Merge pull request #8298 from haskell/mergify/bp/3.8/pr-8292

cabal init -n: avoid extra blank lines (backport #8292)

Author: mergify[bot]

Cabal-syntax/src/Distribution/Fields/Pretty.hs

@@ -89,18 +89,23 @@ data Opts ann = Opts
   }
 
 renderFields :: Opts ann -> [PrettyField ann] -> [String]
-renderFields opts fields = flattenBlocks $ map (renderField opts len) fields
+renderFields opts fields = flattenBlocks blocks
   where
     len = maxNameLength 0 fields
+    blocks = filter (not . null . _contentsBlock) -- empty blocks cause extra newlines #8236
+           $ map (renderField opts len) fields
 
     maxNameLength !acc []                            = acc
     maxNameLength !acc (PrettyField _ name _ : rest) = maxNameLength (max acc (BS.length name)) rest
     maxNameLength !acc (PrettySection {}   : rest)   = maxNameLength acc rest
     maxNameLength !acc (PrettyEmpty : rest) = maxNameLength acc rest
 
--- | Block of lines,
--- Boolean parameter tells whether block should be surrounded by empty lines
-data Block = Block Margin Margin [String]
+-- | Block of lines with flags for optional blank lines before and after
+data Block = Block
+  { _beforeBlock   :: Margin
+  , _afterBlock    :: Margin
+  , _contentsBlock :: [String]
+  }
 
 data Margin = Margin | NoMargin
   deriving Eq

cabal-install/tests/fixtures/init/golden/cabal/cabal-lib-and-exe-no-comments.golden

@@ -49,4 +49,3 @@ test-suite y-test
     build-depends:
         base,
         y
-

cabal-install/tests/fixtures/init/golden/cabal/cabal-lib-and-exe-with-comments.golden

@@ -129,4 +129,3 @@ test-suite y-test
     build-depends:
         base,
         y
-

cabal-install/tests/fixtures/init/golden/cabal/cabal-lib-no-comments.golden

@@ -37,4 +37,3 @@ test-suite y-test
     build-depends:
         base,
         y
-

cabal-install/tests/fixtures/init/golden/cabal/cabal-lib-with-comments.golden

@@ -105,4 +105,3 @@ test-suite y-test
     build-depends:
         base,
         y
-

changelog.d/issue-8236

@@ -0,0 +1,4 @@
+synopsis: cabal init -n: avoid extra blank lines
+packages: cabal-init Cabal-syntax
+issues: #8236
+prs: #8292