mtest: fix unencodable XML chars

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

Closes #9894

Co-authored-by: Tristan Partin <tristan@partin.io>

4 files changed, 121 insertions, 2 deletions

diff --git a/mesonbuild/mtest.py b/mesonbuild/mtest.py
index 8975dcdff..eb56c42be 100644
--- a/mesonbuild/mtest.py
+++ b/mesonbuild/mtest.py
@@ -72,6 +72,26 @@ GNU_ERROR_RETURNCODE = 99
 # Exit if 3 Ctrl-C's are received within one second
 MAX_CTRLC = 3
 
+# Define unencodable xml characters' regex for replacing them with their
+# printable representation
+UNENCODABLE_XML_UNICHRS: T.List[T.Tuple[int, int]] = [
+    (0x00, 0x08), (0x0B, 0x0C), (0x0E, 0x1F), (0x7F, 0x84),
+    (0x86, 0x9F), (0xFDD0, 0xFDEF), (0xFFFE, 0xFFFF)]
+# Not narrow build
+if sys.maxunicode >= 0x10000:
+    UNENCODABLE_XML_UNICHRS.extend([
+        (0x1FFFE, 0x1FFFF), (0x2FFFE, 0x2FFFF),
+        (0x3FFFE, 0x3FFFF), (0x4FFFE, 0x4FFFF),
+        (0x5FFFE, 0x5FFFF), (0x6FFFE, 0x6FFFF),
+        (0x7FFFE, 0x7FFFF), (0x8FFFE, 0x8FFFF),
+        (0x9FFFE, 0x9FFFF), (0xAFFFE, 0xAFFFF),
+        (0xBFFFE, 0xBFFFF), (0xCFFFE, 0xCFFFF),
+        (0xDFFFE, 0xDFFFF), (0xEFFFE, 0xEFFFF),
+        (0xFFFFE, 0xFFFFF), (0x10FFFE, 0x10FFFF)])
+UNENCODABLE_XML_CHR_RANGES = [fr'{chr(low)}-{chr(high)}' for (low, high) in UNENCODABLE_XML_UNICHRS]
+UNENCODABLE_XML_CHRS_RE = re.compile('([' + ''.join(UNENCODABLE_XML_CHR_RANGES) + '])')
+
+
 def is_windows() -> bool:
     platname = platform.system().lower()
     return platname == 'windows'
@@ -1148,14 +1168,21 @@ class TestRunRust(TestRun):
 
 TestRun.PROTOCOL_TO_CLASS[TestProtocol.RUST] = TestRunRust
 
+# Check unencodable characters in xml output and replace them with
+# their printable representation
+def replace_unencodable_xml_chars(original_str: str) -> str:
+    # [1:-1] is needed for removing `'` characters from both start and end
+    # of the string
+    replacement_lambda = lambda illegal_chr: repr(illegal_chr.group())[1:-1]
+    return UNENCODABLE_XML_CHRS_RE.sub(replacement_lambda, original_str)
 
 def decode(stream: T.Union[None, bytes]) -> str:
     if stream is None:
         return ''
     try:
-        return stream.decode('utf-8')
+        return replace_unencodable_xml_chars(stream.decode('utf-8'))
     except UnicodeDecodeError:
-        return stream.decode('iso-8859-1', errors='ignore')
+        return replace_unencodable_xml_chars(stream.decode('iso-8859-1', errors='ignore'))
 
 async def read_decode(reader: asyncio.StreamReader,
                       queue: T.Optional['asyncio.Queue[T.Optional[str]]'],
diff --git a/test cases/unit/110 replace unencodable xml chars/meson.build b/test cases/unit/110 replace unencodable xml chars/meson.build
new file mode 100644
index 000000000..2e6b1b793
--- /dev/null
+++ b/test cases/unit/110 replace unencodable xml chars/meson.build
@@ -0,0 +1,4 @@
+project('replace unencodable xml chars')
+
+test_script = find_program('script.py')
+test('main', test_script)
diff --git a/test cases/unit/110 replace unencodable xml chars/script.py b/test cases/unit/110 replace unencodable xml chars/script.py
new file mode 100644
index 000000000..2f2d4d67b
--- /dev/null
+++ b/test cases/unit/110 replace unencodable xml chars/script.py
@@ -0,0 +1,37 @@
+#!/usr/bin/env python3
+
+import sys
+
+# Print base string(\nHello Meson\n) to see valid chars are not replaced
+print('\n\x48\x65\x6c\x6c\x6f\x20\x4d\x65\x73\x6f\x6e\n')
+# Print invalid input from all known unencodable chars
+print(
+    '\x00\x01\x02\x03\x04\x05\x06\x07\x08\x0b\x0c\x0e\x0f\x10\x11'
+    '\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f\x7f')
+
+# Cover for potential encoding issues
+try:
+    print(
+        '\x80\x81\x82\x83\x84\x86\x87\x88\x89\x8a\x8b\x8c\x8d\x8e\x8f'
+        '\x90\x91\x92\x93\x94\x95\x96\x97\x98\x99\x9a\x9b\x9c\x9d\x9e'
+        '\x9f\ufdd0\ufdd1\ufdd2\ufdd3\ufdd4\ufdd5\ufdd6\ufdd7\ufdd8'
+        '\ufdd9\ufdda\ufddb\ufddc\ufddd\ufdde\ufddf\ufde0\ufde1'
+        '\ufde2\ufde3\ufde4\ufde5\ufde6\ufde7\ufde8\ufde9\ufdea'
+        '\ufdeb\ufdec\ufded\ufdee\ufdef\ufffe\uffff')
+except:
+    pass
+
+# Cover for potential encoding issues
+try:
+    if sys.maxunicode >= 0x10000:
+        print(
+            '\U0001fffe\U0001ffff\U0002fffe\U0002ffff'
+            '\U0003fffe\U0003ffff\U0004fffe\U0004ffff'
+            '\U0005fffe\U0005ffff\U0006fffe\U0006ffff'
+            '\U0007fffe\U0007ffff\U0008fffe\U0008ffff'
+            '\U0009fffe\U0009ffff\U000afffe\U000affff'
+            '\U000bfffe\U000bffff\U000cfffe\U000cffff'
+            '\U000dfffe\U000dffff\U000efffe\U000effff'
+            '\U000ffffe\U000fffff\U0010fffe\U0010ffff')
+except:
+    pass
diff --git a/unittests/allplatformstests.py b/unittests/allplatformstests.py
index 438e4fef5..db8a2f04b 100644
--- a/unittests/allplatformstests.py
+++ b/unittests/allplatformstests.py
@@ -59,6 +59,7 @@ from mesonbuild.linkers import linkers
 
