From 702ce77376dddbbb09e5b18de9be28634180db94 Mon Sep 17 00:00:00 2001
From: Simon Jakobi <simon.jakobi@gmail.com>
Date: Wed, 20 Nov 2019 17:43:36 +0100
Subject: [PATCH 1/6] diag v0

---
 prettyprinter/prettyprinter.cabal             |  1 +
 .../src/Data/Text/Prettyprint/Doc/Internal.hs |  4 ++
 .../Text/Prettyprint/Doc/Internal.hs-boot     | 20 +++++++
 .../Prettyprint/Doc/Internal/Diagnostic.hs    | 52 +++++++++++++++++++
 4 files changed, 77 insertions(+)
 create mode 100644 prettyprinter/src/Data/Text/Prettyprint/Doc/Internal.hs-boot
 create mode 100644 prettyprinter/src/Data/Text/Prettyprint/Doc/Internal/Diagnostic.hs

diff --git a/prettyprinter/prettyprinter.cabal b/prettyprinter/prettyprinter.cabal
index 4f83971d..ffba4310 100644
--- a/prettyprinter/prettyprinter.cabal
+++ b/prettyprinter/prettyprinter.cabal
@@ -27,6 +27,7 @@ library
     exposed-modules:
           Data.Text.Prettyprint.Doc
         , Data.Text.Prettyprint.Doc.Internal
+        , Data.Text.Prettyprint.Doc.Internal.Diagnostic
         , Data.Text.Prettyprint.Doc.Internal.Type
         , Data.Text.Prettyprint.Doc.Render.String
         , Data.Text.Prettyprint.Doc.Render.Text
diff --git a/prettyprinter/src/Data/Text/Prettyprint/Doc/Internal.hs b/prettyprinter/src/Data/Text/Prettyprint/Doc/Internal.hs
index 9c966c25..d1331704 100755
--- a/prettyprinter/src/Data/Text/Prettyprint/Doc/Internal.hs
+++ b/prettyprinter/src/Data/Text/Prettyprint/Doc/Internal.hs
@@ -17,6 +17,9 @@
 -- "Data.Text.Prettyprint.Doc.Internal.Type".
 module Data.Text.Prettyprint.Doc.Internal (
     module Data.Text.Prettyprint.Doc.Internal
+
+    -- * Debugging
+  , diag
 ) where
 
 
@@ -56,6 +59,7 @@ import Data.Monoid hiding ((<>))
 import Data.Functor.Identity
 #endif
 
+import Data.Text.Prettyprint.Doc.Internal.Diagnostic (diag)
 import Data.Text.Prettyprint.Doc.Render.Util.Panic
 
