From aa895b383cc726800d7d6e7e540db96dfe9df1f2 Mon Sep 17 00:00:00 2001
From: Dylan Baker <dylan@pnwbakers.com>
Date: Mon, 23 Aug 2021 14:07:57 -0700
Subject: [PATCH] interpreter: Add a helper for checking constrained inputs

This is quite valuable for enum-like inputs, where only a certain set
of values is allowed.
---
 mesonbuild/interpreter/compiler.py      |  4 ++--
 mesonbuild/interpreter/interpreter.py   |  3 ++-
 mesonbuild/interpreter/type_checking.py | 11 +++++++++++
 unittests/internaltests.py              |  3 ++-
 4 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/mesonbuild/interpreter/compiler.py b/mesonbuild/interpreter/compiler.py
index 7491fce4f..53c3ce0a2 100644
--- a/mesonbuild/interpreter/compiler.py
+++ b/mesonbuild/interpreter/compiler.py
@@ -17,7 +17,7 @@ from ..interpreterbase import (ObjectHolder, noPosargs, noKwargs,
                                InterpreterException)
 from ..interpreterbase.decorators import ContainerTypeInfo, typed_kwargs, KwargInfo, typed_pos_args
 from .interpreterobjects import (extract_required_kwarg, extract_search_dirs)
-from .type_checking import REQUIRED_KW
+from .type_checking import REQUIRED_KW, in_set_validator
 
 if T.TYPE_CHECKING:
     from ..interpreter import Interpreter
@@ -638,7 +638,7 @@ class CompilerHolder(ObjectHolder['Compiler']):
     @typed_kwargs(
         'compiler.get_supported_arguments',
         KwargInfo('checked', str, default='off', since='0.59.0',
-                  validator=lambda s: 'must be one of "warn", "require" or "off"' if s not in ['warn', 'require', 'off'] else None)
+                  validator=in_set_validator({'warn', 'require', 'off'})),
     )
     def get_supported_arguments_method(self, args: T.Tuple[T.List[str]], kwargs: 'GetSupportedArgumentKw') -> T.List[str]:
         supported_args: T.List[str] = []
diff --git a/mesonbuild/interpreter/interpreter.py b/mesonbuild/interpreter/interpreter.py
index c716c8523..5b03e7eb0 100644
--- a/mesonbuild/interpreter/interpreter.py
+++ b/mesonbuild/interpreter/interpreter.py
@@ -55,6 +55,7 @@ from .type_checking import (
     LANGUAGE_KW,
     NATIVE_KW,
     REQUIRED_KW,
+    in_set_validator,
 )
 
 from pathlib import Path
@@ -181,7 +182,7 @@ TEST_KWARGS: T.List[KwargInfo] = [
               validator=lambda x: 'must be an absolute path' if not os.path.isabs(x) else None),
     KwargInfo('protocol', str,
               default='exitcode',
-              validator=lambda x: 'value must be one of "exitcode", "tap", "gtest", "rust"' if x not in {'exitcode', 'tap', 'gtest', 'rust'} else None,
+              validator=in_set_validator({'exitcode', 'tap', 'gtest', 'rust'}),
               since_values={'gtest': '0.55.0', 'rust': '0.57.0'}),
     KwargInfo('depends', ContainerTypeInfo(list, (build.CustomTarget, build.BuildTarget)),
               listify=True, default=[], since='0.46.0'),
diff --git a/mesonbuild/interpreter/type_checking.py b/mesonbuild/interpreter/type_checking.py
index 6088eef9e..dd0411c5a 100644
--- a/mesonbuild/interpreter/type_checking.py
+++ b/mesonbuild/interpreter/type_checking.py
@@ -11,6 +11,17 @@ from ..interpreterbase.decorators import KwargInfo, ContainerTypeInfo
 from ..mesonlib import FileMode, MachineChoice
 
 
+def in_set_validator(choices: T.Set[str]) -> T.Callable[[str], T.Optional[str]]:
+    """Check that the choice given was one of the given set."""
+
+    def inner(check: str) -> T.Optional[str]:
+        if check not in choices:
+            return f"must be one of {', '.join(sorted(choices))}, not {check}"
+        return None
+
+    return inner
+
+
 def _language_validator(l: T.List[str]) -> T.Optional[str]:
     """Validate language keyword argument.
 
diff --git a/unittests/internaltests.py b/unittests/internaltests.py
index a4615d70c..daf3efd33 100644
--- a/unittests/internaltests.py
+++ b/unittests/internaltests.py
@@ -40,6 +40,7 @@ from mesonbuild.mesonlib import (
     LibType, MachineChoice, PerMachine, Version, is_windows, is_osx,
     is_cygwin, is_openbsd, search_version, MesonException, OptionKey,
 )
+from mesonbuild.interpreter.type_checking import in_set_validator
 from mesonbuild.dependencies import PkgConfigDependency
 from mesonbuild.programs import ExternalProgram
 import mesonbuild.modules.pkgconfig
@@ -1376,7 +1377,7 @@ class InternalTests(unittest.TestCase):
             KwargInfo('output', ContainerTypeInfo(dict, str), default={}, deprecated_values={'foo': '0.9'}, since_values={'bar': '1.1'}),
             KwargInfo(
                 'mode', str,
-                validator=lambda x: 'Should be one of "clean", "build", "rebuild"' if x not in {'clean', 'build', 'rebuild', 'deprecated', 'since'} else None,
+                validator=in_set_validator({'clean', 'build', 'rebuild', 'deprecated', 'since'}),
                 deprecated_values={'deprecated': '1.0'},
                 since_values={'since': '1.1'}),
         )