Add support for unparenthesized arrow functions of one parameter

src/Language/JavaScript/Parser/AST.hs

@@ -22,6 +22,7 @@ module Language.JavaScript.Parser.AST
     , JSArrayElement (..)
     , JSCommaList (..)
     , JSCommaTrailingList (..)
+    , JSArrowParameterList (..)
 
     -- Modules
     , JSModuleItem (..)
@@ -170,7 +171,7 @@ data JSExpression
     | JSExpressionParen !JSAnnot !JSExpression !JSAnnot -- ^lb,expression,rb
     | JSExpressionPostfix !JSExpression !JSUnaryOp -- ^expression, operator
     | JSExpressionTernary !JSExpression !JSAnnot !JSExpression !JSAnnot !JSExpression -- ^cond, ?, trueval, :, falseval
-    | JSArrowExpression !JSAnnot !(JSCommaList JSIdent) !JSAnnot !JSAnnot !JSStatement -- ^parameter list,arrow,block`
+    | JSArrowExpression !JSArrowParameterList !JSAnnot !JSStatement -- ^parameter list,arrow,block`
     | JSFunctionExpression !JSAnnot !JSIdent !JSAnnot !(JSCommaList JSIdent) !JSAnnot !JSBlock -- ^fn,name,lb, parameter list,rb,block`
     | JSMemberDot !JSExpression !JSAnnot !JSExpression -- ^firstpart, dot, name
     | JSMemberExpression !JSExpression !JSAnnot !(JSCommaList JSExpression) !JSAnnot -- expr, lb, args, rb
@@ -183,6 +184,11 @@ data JSExpression
     | JSVarInitExpression !JSExpression !JSVarInitializer -- ^identifier, initializer
     deriving (Data, Eq, Show, Typeable)
 
+data JSArrowParameterList
+    = JSUnparenthesizedArrowParameter !JSIdent
+    | JSParenthesizedArrowParameterList !JSAnnot !(JSCommaList JSIdent) !JSAnnot
+    deriving (Data, Eq, Show, Typeable)
+
 data JSBinOp
     = JSBinOpAnd !JSAnnot
     | JSBinOpAs !JSAnnot
@@ -369,7 +375,7 @@ instance ShowStripped JSExpression where
     ss (JSExpressionParen _lp x _rp) = "JSExpressionParen (" ++ ss x ++ ")"
     ss (JSExpressionPostfix xs op) = "JSExpressionPostfix (" ++ ss op ++ "," ++ ss xs ++ ")"
     ss (JSExpressionTernary x1 _q x2 _c x3) = "JSExpressionTernary (" ++ ss x1 ++ "," ++ ss x2 ++ "," ++ ss x3 ++ ")"
-    ss (JSArrowExpression _ n _ _ e) = "JSArrowExpression (" ++ ss n ++ ") => " ++ ss e
+    ss (JSArrowExpression ps _ e) = "JSArrowExpression (" ++ ss ps ++ ") => " ++ ss e
     ss (JSFunctionExpression _ n _lb pl _rb x3) = "JSFunctionExpression " ++ ssid n ++ " " ++ ss pl ++ " (" ++ ss x3 ++ "))"
     ss (JSHexInteger _ s) = "JSHexInteger " ++ singleQuote s
     ss (JSOctal _ s) = "JSOctal " ++ singleQuote s
@@ -388,6 +394,10 @@ instance ShowStripped JSExpression where
     ss (JSVarInitExpression x1 x2) = "JSVarInitExpression (" ++ ss x1 ++ ") " ++ ss x2
     ss (JSSpreadExpression _ x1) = "JSSpreadExpression (" ++ ss x1 ++ ")"
 
+instance ShowStripped JSArrowParameterList where
+    ss (JSUnparenthesizedArrowParameter x) = ss x
+    ss (JSParenthesizedArrowParameterList _ xs _) = ss xs
+
 instance ShowStripped JSModuleItem where
     ss (JSModuleExportDeclaration _ x1) = "JSModuleExportDeclaration (" ++ ss x1 ++ ")"
     ss (JSModuleImportDeclaration _ x1) = "JSModuleImportDeclaration (" ++ ss x1 ++ ")"

src/Language/JavaScript/Parser/Grammar7.y

@@ -1136,10 +1136,16 @@ FunctionExpression : ArrowFunctionExpression     { $1 {- 'ArrowFunctionExpressio
                    | NamedFunctionExpression     { $1 {- 'FunctionExpression2' -} }
 