 
diff --git a/prettyprinter/src/Data/Text/Prettyprint/Doc/Internal.hs-boot b/prettyprinter/src/Data/Text/Prettyprint/Doc/Internal.hs-boot
new file mode 100644
index 00000000..22d1633c
--- /dev/null
+++ b/prettyprinter/src/Data/Text/Prettyprint/Doc/Internal.hs-boot
@@ -0,0 +1,20 @@
+module Data.Text.Prettyprint.Doc.Internal where
+
+import Data.Text (Text)
+
+data Doc ann =
+    Fail
+    | Empty
+    | Char !Char
+    | Text !Int !Text
+    | Line
+    | FlatAlt (Doc ann) (Doc ann)
+    | Cat (Doc ann) (Doc ann)
+    | Nest !Int (Doc ann)
+    | Union (Doc ann) (Doc ann)
+    | Column (Int -> Doc ann)
+    | WithPageWidth (PageWidth -> Doc ann)
+    | Nesting (Int -> Doc ann)
+    | Annotated ann (Doc ann)
+
+data PageWidth
diff --git a/prettyprinter/src/Data/Text/Prettyprint/Doc/Internal/Diagnostic.hs b/prettyprinter/src/Data/Text/Prettyprint/Doc/Internal/Diagnostic.hs
new file mode 100644
index 00000000..a93eca02
--- /dev/null
+++ b/prettyprinter/src/Data/Text/Prettyprint/Doc/Internal/Diagnostic.hs
@@ -0,0 +1,52 @@
+{-# LANGUAGE FlexibleContexts     #-}
+{-# LANGUAGE StandaloneDeriving   #-}
+{-# LANGUAGE UndecidableInstances #-}
+module Data.Text.Prettyprint.Doc.Internal.Diagnostic
+    ( diag
+    , diagS
+    ) where
+
+import Data.Text (Text)
+import {-# SOURCE #-} Data.Text.Prettyprint.Doc.Internal (Doc, PageWidth)
+
+import {-# SOURCE #-} qualified Data.Text.Prettyprint.Doc.Internal as Doc
+
+-- | A copy of the 'Doc' type, used to provide a derived 'Show' instance.
+data Diag ann =
+    Fail
+    | Empty
+    | Char !Char
+    | Text !Int !Text
+    | Line
+    | FlatAlt (Diag ann) (Diag ann)
+    | Cat (Diag ann) (Diag ann)
+    | Nest !Int (Diag ann)
+    | Union (Diag ann) (Diag ann)
+    | Column (Int -> Diag ann)
+    | WithPageWidth (PageWidth -> Diag ann)
+    | Nesting (Int -> Diag ann)
+    | Annotated ann (Diag ann)
+
+deriving instance (Show ann, Show (Int -> Diag ann), Show (PageWidth -> Diag ann)) => Show (Diag ann)
+
+docToDiag :: Doc ann -> Diag ann
+docToDiag doc = case doc of
+    Doc.Fail -> Fail
+    Doc.Empty -> Empty
+    Doc.Char c -> Char c
+    Doc.Text l t -> Text l t
+    Doc.Line -> Line
+    Doc.FlatAlt a b -> FlatAlt (docToDiag a) (docToDiag b)
+    Doc.Cat a b -> Cat (docToDiag a) (docToDiag b)
+    Doc.Nest i d -> Nest i (docToDiag d)
+    Doc.Union a b -> Union (docToDiag a) (docToDiag b)
+    Doc.Column f -> Column (docToDiag . f)
+    Doc.WithPageWidth f -> WithPageWidth (docToDiag . f)
+    Doc.Nesting f -> Nesting (docToDiag . f)
+    Doc.Annotated ann d -> Annotated ann (docToDiag d)
+
+diagS :: (Show ann, Show (Int -> Diag ann), Show (PageWidth -> Diag ann)) => Doc ann -> String
+diagS = show . docToDiag
+
+diag :: (Show ann, Show (Int -> Diag ann), Show (PageWidth -> Diag ann)) => Doc ann -> IO ()
+diag = putStrLn . diagS

From 01fa39dd9fa4483c6405e3a8942b4bbe69dca825 Mon Sep 17 00:00:00 2001
From: Simon Jakobi <simon.jakobi@gmail.com>
Date: Wed, 20 Nov 2019 19:35:45 +0100
Subject: [PATCH 2/6] v0.1

---
 .../src/Data/Text/Prettyprint/Doc/Internal.hs | 70 +++++++++++++++++--
 .../Text/Prettyprint/Doc/Internal.hs-boot     | 19 +----
 .../Prettyprint/Doc/Internal/Diagnostic.hs    | 48 +++----------
 3 files changed, 77 insertions(+), 60 deletions(-)

diff --git a/prettyprinter/src/Data/Text/Prettyprint/Doc/Internal.hs b/prettyprinter/src/Data/Text/Prettyprint/Doc/Internal.hs
index d1331704..31014b01 100755
--- a/prettyprinter/src/Data/Text/Prettyprint/Doc/Internal.hs
+++ b/prettyprinter/src/Data/Text/Prettyprint/Doc/Internal.hs
@@ -17,9 +17,6 @@
 -- "Data.Text.Prettyprint.Doc.Internal.Type".
 module Data.Text.Prettyprint.Doc.Internal (
     module Data.Text.Prettyprint.Doc.Internal
-
-    -- * Debugging
-  , diag
 ) where
 
 
@@ -59,7 +56,8 @@ import Data.Monoid hiding ((<>))
 import Data.Functor.Identity
 #endif
 
-import Data.Text.Prettyprint.Doc.Internal.Diagnostic (diag)
+import Data.Text.Prettyprint.Doc.Internal.Diagnostic (Diag)
+import qualified Data.Text.Prettyprint.Doc.Internal.Diagnostic as Diag
 import Data.Text.Prettyprint.Doc.Render.Util.Panic
 
