build: Store depends in GeneratedList instead of Generator

Since they are actually dependencies out the output not the Generator
itself.

This fixes dependency issues in the ninja backend, allowing Meson to
rebuild more accurately. It also does sometimes in the vs backend, but
there are problems in the vs backend I'm not sure how to solve. The
vsbackend is, itself, so fragile looking I don't want to get too
involved with it.

mesonbuild/backend/vs2010backend.py

@@ -12,7 +12,9 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from __future__ import annotations
 import copy
+import itertools
 import os
 import xml.dom.minidom
 import xml.etree.ElementTree as ET
@@ -318,11 +320,13 @@ class Vs2010Backend(backends.Backend):
                     gen_exe = generator.get_exe()
                     if isinstance(gen_exe, build.Executable):
                         all_deps[gen_exe.get_id()] = gen_exe
-                    for d in generator.depends:
+                    for d in itertools.chain(generator.depends, gendep.depends):
                         if isinstance(d, build.CustomTargetIndex):
                             all_deps[d.get_id()] = d.target
-                        else:
+                        elif isinstance(d, build.Target):
                             all_deps[d.get_id()] = d
+                        # FIXME: we don't handle other kinds of deps correctly here, such
+                        # as GeneratedLists, StructuredSources, and generated File.
 
         if not t or not recursive:
             return all_deps

mesonbuild/build.py

@@ -1720,7 +1720,7 @@ class Generator(HoldableObject):
                 output.depends.add(e.target)
 
             if isinstance(e, (CustomTarget, CustomTargetIndex, GeneratedList)):
-                self.depends.append(e) # BUG: this should go in the GeneratedList object, not this object.
+                output.depends.add(e)
                 fs = [File.from_built_file(state.subdir, f) for f in e.get_outputs()]
             elif isinstance(e, str):
                 fs = [File.from_source_file(state.environment.source_dir, state.subdir, e)]
@@ -1748,7 +1748,7 @@ class GeneratedList(HoldableObject):
 
     def __post_init__(self) -> None:
         self.name = self.generator.exe
-        self.depends: T.Set['CustomTarget'] = set() # Things this target depends on (because e.g. a custom target was used as input)
+        self.depends: T.Set[GeneratedTypes] = set()
         self.infilelist: T.List['File'] = []
         self.outfilelist: T.List[str] = []
         self.outmap: T.Dict[File, T.List[str]] = {}