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[PATCH/RFC 7/7] t7006-pager: if stdout is not a terminal, make a new one

From
Jonathan Nieder <jrnieder@gmail.com>
Date
Feb 19, 2010, 07:23 UTC
Message-ID
<20100219072331.GG29916@progeny.tock>
In-Reply-To
<20100219065010.GA22258@progeny.tock>

Test t7006-pager skips most of its tests except when running with --verbose, for lack of a terminal to use. Thus many of the tests would not get much coverage, since whole testsuite runs with --verbose are rare. Redirecting output to /dev/tty would be problematic because (1) there really could be no controlling terminal and (2) test breakage might manifest itself by the producing extraneous output. Luckily, there is a way around this: Unix98-style pseudo-terminals allow us to create a fake terminal on the fly and capture its output.

Do so. The new test-terminal command to accomplish this uses posix_openpt (from SuSv3) to create a terminal because that is good enough on Linux. I would like some feedback on what platforms are missing that function and thus what alternate interfaces are worth supporting. The perl IO::Tty module could take care of this for us, but I do not think it is worth the extra dependency.

The test-terminal facility can be disabled by passing NO_POSIX_OPENPT=YesPlease to the makefile, in which case the test will revert to its old behavior (skipping most tests unless GIT_TEST_OPTS includes --verbose).

Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
---
Requiring users to add NO_POSIX_OPENPT themselves doesn’t seem so
great.  I did it that way just so I could send something and get
some feedback; a more suitable version would need a way to detect
missing openpt on the fly, for example by noticing the compilation
failure and continuing anyway.
 .gitignore       |    1 +
 Makefile         |    6 +++++
 t/t7006-pager.sh |   28 +++++++++++++++--------
 test-terminal.c  |   62 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 87 insertions(+), 10 deletions(-)
 create mode 100644 test-terminal.c
diff --git a/.gitignore b/.gitignore
index 8df8f88..6b405ba 100644
--- a/.gitignore
+++ b/.gitignore
@@ -169,6 +169,7 @@
 /test-run-command
 /test-sha1
 /test-sigchain
+/test-terminal
 /common-cmds.h
 *.tar.gz
 *.dsc
diff --git a/Makefile b/Makefile
index 7bf2fca..9c900a7 100644
--- a/Makefile
+++ b/Makefile
@@ -45,6 +45,8 @@ all::
 #
 # Define NO_MEMMEM if you don't have memmem.
 #
+# Define NO_POSIX_OPENPT if you don't have posix_openpt (for tests).
+#
 # Define NO_STRLCPY if you don't have strlcpy.
 #
 # Define NO_STRTOUMAX if you don't have strtoumax in the C library.
@@ -1727,6 +1729,10 @@ TEST_PROGRAMS_NEED_X += test-sha1
 TEST_PROGRAMS_NEED_X += test-sigchain
 TEST_PROGRAMS_NEED_X += test-index-version
 
+ifndef NO_POSIX_OPENPT
+TEST_PROGRAMS_NEED_X += test-terminal
+endif
+
 TEST_PROGRAMS = $(patsubst %,%$X,$(TEST_PROGRAMS_NEED_X))
 
 test_bindir_programs := $(patsubst %,bin-wrappers/%,$(BINDIR_PROGRAMS_NEED_X) $(BINDIR_PROGRAMS_NO_X) $(TEST_PROGRAMS_NEED_X))
diff --git a/t/t7006-pager.sh b/t/t7006-pager.sh
index 2e9cb9d..21788e3 100644
--- a/t/t7006-pager.sh
+++ b/t/t7006-pager.sh
@@ -5,18 +5,26 @@ test_description='Test automatic use of a pager.'
 . ./test-lib.sh
 
 rm -f stdout_is_tty
-test_expect_success 'is stdout a terminal?' '
+test_expect_success 'set up terminal for tests' '
 	if test -t 1
 	then
 		: > stdout_is_tty
+	elif test-terminal sh -c "test -t 1"
+	then
+		: > test_terminal_works
 	fi
 '
 
 if test -e stdout_is_tty
 then
+	test_terminal() { "$@"; }
+	test_set_prereq TTY
+elif test -e test_terminal_works
+then
+	test_terminal() { test-terminal "$@"; }
 	test_set_prereq TTY
 else
-	say stdout is not a terminal, so skipping some tests.
+	say no usable terminal, so skipping some tests
 fi
 
 unset GIT_PAGER GIT_PAGER_IN_USE
@@ -30,13 +38,13 @@ test_expect_success 'setup' '
 
 rm -f paginated.out
 test_expect_success TTY 'some commands use a pager' '
-	git log &&
+	test_terminal git log &&
 	test -e paginated.out
 '
 
 rm -f paginated.out
 test_expect_success TTY 'some commands do not use a pager' '
-	git rev-list HEAD &&
+	test_terminal git rev-list HEAD &&
 	! test -e paginated.out
 '
 
@@ -54,7 +62,7 @@ test_expect_success 'no pager when stdout is a regular file' '
 
 rm -f paginated.out
 test_expect_success TTY 'git --paginate rev-list uses a pager' '
-	git --paginate rev-list HEAD  &&
+	test_terminal git --paginate rev-list HEAD &&
 	test -e paginated.out
 '
 
@@ -66,7 +74,7 @@ test_expect_success 'no pager even with --paginate when stdout is a pipe' '
 
 rm -f paginated.out
 test_expect_success TTY 'no pager with --no-pager' '
-	git --no-pager log &&
+	test_terminal git --no-pager log &&
 	! test -e paginated.out
 '
 
