Modernize server build and CI (#322)

* Modernize server build and CI

- Bump the Stackage resolver to lts-20.26 (GHC 9.2.8), the newest
  snapshot compatible with purescript-0.15.15. This requires protolude
  0.3.3 (for lts-20.26's bytestring) and a happy-1.20.0 pin (purescript
  requires happy ==1.20.0 exactly).
- Update the cabal file to cabal-version 2.4, build with -Wall -Werror,
  and remove unused dependencies; delete the redundant Setup.hs
  (build-type: Simple ignores it).
- Clean up server/Main.hs for -Wall: remove dead imports, fix name
  shadowing, and exit with a usage message on bad arguments instead of
  a partial pattern match.
- Remove the -j1 limit from CI server builds; runners have 4 vCPUs and
  16GB of RAM.

* Add cache headers to nginx config

Browsers were heuristically caching the site and the compiled /output
modules because no Cache-Control header was sent; with files dating
from a 2023 deploy, cached clients could be considered fresh for
months. no-cache makes browsers revalidate via ETag: unchanged files
cost a 304, changed files are re-downloaded immediately.

Matches the configuration applied to the live server on 2026-07-05.
Also updates the changelog entries to reference this PR.

Author: thomashoneyman

.github/workflows/ci.yml

@@ -35,7 +35,7 @@ jobs:
           key: ${{ runner.os }}-stack-${{ hashFiles('stack.yaml.lock') }}-${{ hashFiles('trypurescript.cabal') }}
 
       - name: Build server code
-        run: stack --no-terminal -j1 build
+        run: stack --no-terminal build
 
       - name: Build server assets
         if: github.event_name == 'release'

CHANGELOG.md

@@ -11,6 +11,10 @@ New features:
 Bugfixes:
 
 Other improvements:
+- Bump the Stackage resolver from `lts-20.9` to `lts-20.26` (GHC 9.2.5 → 9.2.8), the newest snapshot compatible with `purescript-0.15.15` (#322 by @thomashoneyman)
+- Modernize the server build: `cabal-version: 2.4`, build with `-Wall -Werror` (with attendant cleanup in `server/Main.hs`), remove unused dependencies and the redundant `Setup.hs` (#322 by @thomashoneyman)
+- Speed up CI server builds by removing the `-j1` limit; runners have had 4 vCPUs and 16GB of RAM for years (#322 by @thomashoneyman)
+- Serve the site and the compiled `/output` modules with `Cache-Control: no-cache` so browsers revalidate via ETag instead of heuristically caching a stale client for months after a deploy (#322 by @thomashoneyman)
 
 ## [v2026-07-05.1](https://github.com/purescript/trypurescript/releases/tag/v2026-07-05.1)
 

Setup.hs

@@ -44,6 +44,10 @@ server {
 
     location / {
       root /var/www/trypurescript/public;
+      # Always revalidate (cheap ETag 304s): the HTML references the bundle by
+      # a fixed name, so without this browsers heuristically cache the site
+      # and can serve a stale client for months after a deploy.
+      add_header Cache-Control "no-cache";
     }
 
 }
@@ -86,6 +90,10 @@ server {
     # match to ensure that we only serve JS files.
     location ~ ^/output/(.+\.js)$ {
       add_header Access-Control-Allow-Origin *;
+      # Module URLs are generated by the compiler and change content when the
+      # package set or compiler changes; revalidate so browsers never mix
+      # modules from different deploys.
+      add_header Cache-Control "no-cache";
       alias /var/www/trypurescript/staging/.psci_modules/$1;
     }
 }

deploy/nginx.conf

@@ -6,26 +6,22 @@
 
 module Main (main) where
 
-import           Control.Monad (unless, foldM)
-import           Control.Monad.Error.Class (throwError)
+import           Control.Monad (foldM)
 import           Control.Monad.IO.Class (liftIO)
-import           Control.Monad.Logger (runLogger')
 import qualified Control.Monad.State as State
 import           Control.Monad.Trans (lift)
 import           Control.Monad.Trans.Except (ExceptT(..), runExceptT)
-import           Control.Monad.Trans.Reader (runReaderT)
 import           Control.Monad.Writer.Strict (runWriterT)
 import qualified Data.Aeson as A
 import           Data.Aeson ((.=))
-import           Data.Bifunctor (first, second, bimap)
+import           Data.Bifunctor (second, bimap)
 import qualified Data.ByteString.Lazy as BL
 import           Data.Default (def)
 import           Data.Function (on)
 import qualified Data.IORef as IORef
 import           Data.List (nubBy)
 import qualified Data.List.NonEmpty as NE
 import qualified Data.Map as M
-import           Data.Set (Set)
 import qualified Data.Set as Set
 import           Data.Text (Text)
 import qualified Data.Text as T
@@ -50,6 +46,7 @@ import           System.Environment (getArgs)
 import           System.Exit (exitFailure)
 import           System.FilePath.Glob (glob)
 import qualified System.IO as IO
+import           Text.Read (readMaybe)
 import           Web.Scotty
 import qualified Web.Scotty as Scotty
 
