Separated tracing from logging.

Formerly tracing was just log messages with a DEBUG log
level.  We now make these things independent.  Tracing
can be turned on or off in PandocMonad using `setTrace`;
it is independent of logging.

* Removed `DEBUG` from `Verbosity`.
* Removed `ParserTrace` from `LogMessage`.
* Added `trace`, `setTrace` to `PandocMonad`.

6 files changed, 12 insertions, 21 deletions

diff --git a/src/Text/Pandoc/Readers/HTML.hs b/src/Text/Pandoc/Readers/HTML.hs
index 94f933c4d..e203298b8 100644
--- a/src/Text/Pandoc/Readers/HTML.hs
+++ b/src/Text/Pandoc/Readers/HTML.hs
@@ -71,7 +71,7 @@ import Data.Monoid ((<>))
 import Text.Parsec.Error
 import qualified Data.Set as Set
 import Text.Pandoc.Error
-import Text.Pandoc.Class (PandocMonad, report)
+import Text.Pandoc.Class (PandocMonad(..))
 import Control.Monad.Except (throwError)
 
 -- | Convert HTML-formatted string to 'Pandoc' document.
@@ -162,7 +162,6 @@ pHead = pInTags "head" $ pTitle <|> pMetaTag <|> pBaseTag <|> (mempty <$ pAnyTag
 
 block :: PandocMonad m => TagParser m Blocks
 block = do
-  pos <- getPosition
   res <- choice
             [ eSection
             , eSwitch B.para block
@@ -182,7 +181,7 @@ block = do
             , pPlain
             , pRawHtmlBlock
             ]
-  report $ ParsingTrace (take 60 $ show $ B.toList res) pos
+  trace (take 60 $ show $ B.toList res)
   return res
 
 namespaces :: PandocMonad m => [(String, TagParser m Inlines)]
diff --git a/src/Text/Pandoc/Readers/Markdown.hs b/src/Text/Pandoc/Readers/Markdown.hs
index e1c481311..edb356b39 100644
--- a/src/Text/Pandoc/Readers/Markdown.hs
+++ b/src/Text/Pandoc/Readers/Markdown.hs
@@ -52,7 +52,7 @@ import System.FilePath (addExtension, takeExtension)
 import Text.HTML.TagSoup
 import Text.Pandoc.Builder (Blocks, Inlines)
 import qualified Text.Pandoc.Builder as B
-import Text.Pandoc.Class (PandocMonad, report)
+import Text.Pandoc.Class (PandocMonad(..), report)
 import Text.Pandoc.Definition
 import Text.Pandoc.Emoji (emojis)
 import Text.Pandoc.Logging
@@ -488,7 +488,6 @@ parseBlocks = mconcat <$> manyTill block eof
 
 block :: PandocMonad m => MarkdownParser m (F Blocks)
 block = do
-  pos <- getPosition
   res <- choice [ mempty <$ blanklines
                , codeBlockFenced
                , yamlMetaBlock
@@ -514,8 +513,7 @@ block = do
                , para
                , plain
                ] <?> "block"
-  report $ ParsingTrace
-    (take 60 $ show $ B.toList $ runF res defaultParserState) pos
+  trace (take 60 $ show $ B.toList $ runF res defaultParserState)
   return res
 
 --
diff --git a/src/Text/Pandoc/Readers/MediaWiki.hs b/src/Text/Pandoc/Readers/MediaWiki.hs
index a3ff60c14..e371ff152 100644
--- a/src/Text/Pandoc/Readers/MediaWiki.hs
+++ b/src/Text/Pandoc/Readers/MediaWiki.hs
@@ -52,7 +52,7 @@ import qualified Data.Set as Set
 import Text.HTML.TagSoup
 import Text.Pandoc.Builder (Blocks, Inlines, trimInlines)
 import qualified Text.Pandoc.Builder as B
-import Text.Pandoc.Class (PandocMonad, report)
+import Text.Pandoc.Class (PandocMonad(..))
 import Text.Pandoc.Definition
 import Text.Pandoc.Logging
 import Text.Pandoc.Options
@@ -205,7 +205,6 @@ parseMediaWiki = do
 
 block :: PandocMonad m => MWParser m Blocks
 block = do
-  pos <- getPosition
   res <- mempty <$ skipMany1 blankline
      <|> table
      <|> header
@@ -218,7 +217,7 @@ block = do
      <|> blockTag
      <|> (B.rawBlock "mediawiki" <$> template)
      <|> para
-  report $ ParsingTrace (take 60 $ show $ B.toList res) pos
+  trace (take 60 $ show $ B.toList res)
   return res
 
