GHCi debugger: added a new flag, -fno-print-binding-contents

The contents of bindings show at breakpoints and by :show bindings
is rendered using the same printer that :print uses.
But sometimes the output it gives spans over too many lines and the
user may want to be able to disable it.

compiler/ghci/InteractiveUI.hs

@@ -681,13 +681,18 @@ printTypeOfName session n
 
 printTypeAndContents :: Session -> [Id] -> GHCi ()
 printTypeAndContents session ids = do
-              terms <- mapM (io . GHC.obtainTermB session 10 False) ids
-              docs_terms <- mapM (io . showTerm session) terms                                   
-	      dflags <- getDynFlags
-	      let pefas = dopt Opt_PrintExplicitForalls dflags
-              printForUser $ vcat $ zipWith (\ty cts -> ty <+> equals <+> cts)
-                                            (map (pprTyThing pefas . AnId) ids)
-                                            docs_terms
+  dflags <- getDynFlags
+  let pefas     = dopt Opt_PrintExplicitForalls dflags
+      pcontents = dopt Opt_PrintBindContents dflags
+  if pcontents 
+    then do
+      let depthBound = 100
+      terms      <- mapM (io . GHC.obtainTermB session depthBound False) ids
+      docs_terms <- mapM (io . showTerm session) terms
+      printForUser $ vcat $ zipWith (\ty cts -> ty <+> equals <+> cts)
+                                    (map (pprTyThing pefas . AnId) ids)
+                                    docs_terms
+    else printForUser $ vcat $ map (pprTyThing pefas . AnId) ids
 
 
 specialCommand :: String -> GHCi Bool

compiler/main/DynFlags.hs

@@ -272,6 +272,7 @@ data DynFlag
    | Opt_BreakOnException
    | Opt_BreakOnError
    | Opt_PrintEvldWithShow
+   | Opt_PrintBindContents
    | Opt_GenManifest
    | Opt_EmbedManifest
    | Opt_RunCPSZ
@@ -536,7 +537,8 @@ defaultDynFlags =
             Opt_DoAsmMangling,
 
             Opt_GenManifest,
-            Opt_EmbedManifest
+            Opt_EmbedManifest,
+            Opt_PrintBindContents
             ]
             ++ [f | (ns,f) <- optLevelFlags, 0 `elem` ns]
                     -- The default -O0 options
@@ -1210,6 +1212,7 @@ fFlags = [
   ( "break-on-exception",               Opt_BreakOnException ),
   ( "break-on-error",                   Opt_BreakOnError ),
   ( "print-evld-with-show",             Opt_PrintEvldWithShow ),
+  ( "print-bind-contents",              Opt_PrintBindContents ),
   ( "run-cps",                          Opt_RunCPSZ ),
   ( "convert-to-zipper-and-back",       Opt_ConvertToZipCfgAndBack),
   ( "vectorise",                        Opt_Vectorise ),

docs/users_guide/flags.xml

@@ -522,6 +522,13 @@
 	      <entry>dynamic</entry>
 	      <entry><option>-fno-print-bind-result</option></entry>
 	    </row>
+	    <row>
+	      <entry><option>-fno-print-bind-contents</option></entry>
+	      <entry><link linkend="breakpoints">Turn off printing of binding contents in GHCi</link></entry>
+	      <entry>dynamic</entry>
+	      <entry>-</entry>
+	    </row>
+
 	  </tbody>
 	</tgroup>
       </informaltable>