mtest: refactor common condition into a property of TestRun

For a test to be displayed to stdout without buffering, it has to be
1) in verbose mode 2) not executed in parallel with others
3) not parsed, i.e. not TAP or Rust.  Include these three
conditions in a new property of stdout and use it in the
three places where it matters: when printing the initial
and final delimiters of the output, and when deciding the
console mode to use.

Suggested-by: Jussi Pakkanen <jpakkane@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

mesonbuild/mtest.py

@@ -606,11 +606,9 @@ class ConsoleLogger(TestLogger):
                                  max_left_width=self.max_left_width,
                                  right=test.res.get_text(mlog.colorize_console())))
             print(test.res.get_command_marker() + test.cmdline)
-            if test.needs_parsing:
+            if test.direct_stdout:
-                pass
-            elif not test.is_parallel:
                 print(self.output_start, flush=True)
-            else:
+            elif not test.needs_parsing:
                 print(flush=True)
 
         self.started_tests += 1
@@ -665,7 +663,7 @@ class ConsoleLogger(TestLogger):
 
         if not harness.options.quiet or not result.res.is_ok():
             self.flush()
-            if result.verbose and not result.is_parallel and result.cmdline and not result.needs_parsing:
+            if result.cmdline and result.direct_stdout:
                 print(self.output_end)
                 print(harness.format(result, mlog.colorize_console(), max_left_width=self.max_left_width))
             else:
@@ -898,6 +896,10 @@ class TestRun:
             self._num = TestRun.TEST_NUM
         return self._num
 
+    @property
+    def direct_stdout(self) -> bool:
+        return self.verbose and not self.is_parallel and not self.needs_parsing
+
     @property
     def detail(self) -> str:
         if self.res is TestResult.PENDING:
@@ -1340,7 +1342,7 @@ class SingleTestRunner:
 
         if self.options.gdb:
             self.console_mode = ConsoleUser.GDB
-        elif self.runobj.verbose and not is_parallel and not self.runobj.needs_parsing:
+        elif self.runobj.direct_stdout:
             self.console_mode = ConsoleUser.STDOUT
         else:
             self.console_mode = ConsoleUser.LOGGER