interpreter: Move most of the remaining validation to the Interpreter

What's left requires the Environment, so it will have to be handled in
the interpreter implementation for now.

3 files changed, 26 insertions, 19 deletions

diff --git a/mesonbuild/build.py b/mesonbuild/build.py
index 8241efa1d..03b1f3db8 100644
--- a/mesonbuild/build.py
+++ b/mesonbuild/build.py
@@ -1593,23 +1593,6 @@ class BuildTarget(Target):
     def add_pch(self, language: str, pchlist: T.List[str]) -> None:
         if not pchlist:
             return
-        elif len(pchlist) == 1:
-            if not is_header(pchlist[0]):
-                raise InvalidArguments(f'PCH argument {pchlist[0]} is not a header.')
-        elif len(pchlist) == 2:
-            if is_header(pchlist[0]):
-                if not is_source(pchlist[1]):
-                    raise InvalidArguments('PCH definition must contain one header and at most one source.')
-            elif is_source(pchlist[0]):
-                if not is_header(pchlist[1]):
-                    raise InvalidArguments('PCH definition must contain one header and at most one source.')
-                pchlist = [pchlist[1], pchlist[0]]
-            else:
-                raise InvalidArguments(f'PCH argument {pchlist[0]} is of unknown type.')
-
-            if os.path.dirname(pchlist[0]) != os.path.dirname(pchlist[1]):
-                raise InvalidArguments('PCH files must be stored in the same folder.')
-
         for f in pchlist:
             if not os.path.isfile(os.path.join(self.environment.source_dir, self.subdir, f)):
                 raise MesonException(f'File {f} does not exist.')
diff --git a/mesonbuild/interpreter/type_checking.py b/mesonbuild/interpreter/type_checking.py
index e582cd91b..5dc9127f3 100644
--- a/mesonbuild/interpreter/type_checking.py
+++ b/mesonbuild/interpreter/type_checking.py
@@ -653,7 +653,23 @@ _NAME_PREFIX_KW: KwargInfo[T.Optional[T.Union[str, T.List]]] = KwargInfo(
 
 
 def _pch_validator(args: T.List[str]) -> T.Optional[str]:
-    if len(args) > 2:
+    num_args = len(args)
+    if num_args == 1:
+        if not compilers.is_header(args[0]):
+            return f'PCH argument {args[0]} is not a header.'
+    elif num_args == 2:
+        if compilers.is_header(args[0]):
+            if not compilers.is_source(args[1]):
+                return 'PCH definition must contain one header and at most one source.'
+        elif compilers.is_source(args[0]):
+            if not compilers.is_header(args[1]):
+                return 'PCH definition must contain one header and at most one source.'
+        else:
+            return f'PCH argument {args[0]} has neither a known header or code extension.'
+
+        if os.path.dirname(args[0]) != os.path.dirname(args[1]):
+            return 'PCH files must be stored in the same folder.'
+    elif num_args > 2:
         return 'A maximum of two elements are allowed for PCH arguments'
     return None
 
@@ -663,6 +679,13 @@ def _pch_feature_validator(args: T.List[str]) -> T.Iterable[FeatureCheckBase]:
         yield FeatureDeprecated('PCH source files', '0.50.0', 'Only a single header file should be used.')
 
 
+def _pch_convertor(args: T.List[str]) -> T.List[str]:
+    # Flip so that we always have [header, src]
+    if len(args) == 2 and compilers.is_source(args[0]):
+        return [args[1], args[0]]
+    return args
+
+
 _PCH_ARGS: KwargInfo[T.List[str]] = KwargInfo(
     'pch',
     ContainerTypeInfo(list, str),
@@ -670,6 +693,7 @@ _PCH_ARGS: KwargInfo[T.List[str]] = KwargInfo(
     default=[],
     validator=_pch_validator,
     feature_validator=_pch_feature_validator,
+    convertor=_pch_convertor,
 )
 
 
diff --git a/test cases/failing/87 pch source different folder/test.json b/test cases/failing/87 pch source different folder/test.json
index 0a9d39d6f..fd18d6866 100644
--- a/test cases/failing/87 pch source different folder/test.json
+++ b/test cases/failing/87 pch source different folder/test.json
@@ -1,7 +1,7 @@
 {
   "stdout": [
     {
-      "line": "test cases/failing/87 pch source different folder/meson.build:4:6: ERROR: PCH files must be stored in the same folder."
+      "line": "test cases/failing/87 pch source different folder/meson.build:4:6: ERROR: executable keyword argument \"c_pch\" PCH files must be stored in the same folder."
     }
   ]
 }