From 157fb6f1bcb5af0d93bb588522bb1be86aa2fd71 Mon Sep 17 00:00:00 2001
From: Nick Bowler <nbowler@draconx.ca>
Date: Sat, 8 Feb 2020 11:11:28 -0500
Subject: [PATCH] Improve distribution of Autotest testsuite dependencies.

A fresh distribution tarball includes a generated testsuite, but
does not have the benefit of rules from automatic dependency tracking.

This means if a file included by the testsuite is modified in the
tarball, the build will not detect that testsuite is out of date
and will not try to rebuild it.

A similar scenario occurs if 'make distclean' is run after building
the test suite.

Since modern Automake uses make rules to generate the dependency stubs,
we can use the distributed testsuite dependencies record to produce
an accurate initial list of prerequisites.  And by ensuring that this
file is updated whenever the testsuite is built, we can handle the
'make distclean' case too.
---
 snippet/autotest.mk | 42 +++++++++++++++++++++++++-----------------
 1 file changed, 25 insertions(+), 17 deletions(-)

diff --git a/snippet/autotest.mk b/snippet/autotest.mk
index d5adc9d..badfc9f 100644
--- a/snippet/autotest.mk
+++ b/snippet/autotest.mk
@@ -31,7 +31,7 @@ clean-autotest:
 
 maintainer-clean-local: maintainer-clean-autotest
 maintainer-clean-autotest:
-	rm -f testsuite package.m4
+	rm -f testsuite testsuite.deps package.m4
 .PHONY: maintainerclean-autotest
 
 package.m4: $(top_srcdir)/configure.ac
@@ -53,27 +53,20 @@ DX_AUTOTEST_ERROR = @:; { \
 	  printf 'Autoconf package: <https://gnu.org/s/autoconf/>\n'; \
 	} 1>&2; false
 
-DX_ATFLAGS = -I$(srcdir) $(ATFLAGS)
+DX_AUTOTEST = $(AUTOTEST) -I$(srcdir) $(ATFLAGS)
 
 testsuite: testsuite.at package.m4
 if !HAVE_AUTOTEST
 	$(DX_AUTOTEST_ERROR)
 endif
-	$(AM_V_GEN) $(AUTOTEST) $(DX_ATFLAGS) -p m4_include -o $@.tmp \
+	$(AM_V_GEN) $(DX_AUTOTEST) -p m4_include -o $@.tmp testsuite.at
+	$(AM_V_at) $(DX_AUTOTEST) -t m4_include:'$$1' -o $@.deps.tmp \
 	  testsuite.at
-	$(AM_V_at) :; { \
-	  $(AUTOTEST) $(DX_ATFLAGS) -t m4_include:'$@: $$1' testsuite.at; \
-	  $(AUTOTEST) $(DX_ATFLAGS) -t m4_include:'$$1:' testsuite.at; \
-	} >$(DEPDIR)/$(@F).P
+	$(AM_V_at) exec 3<$@.deps.tmp 4>$(DEPDIR)/$(@F).P; \
+	  while read f <&3; do printf '$@: %s\n%s:\n' "$$f" "$$f" >&4; done
+	$(AM_V_at) mv -f $@.deps.tmp $@.deps
 	$(AM_V_at) mv -f $@.tmp $@
-
 testsuite.deps: testsuite
-if !HAVE_AUTOTEST
-	$(DX_AUTOTEST_ERROR)
-endif
-	$(AM_V_GEN) $(AUTOTEST) $(DX_ATFLAGS) -t m4_include:'$$1' -o $@.tmp \
-	  testsuite.at
-	$(AM_V_at) mv -f $@.tmp $@
 
 dist-hook: dist-autotest-deps
 dist-autotest-deps: testsuite.deps
@@ -91,10 +84,25 @@ DISTCLEANFILES += atconfig $(DEPDIR)/testsuite.P
 @AMDEP_TRUE@@am__include@ @am__quote@$(DEPDIR)/testsuite.P@am__quote@
 
 # Automake 1.16 and newer use make rules to generate the dependency stubs.
-# we must hook those which is kind of annoying to do.  This should be harmless
-# on previous versions which generate the stubs directly in config.status.
+# Use this opportunity to generate accurate prerequisites from distributed
+# testsuite dependencies, needed so that make knows to rebuild the testsuite
+# when source files are modified in a distribution tarball, or after a make
+# distclean.
+#
+# With older Automake the stubs are generated directly in config.status.
+# Since this rule is ignored things should still work but the build may
+# miss modifications to the testsuite on the first build from a tarball.
 _dx_autotest_depfiles = am--depfiles
 $(_dx_autotest_depfiles): $(DEPDIR)/testsuite.P
 $(DEPDIR)/testsuite.P:
 	@$(MKDIR_P) $(@D)
-	@echo '# dummy' >$@-t && mv -f $@-t $@
+	@if test -f $(builddir)/testsuite.deps; then \
+	  exec 3<$(builddir)/testsuite.deps; \
+	elif test -f $(srcdir)/testsuite.deps; then \
+	  exec 3<$(srcdir)/testsuite.deps; \
+	else \
+	  echo '# dummy' >$@-t && exit; \
+	fi; exec 4>$@-t; while read f <&3; do \
+	  printf 'testsuite: %s\n%s:\n' "$$f" "$$f" >&4; \
+	done
+	@mv -f $@-t $@
-- 
2.43.0