gdb/python: allow Value.format_string to return styled output

Add a new argument to the gdb.Value.format_string method, 'styling'.
This argument is False by default.

When this argument is True, then the returned string can contain output
styling escape sequences.

When this argument is False, then the returned string will not contain
any styling escape sequences.

If the returned string is going to be printed to the user, then it is
often nice to retain the GDB styling.

For the testing, we need to adjust the TERM environment variable, as
we do for all the styling tests.  I'm now running all of the C tests
in gdb.python/py-format-string.exp in an environment where styling
could be generated, but only my new test should actually produce
styled output, hopefully this will catch the case where a bug might
cause format_string to always produce styled output.

1 files changed, 17 insertions, 3 deletions

diff --git a/gdb/testsuite/gdb.python/py-format-string.exp b/gdb/testsuite/gdb.python/py-format-string.exp
index 4c78bed..ac1353e 100644
--- a/gdb/testsuite/gdb.python/py-format-string.exp
+++ b/gdb/testsuite/gdb.python/py-format-string.exp
@@ -991,6 +991,13 @@ proc_with_prefix test_invalid_args {} {
     "ValueError: a single character is required.*"
 }
 
+# Check the styling argument to format_string.  This function needs to
+# be called with TERM set such that styling can be applied.
+proc test_styling {} {
+    gdb_test "python print(gdb.parse_and_eval(\"a_point_t\").format_string(styling=True, raw=True))" \
+	"{[style x variable] = 42, [style y variable] = 12}"
+}
+
 # Run all the tests in common for both C and C++.
 proc_with_prefix test_all_common {} {
   # No options.
@@ -1023,9 +1030,16 @@ with_test_prefix "format_string" {
   # Perform C Tests.
   if { [build_inferior "${binfile}" "c"] == 0 } {
     with_test_prefix "lang_c" {
-      set current_lang "c"
-      prepare_gdb "${binfile}"
-      test_all_common
+      save_vars { env(TERM) } {
+	# We run all of these tests in an environment where styling
+	# could work, but we only expect the final call to
+	# test_styling to actually produce any styled output.
+	setenv TERM ansi
+	set current_lang "c"
+	prepare_gdb "${binfile}"
+	test_all_common
+	test_styling
+      }
     }
   }