build: Add structured sources

1 files changed, 55 insertions, 0 deletions

diff --git a/mesonbuild/build.py b/mesonbuild/build.py
index ecbc1d9..033941c 100644
--- a/mesonbuild/build.py
+++ b/mesonbuild/build.py
@@ -452,8 +452,63 @@ class ExtractedObjects(HoldableObject):
             for source in self.get_sources(self.srclist, self.genlist)
         ]
 
+
+@dataclass(eq=False, order=False)
+class StructuredSources(HoldableObject):
+
+    """A container for sources in languages that use filesystem hierarchy.
+
+    Languages like Rust and Cython rely on the layout of files in the filesystem
+    as part of the compiler implementation. This structure allows us to
+    represent the required filesystem layout.
+    """
+
+    sources: T.DefaultDict[str, T.List[T.Union[str, File, CustomTarget, CustomTargetIndex, GeneratedList]]] = field(
+        default_factory=lambda: defaultdict(list))
+
+    def __add__(self, other: StructuredSources) -> StructuredSources:
+        sources = self.sources.copy()
+        for k, v in other.sources.items():
+            sources[k].extend(v)
+        return StructuredSources(sources)
+
+    def __bool__(self) -> bool:
+        return bool(self.sources)
+
+    def first_file(self) -> T.Union[str, File, CustomTarget, CustomTargetIndex, GeneratedList]:
+        """Get the first source in the root
+
+        :return: The first source in the root
+        """
+        return self.sources[''][0]
+
+    def as_list(self) -> T.List[T.Union[str, File, CustomTarget, CustomTargetIndex, GeneratedList]]:
+        return list(itertools.chain.from_iterable(self.sources.values()))
+
+    def needs_copy(self, target: BuildTarget) -> bool:
+        """Do we need to create a structure in the build directory.
+
+        This allows us to avoid making copies if the structures exists in the
+        source dir. Which could happen in situations where a generated source
+        only exists in some configurations
+        """
+        p = pathlib.Path(target.subdir)
+        for files in self.sources.values():
+            for f in files:
+                if isinstance(f, str):
+                    if not (target.environment.source_dir / p / f).exists():
+                        return True
+                elif isinstance(f, File):
+                    if f.is_built:
+                        return True
+                else:
+                    return True
+        return False
+
+
 EnvInitValueType = T.Dict[str, T.Union[str, T.List[str]]]
 
+
 class EnvironmentVariables(HoldableObject):
     def __init__(self, values: T.Optional[EnvInitValueType] = None,
                  init_method: Literal['set', 'prepend', 'append'] = 'set', separator: str = os.pathsep) -> None: