downsweep: Allow TargetFile not to exist when a buffer is given

Currently 'getRootSummary' will fail with an exception if a 'TargetFile' is
given but it does not exist even if an input buffer is passed along for
this target.

In this case it is not necessary for the file to exist since the buffer
will be used as input for the compilation pipeline instead of the file
anyways.

4 files changed, 14 insertions, 18 deletions

diff --git a/compiler/main/GhcMake.hs b/compiler/main/GhcMake.hs
index 5c76f2856d..9a4911f2c1 100644
--- a/compiler/main/GhcMake.hs
+++ b/compiler/main/GhcMake.hs
@@ -1968,7 +1968,7 @@ downsweep hsc_env old_summaries excl_mods allow_dup_roots
         getRootSummary :: Target -> IO (Either ErrMsg ModSummary)
         getRootSummary (Target (TargetFile file mb_phase) obj_allowed maybe_buf)
            = do exists <- liftIO $ doesFileExist file
-                if exists
+                if exists || isJust maybe_buf
                     then Right `fmap` summariseFile hsc_env old_summaries file mb_phase
                                        obj_allowed maybe_buf
                     else return $ Left $ mkPlainErrMsg dflags noSrcSpan $
diff --git a/compiler/main/HscTypes.hs b/compiler/main/HscTypes.hs
index 88edccf5bc..b29143a45b 100644
--- a/compiler/main/HscTypes.hs
+++ b/compiler/main/HscTypes.hs
@@ -505,6 +505,11 @@ data Target
       --
       -- Since GHC version 8.10 modules which require preprocessors such as
       -- Literate Haskell or CPP to run are also supported.
+      --
+      -- If a corresponding source file does not exist on disk this will
+      -- result in a 'SourceError' exception if @targetId = TargetModule _@
+      -- is used. However together with @targetId = TargetFile _@ GHC will
+      -- not complain about the file missing.
     }
 
 data TargetId
diff --git a/testsuite/tests/ghc-api/target-contents/TargetContents.hs b/testsuite/tests/ghc-api/target-contents/TargetContents.hs
index db02dbde2b..eaa30697f8 100644
--- a/testsuite/tests/ghc-api/target-contents/TargetContents.hs
+++ b/testsuite/tests/ghc-api/target-contents/TargetContents.hs
@@ -90,8 +90,7 @@ main = do
 
 data Sync
     = OnDisk   -- | Write generated module to disk
-    | InMemory -- | Only fill targetContents, place an empty dummy module
-               -- on disk though to make Finder shut up though.
+    | InMemory -- | Only fill in targetContents.
 
 ppSync OnDisk   = "D"
 ppSync InMemory = "M"
diff --git a/testsuite/tests/ghc-api/target-contents/TargetContents.stderr b/testsuite/tests/ghc-api/target-contents/TargetContents.stderr
index b0a363c1e5..2743f5135e 100644
--- a/testsuite/tests/ghc-api/target-contents/TargetContents.stderr
+++ b/testsuite/tests/ghc-api/target-contents/TargetContents.stderr
@@ -3,8 +3,6 @@
 A.hs:3:5: error: Variable not in scope: z
 == CPP_D
 == CPP_M
-can't find file: A.hs
-
 == Dep_DD_AB
 == Dep_Error_DD_AB
 
@@ -13,33 +11,27 @@ B.hs:3:5: error: Variable not in scope: z
 
 B.hs:3:5: error: Variable not in scope: z
 == Dep_MM_AB
-can't find file: A.hs
-can't find file: B.hs
-
 == Dep_Error_MM_AB
-can't find file: A.hs
-can't find file: B.hs
 
+B.hs:3:5: error: Variable not in scope: z
 == Dep_Error_MM_A
-can't find file: A.hs
 
+A.hs:3:1: error:
+    Could not find module ‘B’
+    Use -v (or `:set -v` in ghci) to see a list of the files searched for.
 == Dep_DM_AB
-can't find file: B.hs
-
 == Dep_Error_DM_AB
-can't find file: B.hs
 
+B.hs:3:5: error: Variable not in scope: z
 == Dep_Error_DM_A
 
 A.hs:3:1: error:
     Could not find module ‘B’
     Use -v (or `:set -v` in ghci) to see a list of the files searched for.
 == Dep_MD_AB
-can't find file: A.hs
-
 == Dep_Error_MD_AB
-can't find file: A.hs
 
+B.hs:3:5: error: Variable not in scope: z
 == Dep_Error_MD_A
-can't find file: A.hs
 
+B.hs:3:5: error: Variable not in scope: z