the bonnet is up and we're on bricks. Fix it. (qfpl#71)

* Add shell.nix that includes sqlite.

previous shell environment didn't include an application that was necessary for
developing the application. Whoops.

This new shell.nix lets students add their own development tools if they want
to try something out. `ghcid` for example.

* Overhaul: New techniques, new exercises.

Remove hspec-wai dependencies, add waargonaut.

The aeson dependency has been replaced with waargonaut, and the exercises have
been updated to match. Some exercises have been removed.

Add the use of `finally` as a demonstration and reminder that we should be
cleaning up things like connections when an app is done.

Explain the purpose of the `runDB` function so that implementation makes more
sense to students as an exercise.

Add exercise to generalise the error type that is used in the `AppM` transformer
that they implement. This flows onto a later exercise where they reuse this type
to simplify a function that is not part of the core application. This also
allows for an easier introduction of `ExceptT` as an exercise later in the
course when `AppM` is no longer usable.

Add a startup error constructor as making the students add it isn't informative
when compared to the rest of the exercise.

* Remove all duplicate tests. Rebuild Level03.

Level03 has been changed entirely to be centered on writing tests for student
code. The tests are then to be updated by the students as they progress through
the course. There are no duplicated tests and there is a bit more incentive for
students to get in and get their hands dirty with respect to testing their own
work.

Still not sure what to do with doctests just yet. More documentation is required
for that.

* Remove Level03 exe and modules.

* Feedback driven development

* Add tighter bounds for lens.
* Add bounds for old-locale and contravariant.
* Realign some imports.
* Rename 'AppM'' to 'AppM' and 'AppM' to 'App'.
* Clean up an utterly misleading and out of date comment regarding configuration
  package choices. Revert to unremarkable statement about it being JSON.
* Remove redundant import of `Level02.Types` from `tests/Test.hs`.
* Add waargonaut to extra-deps in stack.yaml.
* Bump LTS in stack.yaml to 12.14.
* Fix typos.
* Improve wording, restructure some comments.

* Revert LTS bump, increase contravariant upper bound for GHC 8.6.1

* Try updated stack.yaml

* Update travis.yml:

Bump patch versions of GHC:

* 8.4.3 -> 8.4.4
* 8.6.1 -> 8.6.2

Drop Stack LTS:

6, 9, 10

Add Stack LTS:

11, 12

* Add fixes to help stack nightly builds on travis. Remove some comments in cabal file

* Remove LTS-11, add in-memory db notes to level04

* add workshop levels document for expansion

* Proofread changes.

* Try to use cached GHC downloads for stack on travis

* Remove install ghc flag from stack commands

* Last try to stop stack downloading its own GHC

* Revert stack travis changes. Attempt to pin appar version for 7.10.3.

* Drop support for GHC 7.10.3

.travis.yml

@@ -30,10 +30,10 @@ before_cache:
 
 matrix:
   include:
-  - env: BUILD=cabal
-    compiler: "ghc-7.10.3"
+  # - env: BUILD=cabal
+    # compiler: "ghc-7.10.3"
     # env: TEST=--disable-tests BENCH=--disable-benchmarks
-    addons: {apt: {packages: [ghc-ppa-tools,cabal-install-2.4,ghc-7.10.3], sources: [hvr-ghc]}}
+    # addons: {apt: {packages: [ghc-ppa-tools,cabal-install-2.4,ghc-7.10.3], sources: [hvr-ghc]}}
 
   - env: BUILD=cabal
     compiler: "ghc-8.0.2"
@@ -46,30 +46,22 @@ matrix:
     addons: {apt: {packages: [ghc-ppa-tools,cabal-install-2.4,ghc-8.2.2], sources: [hvr-ghc]}}
 
   - env: BUILD=cabal
-    compiler: "ghc-8.4.3"
+    compiler: "ghc-8.4.4"
     # env: TEST=--disable-tests BENCH=--disable-benchmarks
-    addons: {apt: {packages: [ghc-ppa-tools,cabal-install-2.4,ghc-8.4.3], sources: [hvr-ghc]}}
+    addons: {apt: {packages: [ghc-ppa-tools,cabal-install-2.4,ghc-8.4.4], sources: [hvr-ghc]}}
   - env: BUILD=cabal
-    compiler: "ghc-8.6.1"
+    compiler: "ghc-8.6.2"
     # env: TEST=--disable-tests BENCH=--disable-benchmarks
-    addons: {apt: {packages: [ghc-ppa-tools,cabal-install-2.4,ghc-8.6.1], sources: [hvr-ghc]}}
+    addons: {apt: {packages: [ghc-ppa-tools,cabal-install-2.4,ghc-8.6.2], sources: [hvr-ghc]}}
 
