Fix #9243 so recompilation avoidance works with -fno-code

Summary:
Where we track timestamps of object files, also track timestamps
for interface files.  When -fno-code -fwrite-interface is enabled, use
the interface file timestamp as an extra check to see if the files are
up-to-date.  We had to apply this logic to one-shot and make modes.

This fix would be good to merge into 7.10; it makes using -fno-code
-fwrite-interface for flywheel type checking usable.

Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>

Test Plan: validate and new test cases

Reviewers: austin

Subscribers: carter, thomie

Differential Revision: https://phabricator.haskell.org/D596

GHC Trac Issues: #9243

7 files changed, 37 insertions, 0 deletions

diff --git a/testsuite/tests/driver/retc002/Makefile b/testsuite/tests/driver/retc002/Makefile
new file mode 100644
index 0000000000..528df4b471
--- /dev/null
+++ b/testsuite/tests/driver/retc002/Makefile
@@ -0,0 +1,20 @@
+TOP=../../..
+include $(TOP)/mk/boilerplate.mk
+include $(TOP)/mk/test.mk
+
+# -fforce-recomp makes lots of driver tests trivially pass, so we
+# filter it out from $(TEST_HC_OPTS).
+TEST_HC_OPTS_NO_RECOMP = $(filter-out -fforce-recomp,$(TEST_HC_OPTS))
+
+# Recompilation tests
+
+clean:
+	rm -f *.o*
+	rm -f *.hi*
+
+# Only the first invocation should print any "Compiling" messages
+
+retc002: clean
+	'$(TEST_HC)' $(TEST_HC_OPTS_NO_RECOMP) -fwrite-interface -fno-code --make Q.hs
+	echo Middle >&2
+	'$(TEST_HC)' $(TEST_HC_OPTS_NO_RECOMP) -fwrite-interface -fno-code --make Q.hs
diff --git a/testsuite/tests/driver/retc002/Q.hs b/testsuite/tests/driver/retc002/Q.hs
new file mode 100644
index 0000000000..3565f02de4
--- /dev/null
+++ b/testsuite/tests/driver/retc002/Q.hs
@@ -0,0 +1,3 @@
+module Q where
+
+import {-# SOURCE #-} W
diff --git a/testsuite/tests/driver/retc002/W.hs b/testsuite/tests/driver/retc002/W.hs
new file mode 100644
index 0000000000..3dd7ff92c8
--- /dev/null
+++ b/testsuite/tests/driver/retc002/W.hs
@@ -0,0 +1,3 @@
+module W where
+
+import Q
diff --git a/testsuite/tests/driver/retc002/W.hs-boot b/testsuite/tests/driver/retc002/W.hs-boot
new file mode 100644
index 0000000000..4992c51af8
--- /dev/null
+++ b/testsuite/tests/driver/retc002/W.hs-boot
@@ -0,0 +1 @@
+module W where
diff --git a/testsuite/tests/driver/retc002/all.T b/testsuite/tests/driver/retc002/all.T
new file mode 100644
index 0000000000..47794fbe39
--- /dev/null
+++ b/testsuite/tests/driver/retc002/all.T
@@ -0,0 +1,6 @@
+test('retc002',
+     [when(fast(), skip),
+      clean_cmd('$MAKE -s clean')],
+     run_command,
+     ['$MAKE -s --no-print-directory retc002'])
+
diff --git a/testsuite/tests/driver/retc002/retc002.stderr b/testsuite/tests/driver/retc002/retc002.stderr
new file mode 100644
index 0000000000..56cdd85e1d
--- /dev/null
+++ b/testsuite/tests/driver/retc002/retc002.stderr
@@ -0,0 +1 @@
+Middle
diff --git a/testsuite/tests/driver/retc002/retc002.stdout b/testsuite/tests/driver/retc002/retc002.stdout
new file mode 100644
index 0000000000..e76853f8f8
--- /dev/null
+++ b/testsuite/tests/driver/retc002/retc002.stdout
@@ -0,0 +1,3 @@
+[1 of 3] Compiling W[boot]          ( W.hs-boot, nothing )
+[2 of 3] Compiling Q                ( Q.hs, nothing )
+[3 of 3] Compiling W                ( W.hs, nothing )