Fix recompilation checking for multiple home units

The key part of this change is to store a UnitId in the
`UsageHomeModule` and `UsageHomeModuleInterface`.

* Fine-grained dependency tracking is used if the dependency comes from
  any home unit.
* We actually look up the right module when checking whether we need to
  recompile in the `UsageHomeModuleInterface` case.

These scenarios are both checked by the new tests (
multipleHomeUnits_recomp and multipleHomeUnits_recomp_th )

Fixes #22675

11 files changed, 43 insertions, 0 deletions

diff --git a/testsuite/tests/driver/multipleHomeUnits/Dep.hs b/testsuite/tests/driver/multipleHomeUnits/Dep.hs
new file mode 100644
index 0000000000..8f9b621e15
--- /dev/null
+++ b/testsuite/tests/driver/multipleHomeUnits/Dep.hs
@@ -0,0 +1,3 @@
+module Dep (foo) where
+
+foo = ()
diff --git a/testsuite/tests/driver/multipleHomeUnits/Makefile b/testsuite/tests/driver/multipleHomeUnits/Makefile
index d244bc6834..bd5805207a 100644
--- a/testsuite/tests/driver/multipleHomeUnits/Makefile
+++ b/testsuite/tests/driver/multipleHomeUnits/Makefile
@@ -30,4 +30,9 @@ multipleHomeUnits004_recomp: clean
 multipleHomeUnitsModuleVisibility: clean
 	! '$(TEST_HC)' $(TEST_HC_OPTS) -fhide-source-paths -unit @unitMV -unit @unitMV-import
 
+multipleHomeUnits_recomp: clean
+	'$(TEST_HC)' $(TEST_HC_OPTS) -fhide-source-paths -unit @unitRecomp -unit @unitDep
+	# Doesn't cause recomp when TH is not involved
+	echo "recomp=()" >> Dep.hs
+	'$(TEST_HC)' $(TEST_HC_OPTS) -fhide-source-paths -unit @unitRecomp -unit @unitDep
 
diff --git a/testsuite/tests/driver/multipleHomeUnits/Recomp.hs b/testsuite/tests/driver/multipleHomeUnits/Recomp.hs
new file mode 100644
index 0000000000..42b93f81d5
--- /dev/null
+++ b/testsuite/tests/driver/multipleHomeUnits/Recomp.hs
@@ -0,0 +1,5 @@
+module Recomp where
+
+import Dep
+
+qux = foo
diff --git a/testsuite/tests/driver/multipleHomeUnits/RecompTH.hs b/testsuite/tests/driver/multipleHomeUnits/RecompTH.hs
new file mode 100644
index 0000000000..ee7ee96a78
--- /dev/null
+++ b/testsuite/tests/driver/multipleHomeUnits/RecompTH.hs
@@ -0,0 +1,6 @@
+{-# LANGUAGE TemplateHaskell #-}
+module RecompTH where
+
+import Dep
+
+qux = $(const [| () |] foo)
diff --git a/testsuite/tests/driver/multipleHomeUnits/all.T b/testsuite/tests/driver/multipleHomeUnits/all.T
index 97974e19e2..a21459d74f 100644
--- a/testsuite/tests/driver/multipleHomeUnits/all.T
+++ b/testsuite/tests/driver/multipleHomeUnits/all.T
@@ -59,3 +59,10 @@ test('multipleHomeUnitsPackageImports',
 test('MHU_OptionsGHC', normal, compile_fail, [''])
 
