Rewrite how OneShotCfg.build_modes gets constructed

This is a bit tricky because self.build_modes comes from parsing an
hjson dictionary and is actually a list of dictionaries that describe
build modes.

These get parsed and converted to BuildMode objects by
Mode.create_modes.

I've written a rather silly loose check that makes sure the types look
reasonable, which is enough to let us convince Pyright to allow the
code to claim the correct eventual types.

This commit also fixes an incorrect type in the second argument to
create_modes.

Signed-off-by: Rupert Swarbrick <rswarbrick@lowrisc.org>

Author: rswarbrick

src/dvsim/flow/one_shot.py

@@ -53,7 +53,7 @@ def __init__(self, flow_cfg_file, hjson_data, args, mk_config) -> None:
         self.dut = ""
         self.fusesoc_core = ""
         self.ral_spec = ""
-        self.build_modes = []
+        self.build_modes: Sequence[BuildMode] = []
         self.run_modes = []
         self.regressions = []
         self.max_msg_count = -1
@@ -110,17 +110,34 @@ def _expand(self) -> None:
     def _purge(self) -> None:
         assert self.scratch_path
         log.info("Purging scratch path %s", self.scratch_path)
-        rm_path(self.scratch_path)
+        rm_path(Path(self.scratch_path))
 
     def _create_objects(self) -> None:
-        # Create build and run modes objects
-        build_modes = Mode.create_modes(BuildMode, self.build_modes)
-        self.build_modes = build_modes
-
-        # All defined build modes are being built, h
-        # ence extend all with the global opts.
-        for build_mode in build_modes:
-            build_mode.build_opts.extend(self.build_opts)
+        # Create build modes objects based on the names that were stored in
+        # self.build_modes by the superclass constructor's call to
+        # _merge_hjson.
+        #
+        # We've lied to the type checker about the type of self.build_modes,
+        # giving it the type that it will contain after this function is
+        # complete.
+        mode_dicts: list[dict[object, object]] = []
+        for mode_dict in self.build_modes:
+            if not isinstance(mode_dict, dict):
+                msg = f"Found a build mode item of {mode_dict} when we expected a dict."
+                raise TypeError(msg)
+
+            mode_dicts.append(mode_dict)
+
+        base_modes: Sequence[Mode] = Mode.create_modes(BuildMode, mode_dicts)
+
+        # All defined build modes are being built, so should be extended with
+        # the global opts. Tighten up the inferred type at the same time.
+        self.build_modes = []
+        for mode in base_modes:
+            if not isinstance(mode, BuildMode):
+                raise TypeError("create_modes returned the wrong type")
+            mode.build_opts.extend(self.build_opts)
+            self.build_modes.append(mode)
 
     def _print_list(self) -> None:
         for list_item in self.list_items:

src/dvsim/modes.py

@@ -146,7 +146,7 @@ def merge_mode(self, mode: "Mode") -> None:
         return True
 
     @staticmethod
-    def create_modes(mode_type: "type[Mode]", mdicts: Mapping) -> Sequence["Mode"]:
+    def create_modes(mode_type: "type[Mode]", mdicts: Sequence[Mapping]) -> Sequence["Mode"]:
         """Create modes of type mode_type.
 
         Use the given list of raw dicts Process dependencies.