 
@@ -1628,6 +1626,9 @@ data PageWidth
 
     deriving (Eq, Ord, Show, Typeable)
 
+defaultPageWidth :: PageWidth
+defaultPageWidth = AvailablePerLine 80 1
+
 -- $ Test to avoid surprising behaviour
 -- >>> Unbounded > AvailablePerLine maxBound 1
 -- True
@@ -1643,7 +1644,7 @@ newtype LayoutOptions = LayoutOptions { layoutPageWidth :: PageWidth }
 -- >>> defaultLayoutOptions
 -- LayoutOptions {layoutPageWidth = AvailablePerLine 80 1.0}
 defaultLayoutOptions :: LayoutOptions
-defaultLayoutOptions = LayoutOptions { layoutPageWidth = AvailablePerLine 80 1 }
+defaultLayoutOptions = LayoutOptions { layoutPageWidth = defaultPageWidth }
 
 -- | This is the default layout algorithm, and it is used by 'show', 'putDoc'
 -- and 'hPutDoc'.
@@ -1886,6 +1887,65 @@ renderShowS = \sds -> case sds of
     SAnnPush _ x -> renderShowS x
     SAnnPop x    -> renderShowS x
 
+-- * Debugging
+--
+-- Use the @pretty-simple@ package to get a nicer layout for 'show'n
+-- 'Diag's
+--
+-- >>> Text.Pretty.Simple.pPrintNoColor . diag $ align (vcat ["foo", "bar"])
+-- Column 
+--    [ 
+--        ( 10
+--        , Nesting 
+--            [ 
+--                ( 10
+--                , Cat ( Text 3 "foo" ) 
+--                    ( Cat ( FlatAlt Line Empty ) ( Text 3 "bar" ) )
+--                ) 
+--            ]
+--        ) 
+--    ]
+
+-- | Convert a 'Doc' to its diagnostic representation.
+--
+-- The functions in the 'Column', 'WithPageWidth' and 'Nesting' constructors are
+-- sampled with some default values.
+--
+-- Use `diag'` to control the function inputs yourself.
+--
+-- >>> diag $ align (vcat ["foo", "bar"])
+-- Column [(10,Nesting [(10,Cat (Text 3 "foo") (Cat (FlatAlt Line Empty) (Text 3 "bar")))])]
+diag :: Doc ann -> Diag ann
+diag = diag' [10] [defaultPageWidth] [10]
+
+diag'
+    :: [Int]
+       -- ^ Cursor positions for the 'Column' constructor
+    -> [PageWidth]
+       -- ^ For 'WithPageWidth'
+    -> [Int]
+       -- ^ Nesting levels for 'Nesting'
+    -> Doc ann
+    -> Diag ann
+diag' columns pageWidths nestings = go
+  where
+    go doc = case doc of
+        Fail -> Diag.Fail
+        Empty -> Diag.Empty
+        Char c -> Diag.Char c
+        Text l t -> Diag.Text l t
+        Line -> Diag.Line
+        FlatAlt a b -> Diag.FlatAlt (go a) (go b)
+        Cat a b -> Diag.Cat (go a) (go b)
+        Nest i d -> Diag.Nest i (go d)
+        Union a b -> Diag.Union (go a) (go b)
+        Column f -> Diag.Column (apply f columns)
+        WithPageWidth f -> Diag.WithPageWidth (apply f pageWidths)
+        Nesting f -> Diag.Nesting (apply f nestings)
+        Annotated ann d -> Diag.Annotated ann (go d)
+
+    apply :: (a -> Doc ann) -> [a] -> [(a, Diag ann)]
+    apply f = map (\x -> (x, go (f x)))
 
 
 -- $setup
diff --git a/prettyprinter/src/Data/Text/Prettyprint/Doc/Internal.hs-boot b/prettyprinter/src/Data/Text/Prettyprint/Doc/Internal.hs-boot
index 22d1633c..5ab82870 100644
--- a/prettyprinter/src/Data/Text/Prettyprint/Doc/Internal.hs-boot
+++ b/prettyprinter/src/Data/Text/Prettyprint/Doc/Internal.hs-boot
@@ -1,20 +1,5 @@
 module Data.Text.Prettyprint.Doc.Internal where
 
