driver: Fix interaction of -Wunused-packages and reexported-modules

Spurious warnings were previously emitted if an import came from a
reexport due to how -Wunused-packages were implemented. Removing the
dependency would cause compilation to fail.

The fix is to reimplement the warning a bit more directly, by searching
for which package each import comes from using the normal module finding
functions rather than consulting the EPS. This has the advantage that
the check could be performed at any time after downsweep rather than
also relying on a populated EPS.

Fixes #19518 and #19777

16 files changed, 106 insertions, 0 deletions

diff --git a/testsuite/tests/cabal/t19518/Makefile b/testsuite/tests/cabal/t19518/Makefile
new file mode 100644
index 0000000000..e5a282e13f
--- /dev/null
+++ b/testsuite/tests/cabal/t19518/Makefile
@@ -0,0 +1,44 @@
+TOP=../../..
+include $(TOP)/mk/boilerplate.mk
+include $(TOP)/mk/test.mk
+
+SETUP = ../Setup -v0
+
+# This test is for package reexports and -Wunused-packages working together
+#   1. install p
+#   2. install q (reexporting p modules)
+#   3. install r (using reexports from q)
+#
+# When building r, it should not suggest the import of q package is redundant
+
+t19518: clean
+	$(MAKE) -s --no-print-directory clean
+	'$(GHC_PKG)' init tmp.d
+	'$(TEST_HC)' $(TEST_HC_OPTS) -v0 --make Setup
+	# build p
+	cd p && $(SETUP) clean
+	cd p && $(SETUP) configure $(CABAL_MINIMAL_BUILD) --with-ghc='$(TEST_HC)' --ghc-options='$(TEST_HC_OPTS)' --package-db=../tmp.d --prefix='$(PWD)/$$pkgid'
+	cd p && $(SETUP) build
+	cd p && $(SETUP) copy
+	cd p && $(SETUP) register
+	# build q
+	cd q && $(SETUP) clean
+	cd q && $(SETUP) configure $(CABAL_MINIMAL_BUILD) --with-ghc='$(TEST_HC)' --ghc-options='$(TEST_HC_OPTS)' --package-db=../tmp.d --prefix='$(PWD)/$$pkgid'
+	cd q && $(SETUP) build
+	cd q && $(SETUP) copy
+	cd q && $(SETUP) register
+	# build r
+	cd r && $(SETUP) clean
+	cd r && $(SETUP) configure $(CABAL_MINIMAL_BUILD) --with-ghc='$(TEST_HC)' --ghc-options='$(TEST_HC_OPTS) -Wunused-packages' --package-db=../tmp.d --prefix='$(PWD)/$$pkgid'
+	cd r && $(SETUP) build
+	cd r && $(SETUP) copy
+	cd r && $(SETUP) register
+ifneq "$(CLEANUP)" ""
+	$(MAKE) -s --no-print-directory clean
+endif
+
+clean :
+	'$(GHC_PKG)' unregister --force p >/dev/null 2>&1 || true
+	'$(GHC_PKG)' unregister --force q >/dev/null 2>&1 || true
+	'$(GHC_PKG)' unregister --force r >/dev/null 2>&1 || true
+	$(RM) -r p-* q-* r-* s-* t-* tmp.d *.o *.hi */*.o */*.hi */Setup$(exeext) */dist Setup$(exeext)
diff --git a/testsuite/tests/cabal/t19518/Setup.hs b/testsuite/tests/cabal/t19518/Setup.hs
new file mode 100644
index 0000000000..9a994af677
--- /dev/null
+++ b/testsuite/tests/cabal/t19518/Setup.hs
@@ -0,0 +1,2 @@
+import Distribution.Simple
+main = defaultMain
diff --git a/testsuite/tests/cabal/t19518/all.T b/testsuite/tests/cabal/t19518/all.T
new file mode 100644
index 0000000000..a2cd241a70
--- /dev/null
+++ b/testsuite/tests/cabal/t19518/all.T
@@ -0,0 +1,9 @@
+if config.cleanup:
+   cleanup = 'CLEANUP=1'
+else:
+   cleanup = 'CLEANUP=0'
+
+test('t19518',
+     extra_files(['Setup.hs', 'p/', 'q/', 'r/']),
+     run_command,
+     ['$MAKE -s --no-print-directory t19518 ' + cleanup])
diff --git a/testsuite/tests/cabal/t19518/p/LICENSE b/testsuite/tests/cabal/t19518/p/LICENSE
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/testsuite/tests/cabal/t19518/p/LICENSE
diff --git a/testsuite/tests/cabal/t19518/p/P.hs b/testsuite/tests/cabal/t19518/p/P.hs
new file mode 100644
index 0000000000..f8b82de2ca
--- /dev/null
