From 2c6f39e1a33ac3b8c139d944f9cf3e4464792587 Mon Sep 17 00:00:00 2001
From: Ryan Hendrickson <ryan.hendrickson@alum.mit.edu>
Date: Thu, 25 Jul 2024 19:50:57 -0400
Subject: [PATCH] Support pipe operators

---
 src/Nixfmt/Parser.hs        |  5 ++---
 src/Nixfmt/Types.hs         |  8 +++++++-
 test/diff/operation/in.nix  | 13 +++++++++++++
 test/diff/operation/out.nix | 13 +++++++++++++
 4 files changed, 35 insertions(+), 4 deletions(-)

diff --git a/src/Nixfmt/Parser.hs b/src/Nixfmt/Parser.hs
index f424876f..ddfb558d 100644
--- a/src/Nixfmt/Parser.hs
+++ b/src/Nixfmt/Parser.hs
@@ -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 (..),
@@ -38,7 +38,6 @@ import Nixfmt.Types (
   StringPart (..),
   Term (..),
   Token (..),
-  Trivium (..),
   Whole (..),
   operators,
   tokenText,
@@ -470,7 +469,7 @@ operator t =
                     TMinus -> ">"
                     TMul -> "/"
                     TDiv -> "/*"
-                    TLess -> "="
+                    TLess -> "=|"
                     TGreater -> "="
                     TNot -> "="
                     _ -> ""
diff --git a/src/Nixfmt/Types.hs b/src/Nixfmt/Types.hs
index c41e5841..4af6d939 100644
--- a/src/Nixfmt/Types.hs
+++ b/src/Nixfmt/Types.hs
@@ -424,6 +424,8 @@ data Token
   | TLessEqual
   | TNot
   | TUnequal
+  | TPipeTo
+  | TPipeFrom
   | SOF
   deriving (Eq, Show)
 
@@ -466,7 +468,9 @@ operators =
     ],
     [Op InfixL TAnd],
     [Op InfixL TOr],
-    [Op InfixL TImplies]
+    [Op InfixL TImplies],
+    [Op InfixL TPipeTo],
+    [Op InfixR TPipeFrom]
   ]
 
 tokenText :: Token -> Text
@@ -519,4 +523,6 @@ tokenText TLess = "<"
 tokenText TLessEqual = "<="
 tokenText TNot = "!"
 tokenText TUnequal = "!="
+tokenText TPipeTo = "|>"
+tokenText TPipeFrom = "<|"
 tokenText SOF = ""
diff --git a/test/diff/operation/in.nix b/test/diff/operation/in.nix
index 44d3ba92..70ec4563 100644
--- a/test/diff/operation/in.nix
+++ b/test/diff/operation/in.nix
@@ -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
+  )
 ]
diff --git a/test/diff/operation/out.nix b/test/diff/operation/out.nix
index f094d0d2..f032b244 100644
--- a/test/diff/operation/out.nix
+++ b/test/diff/operation/out.nix
@@ -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
+  )
 ]