prelude.mk: Use BATS to write bunch of tests

In doing so, find and fix a bug in quote.shell that it trimmed trailing
newlines.  The fix involves exporting NL.

prelude.mk

@@ -9,8 +9,8 @@
 ## Outputs ##
 #
 #  String support:
-#  - Variable: NL
-#  - Variable: SPACE
+#  - Variable: export NL
+#  - Variable:        SPACE
 #
 #  Path support:
 #  - Function: path.trimprefix
@@ -70,7 +70,7 @@ joinlist=$(if $(word 2,$2),$(firstword $2)$1$(call joinlist,$1,$(wordlist 2,$(wo
 # Based on
 # https://git.lukeshu.com/autothing/tree/build-aux/Makefile.once.head/00-quote.mk?id=9384e763b00774603208b3d44977ed0e6762a09a
 # but modified to make newlines work with shells other than Bash.
-quote.shell = "$$(printf '%s\n' $(subst $(NL),' ','$(subst ','\'',$1)'))"
+quote.shell = $(subst $(NL),'"$${NL}"','$(subst ','\'',$1)')
 
 # Usage: VAR = $(call lazyonce,VAR,EXPR)
 #

prelude_str.mk

@@ -9,6 +9,7 @@ define NL
 
 
 endef
+export NL
 
 # NOTE: this is not a typo, this is actually how you spell space in Make
 define SPACE

tests/common.bash

@@ -0,0 +1,72 @@
+#!/hint/bash
+
+common_setup() {
+	test_tmpdir="$(mktemp -d)"
+	ln -s "$BATS_TEST_DIRNAME/.." "$test_tmpdir/build-aux"
+	cd "$test_tmpdir"
+	cat >Makefile <<-'__EOT__'
+		.DEFAULT_GOAL = all
+		all:
+		.PHONY: all
+		include build-aux/prelude.mk
+		expr-eq-strict-actual: FORCE; printf '%s' $(call quote.shell,$(EXPR)) > $@
+		expr-eq-echo-actual: FORCE; echo $(EXPR) > $@
+		expr-eq-sloppy-actual: FORCE; echo $(foreach w,$(EXPR),$w) > $@
+	__EOT__
+}
+setup() { common_setup; }
+
+common_teardown() {
+	cd /
+	rm -rf -- "$test_tmpdir"
+}
+teardown() { common_teardown; }
+
+# Usage: check_executable SNIPPET.mk VARNAME
+check_executable() {
+	[[ $# = 2 ]]
+	local snippet=$1
+	local varname=$2
+
+	cat >>Makefile <<-__EOT__
+		include build-aux/${snippet}
+		include build-aux/var.mk
+		all: \$(${varname}) \$(var.)${varname}
+	__EOT__
+
+	make
+
+	local varvalue
+	varvalue="$(cat "build-aux/.var.${varname}")"
+
+	[[ "$varvalue" == /* ]]
+	[[ -f "$varvalue" && -x "$varvalue" ]]
+
+	eval "${varname}=\$varvalue"
+}
+
+check_expr_eq() {
+	[[ $# = 3 ]]
+	local mode=$1
+	local expr=$2
+	local expected=$3
+
+	case "$mode" in
+		strict) printf '%s' "$expected" > expected;;
+		echo) echo $expected > expected;;
+		sloppy) echo $expected > expected;;
+	esac
+
+	make EXPR="$expr" "expr-eq-${mode}-actual"
+
+	diff -u expected "expr-eq-${mode}-actual"
+}
+
+not() {
+	# This isn't just "I find 'not' more readable than '!'", it
+	# serves an actual purpose.  '!' won't trigger an errexit, so
+	# it's no good for assertions.  However, it can affect the
+	# return value of a function, and that function can trigger an
+	# errexit.
+	! "$@"
+}

