[GSoC PATCH v2] test-lib: print escape sequence names

[Pablo Sabater <pabloosabaterr@gmail.com>]

When printing expected/actual characters in failed checks, use
their names (\a, \b, \n, ...) instead of their octal representation,
making it easier to read.

Add tests to test-example-tap.c
Update t0080-unit-test-output.sh to match the desired output

Teach 'print_one_char()' the equivalent name

Signed-off-by: Pablo Sabater <pabloosabaterr@gmail.com>
---
Changes from v1:
reverted unrelated test change '\'' to '\\'' in t0080

 t/helper/test-example-tap.c |  4 +++
 t/t0080-unit-test-output.sh | 52 +++++++++++++++++++++++--------------
 t/unit-tests/test-lib.c     | 19 ++++++++++++--
 3 files changed, 53 insertions(+), 22 deletions(-)

diff --git a/t/helper/test-example-tap.c b/t/helper/test-example-tap.c
index 229d495ecf..998a1f0b42 100644
--- a/t/helper/test-example-tap.c
+++ b/t/helper/test-example-tap.c
@@ -63,6 +63,8 @@ static void t_messages(void)
 	check_str("NULL", NULL);
 	check_char('a', ==, '\n');
 	check_char('\\', ==, '\'');
+	check_char('\a', ==, '\v');
+	check_char('\x00', ==, '\x01');
 }
 
 static void t_empty(void)
@@ -123,6 +125,8 @@ int cmd__example_tap(int argc UNUSED, const char **argv UNUSED)
 		check_str("NULL", NULL);
 		check_char('a', ==, '\n');
 		check_char('\\', ==, '\'');
+		check_char('\a', ==, '\v');
+		check_char('\x00', ==, '\x01');
 	}
 	if_test ("if_test test with no checks")
 		; /* nothing */
diff --git a/t/t0080-unit-test-output.sh b/t/t0080-unit-test-output.sh
index 3db10f095c..66838a00b2 100755
--- a/t/t0080-unit-test-output.sh
+++ b/t/t0080-unit-test-output.sh
@@ -6,10 +6,10 @@ test_description='Test the output of the unit test framework'
 