-import Data.Text (Text)
-
-data Doc ann =
-    Fail
-    | Empty
-    | Char !Char
-    | Text !Int !Text
-    | Line
-    | FlatAlt (Doc ann) (Doc ann)
-    | Cat (Doc ann) (Doc ann)
-    | Nest !Int (Doc ann)
-    | Union (Doc ann) (Doc ann)
-    | Column (Int -> Doc ann)
-    | WithPageWidth (PageWidth -> Doc ann)
-    | Nesting (Int -> Doc ann)
-    | Annotated ann (Doc ann)
-
 data PageWidth
+
+instance Show PageWidth
diff --git a/prettyprinter/src/Data/Text/Prettyprint/Doc/Internal/Diagnostic.hs b/prettyprinter/src/Data/Text/Prettyprint/Doc/Internal/Diagnostic.hs
index a93eca02..a229d5ab 100644
--- a/prettyprinter/src/Data/Text/Prettyprint/Doc/Internal/Diagnostic.hs
+++ b/prettyprinter/src/Data/Text/Prettyprint/Doc/Internal/Diagnostic.hs
@@ -1,17 +1,9 @@
-{-# LANGUAGE FlexibleContexts     #-}
-{-# LANGUAGE StandaloneDeriving   #-}
-{-# LANGUAGE UndecidableInstances #-}
-module Data.Text.Prettyprint.Doc.Internal.Diagnostic
-    ( diag
-    , diagS
-    ) where
+module Data.Text.Prettyprint.Doc.Internal.Diagnostic where
 
 import Data.Text (Text)
-import {-# SOURCE #-} Data.Text.Prettyprint.Doc.Internal (Doc, PageWidth)
+import {-# SOURCE #-} Data.Text.Prettyprint.Doc.Internal (PageWidth)
 
-import {-# SOURCE #-} qualified Data.Text.Prettyprint.Doc.Internal as Doc
-
--- | A copy of the 'Doc' type, used to provide a derived 'Show' instance.
+-- | A variant of 'Doc' for debugging.
 data Diag ann =
     Fail
     | Empty
@@ -22,31 +14,11 @@ data Diag ann =
     | Cat (Diag ann) (Diag ann)
     | Nest !Int (Diag ann)
     | Union (Diag ann) (Diag ann)
-    | Column (Int -> Diag ann)
-    | WithPageWidth (PageWidth -> Diag ann)
-    | Nesting (Int -> Diag ann)
+    | Column [(Int, Diag ann)]
+      -- ^ 'Doc': @(Int -> Diag ann)@
+    | WithPageWidth [(PageWidth, Diag ann)]
+      -- ^ 'Doc': @(PageWidth -> Diag ann)@
+    | Nesting [(Int, Diag ann)]
+      -- ^ 'Doc': @(Int -> Diag ann)@
     | Annotated ann (Diag ann)
-
-deriving instance (Show ann, Show (Int -> Diag ann), Show (PageWidth -> Diag ann)) => Show (Diag ann)
-
-docToDiag :: Doc ann -> Diag ann
-docToDiag doc = case doc of
-    Doc.Fail -> Fail
-    Doc.Empty -> Empty
-    Doc.Char c -> Char c
-    Doc.Text l t -> Text l t
-    Doc.Line -> Line
-    Doc.FlatAlt a b -> FlatAlt (docToDiag a) (docToDiag b)
-    Doc.Cat a b -> Cat (docToDiag a) (docToDiag b)
-    Doc.Nest i d -> Nest i (docToDiag d)
-    Doc.Union a b -> Union (docToDiag a) (docToDiag b)
-    Doc.Column f -> Column (docToDiag . f)
-    Doc.WithPageWidth f -> WithPageWidth (docToDiag . f)
-    Doc.Nesting f -> Nesting (docToDiag . f)
-    Doc.Annotated ann d -> Annotated ann (docToDiag d)
-
-diagS :: (Show ann, Show (Int -> Diag ann), Show (PageWidth -> Diag ann)) => Doc ann -> String
-diagS = show . docToDiag
-
-diag :: (Show ann, Show (Int -> Diag ann), Show (PageWidth -> Diag ann)) => Doc ann -> IO ()
-diag = putStrLn . diagS
+    deriving Show

