From 8412e63213a0e071ade79b74b007d9f0e544513c Mon Sep 17 00:00:00 2001
From: James Brock <jamesbrock@gmail.com>
Date: Wed, 7 Oct 2020 02:00:01 +0900
Subject: [PATCH 1/2] Parsing failure context region (#97)

---
 src/Text/Parsing/Parser.purs | 13 +++++++------
 test/Main.purs               |  9 +++++----
 2 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/src/Text/Parsing/Parser.purs b/src/Text/Parsing/Parser.purs
index 013df83..32be296 100644
--- a/src/Text/Parsing/Parser.purs
+++ b/src/Text/Parsing/Parser.purs
@@ -13,7 +13,7 @@ module Text.Parsing.Parser
   , position
   , fail
   , failWithPosition
-  , label
+  , region
   ) where
 
 import Prelude
@@ -138,8 +138,9 @@ fail message = failWithPosition message =<< position
 failWithPosition :: forall m s a. Monad m => String -> Position -> ParserT s m a
 failWithPosition message pos = throwError (ParseError message pos)
 
--- | If parsing fails inside this labelled context, then prepend the `String`
--- | to the error `String` in the `ParseError`.
-label :: forall m s a. Monad m => String -> ParserT s m a -> ParserT s m a
-label messagePrefix p = catchError p $ \ (ParseError message pos) ->
-  throwError $ ParseError (messagePrefix <> message) pos
+-- | Contextualize parsing failures inside a region. If a parsing failure
+-- | occurs, then the `ParseError` will be transformed by each containing
+-- | `region` as the parser backs out the call stack.
+region :: forall m s a. Monad m => (ParseError -> ParseError) -> ParserT s m a -> ParserT s m a
+region context p = catchError p $ \err -> throwError $ context err
+
diff --git a/test/Main.purs b/test/Main.purs
index 21c0dd5..b2466a0 100644
--- a/test/Main.purs
+++ b/test/Main.purs
@@ -13,7 +13,7 @@ import Data.Tuple (Tuple(..))
 import Effect (Effect)
 import Effect.Console (logShow)
 import Test.Assert (assert')
-import Text.Parsing.Parser (Parser, ParserT, ParseError(..), runParser, parseErrorPosition, label)
+import Text.Parsing.Parser (Parser, ParserT, ParseError(..), runParser, parseErrorPosition, region)
 import Text.Parsing.Parser.Combinators (endBy1, sepBy1, optionMaybe, try, chainl, between)
 import Text.Parsing.Parser.Expr (Assoc(..), Operator(..), buildExprParser)
 import Text.Parsing.Parser.Language (javaStyle, haskellStyle, haskellDef)
@@ -500,11 +500,12 @@ main = do
   case runParser "aa" p of
     Right _ -> assert' "error: ParseError expected!" false
     Left (ParseError message pos) -> do
-      let messageExpected = "context1context2Expected \"b\""
+      let messageExpected = "context1 context2 Expected \"b\""
       assert' ("expected message: " <> messageExpected <> ", message: " <> message) (message == messageExpected)
       logShow messageExpected
    where
-    p = label "context1" $ do
+    prependContext m' (ParseError m pos) = ParseError (m' <> m) pos
+    p = region (prependContext "context1 ") $ do
           _ <- string "a"
-          label "context2" $ do
+          region (prependContext "context2 ") $ do
             string "b"

From 96ab4779abb6bdd35f9e6104a3b24504a08e2df4 Mon Sep 17 00:00:00 2001
From: David Smith <shmish111+github@gmail.com>
Date: Fri, 31 Jan 2020 17:44:44 +0100
Subject: [PATCH 2/2] derive generic instance of Position

---
 bower.json                       |  3 ++-
 spago.dhall                      |  1 +
 src/Text/Parsing/Parser.purs     | 13 ++++++-------
 src/Text/Parsing/Parser/Pos.purs |  3 +++
 test/Main.purs                   |  9 ++++-----
 5 files changed, 16 insertions(+), 13 deletions(-)

