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Extend single-line list formatting beyond function arguments #353

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49 changes: 17 additions & 32 deletions src/Nixfmt/Pretty.hs
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Original file line number Diff line number Diff line change
Expand Up @@ -110,8 +110,8 @@ instance (Pretty a) => Pretty (Item a) where
pretty (Item x) = group x

-- For lists, attribute sets and let bindings
prettyItems :: (Pretty a) => Items a -> Doc
prettyItems (Items items) = go items
prettyItemsWith :: (Pretty a) => Doc -> Items a -> Doc
prettyItemsWith separator (Items items) = go items
where
go [] = mempty
go [item] = pretty item
Expand All @@ -120,9 +120,9 @@ prettyItems (Items items) = go items
pretty (LanguageAnnotation lang)
<> hardspace
<> group stringItem
<> if null rest then mempty else hardline <> go rest
<> if null rest then mempty else separator <> go rest
go (item : rest) =
pretty item <> if null rest then mempty else hardline <> go rest
pretty item <> if null rest then mempty else separator <> go rest

instance Pretty Trivia where
pretty [] = mempty
Expand Down Expand Up @@ -197,7 +197,7 @@ prettySet _ (krec, paropen@(LoneAnn _), Items [], parclose@Ann{preTrivia = []})
-- Singleton sets are allowed to fit onto one line,
-- but apart from that always expand.
prettySet wide (krec, paropen@Ann{trailComment = post}, binders, parclose) =
let !surrounded = surroundWith sep (nest $ pretty post <> prettyItems binders)
let !surrounded = surroundWith sep (nest $ pretty post <> prettyItemsWith hardline binders)
in pretty (fmap (,hardspace) krec)
<> pretty (paropen{trailComment = Nothing})
<> surrounded
Expand Down Expand Up @@ -242,14 +242,16 @@ prettyTerm (List paropen@Ann{trailComment = Nothing} (Items []) parclose@Ann{pre
-- If the brackets are on different lines, keep them like that
sep = if sourceLine paropen /= sourceLine parclose then hardline else hardspace
-- General list
-- Always expand if len > 1
prettyTerm (List paropen@Ann{trailComment = post} items parclose) =
pretty (paropen{trailComment = Nothing})
<> surroundWith sur (nest $ pretty post <> prettyItems items)
<> surroundWith sur (nest $ pretty post <> prettyItemsWith sur items)
<> pretty parclose
where
-- If the brackets are on different lines, keep them like that
sur = if sourceLine paropen /= sourceLine parclose then hardline else line
sur
| sourceLine paropen /= sourceLine parclose = hardline -- If the brackets are on different lines, keep them like that
| length (unItems items) > 6 = hardline -- More than 6 items: always expand
| length (unItems items) > 1 && not (all (isSimple . Term) items) = hardline -- More than 1 item containing non-simple items: expand
| otherwise = line -- Otherwise, try to fit onto one line
prettyTerm (Set krec paropen items parclose) = prettySet False (krec, paropen, items, parclose)
-- Parentheses
prettyTerm (Parenthesized paropen expr parclose@Ann{preTrivia = closePre}) =
Expand Down Expand Up @@ -412,36 +414,19 @@ prettyApp indentFunction pre hasPost f a =
-- This is very hacky, but selections shouldn't be in a priority group,
-- because if they get expanded before anything else,
-- only the `.`-and-after part gets to a new line, which looks very odd
absorbApp (Application f' a'@(Term Selection{})) = group' Transparent (absorbApp f') <> line <> nest (group' RegularG $ absorbInner a')
absorbApp (Application f' a'@(Term Selection{})) = group' Transparent (absorbApp f') <> line <> nest (group' RegularG $ pretty a')
-- If two consecutive arguments are lists, treat them specially: Don't priority expand, and also
-- if one does not fit onto the line then put both on a new line each.
-- Note that this does not handle the case where the two last arguments are lists, as the last argument
-- is handled elsewhere and cannot be pattern-matched here.
absorbApp (Application (Application f' l1@(Term List{})) l2@(Term List{})) =
group' Transparent (group' Transparent (absorbApp f') <> nest (group' RegularG $ line <> group (absorbInner l1) <> line <> group (absorbInner l2)))
absorbApp (Application f' a') = group' Transparent (absorbApp f') <> line <> nest (group' Priority $ absorbInner a')
group' Transparent (group' Transparent (absorbApp f') <> nest (group' RegularG $ line <> group (pretty l1) <> line <> group (pretty l2)))
absorbApp (Application f' a') = group' Transparent (absorbApp f') <> line <> nest (group' Priority $ pretty a')
-- First argument
absorbApp expr
| indentFunction && null comment' = nest $ group' RegularG $ line' <> pretty expr
| otherwise = pretty expr

-- Render the inner arguments of a function call
absorbInner :: Expression -> Doc
-- If lists have only simple items, try to render them single-line instead of expanding
-- This is just a copy of the list rendering code, but with `sepBy line` instead of `sepBy hardline`
absorbInner (Term (List paropen@Ann{trailComment = post'} items parclose))
| length (unItems items) <= 6 && all (isSimple . Term) items =
pretty (paropen{trailComment = Nothing})
<> surroundWith sur (nest $ pretty post' <> sepBy line (unItems items))
<> pretty parclose
where
-- If the brackets are on different lines, keep them like that
sur
| sourceLine paropen /= sourceLine parclose = hardline
| null $ unItems items = hardspace
| otherwise = line
absorbInner expr = pretty expr