 ArrowFunctionExpression :: { AST.JSExpression }
-ArrowFunctionExpression : LParen RParen Arrow StatementOrBlock
-                           { AST.JSArrowExpression $1 AST.JSLNil $2 $3 $4		{- 'ArrowFunctionExpression1' -} }
-                        | LParen FormalParameterList RParen Arrow StatementOrBlock
-                           { AST.JSArrowExpression $1 $2 $3 $4 $5               {- 'ArrowFunctionExpression3' -} }
+ArrowFunctionExpression : ArrowParameterList Arrow StatementOrBlock
+                           { AST.JSArrowExpression $1 $2 $3 }
+
+ArrowParameterList :: { AST.JSArrowParameterList }
+ArrowParameterList : Identifier
+                      { AST.JSUnparenthesizedArrowParameter (identName $1)     }
+                   | LParen RParen
+                      { AST.JSParenthesizedArrowParameterList $1 AST.JSLNil $2 }
+                   | LParen FormalParameterList RParen
+                      { AST.JSParenthesizedArrowParameterList $1 $2 $3         }
 
 StatementOrBlock :: { AST.JSStatement }
 StatementOrBlock : Block MaybeSemi		{ blockToStatement $1 $2 }

src/Language/JavaScript/Pretty/Printer.hs

@@ -72,7 +72,7 @@ instance RenderJS JSExpression where
 
     -- Non-Terminals
     (|>) pacc (JSArrayLiteral         als xs ars)             = pacc |> als |> "[" |> xs |> ars |> "]"
-    (|>) pacc (JSArrowExpression      lp xs rp a x)           = pacc |> lp |> "(" |> xs |> rp |> ")" |> a |> "=>" |> x
+    (|>) pacc (JSArrowExpression      xs a x)                 = pacc |> xs |> a |> "=>" |> x
     (|>) pacc (JSAssignExpression     lhs op rhs)             = pacc |> lhs |> op |> rhs
     (|>) pacc (JSCallExpression       ex lb xs rb)            = pacc |> ex |> lb |> "(" |> xs |> rb |> ")"
     (|>) pacc (JSCallExpressionDot    ex os xs)               = pacc |> ex |> os |> "." |> xs
@@ -93,6 +93,9 @@ instance RenderJS JSExpression where
     (|>) pacc (JSVarInitExpression    x1 x2)                  = pacc |> x1 |> x2
     (|>) pacc (JSSpreadExpression     a e)                    = pacc |> a |> "..." |> e
 
+instance RenderJS JSArrowParameterList where
+    (|>) pacc (JSUnparenthesizedArrowParameter p)             = pacc |> p
+    (|>) pacc (JSParenthesizedArrowParameterList lb ps rb)    = pacc |> lb |> "(" |> ps |> ")" |> rb
 -- -----------------------------------------------------------------------------
 -- Need an instance of RenderJS for every component of every JSExpression or JSAnnot
 -- constuctor.

src/Language/JavaScript/Process/Minify.hs

@@ -148,7 +148,7 @@ instance MinifyJS JSExpression where
 
     -- Non-Terminals
     fix _ (JSArrayLiteral         _ xs _)             = JSArrayLiteral emptyAnnot (map fixEmpty xs) emptyAnnot
-    fix _ (JSArrowExpression _ ps _ _ ss)             = JSArrowExpression emptyAnnot (fixEmpty ps) emptyAnnot emptyAnnot (fixStmt emptyAnnot noSemi ss)
+    fix a (JSArrowExpression ps _ ss)                 = JSArrowExpression (fix a ps) emptyAnnot (fixStmt emptyAnnot noSemi ss)
     fix a (JSAssignExpression     lhs op rhs)         = JSAssignExpression (fix a lhs) (fixEmpty op) (fixEmpty rhs)
     fix a (JSCallExpression       ex _ xs _)          = JSCallExpression (fix a ex) emptyAnnot (fixEmpty xs) emptyAnnot
     fix a (JSCallExpressionDot    ex _ xs)            = JSCallExpressionDot (fix a ex) emptyAnnot (fixEmpty xs)
@@ -169,6 +169,9 @@ instance MinifyJS JSExpression where
     fix a (JSVarInitExpression    x1 x2)              = JSVarInitExpression (fix a x1) (fixEmpty x2)
     fix a (JSSpreadExpression     _ e)                = JSSpreadExpression a (fixEmpty e)
 