From 57c90af4e730c6f560df09cfffa320ebbb487bd6 Mon Sep 17 00:00:00 2001
From: Simon Jakobi <simon.jakobi@gmail.com>
Date: Sun, 12 Jan 2020 21:01:46 +0100
Subject: [PATCH 3/6] Fix haddocks

---
 prettyprinter/src/Data/Text/Prettyprint/Doc/Internal.hs | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/prettyprinter/src/Data/Text/Prettyprint/Doc/Internal.hs b/prettyprinter/src/Data/Text/Prettyprint/Doc/Internal.hs
index 31014b01..fca62286 100755
--- a/prettyprinter/src/Data/Text/Prettyprint/Doc/Internal.hs
+++ b/prettyprinter/src/Data/Text/Prettyprint/Doc/Internal.hs
@@ -15,9 +15,7 @@
 -- For a stable API, use the non-internal modules. For the special case of
 -- writing adaptors to this library’s @'Doc'@ type, see
 -- "Data.Text.Prettyprint.Doc.Internal.Type".
-module Data.Text.Prettyprint.Doc.Internal (
-    module Data.Text.Prettyprint.Doc.Internal
-) where
+module Data.Text.Prettyprint.Doc.Internal where
 
 
 
@@ -1889,8 +1887,10 @@ renderShowS = \sds -> case sds of
 
 -- * Debugging
 --
+-- $standalone-text
+--
 -- Use the @pretty-simple@ package to get a nicer layout for 'show'n
--- 'Diag's
+-- 'Diag's:
 --
 -- >>> Text.Pretty.Simple.pPrintNoColor . diag $ align (vcat ["foo", "bar"])
 -- Column 

From 00d977902fba40c0bd0c1e6de1d0d1de45ccc002 Mon Sep 17 00:00:00 2001
From: Simon Jakobi <simon.jakobi@gmail.com>
Date: Tue, 14 Jan 2020 19:46:02 +0100
Subject: [PATCH 4/6] Move things to Internal.Debug

---
 prettyprinter/prettyprinter.cabal             |  2 +-
 .../src/Data/Text/Prettyprint/Doc/Internal.hs | 64 -------------
 .../Text/Prettyprint/Doc/Internal.hs-boot     |  5 -
 .../Text/Prettyprint/Doc/Internal/Debug.hs    | 96 +++++++++++++++++++
 .../Prettyprint/Doc/Internal/Diagnostic.hs    | 24 -----
 5 files changed, 97 insertions(+), 94 deletions(-)
 delete mode 100644 prettyprinter/src/Data/Text/Prettyprint/Doc/Internal.hs-boot
 create mode 100644 prettyprinter/src/Data/Text/Prettyprint/Doc/Internal/Debug.hs
 delete mode 100644 prettyprinter/src/Data/Text/Prettyprint/Doc/Internal/Diagnostic.hs

diff --git a/prettyprinter/prettyprinter.cabal b/prettyprinter/prettyprinter.cabal
index ffba4310..609c8441 100644
--- a/prettyprinter/prettyprinter.cabal
+++ b/prettyprinter/prettyprinter.cabal
@@ -27,7 +27,7 @@ library
     exposed-modules:
           Data.Text.Prettyprint.Doc
         , Data.Text.Prettyprint.Doc.Internal
-        , Data.Text.Prettyprint.Doc.Internal.Diagnostic
+        , Data.Text.Prettyprint.Doc.Internal.Debug
         , Data.Text.Prettyprint.Doc.Internal.Type
         , Data.Text.Prettyprint.Doc.Render.String
         , Data.Text.Prettyprint.Doc.Render.Text
diff --git a/prettyprinter/src/Data/Text/Prettyprint/Doc/Internal.hs b/prettyprinter/src/Data/Text/Prettyprint/Doc/Internal.hs
index fca62286..f3910f1f 100755
--- a/prettyprinter/src/Data/Text/Prettyprint/Doc/Internal.hs
+++ b/prettyprinter/src/Data/Text/Prettyprint/Doc/Internal.hs
@@ -54,8 +54,6 @@ import Data.Monoid hiding ((<>))
 import Data.Functor.Identity
 #endif
 
-import Data.Text.Prettyprint.Doc.Internal.Diagnostic (Diag)
-import qualified Data.Text.Prettyprint.Doc.Internal.Diagnostic as Diag
 import Data.Text.Prettyprint.Doc.Render.Util.Panic
 
