Improve handling of import statements in GHCi (#20473)

Currently in GHCi, when given a line of user input we:

1. Attempt to parse and handle it as a statement
2. Otherwise, attempt to parse and handle a single import
3. Otherwise, check if there are imports present (and if so display an error message)
4. Otherwise, attempt to parse a module and only handle the declarations

This patch simplifies the process to:

Attempt to parse and handle it as a statement
Otherwise, attempt to parse a module and handle the imports and declarations

This means that multiple imports in a multiline are now accepted, and a multiline containing both imports and declarations is now accepted (as well as when separated by semicolons).

13 files changed, 37 insertions, 26 deletions

diff --git a/compiler/GHC/Driver/Main.hs b/compiler/GHC/Driver/Main.hs
index 26647df369..ffc0cef89d 100644
--- a/compiler/GHC/Driver/Main.hs
+++ b/compiler/GHC/Driver/Main.hs
@@ -74,6 +74,7 @@ module GHC.Driver.Main
     , hscTcRnLookupRdrName
     , hscStmt, hscParseStmtWithLocation, hscStmtWithLocation, hscParsedStmt
     , hscDecls, hscParseDeclsWithLocation, hscDeclsWithLocation, hscParsedDecls
+    , hscParseModuleWithLocation
     , hscTcExpr, TcRnExprMode(..), hscImport, hscKcType
     , hscParseExpr
     , hscParseType
@@ -1937,12 +1938,17 @@ hscDecls :: HscEnv
          -> IO ([TyThing], InteractiveContext)
 hscDecls hsc_env str = hscDeclsWithLocation hsc_env str "<interactive>" 1
 
-hscParseDeclsWithLocation :: HscEnv -> String -> Int -> String -> IO [LHsDecl GhcPs]
-hscParseDeclsWithLocation hsc_env source line_num str = do
-    L _ (HsModule{ hsmodDecls = decls }) <-
+hscParseModuleWithLocation :: HscEnv -> String -> Int -> String -> IO HsModule
+hscParseModuleWithLocation hsc_env source line_num str = do
+    L _ mod <-
       runInteractiveHsc hsc_env $
         hscParseThingWithLocation source line_num parseModule str
-    return decls
+    return mod
+
+hscParseDeclsWithLocation :: HscEnv -> String -> Int -> String -> IO [LHsDecl GhcPs]
+hscParseDeclsWithLocation hsc_env source line_num str = do
+  HsModule { hsmodDecls = decls } <- hscParseModuleWithLocation hsc_env source line_num str
+  return decls
 
 -- | Compile a decls
 hscDeclsWithLocation :: HscEnv
diff --git a/ghc/GHCi/UI.hs b/ghc/GHCi/UI.hs
index fc19207cc2..362fe0b40a 100644
--- a/ghc/GHCi/UI.hs
+++ b/ghc/GHCi/UI.hs
@@ -59,7 +59,7 @@ import GHC ( LoadHowMuch(..), Target(..),  TargetId(..),
              Resume, SingleStep, Ghc,
              GetDocsFailure(..), putLogMsgM, pushLogHookM,
              getModuleGraph, handleSourceError, ms_mod )
-import GHC.Driver.Main (hscParseDeclsWithLocation, hscParseStmtWithLocation)
+import GHC.Driver.Main (hscParseModuleWithLocation, hscParseStmtWithLocation)
 import GHC.Hs.ImpExp
 import GHC.Hs
 import GHC.Driver.Env
@@ -1231,16 +1231,8 @@ runStmt input step = do
            Just stmt ->
              run_stmt stmt
 
-     | GHC.isImport pflags input -> run_import
-
-     -- Every import declaration should be handled by `run_import`. As GHCi
-     -- in general only accepts one command at a time, we simply throw an
-     -- exception when the input contains multiple commands of which at least
-     -- one is an import command (see #10663).
-     | GHC.hasImport pflags input -> throwGhcException
-       (CmdLineError "error: expecting a single import declaration")
-
      -- Otherwise assume a declaration (or a list of declarations)
+     -- and/or import(s) (#20473).
      -- Note: `GHC.isDecl` returns False on input like
      -- `data Infix a b = a :@: b; infixl 4 :@:`
      -- and should therefore not be used here.
@@ -1250,14 +1242,14 @@ runStmt input step = do
          setDumpFilePrefix ic
            -- `-ddump-to-file` must work for normal GHCi compilations /
            --     evaluations. (#17500)
-         decls <- liftIO (hscParseDeclsWithLocation hsc_env source line input)
+         HsModule { hsmodDecls = decls, hsmodImports = imports } <-
+            liftIO (hscParseModuleWithLocation hsc_env source line input)
+         run_imports imports
          run_decls decls
   where
     exec_complete = GHC.ExecComplete (Right []) 0
 
-    run_import = do
-      addImportToContext input
-      return (Just exec_complete)
+    run_imports imports = mapM_ (addImportToContext . unLoc) imports
 
     run_stmt :: GhciMonad m => GhciLStmt GhcPs -> m (Maybe GHC.ExecResult)
     run_stmt stmt = do
@@ -2713,9 +2705,8 @@ setContext starred unstarred = restoreContextOnFailure $ do
                                 -- delete the transient context
   addModulesToContext_ starred unstarred
 
