Support PostgreSQL OPERATOR(...) syntax

Fixes #711

src/languages/postgresql/postgresql.formatter.ts

@@ -368,6 +368,7 @@ export const postgresql: DialectOptions = {
       '::',
       ':',
     ],
+    operatorKeyword: true,
   },
   formatOptions: {
     alwaysDenseOperators: ['::', ':'],

src/lexer/Tokenizer.ts

@@ -130,6 +130,14 @@ export default class Tokenizer {
         regex: cfg.supportsXor ? /XOR\b/iuy : undefined,
         text: toCanonical,
       },
+      ...(cfg.operatorKeyword
+        ? [
+            {
+              type: TokenType.OPERATOR,
+              regex: /OPERATOR *\([^)]+\)/iuy,
+            },
+          ]
+        : []),
       {
         type: TokenType.RESERVED_FUNCTION_NAME,
         regex: regex.reservedWord(cfg.reservedFunctionNames, cfg.identChars),

src/lexer/TokenizerOptions.ts

@@ -98,6 +98,8 @@ export interface TokenizerOptions {
   // Additional operators for property access, in addition to .
   // Like in table.column
   propertyAccessOperators?: string[];
+  // Enables PostgreSQL-specific OPERATOR(...) syntax
+  operatorKeyword?: boolean;
   // Allows custom modifications on the token array.
   // Called after the whole input string has been split into tokens.
   // The result of this will be the output of the tokenizer.

test/postgresql.test.ts

@@ -365,4 +365,16 @@ describe('PostgreSqlFormatter', () => {
       CREATE TABLE foo (text VARCHAR(100));
     `);
   });
+
+  // Issue #711
+  it('supports OPERATOR() syntax', () => {
+    expect(format(`SELECT foo OPERATOR(public.===) bar;`)).toBe(dedent`
+      SELECT
+        foo OPERATOR(public.===) bar;
+    `);
+    expect(format(`SELECT foo operator ( !== ) bar;`)).toBe(dedent`
+      SELECT
+        foo operator ( !== ) bar;
+    `);
+  });
 });