Re #6498 Better in-app information about using a downgraded Stack

commercialhaskell · Feb 26, 2024 · 4b7250a · 4b7250a
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commit 4b7250a
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Showing 3 changed files with 20 additions and 8 deletions.
diff --git a/ChangeLog.md b/ChangeLog.md
@@ -12,7 +12,8 @@ Behavior changes:
 
 * Stack uses the version of the Cabal package that comes with the specified
   version of GHC. Stack no longer supports such Cabal versions before 2.2, which
-  came with versions of GHC before 8.4.
+  came with versions of GHC before 8.4. Due to a bug, Stack 2.15.1 did not
+  support versions of GHC before 8.2.
 * `stack path --global-config`, `--programs`, and `--local-bin` no longer set
   up Stack's environment.
 * The `init` command initialises `stack.yaml` with a `snapshot` key rather than

diff --git a/src/Stack/Build.hs b/src/Stack/Build.hs
@@ -87,14 +87,20 @@ instance Pretty CabalVersionPrettyException where
                 \with the specified version of GHC. However, Stack no longer \
                 \supports such Cabal versions before 2.2. Version"
          , fromString $ versionString cabalVer
-         , flow "was found. To fix this, either use Stack 2.15.1 or earlier or \
-                \use a snapshot that specifies a version of GHC that is 8.4 or \
-                \later. Stackage LTS Haskell 12.0"
+         , flow "was found. To fix this, either use Stack"
+         , downgradeRecommendation
+         , flow "or earlier or use a snapshot that specifies a version of GHC \
+                \that is 8.4 or later. Stackage LTS Haskell 12.0"
          , parens (style Shell "lts-12.0")
          , flow "or later or Nightly 2018-03-13"
          , parens (style Shell "nightly-2018-03-13")
          , flow "or later specify such GHC versions."
          ]
+   where
+    -- Due to a bug, Stack 2.15.1 does not support Cabal < 2.
+    downgradeRecommendation = if cabalVer < mkVersion [2]
+      then "2.13.1"
+      else "2.15.1"
 
 instance Exception CabalVersionPrettyException
 

diff --git a/src/Stack/Setup.hs b/src/Stack/Setup.hs
@@ -1057,16 +1057,21 @@ warnUnsupportedCompilerCabal cp didWarn = do
   notifyIfCabalUntested <- view $ configL . to (.notifyIfCabalUntested)
   if
     | cabalVersion < mkVersion [2, 2] -> do
+            -- Due to a bug, Stack 2.15.1 does not support Cabal < 2.
+        let downgradeRecommendation = if cabalVersion < mkVersion [2]
+              then "2.13.1"
+              else "2.15.1"
         prettyWarnL
           [ flow "Stack uses the version of the Cabal package that comes with \
                  \the specified version of GHC. However, Stack no longer \
                  \supports such Cabal versions before 2.2. Version"
           , fromString (versionString cabalVersion)
           , flow "was found. This invocation of Stack may fail. To fix this, \
-                 \either use Stack 2.15.1 or earlier or use a snapshot that \
-                 \specifies a version of GHC that is 8.4 or later. Stackage \
-                 \LTS Haskell 12.0 or later and Nightly 2018-03-13 or later. \
-                 \Stackage LTS Haskell 12.0"
+                 \either use Stack"
+          , downgradeRecommendation
+          , flow "or earlier or use a snapshot that specifies a version of GHC \
+                 \that is 8.4 or later. Stackage LTS Haskell 12.0 or later and \
+                 \Nightly 2018-03-13 or later. Stackage LTS Haskell 12.0"
           , parens (style Shell "lts-12.0")
           , flow "or later or Nightly 2018-03-13"
           , parens (style Shell "nightly-2018-03-13")