Allow uppercasing of function names separately from keywords

[nene]

Currently we have a single option keywordCase which specifies the case for both keywords and function names.

It would be nice to allow more fine-grained control by having a separate option functionCase to control whether function names should be uppercased or lowercased. It's quite common practice when writing SQL to have different case-convention for the keywords and function names. Most commonly uppercasing keywords and lowercasing function names, like:

SELECT
  round(price * abs(tax)) AS final_price
FROM
  inventory;

This feature is also widespread in many other SQL formatting tools:

• SQLFormat has options for keyword and identifier case
• Instant SQL Formatter has 9 options for various language elements.
• Freeformatter.com has options for keyword and identifier case
• SQL Complete has options for separate casing of alias, function, data-type, identifier, keyword, variable.

[nene]

The initial most obvious solution I had in my head was to distinguish them solely by name, but this won't work as some function name are also keywords used elsewhere in SQL. For example:

• SET() function and UPDATE table SET age = 10 WHERE name = 'John';
• CAST(1 AS INT) casting function and RETURNS INT CAST FROM FLOAT
• SELECT ANY(age>10) aggregate function and SELECT * FROM foo WHERE ProductID = ANY (SELECT id FROM tbl)

Luckily these are fairly rare cases. But still.

Another option would be to look whether function name is followed by open-parenthesis (. This seems more promising, though one has to keep in mind that not every name followed by parenthesis is a function.

[inferrinizzard]

There is also the reverse case: some functions do not require parentheses: ie. CURRENT_DATE, TIMESTAMP, etc.

[jacobsvante]

functionCase would be a great addition to this already awesome project! It just looks strange to me too see PostgreSQL functions in uppercase.

[karlhorky]

Ah this is also closed by my PR for dataTypeCase (uppercasing + lowercasing for data types) + functionCase:

• Add experimental dataTypeCase and functionCase options #673