Convert test protocol into an enum

This gives us better type safety, and will be important as we add more
test methods

4 files changed, 32 insertions, 8 deletions

diff --git a/mesonbuild/backend/backends.py b/mesonbuild/backend/backends.py
index 774764d..ecdf330 100644
--- a/mesonbuild/backend/backends.py
+++ b/mesonbuild/backend/backends.py
@@ -14,6 +14,7 @@
 
 from collections import OrderedDict
 from functools import lru_cache
+import enum
 import json
 import os
 import pickle
@@ -28,12 +29,33 @@ from .. import dependencies
 from .. import mesonlib
 from .. import mlog
 from ..compilers import CompilerArgs, VisualStudioLikeCompiler
-from ..interpreter import Interpreter
 from ..mesonlib import (
     File, MachineChoice, MesonException, OrderedSet, OptionOverrideProxy,
     classify_unity_sources, unholder
 )
 
+if T.TYPE_CHECKING:
+    from ..interpreter import Interpreter
+
+
+class TestProtocol(enum.Enum):
+
+    EXITCODE = 0
+    TAP = 1
+
+    @classmethod
+    def from_str(cls, string: str) -> 'TestProtocol':
+        if string == 'exitcode':
+            return cls.EXITCODE
+        elif string == 'tap':
+            return cls.TAP
+        raise MesonException('unknown test format {}'.format(string))
+
+    def __str__(self) -> str:
+        if self is self.EXITCODE:
+            return 'exitcode'
+        return 'tap'
+
 
 class CleanTrees:
     '''
@@ -91,7 +113,7 @@ class TestSerialisation:
                  needs_exe_wrapper: bool, is_parallel: bool, cmd_args: T.List[str],
                  env: build.EnvironmentVariables, should_fail: bool,
                  timeout: T.Optional[int], workdir: T.Optional[str],
-                 extra_paths: T.List[str], protocol: str, priority: int):
+                 extra_paths: T.List[str], protocol: TestProtocol, priority: int):
         self.name = name
         self.project_name = project
         self.suite = suite
@@ -111,7 +133,7 @@ class TestSerialisation:
         self.priority = priority
         self.needs_exe_wrapper = needs_exe_wrapper
 
-def get_backend_from_name(backend: str, build: T.Optional[build.Build] = None, interpreter: T.Optional[Interpreter] = None) -> T.Optional['Backend']:
+def get_backend_from_name(backend: str, build: T.Optional[build.Build] = None, interpreter: T.Optional['Interpreter'] = None) -> T.Optional['Backend']:
     if backend == 'ninja':
         from . import ninjabackend
         return ninjabackend.NinjaBackend(build, interpreter)
@@ -138,7 +160,7 @@ def get_backend_from_name(backend: str, build: T.Optional[build.Build] = None, i
 # This class contains the basic functionality that is needed by all backends.
 # Feel free to move stuff in and out of it as you see fit.
 class Backend:
-    def __init__(self, build: T.Optional[build.Build], interpreter: T.Optional[Interpreter]):
+    def __init__(self, build: T.Optional[build.Build], interpreter: T.Optional['Interpreter']):
         # Make it possible to construct a dummy backend
         # This is used for introspection without a build directory
         if build is None:
diff --git a/mesonbuild/interpreter.py b/mesonbuild/interpreter.py
index dd1e57b..7b8ca63 100644
--- a/mesonbuild/interpreter.py
+++ b/mesonbuild/interpreter.py
@@ -33,6 +33,7 @@ from .interpreterbase import FeatureNew, FeatureDeprecated, FeatureNewKwargs
 from .interpreterbase import ObjectHolder
 from .modules import ModuleReturnValue
 from .cmake import CMakeInterpreter
+from .backend.backends import TestProtocol
 
 from pathlib import Path, PurePath
 import os
@@ -979,7 +980,7 @@ class Test(InterpreterObject):
         self.should_fail = should_fail
         self.timeout = timeout
         self.workdir = workdir
-        self.protocol = protocol
+        self.protocol = TestProtocol.from_str(protocol)
         self.priority = priority
 
     def get_exe(self):
diff --git a/mesonbuild/mintro.py b/mesonbuild/mintro.py
index d5516d4..54e302b 100644
--- a/mesonbuild/mintro.py
+++ b/mesonbuild/mintro.py
@@ -328,7 +328,7 @@ def get_test_list(testdata) -> T.List[T.Dict[str, T.Union[str, int, T.List[str],
         to['suite'] = t.suite
         to['is_parallel'] = t.is_parallel
         to['priority'] = t.priority
-        to['protocol'] = t.protocol
+        to['protocol'] = str(t.protocol)
         result.append(to)
     return result
 
diff --git a/mesonbuild/mtest.py b/mesonbuild/mtest.py
index 846b474..69da400 100644
--- a/mesonbuild/mtest.py
+++ b/mesonbuild/mtest.py
@@ -43,6 +43,7 @@ from . import environment
 from . import mlog
 from .dependencies import ExternalProgram
 from .mesonlib import MesonException, get_wine_shortpath, split_args
+from .backend.backends import TestProtocol
 
 if T.TYPE_CHECKING:
     from .backend.backends import TestSerialisation
@@ -631,7 +632,7 @@ class SingleTestRunner:
         if not self.options.verbose:
             stdout = tempfile.TemporaryFile("wb+")
             stderr = tempfile.TemporaryFile("wb+") if self.options.split else stdout
-        if self.test.protocol == 'tap' and stderr is stdout:
+        if self.test.protocol is TestProtocol.TAP and stderr is stdout:
             stdout = tempfile.TemporaryFile("wb+")
 
         # Let gdb handle ^C instead of us
@@ -741,7 +742,7 @@ class SingleTestRunner:
         if timed_out:
             return TestRun(self.test, self.test_env, TestResult.TIMEOUT, [], p.returncode, starttime, duration, stdo, stde, cmd)
         else:
-            if self.test.protocol == 'exitcode':
+            if self.test.protocol is TestProtocol.EXITCODE:
                 return TestRun.make_exitcode(self.test, self.test_env, p.returncode, starttime, duration, stdo, stde, cmd)
             else:
                 if self.options.verbose: