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Support pipe operators #227

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Merged
infinisil merged 2 commits into from
Aug 6, 2024
Merged

Support pipe operators #227

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2c6f39e
Support pipe operators
rhendric Jul 25, 2024
55feeb5
Rename pipes to Forward and Backward
dasJ Aug 6, 2024
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5 changes: 2 additions & 3 deletions src/Nixfmt/Parser.hs
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Original file line number Diff line number Diff line change
Expand Up @@ -17,7 +17,7 @@ import Data.Maybe (fromMaybe, mapMaybe, maybeToList)
import Data.Text (Text)
import qualified Data.Text as Text
import Data.Void (Void)
import Nixfmt.Lexer (lexeme, pushTrivia, takeTrivia, whole)
import Nixfmt.Lexer (lexeme, takeTrivia, whole)
import Nixfmt.Parser.Float (floatParse)
import Nixfmt.Types (
Ann (..),
Expand All @@ -38,7 +38,6 @@ import Nixfmt.Types (
StringPart (..),
Term (..),
Token (..),
Trivium (..),
Whole (..),
operators,
tokenText,
Expand Down Expand Up @@ -470,7 +469,7 @@ operator t =
TMinus -> ">"
TMul -> "/"
TDiv -> "/*"
TLess -> "="
TLess -> "=|"
TGreater -> "="
TNot -> "="
_ -> ""
Expand Down
8 changes: 7 additions & 1 deletion src/Nixfmt/Types.hs
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Expand Up @@ -424,6 +424,8 @@ data Token
| TLessEqual
| TNot
| TUnequal
| TPipeForward
| TPipeBackward
| SOF
deriving (Eq, Show)

Expand Down Expand Up @@ -466,7 +468,9 @@ operators =
],
[Op InfixL TAnd],
[Op InfixL TOr],
[Op InfixL TImplies]
[Op InfixL TImplies],
[Op InfixL TPipeForward],
[Op InfixR TPipeBackward]
]

tokenText :: Token -> Text
Expand Down Expand Up @@ -519,4 +523,6 @@ tokenText TLess = "<"
tokenText TLessEqual = "<="
tokenText TNot = "!"
tokenText TUnequal = "!="
tokenText TPipeForward = "|>"
tokenText TPipeBackward = "<|"
tokenText SOF = ""
13 changes: 13 additions & 0 deletions test/diff/operation/in.nix
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Expand Up @@ -156,4 +156,17 @@
z = 30;
}
)

# Experimental pipe operators
(
a // b
|> f "very long argument should justify splitting this over multiple lines"
|> g { }
)

(
g { } <|
f "very long argument should justify splitting this over multiple lines" <|
a // b
)
]
13 changes: 13 additions & 0 deletions test/diff/operation/out.nix
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Expand Up @@ -273,4 +273,17 @@
z = 30;
}
)

# Experimental pipe operators
(
a // b
|> f "very long argument should justify splitting this over multiple lines"
|> g { }
)

(
g { }
<| f "very long argument should justify splitting this over multiple lines"
<| a // b
)
Comment on lines +284 to +288

@roberth roberth Jul 26, 2024

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What I like about the |> formatting is that the functions, that have an equal role, are formatted equally.
This makes it easy to read.

That is not the case here. This formatting makes it seem as if g { } is special and f "..." and a // b are similar, while the opposite is true.

Suggested change
(
g { }
<| f "very long argument should justify splitting this over multiple lines"
<| a // b
)
(
g { } <|
f "very long argument should justify splitting this over multiple lines" <|
a // b
)

A similar effect could be achieved by indenting the first function, but that's a little unusual, and it doesn't make the function operands look quite as equal.

Suggested change
(
g { }
<| f "very long argument should justify splitting this over multiple lines"
<| a // b
)
(
g { }
<| f "very long argument should justify splitting this over multiple lines"
<| a // b
)

@infinisil infinisil Aug 6, 2024

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The first suggested style has the problem that lines might be arbitrarily long, which makes it unclear how the lines relate to, without looking to the right. This is why the standard always puts operators in front.

The second suggested style violates the indentation rule of the standard.

But we also agree that it's not ideal for the first function to look different. For now we don't want to block on this and just go ahead with this PR as is.

It would also be possible for NixOS/rfcs#148 to specify how it should be formatted (though it doesn't actually specify a <| operator right now).

]