     # The Stack builds. We can pass in arbitrary Stack arguments via the ARGS
     # variable, such as using --stack-yaml to point to a different file.
   - env: BUILD=stack ARGS=""
     compiler: ": #stack default"
     addons: {apt: {packages: [libgmp-dev]}}
 
-  - env: BUILD=stack ARGS="--resolver lts-6"
-    compiler: ": #stack 7.10.3"
-    addons: {apt: {packages: [libgmp-dev]}}
-
-  - env: BUILD=stack ARGS="--resolver lts-9"
-    compiler: ": #stack 8.0.2"
-    addons: {apt: {packages: [libgmp-dev]}}
-
-  - env: BUILD=stack ARGS="--resolver lts-10"
-    compiler: ": #stack 8.2.2"
+  - env: BUILD=stack ARGS="--resolver lts-12"
+    compiler: ": #stack 8.4.4"
     addons: {apt: {packages: [libgmp-dev]}}
 
   # Nightly builds are allowed to fail
@@ -82,25 +74,15 @@ matrix:
     compiler: ": #stack default osx"
     os: osx
 
-  # Travis includes an macOS which is incompatible with GHC 7.8.4
-  - env: BUILD=stack ARGS="--resolver lts-6"
-    compiler: ": #stack 7.10.3 osx"
-    os: osx
-
-  - env: BUILD=stack ARGS="--resolver lts-9"
-    compiler: ": #stack 8.0.2 osx"
-    os: osx
-
-  - env: BUILD=stack ARGS="--resolver lts-10"
-    compiler: ": #stack 8.2.2 osx"
+  - env: BUILD=stack ARGS="--resolver lts-12"
+    compiler: ": #stack 8.4.4 osx"
     os: osx
 
   - env: BUILD=stack ARGS="--resolver nightly"
     compiler: ": #stack nightly osx"
     os: osx
 
   allow_failures:
-  #- env: BUILD=stack ARGS="--resolver lts-6"
   - env: BUILD=stack ARGS="--resolver nightly"
 
 before_install:
@@ -134,13 +116,15 @@ install:
   - |
     case "$BUILD" in
       stack)
+        cabal --version
+        ghc --version
         # Add in extra-deps for older snapshots, as necessary
-        stack --no-terminal --install-ghc $ARGS build --bench --dry-run || ( \
-          stack --no-terminal $ARGS build cabal-install && \
+        stack --no-terminal $ARGS --install-ghc build --bench --dry-run || ( \
+          stack --no-terminal $ARGS --install-ghc build cabal-install && \
           stack --no-terminal $ARGS solver --update-config)
 
         # Build the dependencies
-        stack --no-terminal --install-ghc $ARGS test --bench --only-dependencies
+        stack --no-terminal $ARGS test --bench --only-dependencies
         ;;
       cabal)
         cabal --version

README.md

@@ -4,9 +4,9 @@
 
 <img src="https://i.imgur.com/0h9dFhl.png" height="200" width="320" />
 
-This is a brand new course, so there are going to be rough edges. We invite
-you to submit issues or pull requests if you find errors or have suggestions
-on how to improve it.
+This is a new course, so there are going to be rough edges. We invite you to
+submit issues or pull requests if you find errors or have suggestions on how to
+improve it.
 
 This course is designed to be run in a class room with instructors, but we
 would like to make it suitable for self-study as well. Although undertaking
@@ -123,8 +123,8 @@ instructions about what the goal is for that specific level.
 * Level 06 : Add some flexible configuration
 * Level 07 : ReaderT & refactoring
 
--- Coming Soon...
-* Level 08 : (Bonus Round) Lenses & Refactoring
+-- In Development...
+* Level 08 : Lenses & "classy mtl" monad transformers
 
 -- Maybe...
 * Level 09 : Add session controls (login, logout) and a protected route. So we

applied-fp-course.cabal

@@ -48,7 +48,6 @@ tested-with:       GHC==8.6.1
                  , GHC==8.4.3
                  , GHC==8.2.2
                  , GHC==8.0.2
-                 , GHC==7.10.3
 
 source-repository head
     type: git
@@ -60,8 +59,6 @@ library
                            Level01.Core
                          , Level02.Core
                          , Level02.Types
-                         , Level03.Core
-                         , Level03.Types
                          , Level04.Conf
                          , Level04.DB
                          , Level04.DB.Types
@@ -118,13 +115,17 @@ library
                      , bytestring == 0.10.*
                      , text == 1.2.*
                      , optparse-applicative >= 0.13 && < 0.15
-                     , aeson == 1.*
                      , mtl == 2.2.*
                      , time >= 1.4 && < 1.10
+                     , old-locale >= 1.0 && < 1.5
+                     , contravariant >= 1.4 && < 1.6
                      , sqlite-simple == 0.4.*
                      , sqlite-simple-errors == 0.6.*
                      , semigroups == 0.18.*
                      , transformers >= 0.4 && < 0.6
+                     , lens >= 4.15 && < 4.18 
+                     , waargonaut >= 0.4.2 && < 0.5
+                     , attoparsec >= 0.13 && < 0.15
 
