From 4828be7fc42e9ba01935edf878ff4abedf5eb0b0 Mon Sep 17 00:00:00 2001
From: Alexey Milovidov <milovidov@clickhouse.com>
Date: Sat, 30 Jul 2022 23:56:41 +0200
Subject: [PATCH] Fix double escaping in the metadata of FORMAT JSON

---
 src/Formats/JSONUtils.cpp                      |  7 ++++++-
 .../Formats/Impl/JSONRowOutputFormat.h         |  2 +-
 .../02375_double_escaping_json.reference       | 18 ++++++++++++++++++
 .../0_stateless/02375_double_escaping_json.sql |  1 +
 4 files changed, 26 insertions(+), 2 deletions(-)
 create mode 100644 tests/queries/0_stateless/02375_double_escaping_json.reference
 create mode 100644 tests/queries/0_stateless/02375_double_escaping_json.sql

diff --git a/src/Formats/JSONUtils.cpp b/src/Formats/JSONUtils.cpp
index 1ac58760516..7c94b122096 100644
--- a/src/Formats/JSONUtils.cpp
+++ b/src/Formats/JSONUtils.cpp
@@ -529,7 +529,12 @@ namespace JSONUtils
             writeObjectStart(out, 2);
 
             writeTitle<true>("name", out, 3);
-            writeDoubleQuoted(fields[i].name, out);
+
+            /// The field names are pre-escaped to be put into JSON string literal.
+            writeChar('"', out);
+            writeString(fields[i].name, out);
+            writeChar('"', out);
+
             writeFieldDelimiter(out);
             writeTitle<true>("type", out, 3);
             writeJSONString(fields[i].type->getName(), out, settings);
diff --git a/src/Processors/Formats/Impl/JSONRowOutputFormat.h b/src/Processors/Formats/Impl/JSONRowOutputFormat.h
index 3459cc1b7a6..66b8d0f682e 100644
--- a/src/Processors/Formats/Impl/JSONRowOutputFormat.h
+++ b/src/Processors/Formats/Impl/JSONRowOutputFormat.h
@@ -72,7 +72,7 @@ protected:
 
     size_t field_number = 0;
     size_t row_count = 0;
-    NamesAndTypes fields;
+    NamesAndTypes fields;   /// The field names are pre-escaped to be put into JSON string literal.
 
     Statistics statistics;
     FormatSettings settings;
diff --git a/tests/queries/0_stateless/02375_double_escaping_json.reference b/tests/queries/0_stateless/02375_double_escaping_json.reference
new file mode 100644
index 00000000000..23dbe1a59df
--- /dev/null
+++ b/tests/queries/0_stateless/02375_double_escaping_json.reference
@@ -0,0 +1,18 @@
+{
+	"meta":
+	[
+		{
+			"name": "\"",
+			"type": "String"
+		}
+	],
+
+	"data":
+	[
+		{
+			"\"": "\\"
+		}
+	],
+
+	"rows": 1
+}
diff --git a/tests/queries/0_stateless/02375_double_escaping_json.sql b/tests/queries/0_stateless/02375_double_escaping_json.sql
new file mode 100644
index 00000000000..ecfb24fca2e
--- /dev/null
+++ b/tests/queries/0_stateless/02375_double_escaping_json.sql
@@ -0,0 +1 @@
+SELECT '\\' AS `"` FORMAT JSON SETTINGS output_format_write_statistics = 0;