 
@@ -1885,68 +1883,6 @@ renderShowS = \sds -> case sds of
     SAnnPush _ x -> renderShowS x
     SAnnPop x    -> renderShowS x
 
--- * Debugging
---
--- $standalone-text
---
--- Use the @pretty-simple@ package to get a nicer layout for 'show'n
--- 'Diag's:
---
--- >>> Text.Pretty.Simple.pPrintNoColor . diag $ align (vcat ["foo", "bar"])
--- Column 
---    [ 
---        ( 10
---        , Nesting 
---            [ 
---                ( 10
---                , Cat ( Text 3 "foo" ) 
---                    ( Cat ( FlatAlt Line Empty ) ( Text 3 "bar" ) )
---                ) 
---            ]
---        ) 
---    ]
-
--- | Convert a 'Doc' to its diagnostic representation.
---
--- The functions in the 'Column', 'WithPageWidth' and 'Nesting' constructors are
--- sampled with some default values.
---
--- Use `diag'` to control the function inputs yourself.
---
--- >>> diag $ align (vcat ["foo", "bar"])
--- Column [(10,Nesting [(10,Cat (Text 3 "foo") (Cat (FlatAlt Line Empty) (Text 3 "bar")))])]
-diag :: Doc ann -> Diag ann
-diag = diag' [10] [defaultPageWidth] [10]
-
-diag'
-    :: [Int]
-       -- ^ Cursor positions for the 'Column' constructor
-    -> [PageWidth]
-       -- ^ For 'WithPageWidth'
-    -> [Int]
-       -- ^ Nesting levels for 'Nesting'
-    -> Doc ann
-    -> Diag ann
-diag' columns pageWidths nestings = go
-  where
-    go doc = case doc of
-        Fail -> Diag.Fail
-        Empty -> Diag.Empty
-        Char c -> Diag.Char c
-        Text l t -> Diag.Text l t
-        Line -> Diag.Line
-        FlatAlt a b -> Diag.FlatAlt (go a) (go b)
-        Cat a b -> Diag.Cat (go a) (go b)
-        Nest i d -> Diag.Nest i (go d)
-        Union a b -> Diag.Union (go a) (go b)
-        Column f -> Diag.Column (apply f columns)
-        WithPageWidth f -> Diag.WithPageWidth (apply f pageWidths)
-        Nesting f -> Diag.Nesting (apply f nestings)
-        Annotated ann d -> Diag.Annotated ann (go d)
-
-    apply :: (a -> Doc ann) -> [a] -> [(a, Diag ann)]
-    apply f = map (\x -> (x, go (f x)))
-
 
