implement pretty-printing with {:#}

[lovasoa]

• closes [feature] allow pretty-printing #1845

Now,

println!("{:#}", my_statement);

can display

WITH cte AS (
  SELECT
    my_first_column as a,
    col_num_2 as b
  FROM
    my_table
)
SELECT
  a,
  COUNT(*)
FROM
  cte
GROUP BY
  a
HAVING
  COUNT(*) > 1

I am pretty happy about the composability of the resulting code.
Pretty printing is implemented only for select statements, but generalizing this to other statements is almost mechanical and can be done in a subsequent pr.

This will be a real game changer for SQLPage, where error messages are currently often hard to read because of long sql strings.

@alamb @iffyio

[alamb]

TLDR is I think this is a great feature @lovasoa -- thank you so much. I expect it to evolve over time, but this PR has a great foundation

One thought I had was if you would like help adding support for pretty printing other SQL it might be useful to file some tickets explaining / enumerating the other structures. I suspect other people might like to join in and help you

cc @iffyio

[alamb]

that is pretty cool

I wonder about how you will connect this back to your original goal of preserving the original whitespace.

Perhaps eventually this could be passed the original span 🤔

[alamb]

this is awesome

[alamb]

since it is crate private we can change it later, but I think it would likely be helpful eventually to make the indent configurable (for embedded subqueries, for example)

[lovasoa]

Unfortunately we cannot really configure much if we are using rust's existing Display trait...

[alamb]

❤️

[alamb]

this is great

[lovasoa]

I'd love if we could merge this one and then I'll follow up with improvements

[alamb]

I think this is pretty non controversial so let's merge it. @iffyio let us know if you would like any changes

[lovasoa]

Great, thank you @alamb !