 para :: PandocMonad m => MWParser m Blocks
diff --git a/src/Text/Pandoc/Readers/Muse.hs b/src/Text/Pandoc/Readers/Muse.hs
index c1ea1354b..ac19a2382 100644
--- a/src/Text/Pandoc/Readers/Muse.hs
+++ b/src/Text/Pandoc/Readers/Muse.hs
@@ -53,7 +53,7 @@ import Data.Maybe (fromMaybe)
 import Text.HTML.TagSoup
 import Text.Pandoc.Builder (Blocks, Inlines)
 import qualified Text.Pandoc.Builder as B
-import Text.Pandoc.Class (PandocMonad, report)
+import Text.Pandoc.Class (PandocMonad(..))
 import Text.Pandoc.Definition
 import Text.Pandoc.Logging
 import Text.Pandoc.Options
@@ -166,12 +166,11 @@ directive = do
 
 block :: PandocMonad m => MuseParser m (F Blocks)
 block = do
-  pos <- getPosition
   res <- mempty <$ skipMany1 blankline
          <|> blockElements
          <|> para
   skipMany blankline
-  report $ ParsingTrace (take 60 $ show $ B.toList $ runF res defaultParserState) pos
+  trace (take 60 $ show $ B.toList $ runF res defaultParserState)
   return res
 
 blockElements :: PandocMonad m => MuseParser m (F Blocks)
diff --git a/src/Text/Pandoc/Readers/TWiki.hs b/src/Text/Pandoc/Readers/TWiki.hs
index 9e544c4ac..91ee8d1f1 100644
--- a/src/Text/Pandoc/Readers/TWiki.hs
+++ b/src/Text/Pandoc/Readers/TWiki.hs
@@ -42,9 +42,8 @@ import qualified Data.Foldable as F
 import Data.Maybe (fromMaybe)
 import Text.HTML.TagSoup
 import qualified Text.Pandoc.Builder as B
-import Text.Pandoc.Class (PandocMonad, report)
+import Text.Pandoc.Class (PandocMonad(..))
 import Text.Pandoc.Definition
-import Text.Pandoc.Logging
 import Text.Pandoc.Options
 import Text.Pandoc.Parsing hiding (enclosed, macro, nested)
 import Text.Pandoc.Readers.HTML (htmlTag, isCommentTag)
@@ -133,12 +132,11 @@ parseTWiki = do
 
 block :: PandocMonad m => TWParser m B.Blocks
 block = do
-  pos <- getPosition
   res <- mempty <$ skipMany1 blankline
          <|> blockElements
          <|> para
   skipMany blankline
-  report $ ParsingTrace (take 60 $ show $ B.toList res) pos
+  trace (take 60 $ show $ B.toList res)
   return res
 
 blockElements :: PandocMonad m => TWParser m B.Blocks
diff --git a/src/Text/Pandoc/Readers/Textile.hs b/src/Text/Pandoc/Readers/Textile.hs
index 1669e3e51..96b51feef 100644
--- a/src/Text/Pandoc/Readers/Textile.hs
+++ b/src/Text/Pandoc/Readers/Textile.hs
@@ -61,10 +61,9 @@ import Text.HTML.TagSoup (Tag (..), fromAttrib)
 import Text.HTML.TagSoup.Match
 import Text.Pandoc.Builder (Blocks, Inlines, trimInlines)
 import qualified Text.Pandoc.Builder as B
-import Text.Pandoc.Class (PandocMonad, report)
+import Text.Pandoc.Class (PandocMonad(..))
 import Text.Pandoc.CSS
 import Text.Pandoc.Definition
-import Text.Pandoc.Logging
 import Text.Pandoc.Options
 import Text.Pandoc.Parsing
 import Text.Pandoc.Readers.HTML (htmlTag, isBlockTag, isInlineTag)
@@ -143,8 +142,7 @@ blockParsers = [ codeBlock
 block :: PandocMonad m => ParserT [Char] ParserState m Blocks
 block = do
   res <- choice blockParsers <?> "block"
-  pos <- getPosition
-  report $ ParsingTrace (take 60 $ show $ B.toList res) pos
+  trace (take 60 $ show $ B.toList res)
   return res
 
 commentBlock :: PandocMonad m => ParserT [Char] ParserState m Blocks