diff --git a/bower.json b/bower.json
index 3e0f3bb..f89a733 100644
--- a/bower.json
+++ b/bower.json
@@ -29,7 +29,8 @@
     "purescript-maybe": "^4.0.0",
     "purescript-strings": "^4.0.0",
     "purescript-transformers": "^4.1.0",
-    "purescript-unicode": "^4.0.0"
+    "purescript-unicode": "^4.0.0",
+    "purescript-generics-rep": "^6.1.1"
   },
   "devDependencies": {
     "purescript-assert": "^4.0.0",
diff --git a/spago.dhall b/spago.dhall
index b40582a..fabd3c7 100644
--- a/spago.dhall
+++ b/spago.dhall
@@ -3,6 +3,7 @@
   [ "arrays"
   , "assert"
   , "console"
+  , "generics-rep"
   , "effect"
   , "either"
   , "foldable-traversable"
diff --git a/src/Text/Parsing/Parser.purs b/src/Text/Parsing/Parser.purs
index 32be296..013df83 100644
--- a/src/Text/Parsing/Parser.purs
+++ b/src/Text/Parsing/Parser.purs
@@ -13,7 +13,7 @@ module Text.Parsing.Parser
   , position
   , fail
   , failWithPosition
-  , region
+  , label
   ) where
 
 import Prelude
@@ -138,9 +138,8 @@ fail message = failWithPosition message =<< position
 failWithPosition :: forall m s a. Monad m => String -> Position -> ParserT s m a
 failWithPosition message pos = throwError (ParseError message pos)
 
--- | Contextualize parsing failures inside a region. If a parsing failure
--- | occurs, then the `ParseError` will be transformed by each containing
--- | `region` as the parser backs out the call stack.
-region :: forall m s a. Monad m => (ParseError -> ParseError) -> ParserT s m a -> ParserT s m a
-region context p = catchError p $ \err -> throwError $ context err
-
+-- | If parsing fails inside this labelled context, then prepend the `String`
+-- | to the error `String` in the `ParseError`.
+label :: forall m s a. Monad m => String -> ParserT s m a -> ParserT s m a
+label messagePrefix p = catchError p $ \ (ParseError message pos) ->
+  throwError $ ParseError (messagePrefix <> message) pos
diff --git a/src/Text/Parsing/Parser/Pos.purs b/src/Text/Parsing/Parser/Pos.purs
index e65c6f2..6a20dff 100644
--- a/src/Text/Parsing/Parser/Pos.purs
+++ b/src/Text/Parsing/Parser/Pos.purs
@@ -1,6 +1,7 @@
 module Text.Parsing.Parser.Pos where
 
 import Prelude
+import Data.Generic.Rep (class Generic)
 import Data.Foldable (foldl)
 import Data.Newtype (wrap)
 import Data.String (split)
@@ -14,6 +15,8 @@ newtype Position = Position
   , column :: Int
   }
 
+derive instance genericPosition :: Generic Position _
+
 instance showPosition :: Show Position where
   show (Position { line: line, column: column }) =
     "(Position { line: " <> show line <> ", column: " <> show column <> " })"
diff --git a/test/Main.purs b/test/Main.purs
index b2466a0..21c0dd5 100644
--- a/test/Main.purs
+++ b/test/Main.purs
@@ -13,7 +13,7 @@ import Data.Tuple (Tuple(..))
 import Effect (Effect)
 import Effect.Console (logShow)
 import Test.Assert (assert')
-import Text.Parsing.Parser (Parser, ParserT, ParseError(..), runParser, parseErrorPosition, region)
+import Text.Parsing.Parser (Parser, ParserT, ParseError(..), runParser, parseErrorPosition, label)
 import Text.Parsing.Parser.Combinators (endBy1, sepBy1, optionMaybe, try, chainl, between)
 import Text.Parsing.Parser.Expr (Assoc(..), Operator(..), buildExprParser)
 import Text.Parsing.Parser.Language (javaStyle, haskellStyle, haskellDef)
@@ -500,12 +500,11 @@ main = do
   case runParser "aa" p of
     Right _ -> assert' "error: ParseError expected!" false
     Left (ParseError message pos) -> do
-      let messageExpected = "context1 context2 Expected \"b\""
+      let messageExpected = "context1context2Expected \"b\""
       assert' ("expected message: " <> messageExpected <> ", message: " <> message) (message == messageExpected)
       logShow messageExpected
    where
-    prependContext m' (ParseError m pos) = ParseError (m' <> m) pos
-    p = region (prependContext "context1 ") $ do
+    p = label "context1" $ do
           _ <- string "a"
-          region (prependContext "context2 ") $ do
+          label "context2" $ do
             string "b"