Re: [Haskell-cafe] [Haskell-community] technical thoughts on stack

I can give more technical details on warning output: it's purely an issue of compromise between many different (and annoying) ways of displaying things. Firstly, the behavior Chris Allen is commenting: if there is a single local target package that you're building, then all of its GHC output is displayed to the console, including warnings. The dependency output is still sent to log files instead, keeping the console relatively free of output most people will not care about (general feeling I've seen is if a dependency has warnings, you don't want to see them, much less a list of all modules being compiled). The issue is: what happens if you're building multiple local packages? There are a number of options, all of which seem to get in _someone's_ way: 1. What we do today: send all output to the logs 2. Spit output to the console as it occurs, which will interleave content from multiple builds 3. Save the output to a log file, and then display all of the log files to the user at the end, which would result in looking for a needle in a haystack in many cases When I put together the initial code for running builds, I chose (1), which we still have today. It may be interesting to note that I did this mostly based off of my experience with cabal-install doing the same thing (whenever possible, I defaulted with cabal-install behavior, since it got many things right, and regardless is what people were used to). I tested this in the http-client repo by introducing a warning and running: cabal install ./http-client ./http-client-tls/ --ghc-option -Wall You can see the results at: https://gist.github.com/snoyberg/a50f4fc9505aa32aec835630dd749b77 By contrast, `stack build http-client-tls` spits out all of the warnings to the console as they happen. So my recommendation for people who are warning-sensitive and using Stack: 1. Use the `--pedantic` flag to turn on both `-Wall -Werror`. This is doubly-good: not only will you definitely see the warnings, but you won't accidentally miss them by an interim compile. (This can easily happen if you're using the `--file-watch` flag.) 2. Build one package in your project at a time. If people have ideas for other ways of handling this that I haven't listed, let's start a separate thread to discuss them. On Wed, Sep 14, 2016 at 11:26 PM, David McBride wrote:

That's not what I'm observering. I intentially put -Wall and some odd code in a local copy of pipes-csv, stack clean, stack build.

/home/toad/working/pipes-csv-1.4.0/src/Pipes/Csv.hs:216:3: Warning: A do-notation statement discarded a result of type ‘String’ Suppress this warning by saying ‘_ <- getLine’ or by using the flag -fno-warn-unused-do-bind

In another project, stack clean, stack build

pipes-csv-1.4.0: configure pipes-csv-1.4.0: build pipes-csv-1.4.0: copy/register

Nothing at all.

stack.yaml is basically this, but with a few extra packages.

flags: {} packages: - '.' - '../pipes-csv-1.4.0' extra-deps: [] resolver: lts-3.1

stack --version Version 1.1.2 x86_64 hpack-0.14.0

On Wed, Sep 14, 2016 at 4:10 PM, Christopher Allen wrote:

...

I see what is meant now, but it's not really applicable. If I am co-developing a package and its dependencies, I add them as packages (not deps) to my stack.yaml and still get the warnings.

Example:

From the stack.yaml for the package that uses my previous example's library:

packages: - '.' - ../simple-library

Then stack build'ing the project (uses-sl) that depends on simple-library which as a module with a warning:

$ stack build simple-library-0.1.0.0: build Progress: 1/2 -- While building package simple-library-0.1.0.0 using: /home/callen/.stack/setup-exe-cache/x86_64-linux/setup-Simpl e-Cabal-1.24.0.0-ghc-8.0.1 --builddir=.stack-work/dist/x86_64-linux/Cabal-1.24.0.0 build lib:simple-library exe:simple-library-exe --ghc-options " -ddump-hi -ddump-to-file" Process exited with code: ExitFailure 1 Logs have been written to: /home/callen/work/uses-sl/.stack-work/logs/simple-library-0.1.0.0.log

Preprocessing library simple-library-0.1.0.0... [1 of 1] Compiling SimpleLib ( src/SimpleLib.hs, .stack-work/dist/x86_64-linux/Cabal-1.24.0.0/build/SimpleLib.o )

/home/callen/work/simple-library/src/SimpleLib.hs:7:3: warning: [-Wunused-do-bind] A do-notation statement discarded a result of type ‘[Char]’ Suppress this warning by saying ‘_ <- return "hello"’

One of the first things I did when figuring out Stack was to look at how Yesod used it: https://github.com/yesodweb/yesod/blob/master/stack.yaml

On Wed, Sep 14, 2016 at 2:56 PM, David McBride wrote:

...

The rule of thumb seems to be, if you do a stack build and it decides to build multiple packages, it hides this log info.

