mtest: fix unencodable XML chars

[tristan957]

Replace unencodable XML chars with their printable representation, so that, xmllint can parse test outputs without error.

Closes #9894
Closes #10680

[benoit-pierre]

This PR also changes the JSON and text logs (meson-logs/testlog.json & meson-logs/testlog.txt) and the meson test command standard output, breaking, for example, color output (console codes). Was that intended?

[tristan957]

@benoit-pierre let me take a look because that is most certainly not intended

[benoit-pierre]

Glad to hear, tentative patch:

 mesonbuild/mtest.py | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git i/mesonbuild/mtest.py w/mesonbuild/mtest.py
index eb56c42be..8d83d17bd 100644
--- i/mesonbuild/mtest.py
+++ w/mesonbuild/mtest.py
@@ -867,10 +867,10 @@ class JunitBuilder(TestLogger):
                     et.SubElement(testcase, 'system-out').text = subtest.explanation
             if test.stdo:
                 out = et.SubElement(suite, 'system-out')
-                out.text = test.stdo.rstrip()
+                out.text = replace_unencodable_xml_chars(test.stdo.rstrip())
             if test.stde:
                 err = et.SubElement(suite, 'system-err')
-                err.text = test.stde.rstrip()
+                err.text = replace_unencodable_xml_chars(test.stde.rstrip())
         else:
             if test.project not in self.suites:
                 suite = self.suites[test.project] = et.Element(
@@ -893,10 +893,10 @@ class JunitBuilder(TestLogger):
                 suite.attrib['failures'] = str(int(suite.attrib['failures']) + 1)
             if test.stdo:
                 out = et.SubElement(testcase, 'system-out')
-                out.text = test.stdo.rstrip()
+                out.text = replace_unencodable_xml_chars(test.stdo.rstrip())
             if test.stde:
                 err = et.SubElement(testcase, 'system-err')
-                err.text = test.stde.rstrip()
+                err.text = replace_unencodable_xml_chars(test.stde.rstrip())
 
     async def finish(self, harness: 'TestHarness') -> None:
         """Calculate total test counts and write out the xml result."""
@@ -1180,9 +1180,9 @@ def decode(stream: T.Union[None, bytes]) -> str:
     if stream is None:
         return ''
     try:
-        return replace_unencodable_xml_chars(stream.decode('utf-8'))
+        return stream.decode('utf-8')
     except UnicodeDecodeError:
-        return replace_unencodable_xml_chars(stream.decode('iso-8859-1', errors='ignore'))
+        return stream.decode('iso-8859-1', errors='ignore')
 
 async def read_decode(reader: asyncio.StreamReader,
                       queue: T.Optional['asyncio.Queue[T.Optional[str]]'],