-addImportToContext :: GhciMonad m => String -> m ()
-addImportToContext str = restoreContextOnFailure $ do
-  idecl <- GHC.parseImportDecl str
+addImportToContext :: GhciMonad m => ImportDecl GhcPs -> m ()
+addImportToContext idecl = restoreContextOnFailure $ do
   addII (IIDecl idecl)   -- #5836
   setGHCContextFromGHCiState
 
diff --git a/testsuite/tests/ghc-e/should_fail/T9905fail2.stderr b/testsuite/tests/ghc-e/should_fail/T9905fail2.stderr
index 2e3e2d94cc..9143eccae4 100644
--- a/testsuite/tests/ghc-e/should_fail/T9905fail2.stderr
+++ b/testsuite/tests/ghc-e/should_fail/T9905fail2.stderr
@@ -1,3 +1,3 @@
 
-<interactive>:1:19: error:
+<interactive>:0:19: error:
     Module ‘Data.List’ does not export ‘bogusIdentifier’
diff --git a/testsuite/tests/ghci/scripts/T10663.script b/testsuite/tests/ghci/scripts/T10663.script
index 10be57f52a..406d0ca7ee 100644
--- a/testsuite/tests/ghci/scripts/T10663.script
+++ b/testsuite/tests/ghci/scripts/T10663.script
@@ -1 +1,2 @@
-import Data.List; sort [2, 1]
\ No newline at end of file
+import Data.List; xs = sort [2, 1]
+xs
\ No newline at end of file
diff --git a/testsuite/tests/ghci/scripts/T10663.stderr b/testsuite/tests/ghci/scripts/T10663.stderr
deleted file mode 100644
index 7170dbf29c..0000000000
--- a/testsuite/tests/ghci/scripts/T10663.stderr
+++ /dev/null
@@ -1 +0,0 @@
-error: expecting a single import declaration
\ No newline at end of file
diff --git a/testsuite/tests/ghci/scripts/T10663.stdout b/testsuite/tests/ghci/scripts/T10663.stdout
new file mode 100644
index 0000000000..3169929f69
--- /dev/null
+++ b/testsuite/tests/ghci/scripts/T10663.stdout
@@ -0,0 +1 @@
+[1,2]
\ No newline at end of file
diff --git a/testsuite/tests/ghci/scripts/T20473a.script b/testsuite/tests/ghci/scripts/T20473a.script
new file mode 100644
index 0000000000..d84edb4129
--- /dev/null
+++ b/testsuite/tests/ghci/scripts/T20473a.script
@@ -0,0 +1,7 @@
+:{
+import Data.List
+
+xs :: [Int]
+xs = sort [2,1]
+:}
+sort xs
diff --git a/testsuite/tests/ghci/scripts/T20473a.stdout b/testsuite/tests/ghci/scripts/T20473a.stdout
new file mode 100644
index 0000000000..6ed63af507
--- /dev/null
+++ b/testsuite/tests/ghci/scripts/T20473a.stdout
@@ -0,0 +1 @@
+[1,2]
diff --git a/testsuite/tests/ghci/scripts/T20473b.script b/testsuite/tests/ghci/scripts/T20473b.script
new file mode 100644
index 0000000000..4fb53badf3
--- /dev/null
+++ b/testsuite/tests/ghci/scripts/T20473b.script
@@ -0,0 +1,2 @@
+import Data.List; import Data.Function
+on (==) sort [1,2] [2,1]
diff --git a/testsuite/tests/ghci/scripts/T20473b.stdout b/testsuite/tests/ghci/scripts/T20473b.stdout
new file mode 100644
index 0000000000..0ca95142bb
--- /dev/null
+++ b/testsuite/tests/ghci/scripts/T20473b.stdout
@@ -0,0 +1 @@
+True
diff --git a/testsuite/tests/ghci/scripts/T6007.stderr b/testsuite/tests/ghci/scripts/T6007.stderr
index aa2be4ee6d..bd5c31dd57 100644
--- a/testsuite/tests/ghci/scripts/T6007.stderr
+++ b/testsuite/tests/ghci/scripts/T6007.stderr
@@ -2,5 +2,5 @@
 <interactive>:1:19:
     Module ‘System.IO’ does not export ‘does_not_exist’
 
-<interactive>:1:20:
+<interactive>:3:20:
     Module ‘Data.Maybe’ does not export ‘does_not_exist’
diff --git a/testsuite/tests/ghci/scripts/all.T b/testsuite/tests/ghci/scripts/all.T
index d67ff95308..884df5a811 100755
--- a/testsuite/tests/ghci/scripts/all.T
+++ b/testsuite/tests/ghci/scripts/all.T
@@ -348,3 +348,5 @@ test('T20206', normal, ghci_script, ['T20206.script'])
 test('T20217', normal, ghci_script, ['T20217.script'])
 test('T7388', normal, ghci_script, ['T7388.script'])
 test('T20627', normal, ghci_script, ['T20627.script'])
+test('T20473a', normal, ghci_script, ['T20473a.script'])
+test('T20473b', normal, ghci_script, ['T20473b.script'])
diff --git a/testsuite/tests/th/T10019.stdout b/testsuite/tests/th/T10019.stdout
index 85510c1af1..413d875440 100644
--- a/testsuite/tests/th/T10019.stdout
+++ b/testsuite/tests/th/T10019.stdout
@@ -1 +1 @@
-"Constructor from Ghci1.Option: Ghci1.Some :: forall (a_0 :: *) .\n                                             a_0 %1 -> Ghci1.Option a_0"
+"Constructor from Ghci2.Option: Ghci2.Some :: forall (a_0 :: *) .\n                                             a_0 %1 -> Ghci2.Option a_0"