Check generated Course*.hs files are up-to-date

Author: smelc

.github/workflows/haskell.yml

@@ -28,6 +28,11 @@ jobs:
           git clone https://github.com/smelc/exdown
           EXDOWN=exdown/exdown.py ./extract_hs.sh
 
+      - name: Check versioned Course*.hs files are up to date
+        working-directory: slides
+        run: |
+          ./check_golden_diff.sh
+
       - name: Set up GHC ${{ matrix.ghc-version }}
         uses: haskell-actions/setup@v2
         id: setup

slides/Course04.hs

@@ -125,6 +125,6 @@ data Authenticated
 -- @type@ defines aliases (shortcuts)
 type UserWithAuthStatus a = User
 
-authenticate' :: User -> String -> UserWithAuthStatus Authenticated
+authenticate' :: User -> String -> Either String (UserWithAuthStatus Authenticated)
 authenticate' = undefined
 

slides/check_golden_diff.sh

@@ -0,0 +1,14 @@
+#!/usr/bin/env bash
+#
+# Verify that Course*.hs files do not have git modification.
+# Probably you want to execute this file after 'extract_hs.sh'
+
+for file in Course*.hs
+do
+  # Check if there is any modification to file
+  if ! git diff --exit-code "$file"
+  then
+    echo "$file is modified. Please run extract_hs.sh and commit the changes."
+    exit 1
+  fi
+done