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RFC: A different approach to avoiding trailing whitespace #139

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merged 6 commits into from
Jun 30, 2020
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RFC: A different approach to avoiding trailing whitespace #139

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c1969b2
A different approach to avoiding trailing whitespace
sjakobi Jan 26, 2020
3374b8c
Also avoid add trailing whitespace at the end of the document
sjakobi Jan 27, 2020
5b86674
Add comment
sjakobi Jun 14, 2020
5f63588
Try keeping track of the annotation level within `best`
sjakobi Jun 15, 2020
7f24d8c
Revert "Try keeping track of the annotation level within `best`"
sjakobi Jun 17, 2020
9073e36
Add testcase
sjakobi Jun 30, 2020
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10 changes: 9 additions & 1 deletion prettyprinter/src/Data/Text/Prettyprint/Doc/Internal.hs
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Original file line number Diff line number Diff line change
Expand Up @@ -1967,7 +1967,15 @@ layoutWadlerLeijen
Empty -> best nl cc ds
Char c -> let !cc' = cc+1 in SChar c (best nl cc' ds)
Text l t -> let !cc' = cc+l in SText l t (best nl cc' ds)
Line -> SLine i (best i i ds)
Line -> let x = best i i ds
-- Don't produce indentation if there's no
-- following text on the same line.
-- This prevents trailing whitespace.
i' = case x of
SEmpty -> 0
SLine{} -> 0
_ -> i
in SLine i' x
FlatAlt x _ -> best nl cc (Cons i x ds)
Cat x y -> best nl cc (Cons i x (Cons i y ds))
Nest j x -> let !ij = i+j in best nl cc (Cons ij x ds)
Expand Down
10 changes: 10 additions & 0 deletions prettyprinter/test/Testsuite/Main.hs
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Original file line number Diff line number Diff line change
Expand Up @@ -89,6 +89,8 @@ tests = testGroup "Tests"
, testCase "Line within align" regressionUnboundedGroupedLineWithinAlign
]
]
, testCase "Indentation on otherwise empty lines results in trailing whitespace (#139)"
indentationShouldntCauseTrailingWhitespaceOnOtherwiseEmptyLines
]

fusionDoesNotChangeRendering :: FusionDepth -> Property
Expand Down Expand Up @@ -380,3 +382,11 @@ regressionUnboundedGroupedLineWithinAlign
sdoc = layoutPretty (LayoutOptions Unbounded) doc
expected = SChar 'x' (SLine 0 (SChar 'y' SEmpty))
in assertEqual "" expected sdoc

indentationShouldntCauseTrailingWhitespaceOnOtherwiseEmptyLines :: Assertion
indentationShouldntCauseTrailingWhitespaceOnOtherwiseEmptyLines
= let doc :: Doc ()
doc = indent 1 ("x" <> hardline <> hardline <> "y" <> hardline)
sdoc = layoutPretty (LayoutOptions Unbounded) doc
expected = SChar ' ' (SChar 'x' (SLine 0 (SLine 1 (SChar 'y' (SLine 0 SEmpty)))))
in assertEqual "" expected sdoc