@@ -204,9 +201,9 @@ lookupAllConstructors env = P.everywhereOnTypesM $ \case
     other -> pure other
   where
     lookupConstructor :: P.Environment -> P.ProperName 'P.TypeName -> [P.Qualified (P.ProperName 'P.TypeName)]
-    lookupConstructor env nm =
+    lookupConstructor env' nm =
       [ q
-      | (q@(P.Qualified (N.ByModuleName _) thisNm), _) <- M.toList (P.types env)
+      | (q@(P.Qualified (N.ByModuleName _) thisNm), _) <- M.toList (P.types env')
       , thisNm == nm
       ]
 
@@ -216,15 +213,15 @@ lookupAllConstructors env = P.everywhereOnTypesM $ \case
 replaceTypeVariablesAndDesugar :: (Text -> Int -> P.SourceType) -> P.SourceType -> P.SourceType
 replaceTypeVariablesAndDesugar f ty = State.evalState (P.everywhereOnTypesM go ty) (0, M.empty) where
   go = \case
-    P.ParensInType _ ty -> pure ty
+    P.ParensInType _ inner -> pure inner
     P.TypeVar _ s -> do
-      (next, m) <- State.get
+      (n, m) <- State.get
       case M.lookup s m of
         Nothing -> do
-          let ty = f s next
-          State.put (next + 1, M.insert s ty m)
-          pure ty
-        Just ty -> pure ty
+          let unknown = f s n
+          State.put (n + 1, M.insert s unknown m)
+          pure unknown
+        Just unknown -> pure unknown
     other -> pure other
 
 tryParseType :: Text -> Maybe P.SourceType
@@ -242,16 +239,24 @@ main :: IO ()
 main = do
   -- Stop mangled "Compiling ModuleName" text
   IO.hSetBuffering IO.stderr IO.LineBuffering
-  (portString : inputGlobs) <- getArgs
-  let port = read portString
-  inputFiles <- concat <$> traverse glob inputGlobs
-  e <- runExceptT $ do
-    modules <- ExceptT $ I.loadAllModules inputFiles
-    (exts, env) <- ExceptT . I.runMake . I.make $ map (second CST.pureResult) modules
-    namesEnv <- fmap fst . runWriterT $ foldM P.externsEnv P.primEnv exts
-    let
-      allModuleNames = fmap (P.getModuleName . snd) modules
-    pure (allModuleNames, exts, namesEnv, env)
-  case e of
-    Left err -> print err >> exitFailure
-    Right (allModuleNames, exts, namesEnv, env) -> server allModuleNames exts namesEnv env port
+  args <- getArgs
+  case args of
+    portString : inputGlobs
+      | Just port <- readMaybe portString -> run port inputGlobs
+    _ -> do
+      IO.hPutStrLn IO.stderr "Usage: trypurescript PORT INPUT_GLOB..."
+      exitFailure
+  where
+  run :: Int -> [String] -> IO ()
+  run port inputGlobs = do
+    inputFiles <- concat <$> traverse glob inputGlobs
+    e <- runExceptT $ do
+      modules <- ExceptT $ I.loadAllModules inputFiles
+      (exts, env) <- ExceptT . I.runMake . I.make $ map (second CST.pureResult) modules
+      namesEnv <- fmap fst . runWriterT $ foldM P.externsEnv P.primEnv exts
+      let
+        allModuleNames = fmap (P.getModuleName . snd) modules
+      pure (allModuleNames, exts, namesEnv, env)
+    case e of
+      Left err -> print err >> exitFailure
+      Right (allModuleNames, exts, namesEnv, env) -> server allModuleNames exts namesEnv env port

server/Main.hs

@@ -1,4 +1,4 @@
-resolver: lts-20.9
+resolver: lts-20.26
 packages:
   - "."
 