 from mesonbuild.dependencies.pkgconfig import PkgConfigDependency
 from mesonbuild.build import Target, ConfigurationData, Executable, SharedLibrary, StaticLibrary
+from mesonbuild import mtest
 import mesonbuild.modules.pkgconfig
 from mesonbuild.scripts import destdir_join
 
@@ -398,6 +399,56 @@ class AllPlatformTests(BasePlatformTests):
         self.assertTrue(compdb[3]['file'].endswith("libfile4.c"))
         # FIXME: We don't have access to the linker command
 
+    def test_replace_unencodable_xml_chars(self):
+        '''
+        Test that unencodable xml chars are replaced with their
+        printable representation
+        https://github.com/mesonbuild/meson/issues/9894
+        '''
+        # Create base string(\nHello Meson\n) to see valid chars are not replaced
+        base_string_invalid = '\n\x48\x65\x6c\x6c\x6f\x20\x4d\x65\x73\x6f\x6e\n'
+        base_string_valid = '\nHello Meson\n'
+        # Create invalid input from all known unencodable chars
+        invalid_string = (
+            '\x00\x01\x02\x03\x04\x05\x06\x07\x08\x0b\x0c\x0e\x0f\x10\x11'
+            '\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f\x7f'
+            '\x80\x81\x82\x83\x84\x86\x87\x88\x89\x8a\x8b\x8c\x8d\x8e\x8f'
+            '\x90\x91\x92\x93\x94\x95\x96\x97\x98\x99\x9a\x9b\x9c\x9d\x9e'
+            '\x9f\ufdd0\ufdd1\ufdd2\ufdd3\ufdd4\ufdd5\ufdd6\ufdd7\ufdd8'
+            '\ufdd9\ufdda\ufddb\ufddc\ufddd\ufdde\ufddf\ufde0\ufde1'
+            '\ufde2\ufde3\ufde4\ufde5\ufde6\ufde7\ufde8\ufde9\ufdea'
+            '\ufdeb\ufdec\ufded\ufdee\ufdef\ufffe\uffff')
+        if sys.maxunicode >= 0x10000:
+            invalid_string = invalid_string + (
+                '\U0001fffe\U0001ffff\U0002fffe\U0002ffff'
+                '\U0003fffe\U0003ffff\U0004fffe\U0004ffff'
+                '\U0005fffe\U0005ffff\U0006fffe\U0006ffff'
+                '\U0007fffe\U0007ffff\U0008fffe\U0008ffff'
+                '\U0009fffe\U0009ffff\U000afffe\U000affff'
+                '\U000bfffe\U000bffff\U000cfffe\U000cffff'
+                '\U000dfffe\U000dffff\U000efffe\U000effff'
+                '\U000ffffe\U000fffff\U0010fffe\U0010ffff')
+
+        valid_string = base_string_valid + repr(invalid_string)[1:-1] + base_string_valid
+        invalid_string = base_string_invalid + invalid_string + base_string_invalid
+        broken_xml_stream = invalid_string.encode()
+        decoded_broken_stream = mtest.decode(broken_xml_stream)
+        self.assertEqual(decoded_broken_stream, valid_string)
+
+    def test_replace_unencodable_xml_chars_unit(self):
+        '''
+        Test that unencodable xml chars are replaced with their
+        printable representation
+        https://github.com/mesonbuild/meson/issues/9894
+        '''
+        if not shutil.which('xmllint'):
+            raise SkipTest('xmllint not installed')
+        testdir = os.path.join(self.unit_test_dir, '110 replace unencodable xml chars')
+        self.init(testdir)
+        self.run_tests()
+        junit_xml_logs = Path(self.logdir, 'testlog.junit.xml')
+        subprocess.run(['xmllint', junit_xml_logs], check=True)
+
     def test_run_target_files_path(self):
         '''
         Test that run_targets are run from the correct directory