Restore idempotency when formatting comments #1415
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This reduces the complexity of renderSrc slightly without affecting anything else much.
Fixes #1413. Previously the formatter would insert an additional line break before some comments whilst preserving existing line breaks. In order to restore idempotent behaviour, we need to strip a leading newline character from the comment string in those cases, if present.
Test case taken from @AJChapman's bug report (#1413).
sjakobi
approved these changes
Oct 11, 2019
| let x = 1 in x | ||
| -} | ||
| renderSrc | ||
| :: Maybe Src | ||
| -- ^ Source span to render (if present) | ||
| -> (Text -> Text) | ||
| -- ^ Used to preprocess the comment string (e.g. to strip whitespace) |
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It seems to me that it would be more "conventional" to have the function as the first parameter, and the Maybe Src as the second, but I'm not sure whether it's a good idea in this case.
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Hmm, now that you mention it, the ordering is a bit ad-hoc.
Good idea! |
Reads a bit more idiomatic, as suggested by @sjakobi.
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Fixes #1413.
Previously we would repeatedly insert a newline character when formatting certain comments, e.g.
would result in (*)
which, when piped again through
dhall formatresulted inand so on.
With this change we only add a line break if the comment didn't already start with one (equivalently, we remove a leading line break before adding one back), meaning the formatter now stabilises at
in this case.