Implement monadic error handling, get rid of JavaScript exceptions

rightfold / purescript-postgresql-client

https://pursuit.purescript.org/packages/purescript-postgresql-client

BSD 3-Clause "New" or "Revised" License

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Implement monadic error handling, get rid of JavaScript exceptions #29

Closed akheron closed 5 years ago

akheron commented 5 years ago

Add PGError type to model different errors that can happen when querying PostgreSQL. The mapping from SQLSTATE to error was inspired by psycopg2.
Run all actions in a new PG monad, which is just Aff stacked with ExceptT PGError to provide monadic error handling. Any errors caused by database access are not thrown as JavaScript exceptions anymore.
While at it, remove some duplication between query and command by reusing ffiUnsafeQuery in both cases.

Fixes #25

paluh commented 5 years ago

Thanks again @akheron!

Some notes (quotes from chat) for myself so I know what I should do before release:

Update docs
Test paulyoung/literate-purescript before updating README docs
I think those docstrings should be revisited at some point, because some things might not be correct anymore
Also, explaining runExceptT and pointing to its documentation should be done somewhere. Probably in README and near type PG a = ExceptT PGError Aff a

akheron commented 5 years ago

I pushed an update for some docstrings.

paluh commented 5 years ago

F***! The whole review is broken as I've commented above lines which I was interested in and in this form this review is completely unreadable. Probably I have to rewrite it tomorrow ;-)

paluh commented 5 years ago

@akheron Could you read my comments using Files changed tab. All my comments are above the code line of interest ;-)

paluh commented 5 years ago

Thanks a lot @akheron! I'm going to try to compile/test examples from README and finally make a release ;-)

paluh commented 5 years ago

@akheron , @Kamirus I've migrated Thimoteus/literate-purescript and related libs and I'm waiting for its release (possibly also npm "executable" release), so I can update docs, package.json etc. and make proper release. I hope it is going to happen in the next few days. If not I'm going to make release anyway.