@@ -127,7 +135,7 @@ test_expect_success SIMPLEPAGER 'default pager is used by default' '
 	: > default_pager_used
 	EOF
 	chmod +x $less &&
-	PATH=.:$PATH git log &&
+	PATH=.:$PATH test_terminal git log &&
 	test -e default_pager_used
 '
 
@@ -137,7 +145,7 @@ rm -f PAGER_used
 test_expect_success TTY 'PAGER overrides default pager' '
 	PAGER=": > PAGER_used" &&
 	export PAGER &&
-	git log &&
+	test_terminal git log &&
 	test -e PAGER_used
 '
 
@@ -147,7 +155,7 @@ test_expect_success TTY 'core.pager overrides PAGER' '
 	PAGER=: &&
 	export PAGER &&
 	git config core.pager ": > core.pager_used" &&
-	git log &&
+	test_terminal git log &&
 	test -e core.pager_used
 '
 
@@ -156,7 +164,7 @@ test_expect_success TTY 'GIT_PAGER overrides core.pager' '
 	git config core.pager : &&
 	GIT_PAGER=": > GIT_PAGER_used" &&
 	export GIT_PAGER &&
-	git log &&
+	test_terminal git log &&
 	test -e GIT_PAGER_used
 '
 
diff --git a/test-terminal.c b/test-terminal.c
new file mode 100644
index 0000000..f4d6a71
--- /dev/null
+++ b/test-terminal.c
@@ -0,0 +1,62 @@
+#include "cache.h"
+#include "run-command.h"
+
+static void newtty(int *master, int *slave)
+{
+	int fd;
+	const char *term;
+
+	fd = posix_openpt(O_RDWR|O_NOCTTY);
+	if (fd == -1 || grantpt(fd) || unlockpt(fd) || !(term = ptsname(fd)))
+		die_errno("Could not allocate a new pseudo-terminal");
+	*master = fd;
+	*slave = open(term, O_RDWR|O_NOCTTY);
+	if (*slave == -1)
+		die_errno("Could not open pseudo-terminal: %s", term);
+}
+
+static void setup_child(struct child_process *chld,
+			const char **args, int out)
+{
+	memset(chld, 0, sizeof(*chld));
+	chld->argv = args;
+	chld->out = out;
+}
+
+static void xsendfile(int out_fd, int in_fd)
+{
+	char buf[BUFSIZ];
+
+	/* Note: the real sendfile() cannot read from a terminal. */
+	for (;;) {
+		ssize_t n = xread(in_fd, buf, sizeof(buf));
+
+		/*
+		 * It is unspecified by POSIX whether reads
+		 * from a disconnected terminal will return
+		 * EIO (as in AIX 4.x, IRIX, and Linux) or
+		 * end-of-file.  Either is fine.
+		 */
+		if (n == 0 || (n == -1 && errno == EIO))
+			break;
+		if (n == -1)
+			die_errno("cannot read from child");
+		write_or_die(out_fd, buf, n);
+	}
+}
+
+int main(int argc, const char **argv)
+{
+	int masterfd, slavefd;
+	struct child_process chld;
+
+	if (argc < 2 || (argc == 2 && !strcmp(argv[1], "-h")))
+		usage("test-terminal program args");
+
+	newtty(&masterfd, &slavefd);
+	setup_child(&chld, argv + 1, slavefd);
+	if (start_command(&chld))
+		return error("failed to execute child");
+	xsendfile(1, masterfd);
+	return finish_command(&chld);
+}

-- 
1.7.0
Previous: Jonathan NiederNext: Jeff King
Message 15 of 26 in “Re: 'git svn log' no longer uses the pager”
  1. 0/7 Re: 'git svn log' no longer uses the pagerJonathan Nieder, Feb 19, 2010
  2. 1/7 Fix 'git var' usage synopsisJonathan Nieder, Feb 19, 2010
  3. 2/7 Make 'git var GIT_PAGER' always print the configured pagerJonathan Nieder, Feb 19, 2010
  4. 3/7 git.1: Clarify the behavior of the --paginate optionJonathan Nieder, Feb 19, 2010
  5. 4/7 git svn: Fix launching of pagerJonathan Nieder, Feb 19, 2010
  6. 5/7 am: Fix launching of pagerJonathan Nieder, Feb 19, 2010
  7. 6/7 tests: Add tests for automatic use of pagerJonathan Nieder, Feb 19, 2010
  8. Junio C HamanoFeb 20, 2010
  9. 6/7 tests: Add tests for automatic use of pagerJonathan Nieder, Feb 21, 2010
  10. 7/7 t7006-pager: if stdout is not a terminal, make a new oneJonathan Nieder, Feb 21, 2010
  11. Jeff KingFeb 21, 2010
  12. Johannes SixtFeb 22, 2010
  13. 8/7 tests: Fix race condition in t7006-pagerJonathan Nieder, Feb 22, 2010
  14. Jonathan NiederFeb 22, 2010
  15. 7/7 t7006-pager: if stdout is not a terminal, make a new oneJonathan Nieder, Feb 19, 2010
  16. Jeff KingFeb 19, 2010
  17. Jonathan NiederFeb 19, 2010
  18. Jeff KingFeb 19, 2010
  19. Brandon CaseyFeb 19, 2010
  20. Brandon CaseyFeb 20, 2010
  21. Jonathan NiederFeb 20, 2010
  22. Brandon CaseyFeb 20, 2010
  23. 7/7 t7006-pager: if stdout is not a terminal, make a new oneJonathan Nieder, Feb 20, 2010
  24. Junio C HamanoFeb 20, 2010
  25. 7/7 t7006-pager: if stdout is not a terminal, make a new oneJonathan Nieder, Feb 20, 2010
  26. Simplify test-terminal.perlJonathan Nieder, Feb 20, 2010

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