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Add unsafeTextWithLength #230

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Add unsafeTextWithLength #230

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ba7ea40
Add unsafeTextWithLength
reixn Jul 19, 2022
225a25e
Remove unsafeLazyTextWithLength
reixn Jul 19, 2022
ae1d2a6
Improve document on unsafeTextWithLength
reixn Jul 19, 2022
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3 changes: 3 additions & 0 deletions prettyprinter/src/Prettyprinter.hs
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Expand Up @@ -202,6 +202,9 @@ module Prettyprinter (
viaShow, unsafeViaShow,
emptyDoc, nest, line, line', softline, softline', hardline,

-- ** Create from Text (unsafe)
unsafeTextWithLength, unsafeLazyTextWithLength,

-- ** Primitives for alternative layouts
group, flatAlt,

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12 changes: 12 additions & 0 deletions prettyprinter/src/Prettyprinter/Internal.hs
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Expand Up @@ -26,6 +26,9 @@ module Prettyprinter.Internal (
viaShow, unsafeViaShow, unsafeTextWithoutNewlines,
emptyDoc, nest, line, line', softline, softline', hardline,

-- ** create doc directly from Text, unsafe
unsafeTextWithLength, unsafeLazyTextWithLength,

-- ** Primitives for alternative layouts
group, flatAlt,

Expand Down Expand Up @@ -452,6 +455,15 @@ instance Pretty a => Pretty (Maybe a) where
-- Manually use @'hardline'@ if you /definitely/ want newlines.
instance Pretty Text where pretty = vsep . map unsafeTextWithoutNewlines . T.splitOn "\n"

-- | Convert text to Doc. Must not contain newlines.
-- Useful when dealing with wide characters and emojis
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The documentation should clarify why and how this function is useful for dealing with wide characters and emojis.

unsafeTextWithLength :: Text -> Int -> Doc ann
unsafeTextWithLength txt l = Text l txt
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I think this definition is a bit misplaced between these Pretty instances. I suggest placing it below unsafeTextWithoutNewlines.

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The Text invariants need to be handled in some way too:

prettyprinter/prettyprinter/src/Prettyprinter/Internal.hs

Lines 153 to 159 in 0dbe08f

-- | Invariants: at least two characters long, does not contain '\n'. For
-- empty documents, there is @Empty@; for singleton documents, there is
-- @Char@; newlines should be replaced by e.g. @Line@.
--
-- Since the frequently used 'T.length' of 'Text' is /O(length)/, we cache
-- it in this constructor.
| Text !Int !Text


-- | identical to the strict version
unsafeLazyTextWithLength :: Lazy.Text -> Int -> Doc ann
unsafeLazyTextWithLength txt l = Text l (Lazy.toStrict txt)
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What's the use case for this function? I don't imagine that wide characters and emojis will typically exist in the form of a lazy Text values?!

If there's no obvious use case, I'd prefer not to add this function.


-- | (lazy 'Text' instance, identical to the strict version)
instance Pretty Lazy.Text where pretty = pretty . Lazy.toStrict
#endif
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