supportsConstraints test function does not correctly test referential actions

[LunaPresent]

Describe the bug
I made the following change in test/postgresql.test.cs : line 44

-  supportsConstraints(format, ['NO ACTION', 'RESTRICT', 'CASCADE', 'SET NULL', 'SET DEFAULT']);
+  supportsConstraints(format, ['ABSOLUTE BOGUS', 'RESTRICT', 'CASCADE', 'SET NULL', 'SET DEFAULT']);

and then ran yarn test

Expected behavior
At least one test fails on behalf of postgres not supporting the ABSOLUTE BOGUS referential action in an ON {DELETE | UPDATE} referential_action clause

Actual behavior
All tests succeeded

Usage

• How are you calling / using the library? cloned master -> ran yarn -> further steps in this issue
• What SQL language(s) does this apply to? presumably all of them
• Which SQL Formatter version are you using? v15.4.11 (commit ea8c0d5 on master)

The reason I tested this is because I noticed at least postgres only capitalises SET NULL and SET DEFAULT correctly, but then I noticed there exists a test that falsly asserts that RESTRICT, CASCADE and NO ACTION also work. I wanted to contribute a fix but I feel this is a bigger problem that needs to be vetted first.

[nene]

Thanks for reporting, but I think you're expecting too much from this test function.

It tests that ON DELETE NO ACTION, ON DELETE RESTRICT, etc clauses get correctly indented. It doesn't test for capitalization. Its goal is to ensure that at least this syntax works, but it doesn't care whether some other syntax also works. The actual implementation of the formatter doesn't even contain the definition of valid referencial actions anywhere. The implementation only defines bunch of keywords and some sequences of keywords.

Really this all comes down to the fact that SQL Formatter mostly uses various heuristics to format the code. It doesn't actually parse the SQL to properly understand it. It will happily format completely invalid SQL as long as it matches with some expectations.

If you have a problem with capitalization of keywords, please open another issue. However, I should point out that SQL Formatter is fundamentally flawed when it comes to detecting which words are keywords and which are not.

If you want something better, I suggest you check out prettier-plugin-sql-cst which does proper parsing of SQL and correct detection of keywords.