+instance MinifyJS JSArrowParameterList where
+    fix _ (JSUnparenthesizedArrowParameter p)         = JSUnparenthesizedArrowParameter (fixEmpty p)
+    fix _ (JSParenthesizedArrowParameterList _ ps _)  = JSParenthesizedArrowParameterList emptyAnnot (fixEmpty ps) emptyAnnot
 
 fixVarList :: JSCommaList JSExpression -> JSCommaList JSExpression
 fixVarList (JSLCons h _ v) = JSLCons (fixVarList h) emptyAnnot (fixEmpty v)
@@ -302,7 +305,7 @@ instance MinifyJS JSImportNameSpace where
     fix a (JSImportNameSpace _ _ ident) = JSImportNameSpace (JSBinOpTimes a) (JSBinOpAs spaceAnnot) (fixSpace ident)
 
 instance MinifyJS JSImportsNamed where
-    fix _ (JSImportsNamed _ imps _) = JSImportsNamed emptyAnnot (fixEmpty imps) emptyAnnot 
+    fix _ (JSImportsNamed _ imps _) = JSImportsNamed emptyAnnot (fixEmpty imps) emptyAnnot
 
 instance MinifyJS JSImportSpecifier where
     fix _ (JSImportSpecifier x1) = JSImportSpecifier (fixEmpty x1)

test/Test/Language/Javascript/ExpressionParser.hs

@@ -123,6 +123,7 @@ testExpressionParser = describe "Parse expressions:" $ do
         testExpr "function(){}"     `shouldBe` "Right (JSAstExpression (JSFunctionExpression '' () (JSBlock []))))"
         testExpr "function(a){}"    `shouldBe` "Right (JSAstExpression (JSFunctionExpression '' (JSIdentifier 'a') (JSBlock []))))"
         testExpr "function(a,b){}"  `shouldBe` "Right (JSAstExpression (JSFunctionExpression '' (JSIdentifier 'a',JSIdentifier 'b') (JSBlock []))))"
+        testExpr "a => {}"          `shouldBe` "Right (JSAstExpression (JSArrowExpression (JSIdentifier 'a') => JSStatementBlock []))"
         testExpr "(a) => { a + 2 }" `shouldBe` "Right (JSAstExpression (JSArrowExpression ((JSIdentifier 'a')) => JSStatementBlock [JSExpressionBinary ('+',JSIdentifier 'a',JSDecimal '2')]))"
         testExpr "(a, b) => {}"     `shouldBe` "Right (JSAstExpression (JSArrowExpression ((JSIdentifier 'a',JSIdentifier 'b')) => JSStatementBlock []))"
         testExpr "(a, b) => a + b"  `shouldBe` "Right (JSAstExpression (JSArrowExpression ((JSIdentifier 'a',JSIdentifier 'b')) => JSExpressionBinary ('+',JSIdentifier 'a',JSIdentifier 'b')))"

test/Test/Language/Javascript/Minify.hs

@@ -106,6 +106,7 @@ testMinifyExpr = describe "Minify expressions:" $ do
         minifyExpr " function ( a ) { } " `shouldBe` "function(a){}"
         minifyExpr " function ( a , b ) { return a + b ; } " `shouldBe` "function(a,b){return a+b}"
 
+        minifyExpr "a => {}" `shouldBe` "a=>{}"
         minifyExpr "(a) => {}" `shouldBe` "(a)=>{}"
         minifyExpr "( a ) => { a + 2 }" `shouldBe` "(a)=>a+2"
         minifyExpr "(a, b) => a + b" `shouldBe` "(a,b)=>a+b"

test/Test/Language/Javascript/RoundTrip.hs

@@ -63,6 +63,7 @@ testRoundTrip = describe "Roundtrip:" $ do
         testRT "/*a*/x/*b*/=/*c*/{/*d*/get/*e*/ foo/*f*/(/*g*/)/*h*/ {/*i*/return/*j*/ 1/*k*/}/*l*/,/*m*/set/*n*/ foo/*o*/(/*p*/a/*q*/) /*r*/{/*s*/x/*t*/=/*u*/a/*v*/}/*w*/}"
         testRT "... /*a*/ x"
 
+        testRT "a => {}"
         testRT "(a) => { a + 2 }"
         testRT "(a, b) => {}"
         testRT "(a, b) => a + b"