 -- $setup
 --
diff --git a/prettyprinter/src/Data/Text/Prettyprint/Doc/Internal.hs-boot b/prettyprinter/src/Data/Text/Prettyprint/Doc/Internal.hs-boot
deleted file mode 100644
index 5ab82870..00000000
--- a/prettyprinter/src/Data/Text/Prettyprint/Doc/Internal.hs-boot
+++ /dev/null
@@ -1,5 +0,0 @@
-module Data.Text.Prettyprint.Doc.Internal where
-
-data PageWidth
-
-instance Show PageWidth
diff --git a/prettyprinter/src/Data/Text/Prettyprint/Doc/Internal/Debug.hs b/prettyprinter/src/Data/Text/Prettyprint/Doc/Internal/Debug.hs
new file mode 100644
index 00000000..7c726cd2
--- /dev/null
+++ b/prettyprinter/src/Data/Text/Prettyprint/Doc/Internal/Debug.hs
@@ -0,0 +1,96 @@
+-- | __Warning: internal module!__ This means that the API may change
+-- arbitrarily between versions without notice. Depending on this module may
+-- lead to unexpected breakages, so proceed with caution!
+
+module Data.Text.Prettyprint.Doc.Internal.Debug where
+
+import Data.Text (Text)
+import Data.Text.Prettyprint.Doc.Internal (PageWidth, Doc)
+import qualified Data.Text.Prettyprint.Doc.Internal as Doc
+
+-- | A variant of 'Doc' for debugging.
+--
+-- Unlike in the 'Doc' type, the 'Column', 'WithPageWidth' and 'Nesting'
+-- constructors don't contain functions but are \"sampled\" to allow
+-- simple inspection with 'show'.
+data Diag ann =
+    Fail
+    | Empty
+    | Char !Char
+    | Text !Int !Text
+    | Line
+    | FlatAlt (Diag ann) (Diag ann)
+    | Cat (Diag ann) (Diag ann)
+    | Nest !Int (Diag ann)
+    | Union (Diag ann) (Diag ann)
+    | Column [(Int, Diag ann)]
+      -- ^ 'Doc': @(Int -> Diag ann)@
+    | WithPageWidth [(PageWidth, Diag ann)]
+      -- ^ 'Doc': @(PageWidth -> Diag ann)@
+    | Nesting [(Int, Diag ann)]
+      -- ^ 'Doc': @(Int -> Diag ann)@
+    | Annotated ann (Diag ann)
+    deriving Show
+
+-- * Debugging
+--
+-- $standalone-text
+--
+-- Use the @pretty-simple@ package to get a nicer layout for 'show'n
+-- 'Diag's:
+--
+-- >>> Text.Pretty.Simple.pPrintNoColor . diag $ align (vcat ["foo", "bar"])
+-- Column 
+--    [ 
+--        ( 10
+--        , Nesting 
+--            [ 
+--                ( 10
+--                , Cat ( Text 3 "foo" ) 
+--                    ( Cat ( FlatAlt Line Empty ) ( Text 3 "bar" ) )
+--                ) 
+--            ]
+--        ) 
+--    ]
+
+-- | Convert a 'Doc' to its diagnostic representation.
+--
+-- The functions in the 'Column', 'WithPageWidth' and 'Nesting' constructors are
+-- sampled with some default values.
+--
+-- Use `diag'` to control the function inputs yourself.
+--
+-- >>> diag $ align (vcat ["foo", "bar"])
+-- Column [(10,Nesting [(10,Cat (Text 3 "foo") (Cat (FlatAlt Line Empty) (Text 3 "bar")))])]
+diag :: Doc ann -> Diag ann
+diag = diag' [10] [Doc.defaultPageWidth] [10]
+
+diag'
+    :: [Int]
+       -- ^ Cursor positions for the 'Column' constructor
+    -> [PageWidth]
+       -- ^ For 'WithPageWidth'
+    -> [Int]
+       -- ^ Nesting levels for 'Nesting'
+    -> Doc ann
+    -> Diag ann
+diag' columns pageWidths nestings = go
+  where
+    go doc = case doc of
+        Doc.Fail -> Fail
+        Doc.Empty -> Empty
+        Doc.Char c -> Char c
+        Doc.Text l t -> Text l t
+        Doc.Line -> Line
+        Doc.FlatAlt a b -> FlatAlt (go a) (go b)
+        Doc.Cat a b -> Cat (go a) (go b)
+        Doc.Nest i d -> Nest i (go d)
+        Doc.Union a b -> Union (go a) (go b)
+        Doc.Column f -> Column (apply f columns)
+        Doc.WithPageWidth f -> WithPageWidth (apply f pageWidths)
+        Doc.Nesting f -> Nesting (apply f nestings)
+        Doc.Annotated ann d -> Annotated ann (go d)
+
+    apply :: (a -> Doc ann) -> [a] -> [(a, Diag ann)]
+    apply f = map (\x -> (x, go (f x)))
+
diff --git a/prettyprinter/src/Data/Text/Prettyprint/Doc/Internal/Diagnostic.hs b/prettyprinter/src/Data/Text/Prettyprint/Doc/Internal/Diagnostic.hs
deleted file mode 100644
index a229d5ab..00000000
--- a/prettyprinter/src/Data/Text/Prettyprint/Doc/Internal/Diagnostic.hs
+++ /dev/null
@@ -1,24 +0,0 @@
-module Data.Text.Prettyprint.Doc.Internal.Diagnostic where
-
-import Data.Text (Text)
-import {-# SOURCE #-} Data.Text.Prettyprint.Doc.Internal (PageWidth)
-
--- | A variant of 'Doc' for debugging.
-data Diag ann =
-    Fail
-    | Empty
-    | Char !Char
-    | Text !Int !Text
-    | Line
-    | FlatAlt (Diag ann) (Diag ann)
-    | Cat (Diag ann) (Diag ann)
-    | Nest !Int (Diag ann)
-    | Union (Diag ann) (Diag ann)
-    | Column [(Int, Diag ann)]
-      -- ^ 'Doc': @(Int -> Diag ann)@
-    | WithPageWidth [(PageWidth, Diag ann)]
-      -- ^ 'Doc': @(PageWidth -> Diag ann)@
-    | Nesting [(Int, Diag ann)]
-      -- ^ 'Doc': @(Int -> Diag ann)@
-    | Annotated ann (Diag ann)
-    deriving Show

