Virtualize the cwd in GHCi

This fixes the issue where :list would stop working if the
program being debugged side-effected the working directory,
and should prevent other similar issues

diff --git a/compiler/ghci/GhciMonad.hs b/compiler/ghci/GhciMonad.hs
index e56c4de..dc16f25 100644 (file)
--- a/compiler/ghci/GhciMonad.hs
+++ b/compiler/ghci/GhciMonad.hs
@@ -39,6 +39,8 @@ import Data.IORef
 import Data.List
 import Data.Typeable
 import System.CPUTime
+import System.Directory
+import System.Environment
 import System.IO
 import Control.Monad as Monad
 import GHC.Exts
@@ -68,13 +70,14 @@ data GHCiState = GHCiState
         -- remember is here:
         last_command   :: Maybe Command,
         cmdqueue       :: [String],
-        remembered_ctx :: [(CtxtCmd, [String], [String])]
+        remembered_ctx :: [(CtxtCmd, [String], [String])],
              -- we remember the :module commands between :loads, so that
              -- on a :reload we can replay them.  See bugs #2049,
              -- #1873, #1360. Previously we tried to remember modules that
              -- were supposed to be in the context but currently had errors,
              -- but this was complicated.  Just replaying the :module commands
              -- seems to be the right thing.
+        virtual_path   :: FilePath
      }
 
 data CtxtCmd
@@ -193,6 +196,30 @@ printForUserPartWay doc = do
   unqual <- io (GHC.getPrintUnqual session)
   io $ Outputable.printForUserPartWay stdout opt_PprUserLength unqual doc
 
+withVirtualPath :: GHCi a -> GHCi a
+withVirtualPath m = do
+  ghci_wd <- io getCurrentDirectory                -- Store the cwd of GHCi
+  st  <- getGHCiState
+  io$ setCurrentDirectory (virtual_path st)
+  result <- m                                  -- Evaluate in the virtual wd..
+  vwd <- io getCurrentDirectory
+  setGHCiState (st{ virtual_path = vwd})       -- Update the virtual path
+  io$ setCurrentDirectory ghci_wd                  -- ..and restore GHCi wd
+  return result
+
+runStmt :: String -> GHC.SingleStep -> GHCi GHC.RunResult
+runStmt expr step = withVirtualPath$ do
+  session <- getSession
+  st      <- getGHCiState
+  io$ withProgName (progname st) $ withArgs (args st) $
+                    GHC.runStmt session expr step
+
+resume :: GHC.SingleStep -> GHCi GHC.RunResult
+resume step = withVirtualPath$ do
+  session <- getSession
+  io$ GHC.resume session step
+
+
 -- --------------------------------------------------------------------------
 -- timing & statistics
 

diff --git a/compiler/ghci/InteractiveUI.hs b/compiler/ghci/InteractiveUI.hs
index 598341a..c0d9405 100644 (file)
--- a/compiler/ghci/InteractiveUI.hs
+++ b/compiler/ghci/InteractiveUI.hs
@@ -11,12 +11,13 @@ module InteractiveUI ( interactiveUI, ghciWelcomeMsg ) where
 
 #include "HsVersions.h"
 
-import GhciMonad
+import qualified GhciMonad
+import GhciMonad hiding (runStmt)
 import GhciTags
 import Debugger
 
 -- The GHC interface
-import qualified GHC
+import qualified GHC hiding (resume, runStmt)
 import GHC              ( Session, LoadHowMuch(..), Target(..),  TargetId(..),
                           Module, ModuleName, TyThing(..), Phase,
                           BreakIndex, SrcSpan, Resume, SingleStep )
@@ -335,6 +336,8 @@ interactiveUI session srcs maybe_exprs = do
 
    default_editor <- findEditor
 
+   cwd <- getCurrentDirectory
+
    startGHCi (runGHCi srcs maybe_exprs)
         GHCiState{ progname = "<interactive>",
                    args = [],
@@ -349,7 +352,8 @@ interactiveUI session srcs maybe_exprs = do
                    tickarrays = emptyModuleEnv,
                    last_command = Nothing,
                    cmdqueue = [],
-                   remembered_ctx = []
+                   remembered_ctx = [],
+                   virtual_path   = cwd
                  }
 
 #ifdef USE_EDITLINE
@@ -685,13 +689,9 @@ runStmt stmt step
  | null (filter (not.isSpace) stmt) = return False
  | ["import", mod] <- words stmt    = keepGoing setContext ('+':mod)
  | otherwise
- = do st <- getGHCiState
-      session <- getSession
-      result <- io $ withProgName (progname st) $ withArgs (args st) $
-                    GHC.runStmt session stmt step
+ = do result <- GhciMonad.runStmt stmt step
       afterRunStmt (const True) result
 
-
 --afterRunStmt :: GHC.RunResult -> GHCi Bool
                                  -- False <=> the statement failed to compile
 afterRunStmt :: (SrcSpan -> Bool) -> GHC.RunResult -> GHCi Bool
@@ -719,7 +719,7 @@ afterRunStmt step_here run_result = do
                st <- getGHCiState
                enqueueCommands [stop st]
                return ()
-         | otherwise -> io(GHC.resume session GHC.SingleStep) >>= 
+         | otherwise -> resume GHC.SingleStep >>=
                         afterRunStmt step_here >> return ()
      _ -> return ()
 
@@ -1946,8 +1946,7 @@ continueCmd = noArgs $ doContinue (const True) GHC.RunToCompletion
 -- doContinue :: SingleStep -> GHCi ()
 doContinue :: (SrcSpan -> Bool) -> SingleStep -> GHCi ()
 doContinue pred step = do 
-  session <- getSession
-  runResult <- io $ GHC.resume session step
+  runResult <- resume step
   afterRunStmt pred runResult
   return ()