tests/prelude.bats

@@ -0,0 +1,171 @@
+#!/usr/bin/env bats
+
+load common
+
+@test "prelude.mk: joinlist with separator" {
+	check_expr_eq echo '$(call joinlist,/,foo bar baz)' 'foo/bar/baz'
+}
+
+@test "prelude.mk: joinlist without separator" {
+	check_expr_eq echo '$(call joinlist,,foo bar baz)' 'foobarbaz'
+}
+
+@test "prelude.mk: quote.shell" {
+	# This test relies on the fact that 'var.mk' is implemented
+	# using `quote.shell`.
+	cat >>Makefile <<-'__EOT__'
+		include build-aux/prelude.mk
+		include build-aux/var.mk
+		define actual
+		some'string"with`special characters)
+		and newlines	and tabs
+		and 2 trailing newlines
+
+
+		endef
+		all: $(var.)actual
+	__EOT__
+
+	make
+	printf 'some'\''string"with`special characters)\nand newlines\tand tabs\nand 2 trailing newlines\n\n' > expected
+	diff -u expected build-aux/.var.actual
+}
+
+@test "prelude.mk: lazyonce" {
+	cat >>Makefile <<-'__EOT__'
+		include build-aux/prelude.mk
+		var = $(call lazyonce,var,$(info eval-time)value)
+		$(info before)
+		$(info a: $(var))
+		$(info b: $(var))
+		$(info c: $(var))
+		all: noop
+		noop: ; @true
+		.PHONY: noop
+	__EOT__
+
+	make > actual
+	printf '%s\n' > expected \
+	       'before' \
+	       'eval-time' \
+	       'a: value' \
+	       'b: value' \
+	       'c: value'
+	diff -u expected actual
+}
+
+@test "prelude.mk: build-aux.dir" {
+	cat >>Makefile <<-'__EOT__'
+		include build-aux/prelude.mk
+		include build-aux/var.mk
+		all: $(var.)build-aux.dir
+	__EOT__
+
+	make
+	# Check that it points to the right place
+	[[ "$(cat build-aux/.var.build-aux.dir)" -ef build-aux ]]
+}
+
+@test "prelude.mk: build-aux.bindir" {
+	cat >>Makefile <<-'__EOT__'
+		include build-aux/prelude.mk
+		include build-aux/var.mk
+		all: $(build-aux.bindir) $(var.)build-aux.bindir
+	__EOT__
+
+	make
+	# Check that it points to the right place
+	[[ "$(cat build-aux/.var.build-aux.bindir)" -ef build-aux/bin ]]
+	# Check that it's absolute
+	[[ "$(cat build-aux/.var.build-aux.bindir)" == /* ]]
+}
+
+@test "prelude.mk: FLOCK" {
+	if ! type flock &>/dev/null && ! type go &>/dev/null; then
+		skip
+	fi
+	check_executable prelude.mk FLOCK
+	if which flock &>/dev/null; then
+		[[ "$FLOCK" == "$(which flock)" ]]
+	fi
+
+	# TODO: Check that $FLOCK behaves correctly
+}
+
+@test "prelude.mk: COPY_IFCHANGED" {
+	check_executable prelude.mk COPY_IFCHANGED
+
+	# TODO: Check that $COPY_IFCHANGED behaves correctly
+}
+
+@test "prelude.mk: MOVE_IFCHANGED" {
+	check_executable prelude.mk MOVE_IFCHANGED
+
+	# TODO: Check that $MOVE_IFCHANGED behaves correctly
+}
+
+@test "prelude.mk: WRITE_IFCHANGED" {
+	check_executable prelude.mk WRITE_IFCHANGED
+
+	# TODO: Check that $WRITE_IFCHANGED behaves correctly
+}
+
+@test "prelude.mk: TAP_DRIVER" {
+	check_executable prelude.mk TAP_DRIVER
+
+	# TODO: Check that $TAP_DRIVER behaves correctly
+}
+
+@test "prelude.mk: clobber" {
+	if ! [[ -e build-aux/.git ]]; then
+		# Because we check `git clean -ndx` to make sure
+		# things are clean.
+		skip
+	fi
+	# Let's not work with a symlink for this test
+	rm "$test_tmpdir/build-aux"
+	cp -a "$BATS_TEST_DIRNAME/.." "$test_tmpdir/build-aux"
+	(cd build-aux && git clean -fdx)
+
+	cat >>Makefile <<-'__EOT__'
+		include build-aux/prelude.mk
+		include build-aux/var.mk
+		all: $(COPY_IFCHANGED) $(MOVE_IFCHANGED) $(WRITE_IFCHANGED) $(TAP_DRIVER)
+	__EOT__
+
+	[[ -d build-aux ]]
+	[[ ! -d build-aux/bin ]]
+	make all
+	[[ -d build-aux/bin ]]
+	[[ -f build-aux/bin/copy-ifchanged && -x build-aux/bin/copy-ifchanged ]]
+	[[ -n "$(cd build-aux && git clean -ndx)" ]]
+	make clobber
+	[[ -d build-aux ]]
+	[[ ! -d build-aux/bin ]]
+	[[ -z "$(cd build-aux && git clean -ndx)" ]]
+}
+
+@test "prelude.mk: build-aux.bin-go.rule" {
+	# TODO
+}
+
+@test "prelude.mk: FORCE" {
+	cat >>Makefile <<-'__EOT__'
+		include build-aux/prelude.mk
+		all: without-force with-force
+		without-force: ; touch $@
+		with-force: FORCE ; touch $@
+	__EOT__
+
+	make
+	cp -a with-force with-force.bak
+	cp -a without-force without-force.bak
+
+	sleep 2
+
+	make
+	ls -l
+	[[ with-force -nt with-force.bak ]]
+	[[ ! without-force -nt without-force.bak ]]
+	[[ ! without-force -ot without-force.bak ]]
+}

tests/prelude_go.bats

@@ -0,0 +1,15 @@
+#!/usr/bin/env bats
+
+load common
+
+@test "prelude_go.mk: GOHOSTOS" {
+	# TODO
+}
+
+@test "prelude_go.mk: GOHOSTARCH" {
+	# TODO
+}
+
+@test "prelude_go.mk: _prelude.go.lock" {
+	# TODO
+}

tests/prelude_path.bats

@@ -0,0 +1,11 @@
+#!/usr/bin/env bats
+
+load common
+
+@test "prelude_path.mk: path.trimprefix" {
+	check_expr_eq echo '$(call path.trimprefix,foo/bar,foo/bar foo/bar/baz qux)' '. baz qux'
+}
+
+@test "prelude_path.mk: path.addprefix" {
+	check_expr_eq echo '$(call path.addprefix,foo/bar,. baz)' 'foo/bar foo/bar/baz'
+}

tests/prelude_str.bats

@@ -0,0 +1,13 @@
+#!/usr/bin/env bats
+
+load common
+
+@test "prelude_str.mk: NL" {
+	# Honestly, this checks `quote.shell` more than it does NL.
+	check_expr_eq strict '$(NL)' $'\n'
+}
+
+@test "prelude_str.mk: SPACE" {
+	# Honestly, this checks `quote.shell` more than it does SPACE.
+	check_expr_eq strict '$(SPACE)' ' '
+}