Add support for string literal concatenation (#2003)

Co-authored-by: Ifeanyi Ubah <ify1992@yahoo.com>

src/dialect/mod.rs

@@ -476,6 +476,12 @@ pub trait Dialect: Debug + Any {
         false
     }
 
+    /// Returns true if the dialect supports concatenating of string literal
+    /// Example: `SELECT 'Hello ' "world" => SELECT 'Hello world'`
+    fn supports_string_literal_concatenation(&self) -> bool {
+        false
+    }
+
     /// Does the dialect support trailing commas in the projection list?
     fn supports_projection_trailing_commas(&self) -> bool {
         self.supports_trailing_commas()

src/dialect/mysql.rs

@@ -71,6 +71,11 @@ impl Dialect for MySqlDialect {
         true
     }
 
+    /// see <https://dev.mysql.com/doc/refman/8.4/en/string-functions.html#function_concat>
+    fn supports_string_literal_concatenation(&self) -> bool {
+        true
+    }
+
     fn ignores_wildcard_escapes(&self) -> bool {
         true
     }

src/parser/mod.rs

@@ -9914,8 +9914,12 @@ impl<'a> Parser<'a> {
             // bigdecimal feature is enabled, and is otherwise a no-op
             // (i.e., it returns the input string).
             Token::Number(n, l) => ok_value(Value::Number(Self::parse(n, span.start)?, l)),
-            Token::SingleQuotedString(ref s) => ok_value(Value::SingleQuotedString(s.to_string())),
-            Token::DoubleQuotedString(ref s) => ok_value(Value::DoubleQuotedString(s.to_string())),
+            Token::SingleQuotedString(ref s) => ok_value(Value::SingleQuotedString(
+                self.maybe_concat_string_literal(s.to_string()),
+            )),
+            Token::DoubleQuotedString(ref s) => ok_value(Value::DoubleQuotedString(
+                self.maybe_concat_string_literal(s.to_string()),
+            )),
             Token::TripleSingleQuotedString(ref s) => {
                 ok_value(Value::TripleSingleQuotedString(s.to_string()))
             }
@@ -9985,6 +9989,18 @@ impl<'a> Parser<'a> {
         }
     }
 
+    fn maybe_concat_string_literal(&mut self, mut str: String) -> String {
+        if self.dialect.supports_string_literal_concatenation() {
+            while let Token::SingleQuotedString(ref s) | Token::DoubleQuotedString(ref s) =
+                self.peek_token_ref().token
+            {
+                str.push_str(s.clone().as_str());
+                self.advance_token();
+            }
+        }
+        str
+    }
+
     /// Parse an unsigned numeric literal
     pub fn parse_number_value(&mut self) -> Result<ValueWithSpan, ParserError> {
         let value_wrapper = self.parse_value()?;

tests/sqlparser_common.rs

@@ -17150,3 +17150,13 @@ fn test_parse_semantic_view_table_factor() {
         _ => panic!("Expected Query statement"),
     }
 }
+
+#[test]
+fn parse_adjacent_string_literal_concatenation() {
+    let sql = r#"SELECT 'M' "y" 'S' "q" 'l'"#;
+    let dialects = all_dialects_where(|d| d.supports_string_literal_concatenation());
+    dialects.one_statement_parses_to(sql, r"SELECT 'MySql'");
+
+    let sql = "SELECT * FROM t WHERE col = 'Hello' \n ' ' \t 'World!'";
+    dialects.one_statement_parses_to(sql, r"SELECT * FROM t WHERE col = 'Hello World!'");
+}