Wow, looks very promising. сб, 5 авг. 2017 г. в 17:29, <haskell-requ...@haskell.org>:
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[ANN] brittany - haskell source code formatting tool - > hackage release (lennart spitzner) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Fri, 4 Aug 2017 15:01:51 +0200 > From: lennart spitzner <hexago...@hexagoxel.de> > To: undisclosed-recipients: ; > Subject: [Haskell] [ANN] brittany - haskell source code formatting > tool - hackage release > Message-ID: <14f23926-b296-865d-7eeb-1a232427f...@hexagoxel.de> > Content-Type: text/plain; charset=utf-8 > > Greetings, > > I am happy to (finally) announce the first hackage release of brittany, a > configurable haskell source code formatter based on ghc-exactprint [2]. > > https://hackage.haskell.org/package/brittany > https://github.com/lspitzner/brittany > > > *Introduction* > > Brittany aims to nicely layout the code and retain empty lines and > comments as > they appear in the input. For that it uses a fundamentally different > approach > (see [7]/theory) than other formatters. The project is not finished, yet it > already is usable and produces better results than other formatters in many > cases. Of course these words come from its creator, so see for yourself: I > have included some examples at the bottom of this mail; see [3] and [4] for > some more. > > I wish to stress that this project will only progress at a very slow speed > barring support from the community. I hereby offer to work on this and ask > for funding. See the "future" paragraph below. > > > *Changelog* > > Since the "alpha-release" announced previously [5] the most important > changes > are: > > - Release under the AGPL-v3; > - Release on hackage; > - Make horizontal alignment less aggressive by default (see example [6]); > - Add high-level documentation (see [7]). This might be of interest to > anyone > considering to write a formatter (haskell or even otherwise); > - Improve testsuite setup; > - Improve layouting in many many cases and fix various bugs; > - Add a library interface (this integrates with haskell-ide-engine [8]); > > Brittany still.. > > - does not touch anything other than top-level type signatures and > bindings (imports, classes, instances, data decls, .. are not modified); > - contains some bugs (but it checks its own output for validity and > aborts); > - does not handle many "uncommon" syntactic constructs/extentions > (e.g. arrow notation); > > In preparation of this release the `butcher` and `czipwith` packages were > published on hackage as well. I will cover those in separate announcements. > > > *Building* > > Brittany currently requires ghc-8.0 (no support for previous ghc versions > is > planned, but 8.2 will be). Now that this package is on hackage, cabal users > should be able to install it directly; stack users will currently have to > clone > and go from there (a stack.yaml is provided). Detailed building guides for > cabal, cabal-new and stack are in the project README. > > Inclusion in stackage is coming as soon as all dependencies are included. > > > *Known issues* > > - Bad performance for large inputs (really noticeable at >1k loc). The > cause > is already determined - quadratic instead of linear complexity in one > specific function (see issue #34 [9]). Should be fixable and has high > priority. > - The config (file) lacks documentation. > - Comments are not always reproduced exactly when reformatting. There is a > lack > of testcases for comments in the testsuite. There is the known case of > comments in List/MonadComprehensions that currently breaks idempotency > (the > comments move further left each roundtrip through brittany) where a > solution > will most likely involve some non-trivial changes in ghc-exactprint > (see [10]). > - As mentioned above: only certain module elements are transformed, and > not all syntactical constructs are supported. re-layouting of imports, > data > decls, classes and instances are on the radar, but all require a good > amount > of work. > - CPP is not officially supported. This is mostly a WONTFIX. One can > enable it > by force, and it works to a degree, but it is relatively easy to find > cases > where it will break (conditional code not being reformatted, leading to > syntax errors and theoretically also to change semantics)). > - No fine-grained (per file or even per-function) control/configuration, > e.g. > it is not yet possible to add some pragma/comment to disable reformatting > this one carefully layouted-by-hand function that brittany messes up. > - No adaption to ghc-8.2 yet. > > > *Future/Outlook* > > As far as I can tell brittany already works rather well - I use it all the > time, even though I still run into issues from time to time. Still, > brittany is > not finished (these projects never really are, are they?). > > Up on my list are ghc-8.2 adaption, fixing the performance bug mentioned > above, > layouting of data decls, layouting of instances, and controlling > behaviour/config via flags in the source (as comments). > But implementing new functionality costs a lot of time, even with the DSL > used > internally: One has to understand the GHC AST (which is not always > documented), > think of all possible interactions ("do users really use record syntax when > having more than one constructor?" "are GADT records a thing?"), write the > layouting transformation and test it. > > I have already invested a good amount of my free time into this project > but its > scope is too large and I decided to put a limit on my personal investment. > This means that barring some form of support from the community I don't > see new > features being implemented at any certain pace. This leaves the following > paths: > > 1) This project is supported monetarily: I hereby offer to (part-time) > work on > this provided appropriate funding. I am not sure who exactly might be > interested in providing this kind of support - I am no student anymore > so > GSoC is out of the question. Feel free to contact me on- or off-list if > interested. > > 2) (More) Contributors add tests, report (and maybe fix) bugs and most > importantly implement new functionality (layouting for any syntactic > constructs of the haskell language not yet supported, etc.) > > I realize that this is not a trivial project to dive into, and there is > a > good amount of stuff one has to get familiar with before one can start > making use of the abstractions (the DSL) provided. > > On the other hand, I _think_ that the project source code is relatively > well-structured (although in-source comments are really sparse, > admittedly) > and the high-level (markdown) documentation <strike>will scare everyone > away due to their length</strike> will allow understanding the project > relatively quickly. > > 3) The project will progress only rather slowly. > > Regardless I plan to continue maintaining this project, fix bugs as they > come > up and also work on expanding functionality when I find the time. > > > *Contributing* > > In ascending order of involvement, you can contribute by: > > - Reporting issues, especially instances of bad layouting (especially when > it > is not a pure matter of opinion); > - Add to the testsuite, specifically to the `tests.blt` file of the > `littests` > test. It contains a large number of tests already, but the coverage is > not > very good. > - If you want to really help implementing more stuff, the high-level docs > [7] > are the right place to get a rough overview, especially the theory > document > [11]. I have not documented how to write new layouters yet, so for now I > recommend looking at the existing ones, e.g. in `Expr.hs`. > > > -- lennart > > > [1] https://hackage.haskell.org/package/brittany > https://github.com/lspitzner/brittany/ > [2] https://mpickering.github.io/posts/2015-07-23-ghc-exactprint.html > https://hackage.haskell.org/package/ghc-exactprint > [3] > https://github.com/lspitzner/brittany/blob/da692a4341399390018fb03773e15865d967fb8c/doc/showcases/BrittanyComparison.md > [4] https://github.com/lspitzner/brittany/tree/master/doc/showcases > [5] > https://mail.haskell.org/pipermail/haskell-cafe/2016-September/124793.html > [6] > https://github.com/lspitzner/brittany/blob/da692a4341399390018fb03773e15865d967fb8c/doc/showcases/Layout_Alignment.md#items-that-are-not-single-line-break-up-alignment > [7] > https://github.com/lspitzner/brittany/blob/master/doc/implementation/index.md > [8] https://github.com/haskell/haskell-ide-engine > [9] https://github.com/lspitzner/brittany/issues/34 > [10] https://github.com/alanz/ghc-exactprint/issues/53 > [11] > https://github.com/lspitzner/brittany/blob/master/doc/implementation/theory.md > > > -- > > some layouting examples - would be (re)produced in exactly this way by > brittany: > > > main = do > > > > now <- getCurrentTime > > let (_, _, week) = toWeekDate . utctDay $ now > > putStrLn $ ("it's "++) $ case week of > > 6 -> "the weekend" > > 7 -> "the weekend" > > _ -> "a weekday" > > > > localtime <- utcToLocalZonedTime now > > let hr = todHour . localTimeOfDay . zonedTimeToLocalTime $ localtime > > case hr of > > _ | hr < 12 -> putStrLn "it's before noon" > > | otherwise -> putStrLn "it's after noon" > > > -- Newlines are used sparingly: Only after "do" and when the > > -- `liftBaseOpDiscard` application would lead to overflowing 80 columns. > > main :: IO () > > main = do > > pool <- createPostgresqlPool (toS databaseConnectionString) 10 > > initiate $ \chan -> forever $ do > > flip runDbConn pool $ do > > makeSureQueueIsFull chan > > void $ liftBaseOpDiscard (consumeMsgs chan responseQueue Ack) > > (uncurry processMsg) > > threadDelay 1000000 > > > -- Alignment of patterns > > go [] "" = True > > go [WildCard ] "" = True > > go (WildCard :rest) (c:cs) = go rest (c : cs) || go (WildCard : rest) > cs > > go (Union globs:rest) cs = any (\glob -> go (glob ++ rest) cs) globs > > go [] (_:_) = False > > go (_:_) "" = False > > > > > ------------------------------ > > Subject: Digest Footer > > _______________________________________________ > Haskell mailing list > Haskell@haskell.org > http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell > > > ------------------------------ > > End of Haskell Digest, Vol 168, Issue 3 > *************************************** >
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