-- Render the last argument of a function call
absorbLast :: Expression -> Doc
absorbLast (Term t)
Expand Down Expand Up @@ -512,9 +497,9 @@ prettyApp indentFunction pre hasPost f a =
group' RegularG $
(pre <> group' Transparent (absorbApp fWithoutCommandAndWithoutArg))
<> line
<> nest (group (absorbInner l1))
<> nest (group (pretty l1))
<> line
<> nest (group (absorbInner l2))
<> nest (group (pretty l2))
<> post
_ ->
renderSimple
Expand Down Expand Up @@ -696,7 +681,7 @@ instance Pretty Expression where
convertTrailing (Just (TrailingComment t)) = [LineComment (" " <> t)]

letPart = group $ pretty let_ <> hardline <> letBody
letBody = nest $ prettyItems binders
letBody = nest $ prettyItemsWith hardline binders
inPart =
group $
pretty in_
Expand Down
13 changes: 2 additions & 11 deletions test/correct-indent-4.nix
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Expand Up @@ -466,12 +466,7 @@ rec {
}:
assert isInt depthLimit;
let
specialAttrs = [
"__functor"
"__functionArgs"
"__toString"
"__pretty"
];
specialAttrs = [ "__functor" "__functionArgs" "__toString" "__pretty" ];
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@MattSturgeon MattSturgeon Oct 30, 2025

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Another example that benefits from being expanded:

Suggested change
specialAttrs = [ "__functor" "__functionArgs" "__toString" "__pretty" ];
specialAttrs = [
"__functor"
"__functionArgs"
"__toString"
"__pretty"
];

stepIntoAttr = evalNext: name: if elem name specialAttrs then id else evalNext;
transform =
depth:
Expand Down Expand Up @@ -543,11 +538,7 @@ rec {
else if isString v then
let
lines = filter (v: !isList v) (split "\n" v);
escapeSingleline = escape [
"\\"
"\""
"\${"
];
escapeSingleline = escape [ "\\" "\"" "\${" ];
escapeMultiline = replaceStrings [ "\${" "''" ] [ "''\${" "'''" ];
singlelineResult =
"\"" + concatStringsSep "\\n" (map escapeSingleline lines) + "\"";
Expand Down
6 changes: 1 addition & 5 deletions test/diff/apply/out-pure.nix
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Expand Up @@ -155,11 +155,7 @@
utils.lib.eachDefaultSystem (system: { });
}
{
escapeSingleline = libStr.escape [
"\\"
''"''
"\${"
];
escapeSingleline = libStr.escape [ "\\" ''"'' "\${" ];
escapeMultiline = libStr.replaceStrings [ "\${" "''" ] [ "''\${" "'''" ];
test =
foo
Expand Down
45 changes: 9 additions & 36 deletions test/diff/apply_with_lists/out-pure.nix
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Original file line number Diff line number Diff line change
Expand Up @@ -2,10 +2,7 @@

[
(f [ ] [ rhs lhs ])
(lib.mkMerge [
false
false
])
(lib.mkMerge [ false false ])
(replaceStrings
[ "\${" "''" ]
#force multiline
Expand Down Expand Up @@ -46,30 +43,12 @@
[ "services" "xserver" "displayManager" "sddm" "enable" ]
[ "services" "displayManager" "sddm" "enable" ]
)
(map (
buildAllowCommand "allow" [
"snapshot"
"mount"
"destroy"
]
))
(map
(
x:
"${x} ${
escapeShellArgs [
stateDir
workDir
logsDir
]
}"
)
[
"+${unconfigureRunner}" # runs as root
configureRunner
setupWorkDir
]
)
(map (buildAllowCommand "allow" [ "snapshot" "mount" "destroy" ]))
(map (x: "${x} ${escapeShellArgs [ stateDir workDir logsDir ]}") [
"+${unconfigureRunner}" # runs as root
configureRunner
setupWorkDir
])
(lib.checkListOfEnum "${pname}: theme accent"
[ "Blue" "Flamingo" "Green" ]
[ accent ]
Expand All @@ -82,17 +61,11 @@
[ coq.coq-version ssreflect.version ]
[
{
cases = [
(lib.versions.range "8.15" "8.20")
lib.pred.true
];
cases = [ (lib.versions.range "8.15" "8.20") lib.pred.true ];
out = "2.0.4";
}
{
cases = [
"8.5"
lib.pred.true
];
cases = [ "8.5" lib.pred.true ];
out = "20170512";
}
]
Expand Down
35 changes: 7 additions & 28 deletions test/diff/apply_with_lists/out.nix
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Original file line number Diff line number Diff line change
Expand Up @@ -2,10 +2,7 @@

[
(f [ ] [ rhs lhs ])
(lib.mkMerge [
false
false
])
(lib.mkMerge [ false false ])
(replaceStrings
[ "\${" "''" ]
#force multiline
Expand Down Expand Up @@ -52,30 +49,12 @@
]
[ "services" "displayManager" "sddm" "enable" ]
)
(map (
buildAllowCommand "allow" [
"snapshot"
"mount"
"destroy"
]
))
(map
(
x:
"${x} ${
escapeShellArgs [
stateDir
workDir
logsDir
]
}"
)
[
"+${unconfigureRunner}" # runs as root
configureRunner
setupWorkDir
]
)
(map (buildAllowCommand "allow" [ "snapshot" "mount" "destroy" ]))
(map (x: "${x} ${escapeShellArgs [ stateDir workDir logsDir ]}") [
"+${unconfigureRunner}" # runs as root
configureRunner
setupWorkDir
])
(lib.checkListOfEnum "${pname}: theme accent"
[
"Blue"
Expand Down
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