itself loads on those versions.

Checked with `ruby -c` on Ruby 2.7.0, 2.7.2, 2.7.3, and 3.0.7, and with the test suite on Ruby 2.7.2 and 3.0.7.

Author: koic

CHANGES.md

@@ -2,6 +2,8 @@
 
 ### Unreleased
 
+* Fix `JSON.load_file` and `JSON.load_file!` to load on Ruby 2.7.0 through 2.7.2, which cannot parse a leading parameter before `...`.
+
 ### 2026-09-08 (3.0.1)
 
 * Restore the `limit` positional argument of `JSON.dump`.

lib/json/common.rb

@@ -324,8 +324,8 @@ def parse!(source, **options)
   #   parse(File.read(path), **)
   #
   # See method #parse.
-  def load_file(filespec, ...)
-    parse(File.read(filespec, encoding: Encoding::UTF_8), ...)
+  def load_file(filespec, **options)
+    parse(File.read(filespec, encoding: Encoding::UTF_8), **options)
   end
 
   # :call-seq:
@@ -335,8 +335,8 @@ def load_file(filespec, ...)
   #   JSON.parse!(File.read(path), **)
   #
   # See method #parse!
-  def load_file!(filespec, ...)
-    parse!(File.read(filespec, encoding: Encoding::UTF_8), ...)
+  def load_file!(filespec, **options)
+    parse!(File.read(filespec, encoding: Encoding::UTF_8), **options)
   end
 
   # :call-seq:

test/json/json_parser_test.rb

@@ -771,7 +771,7 @@ def []=(k, v)
       @attrs[k.to_sym] = v
     end
 
-    def method_missing(name, ...)
+    def method_missing(name, *)
       @attrs.fetch(name) do
         super
       end