@@ -8,8 +8,11 @@ extra-deps:
   - process-1.6.13.1
   # The Cabal library is not in Stackage
   - Cabal-3.6.3.0
-  # Protolude is not yet in resolver snapshot
-  - protolude-0.3.1
+  # Protolude is not in the resolver snapshot; 0.3.3 (not 0.3.1) is needed
+  # for compatibility with the bytestring version in lts-20.26
+  - protolude-0.3.3
+  # purescript pins happy ==1.20.0, but lts-20.26 ships happy-1.20.1.1
+  - happy-1.20.0
 
 flags:
   these:

stack.yaml

@@ -1,7 +1,7 @@
 # This file was autogenerated by Stack.
 # You should not edit this file by hand.
 # For more information, please see the documentation at:
-#   https://docs.haskellstack.org/en/stable/lock_files
+#   https://docs.haskellstack.org/en/stable/topics/lock_files
 
 packages:
 - completed:
@@ -33,15 +33,22 @@ packages:
   original:
     hackage: Cabal-3.6.3.0
 - completed:
-    hackage: protolude-0.3.1@sha256:1cc9e5a5c26c33a43c52b554443dd9779fef13974eaa0beec7ca6d2551b400da,2647
+    hackage: protolude-0.3.3@sha256:0106615f6fe08de16fe512852c728797db17374d36b4a4ec8187563e924b2439,2261
     pantry-tree:
-      sha256: 6452a6ca8d395f7d810139779bb0fd16fc1dbb00f1862630bc08ef5a100430f9
-      size: 1645
+      sha256: 174c107f3c3af1dc23330ff4431445830aac4b4fdba326e3e654eb491d6e9ca6
+      size: 1594
   original:
-    hackage: protolude-0.3.1
+    hackage: protolude-0.3.3
+- completed:
+    hackage: happy-1.20.0@sha256:5d47dc221a9fe964e36aaaa2e1ab7e8f085a225fd6528d6eff310b92360bbe99,5732
+    pantry-tree:
+      sha256: ff2e7df7cfe8746eedc6f69c225fa8c899c26d28f1c4964eeb00a5d757d30351
+      size: 8749
+  original:
+    hackage: happy-1.20.0
 snapshots:
 - completed:
-    sha256: c11fcbeb1aa12761044755b1109d16952ede2cb6147ebde777dd5cb38f784501
-    size: 649333
-    url: https://raw.githubusercontent.com/commercialhaskell/stackage-snapshots/master/lts/20/9.yaml
-  original: lts-20.9
+    sha256: 5a59b2a405b3aba3c00188453be172b85893cab8ebc352b1ef58b0eae5d248a2
+    size: 650475
+    url: https://raw.githubusercontent.com/commercialhaskell/stackage-snapshots/master/lts/20/26.yaml
+  original: lts-20.26

stack.yaml.lock

@@ -1,41 +1,36 @@
+cabal-version: 2.4
 name: trypurescript
 version: 1.0.0
-cabal-version: >=1.8
 build-type: Simple
-license: BSD3
+license: BSD-3-Clause
 license-file: LICENSE
 copyright: (c) Phil Freeman 2013
 maintainer: paf31@cantab.net
 synopsis: Interactive PureScript in the Browser
 description: A simple web app for trying out the PureScript compiler
 category: Web
 author: Phil Freeman
-data-dir: ""
 
 executable trypurescript
     -- Since no one depends on this project as a library,
-    -- packages below are `-any` because their versions are determined
-    -- by the `stack.yml` file. Versions correspond to the ones
-    -- specified in the resolver (i.e. the package set)
+    -- packages below are unbounded because their versions are
+    -- determined by the `stack.yaml` file. Versions correspond to the
+    -- ones specified in the resolver (i.e. the package set)
     -- unless it is a versioned library added via `extra-deps` field.
-    build-depends: base -any,
-                   aeson -any,
-                   bytestring -any,
-                   data-default -any,
-                   directory -any,
-                   filepath -any,
-                   Glob -any,
-                   scotty -any,
+    build-depends: base,
+                   aeson,
+                   bytestring,
+                   containers,
+                   data-default,
+                   Glob,
+                   mtl,
                    purescript,
-                   containers -any,
-                   http-types -any,
-                   transformers -any,
-                   mtl -any,
-                   text -any,
-                   time -any,
-                   warp -any
+                   scotty,
+                   text,
+                   time,
+                   transformers,
+                   warp
     hs-source-dirs: server
     main-is: Main.hs
-    buildable: True
-    other-modules: Main
-    ghc-options: -Werror -O2 -threaded -rtsopts
+    default-language: Haskell2010
+    ghc-options: -Wall -Werror -O2 -threaded -rtsopts