I understand why it does that, I should be able to build lens without worrying about tons of spurious output, but at the same time it is common for me to have an entire tree of packages I'm developing and it often obscures errors that are happening in my own packages. At the very least, if it is only building local packages, I'd very much like to see that output.

On Wed, Sep 14, 2016 at 3:42 PM, Patrick Pelletier wrote:

...

On 9/14/16 12:21 PM, Christopher Allen wrote:

...

What are you talking about?

$ stack build simple-library-0.1.0.0: unregistering (local file changes: src/Lib.hs) simple-library-0.1.0.0: build Preprocessing library simple-library-0.1.0.0... [1 of 1] Compiling Lib ( src/Lib.hs, .stack-work/dist/x86_64-linux/Cabal-1.24.0.0/build/Lib.o )

/home/callen/work/simple-library/src/Lib.hs:7:3: warning: [-Wunused-do-bind] A do-notation statement discarded a result of type ‘[Char]’ Suppress this warning by saying ‘_ <- return "woot"’ Preprocessing executable 'simple-library-exe' for simple-library-0.1.0.0...

Weird. That's not how it works for me:

whiteandnerdy:normalize ppelleti$ stack build normalization-insensitive-2.0: unregistering (local file changes: Data/Unicode/NormalizationInsensitive.hs Data/Unicode/NormalizationInsensitive/Internal.hs) normalization-insensitive-2.0: configure normalization-insensitive-2.0: build normalization-insensitive-2.0: copy/register photos-0.1.0.0: configure photos-0.1.0.0: build photos-0.1.0.0: copy/register Completed 2 action(s). whiteandnerdy:normalize ppelleti$ cat .stack-work/logs/normalization-insensitive-2.0.log Configuring normalization-insensitive-2.0... Preprocessing library normalization-insensitive-2.0... [1 of 3] Compiling Data.Unicode.NormalizationInsensitive.Internal ( Data/Unicode/NormalizationInsensitive/Internal.hs, .stack-work/dist/x86_64-osx/Cabal-1.22.5.0/build/Data/Unicod

e/NormalizationInsensitive/Internal.o

...

)

Data/Unicode/NormalizationInsensitive/Internal.hs:30:1: Warning: The import of ‘Data.Bool’ is redundant except perhaps to import instances from ‘Data.Bool’ To import instances alone, use: import Data.Bool()

Data/Unicode/NormalizationInsensitive/Internal.hs:38:1: Warning: The import of ‘otherwise, &&, <=, +’ from module ‘Prelude’ is redundant

Data/Unicode/NormalizationInsensitive/Internal.hs:57:1: Warning: Module ‘Data.ByteString.UTF8.Normalize’ is deprecated: Convert ByteString to Text and then normalize

Data/Unicode/NormalizationInsensitive/Internal.hs:135:1: Warning: Top-level binding with no type signature: mode :: NormalizationMode

Data/Unicode/NormalizationInsensitive/Internal.hs:143:17: Warning: In the use of ‘B.normalize’ (imported from Data.ByteString.UTF8.Normalize): Deprecated: "Convert ByteString to Text and then normalize"

Data/Unicode/NormalizationInsensitive/Internal.hs:147:33: Warning: In the use of ‘B.normalize’ (imported from Data.ByteString.UTF8.Normalize): Deprecated: "Convert ByteString to Text and then normalize" [2 of 3] Compiling Data.Unicode.NormalizationInsensitive.Unsafe ( Data/Unicode/NormalizationInsensitive/Unsafe.hs, .stack-work/dist/x86_64-osx/Cabal-1.22.5.0/build/Data/Unicod e/NormalizationInsensitive/Unsafe.o ) [3 of 3] Compiling Data.Unicode.NormalizationInsensitive ( Data/Unicode/NormalizationInsensitive.hs, .stack-work/dist/x86_64-osx/Cabal-1.22.5.0/build/Data/Unicod e/NormalizationInsensitive.o )

Data/Unicode/NormalizationInsensitive.hs:25:31: Warning: ‘normalize’ is exported by ‘Normalizable(normalize)’ and ‘normalize’ In-place registering normalization-insensitive-2.0... Installing library in

/Users/ppelleti/programming/haskell/normalize/.stack-work/in stall/x86_64-osx/lts-6.1/7.10.3/lib/x86_64-osx-ghc-7.10.3/ normalization-insensitive-2.0-KLVtcrPtbow6nG8kRB6WPM Registering normalization-insensitive-2.0... whiteandnerdy:normalize ppelleti$

I hadn't even been aware of these warnings in the package I was developing, until Harendra Kumar pointed them out to me, after I had uploaded a candidate to Hackage.

--Patrick

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-- Chris Allen Currently working on http://haskellbook.com

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