+++ b/testsuite/tests/cabal/t19518/p/P.hs
@@ -0,0 +1,3 @@
+module P where
+data P = P
+p = True
diff --git a/testsuite/tests/cabal/t19518/p/P2.hs b/testsuite/tests/cabal/t19518/p/P2.hs
new file mode 100644
index 0000000000..769760dff8
--- /dev/null
+++ b/testsuite/tests/cabal/t19518/p/P2.hs
@@ -0,0 +1 @@
+module P2 where
diff --git a/testsuite/tests/cabal/t19518/p/Setup.hs b/testsuite/tests/cabal/t19518/p/Setup.hs
new file mode 100644
index 0000000000..9a994af677
--- /dev/null
+++ b/testsuite/tests/cabal/t19518/p/Setup.hs
@@ -0,0 +1,2 @@
+import Distribution.Simple
+main = defaultMain
diff --git a/testsuite/tests/cabal/t19518/p/p.cabal b/testsuite/tests/cabal/t19518/p/p.cabal
new file mode 100644
index 0000000000..989156c5be
--- /dev/null
+++ b/testsuite/tests/cabal/t19518/p/p.cabal
@@ -0,0 +1,11 @@
+name:                p
+version:             0.1.0.0
+license-file:        LICENSE
+author:              Edward Z. Yang
+maintainer:          ezyang@cs.stanford.edu
+build-type:          Simple
+cabal-version:       >=1.21
+
+library
+  exposed-modules:     P, P2
+  build-depends:       base
diff --git a/testsuite/tests/cabal/t19518/q/LICENSE b/testsuite/tests/cabal/t19518/q/LICENSE
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/testsuite/tests/cabal/t19518/q/LICENSE
diff --git a/testsuite/tests/cabal/t19518/q/Q.hs b/testsuite/tests/cabal/t19518/q/Q.hs
new file mode 100644
index 0000000000..721b231aa1
--- /dev/null
+++ b/testsuite/tests/cabal/t19518/q/Q.hs
@@ -0,0 +1,4 @@
+module Q where
+import P
+data Q = Q
+q = not p
diff --git a/testsuite/tests/cabal/t19518/q/Setup.hs b/testsuite/tests/cabal/t19518/q/Setup.hs
new file mode 100644
index 0000000000..9a994af677
--- /dev/null
+++ b/testsuite/tests/cabal/t19518/q/Setup.hs
@@ -0,0 +1,2 @@
+import Distribution.Simple
+main = defaultMain
diff --git a/testsuite/tests/cabal/t19518/q/q.cabal b/testsuite/tests/cabal/t19518/q/q.cabal
new file mode 100644
index 0000000000..c455f6ad44
--- /dev/null
+++ b/testsuite/tests/cabal/t19518/q/q.cabal
@@ -0,0 +1,12 @@
+name:                q
+version:             0.1.0.0
+license-file:        LICENSE
+author:              Edward Z. Yang
+maintainer:          ezyang@cs.stanford.edu
+build-type:          Simple
+cabal-version:       >=1.21
+
+library
+  exposed-modules:     Q
+  reexported-modules:  P
+  build-depends:       base, p
diff --git a/testsuite/tests/cabal/t19518/r/LICENSE b/testsuite/tests/cabal/t19518/r/LICENSE
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/testsuite/tests/cabal/t19518/r/LICENSE
diff --git a/testsuite/tests/cabal/t19518/r/R.hs b/testsuite/tests/cabal/t19518/r/R.hs
new file mode 100644
index 0000000000..ac9344a524
--- /dev/null
+++ b/testsuite/tests/cabal/t19518/r/R.hs
@@ -0,0 +1,3 @@
+module R where
+import P
+r = p
diff --git a/testsuite/tests/cabal/t19518/r/Setup.hs b/testsuite/tests/cabal/t19518/r/Setup.hs
new file mode 100644
index 0000000000..9a994af677
--- /dev/null
+++ b/testsuite/tests/cabal/t19518/r/Setup.hs
@@ -0,0 +1,2 @@
+import Distribution.Simple
+main = defaultMain
diff --git a/testsuite/tests/cabal/t19518/r/r.cabal b/testsuite/tests/cabal/t19518/r/r.cabal
new file mode 100644
index 0000000000..f39aa659f7
--- /dev/null
+++ b/testsuite/tests/cabal/t19518/r/r.cabal
@@ -0,0 +1,11 @@
+name:                r
+version:             0.1.0.0
+license-file:        LICENSE
+author:              Edward Z. Yang
+maintainer:          ezyang@cs.stanford.edu
+build-type:          Simple
+cabal-version:       >=1.21
+
+library
+  exposed-modules:     R
+  build-depends:       base, q