 test_expect_success 'TAP output from unit tests' - <<\EOT
 	cat >expect <<-EOF &&
-	# BUG: check outside of test at t/helper/test-example-tap.c:75
+	# BUG: check outside of test at t/helper/test-example-tap.c:77
 	ok 1 - passing test
 	ok 2 - passing test and assertion return 1
-	# check "1 == 2" failed at t/helper/test-example-tap.c:79
+	# check "1 == 2" failed at t/helper/test-example-tap.c:81
 	#    left: 1
 	#   right: 2
 	not ok 3 - failing test
@@ -34,53 +34,65 @@ test_expect_success 'TAP output from unit tests' - <<\EOT
 	not ok 15 - failing check after TEST_TODO()
 	ok 16 - failing check after TEST_TODO() returns 0
 	# check "!strcmp("\thello\\\\", "there\"\n")" failed at t/helper/test-example-tap.c:62
-	#    left: "\011hello\\\\"
-	#   right: "there\"\012"
+	#    left: "\thello\\\\"
+	#   right: "there\"\n"
 	# check "!strcmp("NULL", NULL)" failed at t/helper/test-example-tap.c:63
 	#    left: "NULL"
 	#   right: NULL
 	# check "'a' == '\n'" failed at t/helper/test-example-tap.c:64
 	#    left: 'a'
-	#   right: '\012'
+	#   right: '\n'
 	# check "'\\\\' == '\\''" failed at t/helper/test-example-tap.c:65
 	#    left: '\\\\'
 	#   right: '\\''
+	# check "'\a' == '\v'" failed at t/helper/test-example-tap.c:66
+	#    left: '\a'
+	#   right: '\v'
+	# check "'\x00' == '\x01'" failed at t/helper/test-example-tap.c:67
+	#    left: '\000'
+	#   right: '\001'
 	not ok 17 - messages from failing string and char comparison
-	# BUG: test has no checks at t/helper/test-example-tap.c:94
+	# BUG: test has no checks at t/helper/test-example-tap.c:96
 	not ok 18 - test with no checks
 	ok 19 - test with no checks returns 0
 	ok 20 - if_test passing test
-	# check "1 == 2" failed at t/helper/test-example-tap.c:100
+	# check "1 == 2" failed at t/helper/test-example-tap.c:102
 	#    left: 1
 	#   right: 2
 	not ok 21 - if_test failing test
 	not ok 22 - if_test passing TEST_TODO() # TODO
-	# todo check 'check(1)' succeeded at t/helper/test-example-tap.c:104
+	# todo check 'check(1)' succeeded at t/helper/test-example-tap.c:106
 	not ok 23 - if_test failing TEST_TODO()
-	# check "0" failed at t/helper/test-example-tap.c:106
+	# check "0" failed at t/helper/test-example-tap.c:108
 	# skipping test - missing prerequisite
-	# skipping check '1' at t/helper/test-example-tap.c:108
+	# skipping check '1' at t/helper/test-example-tap.c:110
 	ok 24 - if_test test_skip() # SKIP
 	# skipping test - missing prerequisite
 	ok 25 - if_test test_skip() inside TEST_TODO() # SKIP
-	# check "0" failed at t/helper/test-example-tap.c:113
+	# check "0" failed at t/helper/test-example-tap.c:115
 	not ok 26 - if_test TEST_TODO() after failing check
-	# check "0" failed at t/helper/test-example-tap.c:119
+	# check "0" failed at t/helper/test-example-tap.c:121
 	not ok 27 - if_test failing check after TEST_TODO()
-	# check "!strcmp("\thello\\\\", "there\"\n")" failed at t/helper/test-example-tap.c:122
-	#    left: "\011hello\\\\"
-	#   right: "there\"\012"
-	# check "!strcmp("NULL", NULL)" failed at t/helper/test-example-tap.c:123
+	# check "!strcmp("\thello\\\\", "there\"\n")" failed at t/helper/test-example-tap.c:124
+	#    left: "\thello\\\\"
+	#   right: "there\"\n"
+	# check "!strcmp("NULL", NULL)" failed at t/helper/test-example-tap.c:125
 	#    left: "NULL"
 	#   right: NULL
-	# check "'a' == '\n'" failed at t/helper/test-example-tap.c:124
+	# check "'a' == '\n'" failed at t/helper/test-example-tap.c:126
 	#    left: 'a'
-	#   right: '\012'
-	# check "'\\\\' == '\\''" failed at t/helper/test-example-tap.c:125
+	#   right: '\n'
+	# check "'\\\\' == '\\''" failed at t/helper/test-example-tap.c:127
 	#    left: '\\\\'
 	#   right: '\\''
+	# check "'\a' == '\v'" failed at t/helper/test-example-tap.c:128
+	#    left: '\a'
+	#   right: '\v'
+	# check "'\x00' == '\x01'" failed at t/helper/test-example-tap.c:129
+	#    left: '\000'
+	#   right: '\001'
 	not ok 28 - if_test messages from failing string and char comparison
-	# BUG: test has no checks at t/helper/test-example-tap.c:127
+	# BUG: test has no checks at t/helper/test-example-tap.c:131
 	not ok 29 - if_test test with no checks
 	1..29
 	EOF
diff --git a/t/unit-tests/test-lib.c b/t/unit-tests/test-lib.c
index 87e1f5c201..72ee20a06f 100644
--- a/t/unit-tests/test-lib.c
+++ b/t/unit-tests/test-lib.c
@@ -396,8 +396,23 @@ int check_uint_loc(const char *loc, const char *check, int ok,
 static void print_one_char(char ch, char quote)
 {
 	if ((unsigned char)ch < 0x20u || ch == 0x7f) {
-		/* TODO: improve handling of \a, \b, \f ... */
-		printf("\\%03o", (unsigned char)ch);
+		char esc;
+		switch (ch) {
+		case '\a': esc = 'a'; break;
+		case '\b': esc = 'b'; break;
+		case '\t': esc = 't'; break;
+		case '\n': esc = 'n'; break;
+		case '\v': esc = 'v'; break;
+		case '\f': esc = 'f'; break;
+		case '\r': esc = 'r'; break;
+		default: esc = 0; break;
+		}
+		if (esc) {
+			putc('\\', stdout);
+			putc(esc, stdout);
+		} else {
+			printf("\\%03o", (unsigned char)ch);
+		}
 	} else {
 		if (ch == '\\' || ch == quote)
 			putc('\\', stdout);
-- 
2.43.0