From bfdf02ea7290d1d76e457ffbb15cfef5e64bf547 Mon Sep 17 00:00:00 2001
From: Jean Boussier <jean.boussier@gmail.com>
Date: Fri, 18 Oct 2024 15:36:57 +0200
Subject: [PATCH] pretty_generate: don't apply object_nl / array_nl for empty
 containers

Fix: https://github.com/ruby/json/issues/437

Before:

```json
{
  "foo": {
  },
  "bar": [
  ]
}
```

After:

```json
{
  "foo": {},
  "bar": []
}
```
---
 ext/json/generator/generator.c   | 14 ++++++++++++++
 test/json/json_generator_test.rb |  7 +++++++
 2 files changed, 21 insertions(+)

diff --git a/ext/json/generator/generator.c b/ext/json/generator/generator.c
index c35e86d9b8..fbfa2c724e 100644
--- a/ext/json/generator/generator.c
+++ b/ext/json/generator/generator.c
@@ -681,6 +681,13 @@ static void generate_json_object(FBuffer *buffer, VALUE Vstate, JSON_Generator_S
     if (max_nesting != 0 && depth > max_nesting) {
         rb_raise(eNestingError, "nesting of %ld is too deep", --state->depth);
     }
+
+    if (RHASH_SIZE(obj) == 0) {
+        fbuffer_append(buffer, "{}", 2);
+        --state->depth;
+        return;
+    }
+
     fbuffer_append_char(buffer, '{');
 
     arg.buffer = buffer;
@@ -709,6 +716,13 @@ static void generate_json_array(FBuffer *buffer, VALUE Vstate, JSON_Generator_St
     if (max_nesting != 0 && depth > max_nesting) {
         rb_raise(eNestingError, "nesting of %ld is too deep", --state->depth);
     }
+
+    if (RARRAY_LEN(obj) == 0) {
+        fbuffer_append(buffer, "[]", 2);
+        --state->depth;
+        return;
+    }
+
     fbuffer_append_char(buffer, '[');
     if (RB_UNLIKELY(state->array_nl)) fbuffer_append(buffer, state->array_nl, state->array_nl_len);
     for(i = 0; i < RARRAY_LEN(obj); i++) {
diff --git a/test/json/json_generator_test.rb b/test/json/json_generator_test.rb
index 7dc45e3a52..32712c8343 100755
--- a/test/json/json_generator_test.rb
+++ b/test/json/json_generator_test.rb
@@ -90,10 +90,17 @@ EOT
 
   def test_generate_pretty
     json = pretty_generate({})
+    assert_equal('{}', json)
+
+    json = pretty_generate({1=>{}, 2=>[], 3=>4})
     assert_equal(<<'EOT'.chomp, json)
 {
+  "1": {},
+  "2": [],
+  "3": 4
 }
 EOT
+
     json = pretty_generate(@hash)
     # hashes aren't (insertion) ordered on every ruby implementation
     # assert_equal(@json3, json)