Re: [PATCH] gdb/python: allow Value.format_string to return styled output

[Andrew Burgess <aburgess@redhat.com>]

* Simon Marchi via Gdb-patches <gdb-patches@sourceware.org> [2022-01-25 11:27:09 -0500]:

> 
> 
> On 2022-01-25 11:07, Andrew Burgess wrote:
> > * Simon Marchi via Gdb-patches <gdb-patches@sourceware.org> [2022-01-25 07:56:52 -0500]:
> > 
> >> LGTM, just two small comments:
> >>
> >>> @@ -725,6 +728,7 @@ valpy_format_string (PyObject *self, PyObject *args, PyObject *kw)
> >>>      return NULL;
> >>>    if (!copy_py_bool_obj (&opts.static_field_print, static_members_obj))
> >>>      return NULL;
> >>> +  bool styling_p = (styling_obj != nullptr) && PyObject_IsTrue (styling_obj);
> >>
> >> Can styling_obj actually be nullptr?
> > 
> > Sure, the new 'styling' argument is optional, after the "|" in the
> > gdb_PyArg_ParseTupleAndKeywords call, so if 'styling' isn't given
> > styling_obj will be left as it's default value, which is nullptr.
> > 
> > I guess I could initialise styling_obj to Py_False, maybe that would
> > be nicer?
> 
> Either way, what you have is fine.  It's just that I read the doc for
> the "O" specifier, and it says "The pointer stored is not NULL.".  But
> that's only if the value is present.  I never remember that part.

Cool.  Thanks for the review.  I'll wait for a doc review from Eli
before pushing.

The updated patch is below.

Thanks,
Andrew

---

commit 7e8ebb30bdf3217b380bc5130d34bae9ba6c1a35
Author: Andrew Burgess <aburgess@redhat.com>
Date:   Mon Jan 24 15:29:49 2022 +0000

    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.

diff --git a/gdb/NEWS b/gdb/NEWS
index 8c13cefb22f..5b71d6a1c08 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -146,6 +146,13 @@ show debug lin-lwp
   ** New function gdb.host_charset(), returns a string, which is the
      name of the current host charset.
 
+  ** The gdb.Value.format_string method now takes a 'styling'
+     argument, which is a boolean.  When true, the returned string can
+     include escape sequences to apply styling.  The styling will only
+     be present if styling is otherwise turned on in GDB (see 'help
+     set styling').  When false, which is the default if the argument
+     is not given, then no styling is applied to the returned string.
+
 * New features in the GDB remote stub, GDBserver
 
   ** GDBserver is now supported on OpenRISC GNU/Linux.
diff --git a/gdb/doc/python.texi b/gdb/doc/python.texi
index f02380a27f4..0b3235018bb 100644
--- a/gdb/doc/python.texi
+++ b/gdb/doc/python.texi
@@ -1048,6 +1048,16 @@
 the returned string.  For instance, @code{'x'} is equivalent to using the
 @value{GDBN} command @code{print} with the @code{/x} option and formats
 the value as a hexadecimal number.
+
+@item styling
+@code{True} if @value{GDBN} should apply styling to the returned
+string.  When styling is applied, the returned string might contain
+ANSI terminal escape sequences.  Escape sequences will only be
+included if styling is turned on, @xref{Output Styling}.
+Additionally, @value{GDBN} only styles some value contents, so not
+every output string will contain escape sequences.
+
+When @code{False}, which is the default, no output styling is applied.
 @end table
 @end defun
 
diff --git a/gdb/python/py-value.c b/gdb/python/py-value.c
index 70b33d5a27b..12034657c31 100644
--- a/gdb/python/py-value.c
+++ b/gdb/python/py-value.c
@@ -636,6 +636,7 @@ valpy_format_string (PyObject *self, PyObject *args, PyObject *kw)
       "symbols",		/* See set print symbol on|off.  */
       "unions",			/* See set print union on|off.  */
       "address",		/* See set print address on|off.  */
+      "styling",		/* Should we apply styling.  */
       /* C++ options.  */
       "deref_refs",		/* No corresponding setting.  */
       "actual_objects",		/* See set print object on|off.  */
@@ -680,13 +681,14 @@ valpy_format_string (PyObject *self, PyObject *args, PyObject *kw)
   PyObject *symbols_obj = NULL;
   PyObject *unions_obj = NULL;
   PyObject *address_obj = NULL;
+  PyObject *styling_obj = Py_False;
   PyObject *deref_refs_obj = NULL;
   PyObject *actual_objects_obj = NULL;
   PyObject *static_members_obj = NULL;
   char *format = NULL;
   if (!gdb_PyArg_ParseTupleAndKeywords (args,
 					kw,
-					"|O!O!O!O!O!O!O!O!O!O!IIIs",
+					"|O!O!O!O!O!O!O!O!O!O!O!IIIs",
 					keywords,
 					&PyBool_Type, &raw_obj,
 					&PyBool_Type, &pretty_arrays_obj,
@@ -695,6 +697,7 @@ valpy_format_string (PyObject *self, PyObject *args, PyObject *kw)
 					&PyBool_Type, &symbols_obj,
 					&PyBool_Type, &unions_obj,
 					&PyBool_Type, &address_obj,
+					&PyBool_Type, &styling_obj,
 					&PyBool_Type, &deref_refs_obj,
 					&PyBool_Type, &actual_objects_obj,
 					&PyBool_Type, &static_members_obj,
@@ -749,7 +752,7 @@ valpy_format_string (PyObject *self, PyObject *args, PyObject *kw)
 	}
     }
 
-  string_file stb;
+  string_file stb (PyObject_IsTrue (styling_obj));
 
   try
     {
diff --git a/gdb/testsuite/gdb.python/py-format-string.exp b/gdb/testsuite/gdb.python/py-format-string.exp
index 4c78bed1203..ac1353ea2e3 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
+      }
     }
   }