Class: Add stResourcePath to CommonState, getResourcePath, setResourcePath.

To be used in implementing `\graphicspath` in LaTeX, and possibly
in things like PDF production via context.

Use resource path in fetchItem.

Issue an info message if we get a resource from somewhere other
than ".".

Added UsingResourceFrom to log message.

src/Text/Pandoc/Class.hs

@@ -1,5 +1,6 @@
 {-# LANGUAGE DeriveFunctor, DeriveDataTypeable, TypeSynonymInstances,
-FlexibleInstances, GeneralizedNewtypeDeriving, FlexibleContexts #-}
+FlexibleInstances, GeneralizedNewtypeDeriving, FlexibleContexts,
+StandaloneDeriving #-}
 
 {-
 Copyright (C) 2016 Jesse Rosenthal <jrosenthal@jhu.edu>
@@ -50,6 +51,8 @@ module Text.Pandoc.Class ( PandocMonad(..)
                          , fetchItem
                          , getInputFiles
                          , getOutputFile
+                         , setResourcePath
+                         , getResourcePath
                          , PandocIO(..)
                          , PandocPure(..)
                          , FileTree(..)
@@ -88,7 +91,7 @@ import qualified Data.ByteString as B
 import qualified Data.ByteString.Lazy as BL
 import qualified System.Environment as IO (lookupEnv)
 import System.FilePath.Glob (match, compile)
-import System.FilePath ((</>), takeExtension, dropExtension)
+import System.FilePath ((</>), takeExtension, dropExtension, isRelative)
 import qualified System.FilePath.Glob as IO (glob)
 import qualified System.Directory as IO (getModificationTime)
 import Control.Monad as M (fail)
@@ -165,6 +168,12 @@ getInputFiles = getsCommonState stInputFiles
 getOutputFile :: PandocMonad m => m (Maybe FilePath)
 getOutputFile = getsCommonState stOutputFile
 
+setResourcePath :: PandocMonad m => [FilePath] -> m ()
+setResourcePath ps = modifyCommonState $ \st -> st{stResourcePath = ps}
+
+getResourcePath :: PandocMonad m => m [FilePath]
+getResourcePath = getsCommonState stResourcePath
+
 getPOSIXTime :: (PandocMonad m) => m POSIXTime
 getPOSIXTime = utcTimeToPOSIXSeconds <$> getCurrentTime
 
@@ -183,11 +192,12 @@ readFileFromDirs (d:ds) f = catchError
 
 --
 
-data CommonState = CommonState { stLog        :: [LogMessage]
-                               , stMediaBag   :: MediaBag
-                               , stInputFiles :: Maybe [FilePath]
-                               , stOutputFile :: Maybe FilePath
-                               , stVerbosity  :: Verbosity
+data CommonState = CommonState { stLog          :: [LogMessage]
+                               , stMediaBag     :: MediaBag
+                               , stInputFiles   :: Maybe [FilePath]
+                               , stOutputFile   :: Maybe FilePath
+                               , stResourcePath :: [FilePath]
+                               , stVerbosity    :: Verbosity
                                }
 
 instance Default CommonState where
@@ -195,6 +205,7 @@ instance Default CommonState where
                     , stMediaBag = mempty
                     , stInputFiles = Nothing
                     , stOutputFile = Nothing
+                    , stResourcePath = ["."]
                     , stVerbosity = WARNING
                     }
 
@@ -289,7 +300,10 @@ downloadOrRead sourceURL s = do
                  readLocalFile $ dropWhile (=='/') (uriPath u')
             _ -> readLocalFile fp -- get from local file system
    where readLocalFile f = do
-             cont <- readFileStrict f
+             resourcePath <- getResourcePath
+             cont <- if isRelative f
+                        then withPaths resourcePath readFileStrict f
+                        else readFileStrict f
              return (cont, mime)
          httpcolon = URI{ uriScheme = "http:",
                           uriAuthority = Nothing,
@@ -306,6 +320,16 @@ downloadOrRead sourceURL s = do
          convertSlash '\\' = '/'
          convertSlash x    = x
 
+withPaths :: PandocMonad m => [FilePath] -> (FilePath -> m a) -> FilePath -> m a
+withPaths [] _ fp = throwError $ PandocIOError fp
+                       (userError "file not found in resource path")
+withPaths (p:ps) action fp =
+  catchError (do res <- action (p </> fp)
+                 when (p /= ".") $
+                   report $ UsingResourceFrom fp p
+                 return res)
+             (\_ -> withPaths ps action fp)
+
 data PureState = PureState { stStdGen     :: StdGen
                            , stWord8Store :: [Word8] -- should be
                                                      -- inifinite,

src/Text/Pandoc/Logging.hs

@@ -74,6 +74,7 @@ data LogMessage =
   | CouldNotConvertTeXMath String String
   | CouldNotParseCSS String
   | Fetching String
+  | UsingResourceFrom FilePath FilePath
   deriving (Show, Eq, Data, Ord, Typeable, Generic)
 
 instance ToJSON LogMessage where
@@ -163,6 +164,10 @@ instance ToJSON LogMessage where
       Fetching fp ->
            ["type" .= String "CouldNotParseCSS",
             "path" .= Text.pack fp]
+      UsingResourceFrom resource dir ->
+           ["type" .= String "UsingResourceFrom",
+            "resource" .= Text.pack resource,
+            "path" .= Text.pack dir]
 
 showPos :: SourcePos -> String
 showPos pos = sn ++ "line " ++
@@ -220,6 +225,8 @@ showLogMessage msg =
          "Could not parse CSS" ++ if null m then "" else (':':'\n':m)
        Fetching fp ->
          "Fetching " ++ fp ++ "..."
+       UsingResourceFrom fp dir ->
+         "Using " ++ fp ++ " from " ++ dir
 
 messageVerbosity:: LogMessage -> Verbosity
 messageVerbosity msg =
@@ -242,3 +249,4 @@ messageVerbosity msg =
        CouldNotConvertTeXMath{} -> WARNING
        CouldNotParseCSS{} -> WARNING
        Fetching{} -> INFO
+       UsingResourceFrom{} -> INFO