From 836031bcec33f6a0b681065e0f20c2a73f91b7da Mon Sep 17 00:00:00 2001
From: Simon Jakobi <simon.jakobi@gmail.com>
Date: Tue, 14 Jan 2020 19:46:40 +0100
Subject: [PATCH 5/6] Haddock bit

---
 prettyprinter/src/Data/Text/Prettyprint/Doc/Internal/Debug.hs | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/prettyprinter/src/Data/Text/Prettyprint/Doc/Internal/Debug.hs b/prettyprinter/src/Data/Text/Prettyprint/Doc/Internal/Debug.hs
index 7c726cd2..98a14ed8 100644
--- a/prettyprinter/src/Data/Text/Prettyprint/Doc/Internal/Debug.hs
+++ b/prettyprinter/src/Data/Text/Prettyprint/Doc/Internal/Debug.hs
@@ -1,6 +1,8 @@
 -- | __Warning: internal module!__ This means that the API may change
 -- arbitrarily between versions without notice. Depending on this module may
 -- lead to unexpected breakages, so proceed with caution!
+--
+-- This module provides debugging helpers for inspecting 'Doc's.
 
 module Data.Text.Prettyprint.Doc.Internal.Debug where
 

From 7ad4522ac077c28d8c5eb0efe7a65e2f8065951e Mon Sep 17 00:00:00 2001
From: Simon Jakobi <simon.jakobi@gmail.com>
Date: Sun, 19 Jan 2020 22:26:34 +0100
Subject: [PATCH 6/6] Move around haddocks

---
 .../Text/Prettyprint/Doc/Internal/Debug.hs    | 39 +++++++++----------
 1 file changed, 18 insertions(+), 21 deletions(-)

diff --git a/prettyprinter/src/Data/Text/Prettyprint/Doc/Internal/Debug.hs b/prettyprinter/src/Data/Text/Prettyprint/Doc/Internal/Debug.hs
index 98a14ed8..c6f0bc79 100644
--- a/prettyprinter/src/Data/Text/Prettyprint/Doc/Internal/Debug.hs
+++ b/prettyprinter/src/Data/Text/Prettyprint/Doc/Internal/Debug.hs
@@ -3,6 +3,24 @@
 -- lead to unexpected breakages, so proceed with caution!
 --
 -- This module provides debugging helpers for inspecting 'Doc's.
+--
+-- Use the @pretty-simple@ package to get a nicer layout for 'show'n
+-- 'Diag's:
+--
+-- >>> Text.Pretty.Simple.pPrintNoColor . diag $ align (vcat ["foo", "bar"])
+-- Column
+--    [
+--        ( 10
+--        , Nesting
+--            [
+--                ( 10
+--                , Cat ( Text 3 "foo" )
+--                    ( Cat ( FlatAlt Line Empty ) ( Text 3 "bar" ) )
+--                )
+--            ]
+--        )
+--    ]
+
 
 module Data.Text.Prettyprint.Doc.Internal.Debug where
 
@@ -34,27 +52,6 @@ data Diag ann =
     | Annotated ann (Diag ann)
     deriving Show
 
--- * Debugging
---
--- $standalone-text
---
--- Use the @pretty-simple@ package to get a nicer layout for 'show'n
--- 'Diag's:
---
--- >>> Text.Pretty.Simple.pPrintNoColor . diag $ align (vcat ["foo", "bar"])
--- Column 
---    [ 
---        ( 10
---        , Nesting 
---            [ 
---                ( 10
---                , Cat ( Text 3 "foo" ) 
---                    ( Cat ( FlatAlt Line Empty ) ( Text 3 "bar" ) )
---                ) 
---            ]
---        ) 
---    ]
-
 -- | Convert a 'Doc' to its diagnostic representation.
 --
 -- The functions in the 'Column', 'WithPageWidth' and 'Nesting' constructors are