   -- Directories containing source files.
   hs-source-dirs:      src
@@ -139,59 +140,35 @@ test-suite app-fp-tests
   hs-source-dirs:      tests
   main-is:             Test.hs
 
-  other-modules:       Level03Tests
-                     , Level04Tests
-                     , Level05Tests
-                     , Level06Tests
-                     , Level07Tests
-
-                     , Helpers
-
   build-depends:       base >= 4.8 && <4.13
                      , applied-fp-course
                      , wai == 3.2.*
                      , wai-extra == 3.0.*
                      , http-types >= 0.9 && < 0.13
                      , tasty >= 0.8 && < 1.2
                      , tasty-hunit >= 0.9 && < 0.11
-                     , hspec >= 2.2 && < 3.0
-                     , hspec-wai >= 0.6 && < 0.10
+                     , tasty-wai >= 0.1 && < 0.2
                      , bytestring == 0.10.*
                      , text == 1.2.*
                      , mtl == 2.2.*
                      , semigroups == 0.18.*
                      , transformers >= 0.4 && < 0.6
-                     , mmorph
+
+                     -- [Challenge] Packages
+                     , hedgehog >= 0.6 && < 0.7
+                     , tasty-hedgehog >= 0.2 && < 0.3
 
 test-suite doctests
   -- Base language which the package is written in.
   default-language:    Haskell2010
   type:                exitcode-stdio-1.0
 
-  other-modules:       Level04Tests
-                     , Level05Tests
-                     , Level06Tests
-                     , Level07Tests
-                     , Helpers
-
   ghc-options:         -threaded
   main-is:             doctests.hs
   hs-source-dirs:      tests
   build-depends:       base >= 4.8 && <4.13
-                     , applied-fp-course
-                     , mtl == 2.2.*
-                     , hspec >= 2.2 && < 3.0
-                     , hspec-wai >= 0.6 && < 0.10
                      , doctest >= 0.11 && < 0.17
-                     , semigroups == 0.18.*
-                     , tasty >= 0.8 && < 1.2
-                     , tasty-hunit >= 0.9 && < 0.11
-                     , bytestring == 0.10.*
-                     , wai == 3.2.*
-                     , wai-extra == 3.0.*
-                     , http-types >= 0.9 && < 0.13
-                     , transformers >= 0.4 && < 0.6
-                     , mmorph
+                     , applied-fp-course
 
 -- Level Executables
 executable level01-exe
@@ -216,17 +193,6 @@ executable level02-exe
   -- Base language which the package is written in.
   default-language:    Haskell2010
 
-executable level03-exe
-  -- .hs or .lhs file containing the Main module.
-  main-is:             Level03.hs
-  -- Directories containing source files.
-  hs-source-dirs:      exe
-  -- Other library packages from which modules are imported.
-  build-depends:       base >=4.8 && <4.13
-                     , applied-fp-course
-  -- Base language which the package is written in.
-  default-language:    Haskell2010
-
 executable level04-exe
   -- .hs or .lhs file containing the Main module.
   main-is:             Level04.hs

applied-fp-course.nix

@@ -1,7 +1,9 @@
-{ mkDerivation, aeson, base, bytestring, doctest, hspec, hspec-wai
-, http-types, mtl, optparse-applicative, semigroups, sqlite-simple
-, sqlite-simple-errors, stdenv, tasty, tasty-hunit, text, time
-, transformers, wai, wai-extra, warp, mmorph
+{ mkDerivation, attoparsec, base, bytestring, contravariant
+, doctest, hedgehog, http-types, lens, mtl, old-locale
+, optparse-applicative, semigroups, sqlite-simple
+, sqlite-simple-errors, stdenv, tasty, tasty-hedgehog, tasty-hunit
+, tasty-wai, text, time, transformers, waargonaut, wai, wai-extra
+, warp
 }:
 mkDerivation {
   pname = "applied-fp-course";
@@ -10,14 +12,15 @@ mkDerivation {
   isLibrary = true;
   isExecutable = true;
   libraryHaskellDepends = [
-    aeson base bytestring http-types mtl optparse-applicative
-    semigroups sqlite-simple sqlite-simple-errors text time
-    transformers wai warp
+    attoparsec base bytestring contravariant http-types lens mtl
+    old-locale optparse-applicative semigroups sqlite-simple
+    sqlite-simple-errors text time transformers waargonaut wai warp
   ];
   executableHaskellDepends = [ base ];
   testHaskellDepends = [
-    base bytestring doctest hspec hspec-wai http-types mtl tasty
-    tasty-hunit text wai wai-extra mmorph
+    base bytestring doctest hedgehog http-types mtl semigroups tasty
+    tasty-hedgehog tasty-hunit tasty-wai text transformers wai
+    wai-extra
   ];
   description = "Simplest of web apps for educational purposes";
   license = stdenv.lib.licenses.bsd3;

default.nix

@@ -8,7 +8,23 @@ let
                       then pkgs.haskellPackages
                       else pkgs.haskell.packages.${compiler};
 