 test('multipleHomeUnits_loop', [extra_files([ 'a/', 'unitA', 'loop', 'unitLoop'])], multiunit_compile, [['unitA', 'unitLoop'], '-fhide-source-paths'])
+
+test('multipleHomeUnits_recomp', [copy_files,extra_files([ 'Recomp.hs', 'unitRecomp', 'unitDep', 'Dep.hs'])], makefile_test, [])
+
+test('multipleHomeUnits_recomp_th', [filter_stdout_lines(r'.*Compiling.*'), copy_files, extra_files(['thRecomp.script', 'unitRecompTH', 'unitDep', 'RecompTH.hs', 'Dep.hs', '../../ghci/shell.hs'])  , extra_run_opts('-v1 -unit @unitRecompTH -unit @unitDep')], ghci_script, ['thRecomp.script'])
+
+
+
diff --git a/testsuite/tests/driver/multipleHomeUnits/multipleHomeUnits_recomp.stdout b/testsuite/tests/driver/multipleHomeUnits/multipleHomeUnits_recomp.stdout
new file mode 100644
index 0000000000..1fbd0c9e1e
--- /dev/null
+++ b/testsuite/tests/driver/multipleHomeUnits/multipleHomeUnits_recomp.stdout
@@ -0,0 +1,3 @@
+[1 of 2] Compiling Dep[dep]
+[2 of 2] Compiling Recomp[recomp]
+[1 of 2] Compiling Dep[dep] [Source file changed]
diff --git a/testsuite/tests/driver/multipleHomeUnits/multipleHomeUnits_recomp_th.stdout b/testsuite/tests/driver/multipleHomeUnits/multipleHomeUnits_recomp_th.stdout
new file mode 100644
index 0000000000..4e57668849
--- /dev/null
+++ b/testsuite/tests/driver/multipleHomeUnits/multipleHomeUnits_recomp_th.stdout
@@ -0,0 +1,8 @@
+GHCi, version 9.7.20230119: https://www.haskell.org/ghc/  :? for help
+[1 of 2] Compiling Dep              ( Dep.hs, interpreted )[dep]
+[2 of 2] Compiling RecompTH         ( RecompTH.hs, interpreted )[recomp]
+Ok, two modules loaded.
+ghci> ghci> ghci> [1 of 2] Compiling Dep              ( Dep.hs, interpreted )[dep] [Source file changed]
+[2 of 2] Compiling RecompTH         ( RecompTH.hs, interpreted )[recomp] [Dep changed (interface)]
+Ok, two modules loaded.
+ghci> Leaving GHCi.
diff --git a/testsuite/tests/driver/multipleHomeUnits/thRecomp.script b/testsuite/tests/driver/multipleHomeUnits/thRecomp.script
new file mode 100644
index 0000000000..d16ddc4a16
--- /dev/null
+++ b/testsuite/tests/driver/multipleHomeUnits/thRecomp.script
@@ -0,0 +1,3 @@
+shell s = System.Process.rawSystem "sh" ["-c", s] >> return ()
+shell "echo \"recomp=()\" >> Dep.hs"
+:r
diff --git a/testsuite/tests/driver/multipleHomeUnits/unitDep b/testsuite/tests/driver/multipleHomeUnits/unitDep
new file mode 100644
index 0000000000..b11a7baaf0
--- /dev/null
+++ b/testsuite/tests/driver/multipleHomeUnits/unitDep
@@ -0,0 +1 @@
+-i Dep -outputdir=dep -this-unit-id dep
diff --git a/testsuite/tests/driver/multipleHomeUnits/unitRecomp b/testsuite/tests/driver/multipleHomeUnits/unitRecomp
new file mode 100644
index 0000000000..f30b19fa5c
--- /dev/null
+++ b/testsuite/tests/driver/multipleHomeUnits/unitRecomp
@@ -0,0 +1 @@
+-i Recomp -outputdir=recomp -this-unit-id recomp -package-id dep
diff --git a/testsuite/tests/driver/multipleHomeUnits/unitRecompTH b/testsuite/tests/driver/multipleHomeUnits/unitRecompTH
new file mode 100644
index 0000000000..867e522ec4
--- /dev/null
+++ b/testsuite/tests/driver/multipleHomeUnits/unitRecompTH
@@ -0,0 +1 @@
+-i RecompTH -outputdir=recomp -this-unit-id recomp -package-id dep