Fix OFFSET() formatting for BigQuery

Author: nene

src/languages/bigquery.formatter.ts

@@ -867,14 +867,14 @@ function postProcess(tokens: Token[]): Token[] {
   return detectArraySubscripts(combineParameterizedTypes(tokens));
 }
 
-// Converts OFFSET token inside array from RESERVED_COMMAND to RESERVED_KEYWORD
+// Converts OFFSET token inside array from RESERVED_COMMAND to RESERVED_FUNCTION_NAME
 // See: https://cloud.google.com/bigquery/docs/reference/standard-sql/functions-and-operators#array_subscript_operator
 function detectArraySubscripts(tokens: Token[]) {
   let prevToken = EOF_TOKEN;
   return tokens.map(token => {
     if (token.value === 'OFFSET' && prevToken.value === '[') {
       prevToken = token;
-      return { ...token, type: TokenType.RESERVED_KEYWORD };
+      return { ...token, type: TokenType.RESERVED_FUNCTION_NAME };
     } else {
       prevToken = token;
       return token;

test/bigquery.test.ts

@@ -180,7 +180,6 @@ describe('BigQueryFormatter', () => {
   });
 
   // Regression test for issue #243
-  // TODO: Incorrect formatting of OFFSET()
   it('supports array subscript operator', () => {
     expect(
       format(`
@@ -192,7 +191,7 @@ describe('BigQueryFormatter', () => {
     `)
     ).toBe(dedent`
       SELECT
-        item_array[OFFSET (1)] AS item_offset,
+        item_array[OFFSET(1)] AS item_offset,
         item_array[ORDINAL(1)] AS item_ordinal,
         item_array[SAFE_OFFSET(6)] AS item_safe_offset,
         item_array[SAFE_ORDINAL(6)] AS item_safe_ordinal