-  drv = haskellPackages.callPackage ./applied-fp-course.nix {};
+  sources = {
+    tasty-wai = import ./nix/tasty-wai.nix;
+    waarg = import ./nix/waargonaut.nix;
+  };
+
+  waarg-deps = import "${sources.waarg}/waargonaut-deps.nix";
+
+  modifiedHaskellPackages = haskellPackages.override (old: {
+    overrides = pkgs.lib.composeExtensions
+      (old.overrides or (_: _: {}))
+      (self: super: (waarg-deps pkgs self super) // {
+        tasty-wai = self.callCabal2nix "tasty-wai" sources.tasty-wai {};
+        waargonaut = self.callCabal2nix "waargonaut" sources.waarg {};
+      });
+  });
+
+  drv = modifiedHaskellPackages.callPackage ./applied-fp-course.nix {};
 
 in
-  if pkgs.lib.inNixShell then drv.env else drv
+  drv

exe/Level06.hs

@@ -6,4 +6,4 @@ import qualified Level06.Core as Core
 -- executable. So our ``exe/Main.hs`` is a straightforward and unremarkable
 -- affair.
 main :: IO ()
-main = Core.runApp
+main = Core.runApplication

exe/Level07.hs

@@ -6,4 +6,4 @@ import qualified Level07.Core as Core
 -- executable. So our ``exe/Main.hs`` is a straightforward and unremarkable
 -- affair.
 main :: IO ()
-main = Core.runApp
+main = Core.runApplication

nix/tasty-wai.json

@@ -0,0 +1,7 @@
+{
+  "url": "https://github.com/qfpl/tasty-wai",
+  "rev": "17ae906f318a222eb30a22b6b334399a0ca436a9",
+  "date": "2018-12-04T14:31:04+10:00",
+  "sha256": "16j3qbpwxbl4n2pvck91k6gz2541pkfdpxn4l47nf1s9jx9yaa7f",
+  "fetchSubmodules": true
+}

nix/tasty-wai.nix

@@ -0,0 +1,13 @@
+let
+  initialNixpkgs = import <nixpkgs> {};
+
+  sources = rec {
+    tasty-wai-pinned = initialNixpkgs.pkgs.lib.importJSON ./tasty-wai.json;
+    tasty-wai = initialNixpkgs.pkgs.fetchFromGitHub {
+      owner = "qfpl";
+      repo = "tasty-wai";
+      inherit (tasty-wai-pinned) rev sha256;
+    };
+  };
+in
+  sources.tasty-wai

nix/waargonaut.json

@@ -0,0 +1,7 @@
+{
+  "url": "https://github.com/qfpl/waargonaut",
+  "rev": "7d868c5ca568797345cee762a499488227238b1f",
+  "date": "2018-11-29T12:55:15+10:00",
+  "sha256": "1hr0iyzcamgknsx4830rzvfxy6ykslnalfvbxb6k7h8ywkd2zzc2",
+  "fetchSubmodules": true
+}

nix/waargonaut.nix

@@ -0,0 +1,13 @@
+let
+  initialNixpkgs = import <nixpkgs> {};
+
+  sources = rec {
+    waargonaut-pinned = initialNixpkgs.pkgs.lib.importJSON ./waargonaut.json;
+    waargonaut = initialNixpkgs.pkgs.fetchFromGitHub {
+      owner = "qfpl";
+      repo = "waargonaut";
+      inherit (waargonaut-pinned) rev sha256;
+    };
+  };
+in
+  sources.waargonaut

shell.nix

@@ -0,0 +1,25 @@
+{ nixpkgs ? import <nixpkgs> {}
+, compiler ? "default"
+}:
+let
+  inherit (nixpkgs) pkgs;
+
+  # Grab our course derivation
+  course = import ./. { inherit nixpkgs compiler; };
+
+  # Override the basic derivation so we can have a more fully feature
+  # environment for hacking on the course material
+  courseDevEnv = (pkgs.haskell.lib.addBuildTools course
+    [ # Include the SQLite Database application
+      nixpkgs.sqlite
+
+      # 'ghcid' auto reloading tool
+      nixpkgs.haskellPackages.ghcid
+    ]
+  # We don't want nix to build the thing, we want the environment so we can
+  # build the thing.
+  ).env;
+
+in
+  # Fly, my pretties!
+  courseDevEnv