From 150e05f9062a4a6ec4c4b95db4f4a4112606589c Mon Sep 17 00:00:00 2001
From: otegami <otegami@clear-code.com>
Date: Tue, 24 Dec 2024 18:29:45 +0900
Subject: [PATCH 1/2] support for forzen string literals

Issue

When running tests with Ruby 3.4.0rc1, the following warnings are displayed.

```console
$ rake test
Run options: --seed 46514

/work/ruby/json-stream/lib/json/stream/parser.rb:549: warning: literal string will be frozen in the future (run with --debug-frozen-string-literal for more information)
/work/ruby/json-stream/lib/json/stream/parser.rb:555: warning: literal string will be frozen in the future (run with --debug-frozen-string-literal for more information)
```

Cuases

According to https://bugs.ruby-lang.org/issues/20205, string
literals may be frozen by default in future Ruby versions
(potentially Ruby 4.0+).
Starting from Ruby 3.4.0, warnings like `warning: literal string
will be frozen in the future` are shown if string literals are
mutable.

Solution

We explicitly make string literals mutable using `+"string literal"`
Additionally, we add `# frozen_string_literal: true` at the top of
the affected files and handle the warnings to ensure compatibility
with Ruby versions before 3.4.0.
---
 lib/json/stream/buffer.rb |  4 +++-
 lib/json/stream/parser.rb | 18 ++++++++++--------
 2 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/lib/json/stream/buffer.rb b/lib/json/stream/buffer.rb
index cbefd8b..56c531f 100644
--- a/lib/json/stream/buffer.rb
+++ b/lib/json/stream/buffer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module JSON
   module Stream
     # A character buffer that expects a UTF-8 encoded stream of bytes.
@@ -29,7 +31,7 @@ def initialize
       def <<(data)
         # Avoid state machine for complete UTF-8.
         if @buffer.empty?
-          data.force_encoding(Encoding::UTF_8)
+          (+data).force_encoding(Encoding::UTF_8)
           return data if data.valid_encoding?
         end
 
diff --git a/lib/json/stream/parser.rb b/lib/json/stream/parser.rb
index 33e7925..7e7e22b 100644
--- a/lib/json/stream/parser.rb
+++ b/lib/json/stream/parser.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module JSON
   module Stream
     # Raised on any invalid JSON text.
@@ -102,8 +104,8 @@ def initialize(&block)
 
         # Track parse stack.
         @stack = []
-        @unicode = ""
-        @buf = ""
+        @unicode = +""
+        @buf = +""
         @pos = -1
 
         # Register any observers in the block.
@@ -178,7 +180,7 @@ def <<(data)
                 @state = :end_key
                 notify(:key, @buf)
               end
-              @buf = ""
+              @buf = +""
             when BACKSLASH
               @state = :start_escape
             when CONTROL
@@ -270,7 +272,7 @@ def <<(data)
               @buf << ch
             else
               end_value(@buf.to_i)
-              @buf = ""
+              @buf = +""
               @pos -= 1
               redo
             end
@@ -291,7 +293,7 @@ def <<(data)
               @buf << ch
             else
               end_value(@buf.to_f)
-              @buf = ""
+              @buf = +""
               @pos -= 1
               redo
             end
@@ -310,7 +312,7 @@ def <<(data)
             else
               error('Expected 0-9 digit') unless @buf =~ DIGIT_END
               end_value(@buf.to_f)
-              @buf = ""
+              @buf = +""
               @pos -= 1
               redo
             end
@@ -326,7 +328,7 @@ def <<(data)
               @buf << ch
             else
               end_value(@buf.to_i)
-              @buf = ""
+              @buf = +""
               @pos -= 1
               redo
             end
@@ -503,7 +505,7 @@ def keyword(word, value, re, ch)
 
         if @buf.size == word.size
           if @buf == word
-            @buf = ""
+            @buf = +""
             end_value(value)
           else
             error("Expected #{word} keyword")

From d97d4d243dc5e43566e93aedd3ff204c11a12828 Mon Sep 17 00:00:00 2001
From: otegami <otegami@clear-code.com>
Date: Wed, 25 Dec 2024 16:18:07 +0900
Subject: [PATCH 2/2] use `dup` instead because the previous change doesn't
 release froze literals

---
 lib/json/stream/buffer.rb | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lib/json/stream/buffer.rb b/lib/json/stream/buffer.rb
index 56c531f..f139060 100644
--- a/lib/json/stream/buffer.rb
+++ b/lib/json/stream/buffer.rb
@@ -31,7 +31,8 @@ def initialize
       def <<(data)
         # Avoid state machine for complete UTF-8.
         if @buffer.empty?
-          (+data).force_encoding(Encoding::UTF_8)
+          data = data.dup
+          data.force_encoding(Encoding::UTF_8)
           return data if data.valid_encoding?
         end