Add comment support #15

[mookjp]

WHAT

• Add supports comments in DDL; only manual addition
  • I know there's already issue to store the comments both in importing and exporting on Preserve comments for schema.sql #15, but it supports only manual addition of comments so that we can leave some comments and restored them on local if they are missed by other wrench operation, temporarily

WHY

• Supporting comments on DDL is helpful, if it is only manual addition temporarily

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[mookjp]

@googlebot I signed it!

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[mookjp]

I will think about the better approach like #15 and left this PR until then!

[vvakame]

@110y how about this PR? I need comment support 😉

[halmai]

I would also need to add comments to the scripts but unfortunately, a regexp-based solution is not reliable enough.

For example, if there is a command like this in the script:

INSERT INTO mytable (field) VALUES ('-- hello --')

it will become wrong:

INSERT INTO mytable (field) VALUES ('

illustration: https://play.golang.org/p/28ELu7ugA2D

I think a more careful parsing is needed.

I am happy to implement it but don't want to take it out from your hand either. Please, let me know if you have time for it, otherwise I will start working on it.

Another note: maybe not everybody is happy with a breaking change how wrench works. Therefore, I would be more conservative and would add a command-line option to turn ON the comment removal. The default behaviour should be the original behaviour.

consider this: #32 (comment)

[110y]

@mookjp @halmai

Sorry for tooooo late, but now wrench support writing comments to DDL/DML files by this PR: #54, which parses DDL/DML and ignore comments by using spansql.

So, let me close this PR, thank you so much 🙏